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| author | marha <marha@users.sourceforge.net> | 2010-08-07 14:34:01 +0000 |
|---|---|---|
| committer | marha <marha@users.sourceforge.net> | 2010-08-07 14:34:01 +0000 |
| commit | 9941d1bb9c10232b83e86c4c5df5092e81a12c1b (patch) | |
| tree | e8ce3d9af12c74753a8d03707bde27ae16a1e5da /libxcb | |
| parent | c002a3759f837a569c1c47241923fd03087f0ce7 (diff) | |
| parent | 4e3f3e7b8cc2c617187bdf23a9948bfd5121074e (diff) | |
| download | vcxsrv-9941d1bb9c10232b83e86c4c5df5092e81a12c1b.tar.gz vcxsrv-9941d1bb9c10232b83e86c4c5df5092e81a12c1b.tar.bz2 vcxsrv-9941d1bb9c10232b83e86c4c5df5092e81a12c1b.zip | |
svn merge ^/branches/released .
Diffstat (limited to 'libxcb')
| -rw-r--r-- | libxcb/doc/tutorial/index.html | 9042 |
1 files changed, 4521 insertions, 4521 deletions
diff --git a/libxcb/doc/tutorial/index.html b/libxcb/doc/tutorial/index.html index aa3ae1706..bb3338869 100644 --- a/libxcb/doc/tutorial/index.html +++ b/libxcb/doc/tutorial/index.html @@ -1,4521 +1,4521 @@ -<!DOCTYPE html public "-//W3C//DTD HTML 4.01 Transitional//EN" -"http://www.w3.org/TR/html4/loose.dtd"> - -<html> - -<head> - <title>Basic Graphics Programming With The XCB Library</title> - <meta http-equiv="content-type" content="text/html; charset=iso-8859-1"> - <link href="xcb.css" rel="stylesheet" type="text/css"> -</head> - -<body> - <div class="title"> - Basic Graphics Programming With The XCB Library - </div> - <div class="toc"> - <ol> - <li><a class="section" href="#intro">Introduction</a> - <li><a class="section" href="#Xmodel">The client and server model of the X window system</a> - <li><a class="section" href="#asynch">GUI programming: the asynchronous model</a> - <li><a class="section" href="#notions">Basic XCB notions</a> - <ol> - <li><a class="subsection" href="#conn">The X Connection</a> - <li><a class="subsection" href="#requestsreplies">Requests and replies: the Xlib killers</a> - <li><a class="subsection" href="#gc">The Graphics Context</a> - <li>Object handles - <li>Memory allocation for XCB structures - <li><a class="subsection" href="#events">Events</a> - </ol> - <li><a class="section" href="#use">Using XCB-based programs</a> - <ol> - <li><a class="subsection" href="#inst">Installation of XCB</a> - <li><a class="subsection" href="#comp">Compiling XCB-based programs</a> - </ol> - <li><a class="section" href="#openconn">Opening and closing the connection to an X server</a> - <li><a class="section" href="#screen">Checking basic information about a connection</a> - <li><a class="section" href="#helloworld">Creating a basic window - the "hello world" program</a> - <li><a class="section" href="#drawing">Drawing in a window</a> - <ol> - <li><a class="subsection" href="#allocgc">Allocating a Graphics Context</a> - <li><a class="subsection" href="#changegc">Changing the attributes of a Graphics Context</a> - <li><a class="subsection" href="#drawingprim">Drawing primitives: point, line, box, circle,...</a> - </ol> - <li><a class="section" href="#xevents">X Events</a> - <ol> - <li><a class="subsection" href="#register">Registering for event types using event masks</a> - <li><a class="subsection" href="#loop">Receiving events: writing the events loop</a> - <li><a class="subsection" href="#expose">Expose events</a> - <li><a class="subsection" href="#userinput">Getting user input</a> - <ol> - <li><a class="subsubsection" href="#mousepressrelease">Mouse button press and release events</a> - <li><a class="subsubsection" href="#mousemvnt">Mouse movement events</a> - <li><a class="subsubsection" href="#mouseenter">Mouse pointer enter and leave events</a> - <li><a class="subsubsection" href="#focus">The keyboard focus</a> - <li><a class="subsubsection" href="#keypress">Keyboard press and release events</a> - </ol> - <li><a class="subsection" href="#eventex">X events: a complete example</a> - </ol> - <li><a class="section" href="#font">Handling text and fonts</a> - <ol> - <li><a class="subsection" href="#fontstruct">The Font structure</a> - <li><a class="subsection" href="#openingfont">Opening a Font</a> - <li><a class="subsection" href="#assigningfont">Assigning a Font to a Graphic Context</a> - <li><a class="subsection" href="#drawingtext">Drawing text in a drawable</a> - <li><a class="subsection" href="#fontcompleteexample">Complete example</a> - </ol> - <li>Windows hierarchy - <ol> - <li>Root, parent and child windows - <li>Events propagation - </ol> - <li><a class="section" href="#wm">Interacting with the window manager</a> - <ol> - <li><a class="subsection" href="#wmprop">Window properties</a> - <li><a class="subsection" href="#wmname">Setting the window name and icon name</a> - <li>Setting preferred window size(s) - <li>Setting miscellaneous window manager hints - <li>Setting an application's icon - <li>Obeying the delete-window protocol - </ol> - <li><a class="section" href="#winop">Simple window operations</a> - <ol> - <li><a class="subsection" href="#winmap">Mapping and unmapping a window</a> - <li><a class="subsection" href="#winconf">Configuring a window</a> - <li><a class="subsection" href="#winmove">Moving a window around the screen</a> - <li><a class="subsection" href="#winsize">Resizing a window</a> - <li><a class="subsection" href="#winstack">Changing windows stacking order: raise and lower</a> - <li>Iconifying and de-iconifying a window - <li><a class="subsection" href="#wingetinfo">Getting informations about a window</a> - </ol> - <li><a class="section" href="#usecolor">Using colors to paint the rainbow</a> - <ol> - <li><a class="subsection" href="#colormap">Color maps</a> - <li><a class="subsection" href="#colormapalloc">Allocating and freeing Color Maps</a> - <li><a class="subsection" href="#alloccolor">Allocating and freeing a color entry</a> - <li>Drawing with a color - </ol> - <li><a class="section" href="#pixmaps">X Bitmaps and Pixmaps</a> - <ol> - <li><a class="subsection" href="#pixmapswhat">What is a X Bitmap ? An X Pixmap ?</a> - <li>Loading a bitmap from a file - <li>Drawing a bitmap in a window - <li><a class="subsection" href="#pixmapscreate">Creating a pixmap</a> - <li><a class="subsection" href="#pixmapsdraw">Drawing a pixmap in a window</a> - <li><a class="subsection" href="#pixmapsfree">Freeing a pixmap</a> - </ol> - <li><a class="subsection" href="#mousecursor">Messing with the mouse cursor</a> - <ol> - <li><a class="subsection" href="#mousecursorcreate">Creating and destroying a mouse cursor</a> - <li><a class="subsection" href="#mousecursorset">Setting a window's mouse cursor</a> - <li><a class="subsection" href="#mousecursorexample">Complete example</a> - </ol> - <li><a class="subsection" href="#translation">Translation of basic Xlib functions and macros</a> - <ol> - <li><a class="subsection" href="#displaystructure">Members of the Display structure</a> - <ol> - <li><a class="subsection" href="#ConnectionNumber">ConnectionNumber</a> - <li><a class="subsection" href="#DefaultScreen">DefaultScreen</a> - <li><a class="subsection" href="#QLength">QLength</a> - <li><a class="subsection" href="#ScreenCount">ScreenCount</a> - <li><a class="subsection" href="#ServerVendor">ServerVendor</a> - <li><a class="subsection" href="#ProtocolVersion">ProtocolVersion</a> - <li><a class="subsection" href="#ProtocolRevision">ProtocolRevision</a> - <li><a class="subsection" href="#VendorRelease">VendorRelease</a> - <li><a class="subsection" href="#DisplayString">DisplayString</a> - <li><a class="subsection" href="#BitmapUnit">BitmapUnit</a> - <li><a class="subsection" href="#BitmapBitOrder">BitmapBitOrder</a> - <li><a class="subsection" href="#BitmapPad">BitmapPad</a> - <li><a class="subsection" href="#ImageByteOrder">ImageByteOrder</a> - </ol> - <li><a class="subsection" href="#screenofdisplay">ScreenOfDisplay related functions</a> - <ol> - <li><a class="subsection" href="#ScreenOfDisplay">ScreenOfDisplay</a> - <li><a class="subsection" href="#DefaultScreenOfDisplay">DefaultScreenOfDisplay</a> - <li><a class="subsection" href="#RootWindow">RootWindow / RootWindowOfScreen</a> - <li><a class="subsection" href="#DefaultRootWindow">DefaultRootWindow</a> - <li><a class="subsection" href="#DefaultVisual">DefaultVisual / DefaultVisualOfScreen</a> - <li><a class="subsection" href="#DefaultGC">DefaultGC / DefaultGCOfScreen</a> - <li><a class="subsection" href="#BlackPixel">BlackPixel / BlackPixelOfScreen</a> - <li><a class="subsection" href="#WhitePixel">WhitePixel / WhitePixelOfScreen</a> - <li><a class="subsection" href="#DisplayWidth">DisplayWidth / WidthOfScreen</a> - <li><a class="subsection" href="#DisplayHeight">DisplayHeight / HeightOfScreen</a> - <li><a class="subsection" href="#DisplayWidthMM">DisplayWidthMM / WidthMMOfScreen</a> - <li><a class="subsection" href="#DisplayHeightMM">DisplayHeightMM / HeightMMOfScreen</a> - <li><a class="subsection" href="#DisplayPlanes">DisplayPlanes / DefaultDepth / DefaultDepthOfScreen / PlanesOfScreen</a> - <li><a class="subsection" href="#DefaultColormap">DefaultColormap / DefaultColormapOfScreen</a> - <li><a class="subsection" href="#MinCmapsOfScreen">MinCmapsOfScreen</a> - <li><a class="subsection" href="#MaxCmapsOfScreen">MaxCmapsOfScreen</a> - <li><a class="subsection" href="#DoesSaveUnders">DoesSaveUnders</a> - <li><a class="subsection" href="#DoesBackingStore">DoesBackingStore</a> - <li><a class="subsection" href="#EventMaskOfScreen">EventMaskOfScreen</a> - </ol> - <li><a class="subsection" href="#misc">Miscellaneaous macros</a> - <ol> - <li><a class="subsection" href="#DisplayOfScreen">DisplayOfScreen</a> - <li><a class="subsection" href="#DisplayCells">DisplayCells / CellsOfScreen</a> - </ol> - </ol> - </ol> - </div> - <div class="section"> - <ol> - <li class="title"><a name="intro">Introduction</a> - <p> - This tutorial is based on the - <a href="http://users.actcom.co.il/~choo/lupg/tutorials/xlib-programming/xlib-programming.html">Xlib Tutorial</a> - written by <a href="mailto:choor at atcom dot co dot il">Guy Keren</a>. The - author allowed me to take some parts of his text, mainly the text which - deals with the X Windows generality. - </p> - <p> - This tutorial is intended for people who want to start to program - with the <a href="http://xcb.freedesktop.org">XCB</a> - library. keep in mind that XCB, like the - <a href="http://tronche.com/gui/x/xlib/introduction">Xlib</a> - library, isn't what most programmers wanting to write X - applications are looking for. They should use a much higher - level GUI toolkit like Motif, - <a href="http://www.lesstif.org">LessTiff</a>, - <a href="http://www.gtk.org">GTK</a>, - <a href="http://www.trolltech.com">QT</a>, - <a href="http://www.enlightenment.org">EWL</a>, - <a href="http://www.enlightenment.org">ETK</a>, or use - <a href="http://cairographics.org">Cairo</a>. - However, - we need to start somewhere. More than this, knowing how things - work down below is never a bad idea. - </p> - <p> - After reading this tutorial, one should be able to write very - simple graphical programs, but not programs with decent user - interfaces. For such programs, one of the previously mentioned - libraries should be used. - </p> - <p> - But what is XCB? Xlib has been - the standard C binding for the <a href="http://www.x.org">X - Window System</a> protocol for many years now. It is an - excellent piece of work, but there are applications for which it - is not ideal, for example: - </p> - <ul> - <li><b>Small platforms</b>: Xlib is a large piece of code, and - it's difficult to make it smaller - <li><b>Latency hiding</b>: Xlib requests requiring a reply are - effectively synchronous: they block until the reply appears, - whether the result is needed immediately or not. - <li><b>Direct access to the protocol</b>: Xlib does quite a - bit of caching, layering, and similar optimizations. While this - is normally a feature, it makes it difficult to simply emit - specified X protocol requests and process specific - responses. - <li><b>Threaded applications</b>: While Xlib does attempt to - support multithreading, the API makes this difficult and - error-prone. - <li><b>New extensions</b>: The Xlib infrastructure provides - limited support for the new creation of X extension client side - code. - </ul> - <p> - For these reasons, among others, XCB, an X C binding, has been - designed to solve the above problems and thus provide a base for - </p> - <ul> - <li>Toolkit implementation. - <li>Direct protocol-level programming. - <li>Lightweight emulation of commonly used portions of the - Xlib API. - </ul> - <br> - <li class="title"><a name="Xmodel">The client and server model of the X window system</a> - <p> - The X Window System was developed with one major goal: - flexibility. The idea was that the way things look is one thing, - but the way things work is another matter. Thus, the lower - levels provide the tools required to draw windows, handle user - input, allow drawing graphics using colors (or black and white - screens), etc. To this point, a decision was made to separate - the system into two parts. A client that decides what to do, and - a server that actually draws on the screen and reads user input - in order to send it to the client for processing. - </p> - <p> - This model is the complete opposite of what is used to when - dealing with clients and servers. In our case, the user sits - near the machine controlled by the server, while the client - might be running on a remote machine. The server controls the - screens, mouse and keyboard. A client may connect to the server, - request that it draws a window (or several windows), and ask the - server to send it any input the user sends to these - windows. Thus, several clients may connect to a single X server - (one might be running mail software, one running a WWW - browser, etc). When input is sent by the user to some window, - the server sends a message to the client controlling this window - for processing. The client decides what to do with this input, - and sends the server requests for drawing in the window. - </p> - <p> - The whole session is carried out using the X message - protocol. This protocol was originally carried over the TCP/IP - protocol suite, allowing the client to run on any machine - connected to the same network that the server is. Later on, the - X servers were extended to allow clients running on the local - machine with more optimized access to the server (note that an X - protocol message may be several hundreds of KB in size), such as - using shared memory, or using Unix domain sockets (a method for - creating a logical channel on a Unix system between two processes). - </p> - <li class="title"><a name="asynch">GUI programming: the asynchronous model</a> - <p> - Unlike conventional computer programs, that carry some serial - nature, a GUI program usually uses an asynchronous programming - model, also known as "event-driven programming". This means that - that program mostly sits idle, waiting for events sent by the X - server, and then acts upon these events. An event may say "The - user pressed the 1st button mouse in spot (x,y)", or "The window - you control needs to be redrawn". In order for the program to be - responsive to the user input, as well as to refresh requests, it - needs to handle each event in a rather short period of time - (e.g. less that 200 milliseconds, as a rule of thumb). - </p> - <p> - This also implies that the program may not perform operations - that might take a long time while handling an event (such as - opening a network connection to some remote server, or - connecting to a database server, or even performing a long file - copy operation). Instead, it needs to perform all these - operations in an asynchronous manner. This may be done by using - various asynchronous models to perform the longish operations, - or by performing them in a different process or thread. - </p> - <p> - So the way a GUI program looks is something like that: - </p> - <ol> - <li>Perform initialization routines. - <li>Connect to the X server. - <li>Perform X-related initialization. - <li>While not finished: - <ol> - <li>Receive the next event from the X server. - <li>Handle the event, possibly sending various drawing - requests to the X server. - <li>If the event was a quit message, exit the loop. - </ol> - <li>Close down the connection to the X server. - <li>Perform cleanup operations. - </ol> - <br> - <li class="title"><a name="notions">Basic XCB notions</a> - <p> - XCB has been created to eliminate the need for - programs to actually implement the X protocol layer. This - library gives a program a very low-level access to any X - server. Since the protocol is standardized, a client using any - implementation of XCB may talk with any X server (the same - occurs for Xlib, of course). We now give a brief description of - the basic XCB notions. They will be detailed later. - </p> - <ol> - <li class="subtitle"><a name="conn">The X Connection</a> - <p> - The major notion of using XCB is the X Connection. This is a - structure representing the connection we have open with a - given X server. It hides a queue of messages coming from the - server, and a queue of pending requests that our client - intends to send to the server. In XCB, this structure is named - 'xcb_connection_t'. It is analogous to the Xlib Display. - When we open a connection to an X server, the - library returns a pointer to such a structure. Later, we - supply this pointer to any XCB function that should send - messages to the X server or receive messages from this server. - </p> - <li class="subtitle"><a name="requestsreplies">Requests and - replies: the Xlib killers</a> - <p> - To ask for information from the X server, we have to make a request - and ask for a reply. With Xlib, these two tasks are - automatically done: Xlib locks the system, sends a request, - waits for a reply from the X server and unlocks. This is - annoying, especially if one makes a lot of requests to the X - server. Indeed, Xlib has to wait for the end of a reply - before asking for the next request (because of the locks that - Xlib sends). For example, here is a time-line of N=4 - requests/replies with Xlib, with a round-trip latency - <b>T_round_trip</b> that is 5 times long as the time required - to write or read a request/reply (<b>T_write/T_read</b>): - </p> - <pre class="text"> - W-----RW-----RW-----RW-----R -</pre> - <ul> - <li>W: Writing request - <li>-: Stalled, waiting for data - <li>R: Reading reply - </ul> - <p> - The total time is N * (T_write + T_round_trip + T_read). - </p> - <p> - With XCB, we can suppress most of the round-trips as the - requests and the replies are not locked. We usually send a - request, then XCB returns to us a <b>cookie</b>, which is an - identifier. Then, later, we ask for a reply using this - <b>cookie</b> and XCB returns a - pointer to that reply. Hence, with XCB, we can send a lot of - requests, and later in the program, ask for all the replies - when we need them. Here is the time-line for 4 - requests/replies when we use this property of XCB: - </p> - <pre class="text"> - WWWW--RRRR -</pre> - <p> - The total time is N * T_write + max (0, T_round_trip - (N-1) * - T_write) + N * T_read. Which can be considerably faster than - all those Xlib round-trips. - </p> - <p> - Here is a program that computes the time to create 500 atoms - with Xlib and XCB. It shows the Xlib way, the bad XCB way - (which is similar to Xlib) and the good XCB way. On my - computer, XCB is 25 times faster than Xlib. - </p> - <pre class="code"> -#include <stdlib.h> -#include <stdio.h> -#include <string.h> -#include <sys/time.h> - -#include <xcb/xcb.h> - -#include <X11/Xlib.h> - -double -get_time(void) -{ - struct timeval timev; - - gettimeofday(&timev, NULL); - - return (double)timev.tv_sec + (((double)timev.tv_usec) / 1000000); -} - -int -main () -{ - xcb_connection_t *c; - xcb_atom_t *atoms; - xcb_intern_atom_cookie_t *cs; - char **names; - int count; - int i; - double start; - double end; - double diff; - - /* Xlib */ - Display *disp; - Atom *atoms_x; - double diff_x; - - c = xcb_connect (NULL, NULL); - - count = 500; - atoms = (xcb_atom_t *)malloc (count * sizeof (atoms)); - names = (char **)malloc (count * sizeof (char *)); - - /* init names */ - for (i = 0; i < count; ++i) { - char buf[100]; - - sprintf (buf, "NAME%d", i); - names[i] = strdup (buf); - } - - /* bad use */ - start = get_time (); - - for (i = 0; i < count; ++i) - atoms[i] = xcb_intern_atom_reply (c, - xcb_intern_atom (c, - 0, - strlen(names[i]), - names[i]), - NULL)->atom; - - end = get_time (); - diff = end - start; - printf ("bad use time : %f\n", diff); - - /* good use */ - start = get_time (); - - cs = (xcb_intern_atom_cookie_t *) malloc (count * sizeof(xcb_intern_atom_cookie_t)); - for(i = 0; i < count; ++i) - cs[i] = xcb_intern_atom (c, 0, strlen(names[i]), names[i]); - - for(i = 0; i < count; ++i) { - xcb_intern_atom_reply_t *r; - - r = xcb_intern_atom_reply(c, cs[i], 0); - if(r) - atoms[i] = r->atom; - free(r); - } - - end = get_time (); - printf ("good use time : %f\n", end - start); - printf ("ratio : %f\n", diff / (end - start)); - diff = end - start; - - /* free var */ - free (atoms); - free (cs); - - xcb_disconnect (c); - - /* Xlib */ - disp = XOpenDisplay (getenv("DISPLAY")); - - atoms_x = (Atom *)malloc (count * sizeof (atoms_x)); - - start = get_time (); - - for (i = 0; i < count; ++i) - atoms_x[i] = XInternAtom(disp, names[i], 0); - - end = get_time (); - diff_x = end - start; - printf ("Xlib use time : %f\n", diff_x); - printf ("ratio : %f\n", diff_x / diff); - - free (atoms_x); - for (i = 0; i < count; ++i) - free (names[i]); - free (names); - - XCloseDisplay (disp); - - return 0; -} -</pre> - <li class="subtitle"><a name="gc">The Graphic Context</a> - <p> - When we perform various drawing operations (graphics, text, - etc), we may specify various options for controlling how the - data will be drawn (what foreground and background colors to - use, how line edges will be connected, what font to use when - drawing some text, etc). In order to avoid the need to supply - hundreds of parameters to each drawing function, a graphical - context structure is used. We set the various drawing options - in this structure, and then we pass a pointer to this - structure to any drawing routines. This is rather handy, as we - often need to perform several drawing requests with the same - options. Thus, we would initialize a graphical context, set - the desired options, and pass this structure to all drawing - functions. - </p> - <p> - Note that graphic contexts have no client-side structure in - XCB, they're just XIDs. Xlib has a client-side structure - because it caches the GC contents so it can avoid making - redundant requests, but of course XCB doesn't do that. - </p> - <li class="subtitle"><a name="events">Events</a> - <p> - A structure is used to pass events received from the X - server. XCB supports exactly the events specified in the - protocol (33 events). This structure contains the type - of event received (including a bit for whether it came - from the server or another client), as well as the data associated with the - event (e.g. position on the screen where the event was - generated, mouse button associated with the event, region of - the screen associated with a "redraw" event, etc). The way to - read the event's data depends on the event type. - </p> - </ol> - <br> - <li class="title"><a name="use">Using XCB-based programs</a> - <br> - <ol> - <li class="subtitle"><a name="inst">Installation of XCB</a> - <p> - <b>TODO:</b> These instructions are out of date. - Just reference the <a href="http://xcb.freedesktop.org/">main XCB page</a> - so we don't have to maintain these instructions in more than - one place. - </p> - <p> - To build XCB from source, you need to have installed at - least: - </p> - <ul> - <li>pkgconfig 0.15.0 - <li><a href="http://www.gnu.org/software/automake/">automake 1.7</a> - <li><a href="http://www.gnu.org/software/autoconf/">autoconf 2.50</a> - <li><a href="http://www.check.org">check</a> - <li><a href="http://xmlsoft.org/XSLT/">xsltproc</a> - <li><a href="http://www.gnu.org/software/gperf/">gperf 3.0.1</a> - </ul> - <p> - You have to checkout in the git repository the following modules: - </p> - <ul> - <li>Xau from xlibs - <li>xcb-proto - <li>xcb - </ul> - <p> - Note that xcb-proto exists only to install header - files, so typing 'make' or 'make all' will produce the message - "Nothing to be done for 'all'". That's normal. - </p> - <li class="subtitle"><a name="comp">Compiling XCB-based programs</a> - <p> - Compiling XCB-based programs requires linking them with the XCB - library. This is easily done thanks to pkgconfig: - </p> - <pre class="text"> -gcc -Wall prog.c -o prog `pkg-config --cflags --libs xcb` -</pre> - </ol> - <li class="title"><a name="openconn">Opening and closing the connection to an X server</a> - <p> - An X program first needs to open the connection to the X - server. There is a function that opens a connection. It requires - the display name, or NULL. In the latter case, the display name - will be the one in the environment variable DISPLAY. - </p> - <pre class="code"> -<span class="type">xcb_connection_t</span> *xcb_connect (<span class="keyword">const</span> <span class="type">char</span> *displayname, - <span class="type">int</span> *screenp); -</pre> - <p> - The second parameter returns the screen number used for the - connection. The returned structure describes an XCB connection - and is opaque. Here is how the connection can be opened: - </p> - <pre class="code"> -#<span class="include">include</span> <span class="string"><xcb/xcb.h></span> - -<span class="type">int</span> -<span class="function">main</span> () -{ - <span class="type">xcb_connection_t</span> *c; - - /* Open the connection to the X server. Use the DISPLAY environment variable as the default display name */ - c = xcb_connect (NULL, NULL); - - <span class="keyword">return</span> 0; -} -</pre> - <p> - To close a connection, it suffices to use: - </p> - <pre class="code"> -<span class="type">void</span> xcb_disconnect (<span class="type">xcb_connection_t</span> *c); -</pre> - <div class="comp"> - <div class="title"> - Comparison Xlib/XCB - </div> - <div class="xlib"> - <ul> - <li>XOpenDisplay () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_connect () - </ul> - </div> - <div class="xlib"> - <ul> - <li>XCloseDisplay () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_disconnect () - </ul> - </div> - </div> - <br> - <li class="title"><a name="screen">Checking basic information about a connection</a> - <p> - Once we have opened a connection to an X server, we should check some - basic information about it: what screens it has, what is the - size (width and height) of the screen, how many colors it - supports (black and white ? grey scale ?, 256 colors ? more ?), - and so on. We get such information from the xcb_screen_t - structure: - </p> - <pre class="code"> -typedef struct { - xcb_window_t root; - xcb_colormap_t default_colormap; - uint32_t white_pixel; - uint32_t black_pixel; - uint32_t current_input_masks; - uint16_t width_in_pixels; - uint16_t height_in_pixels; - uint16_t width_in_millimeters; - uint16_t height_in_millimeters; - uint16_t min_installed_maps; - uint16_t max_installed_maps; - xcb_visualid_t root_visual; - uint8_t backing_stores; - uint8_t save_unders; - uint8_t root_depth; - uint8_t allowed_depths_len; -} xcb_screen_t; -</pre> - <p> - We could retrieve the first screen of the connection by using the - following function: - </p> - <pre class="code"> -xcb_screen_iterator_t xcb_setup_roots_iterator (xcb_setup_t *R); -</pre> - <p> - Here is a small program that shows how to use this function: - </p> - <pre class="code"> -#include <stdio.h> - -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - int screen_nbr; - xcb_screen_iterator_t iter; - - /* Open the connection to the X server. Use the DISPLAY environment variable */ - c = xcb_connect (NULL, &screen_nbr); - - /* Get the screen #screen_nbr */ - iter = xcb_setup_roots_iterator (xcb_get_setup (c)); - for (; iter.rem; --screen_nbr, xcb_screen_next (&iter)) - if (screen_nbr == 0) { - screen = iter.data; - break; - } - - printf ("\n"); - printf ("Informations of screen %ld:\n", screen->root); - printf (" width.........: %d\n", screen->width_in_pixels); - printf (" height........: %d\n", screen->height_in_pixels); - printf (" white pixel...: %ld\n", screen->white_pixel); - printf (" black pixel...: %ld\n", screen->black_pixel); - printf ("\n"); - - return 0; -} -</pre> - <li class="title"><a name="helloworld">Creating a basic window - the "hello world" program</a> - <p> - After we got some basic information about our screen, we can - create our first window. In the X Window System, a window is - characterized by an Id. So, in XCB, a window is of type: - </p> - <pre class="code"> -typedef uint32_t xcb_window_t; -</pre> - <p> - We first ask for a new Id for our window, with this function: - </p> - <pre class="code"> -xcb_window_t xcb_generate_id(xcb_connection_t *c); -</pre> - <p> - Then, XCB supplies the following function to create new windows: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_create_window (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */ - uint8_t depth, /* Depth of the screen */ - xcb_window_t wid, /* Id of the window */ - xcb_window_t parent, /* Id of an existing window that should be the parent of the new window */ - int16_t x, /* X position of the top-left corner of the window (in pixels) */ - int16_t y, /* Y position of the top-left corner of the window (in pixels) */ - uint16_t width, /* Width of the window (in pixels) */ - uint16_t height, /* Height of the window (in pixels) */ - uint16_t border_width, /* Width of the window's border (in pixels) */ - uint16_t _class, - xcb_visualid_t visual, - uint32_t value_mask, - const uint32_t *value_list); -</pre> - <p> - The fact that we created the window does not mean that it will - be drawn on screen. By default, newly created windows are not - mapped on the screen (they are invisible). In order to make our - window visible, we use the function <span class="code">xcb_map_window()</span>, whose - prototype is - </p> - <pre class="code"> -xcb_void_cookie_t xcb_map_window (xcb_connection_t *c, - xcb_window_t window); -</pre> - <p> - Finally, here is a small program to create a window of size - 150x150 pixels, positioned at the top-left corner of the screen: - </p> - <pre class="code"> -#include <unistd.h> /* pause() */ - -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_window_t win; - - /* Open the connection to the X server */ - c = xcb_connect (NULL, NULL); - - /* Get the first screen */ - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* Ask for our window's Id */ - win = xcb_generate_id(c); - - /* Create the window */ - xcb_create_window (c, /* Connection */ - XCB_COPY_FROM_PARENT, /* depth (same as root)*/ - win, /* window Id */ - screen->root, /* parent window */ - 0, 0, /* x, y */ - 150, 150, /* width, height */ - 10, /* border_width */ - XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */ - screen->root_visual, /* visual */ - 0, NULL); /* masks, not used yet */ - - /* Map the window on the screen */ - xcb_map_window (c, win); - - /* Make sure commands are sent before we pause, so window is shown */ - xcb_flush (c); - - pause (); /* hold client until Ctrl-C */ - - return 0; -} -</pre> - <p> - In this code, you see one more function - <span class="code">xcb_flush()</span>, not explained - yet. It is used to flush all the pending requests. More - precisely, there are 2 functions that do such things. The first - one is <span class="code">xcb_flush()</span>: - </p> - <pre class="code"> -int xcb_flush (xcb_connection_t *c); -</pre> - <p> - This function flushes all pending requests to the X server (much - like the <span class="code">fflush()</span> function is used to - flush standard output). The second function is - <span class="code">xcb_aux_sync()</span>: - </p> - <pre class="code"> -int xcb_aux_sync (xcb_connection_t *c); -</pre> - <p> - This functions also flushes all pending requests to the X - server, and then waits until the X server finishing processing - these requests. In a normal program, this will not be necessary - (we'll see why when we get to write a normal X program), but for - now, we put it there. - </p> - <p> - The window that is created by the above code has a non defined - background. This one can be set to a specific color, - thanks to the two last parameters of - <span class="code">xcb_create_window()</span>, which are not - described yet. See the subsections - <a href="#winconf">Configuring a window</a> or - <a href="#winconf">Registering for event types using event masks</a> - for examples on how to use these parameters. In addition, as no - events are handled, you have to make a Ctrl-C to interrupt the - program. - </p> - <p> - <b>TODO</b>: one should tell what these functions return and - about the generic error - </p> - <div class="comp"> - <div class="title"> - Comparison Xlib/XCB - </div> - <div class="xlib"> - <ul> - <li>XCreateWindow () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_generate_id () - <li>xcb_create_window () - </ul> - </div> - </div> - <br> - <li class="title"><a name="drawing">Drawing in a window</a> - <p> - Drawing in a window can be done using various graphical - functions (drawing pixels, lines, rectangles, etc). In order to - draw in a window, we first need to define various general - drawing parameters (what line width to use, which color to draw - with, etc). This is done using a graphical context. - </p> - <ol> - <li class="subtitle"><a name="allocgc">Allocating a Graphics Context</a> - <p> - As we said, a graphical context defines several attributes to - be used with the various drawing functions. For this, we - define a graphical context. We can use more than one graphical - context with a single window, in order to draw in multiple - styles (different colors, different line widths, etc). In XCB, - a Graphics Context is, as a window, characterized by an Id: - </p> - <pre class="code"> -typedef uint32_t xcb_gcontext_t; -</pre> - <p> - We first ask the X server to attribute an Id to our graphic - context with this function: - </p> - <pre class="code"> -xcb_gcontext_t xcb_generate_id (xcb_connection_t *c); -</pre> - <p> - Then, we set the attributes of the graphic context with this function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_create_gc (xcb_connection_t *c, - xcb_gcontext_t cid, - xcb_drawable_t drawable, - uint32_t value_mask, - const uint32_t *value_list); -</pre> - <p> - We give now an example on how to allocate a graphic context - that specifies that each drawing function that uses it will - draw in foreground with a black color. - </p> - <pre class="code"> -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_drawable_t win; - xcb_gcontext_t black; - uint32_t mask; - uint32_t value[1]; - - /* Open the connection to the X server and get the first screen */ - c = xcb_connect (NULL, NULL); - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* Create a black graphic context for drawing in the foreground */ - win = screen->root; - black = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND; - value[0] = screen->black_pixel; - xcb_create_gc (c, black, win, mask, value); - - return 0; -} -</pre> - <p> - Note should be taken regarding the role of "value_mask" and - "value_list" in the prototype of <span class="code">xcb_create_gc()</span>. Since a - graphic context has many attributes, and since we often just - want to define a few of them, we need to be able to tell the - <span class="code">xcb_create_gc()</span> which attributes we - want to set. This is what the "value_mask" parameter is - for. We then use the "value_list" parameter to specify actual - values for the attribute we defined in "value_mask". Thus, for - each constant used in "value_list", we will use the matching - constant in "value_mask". In this case, we define a graphic - context with one attribute: when drawing (a point, a line, - etc), the foreground color will be black. The rest of the - attributes of this graphic context will be set to their - default values. - </p> - <p> - See the next Subsection for more details. - </p> - <div class="comp"> - <div class="title"> - Comparison Xlib/XCB - </div> - <div class="xlib"> - <ul> - <li>XCreateGC () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_generate_id () - <li>xcb_create_gc () - </ul> - </div> - </div> - <br> - <li class="subtitle"><a name="changegc">Changing the attributes of a Graphics Context</a> - <p> - Once we have allocated a Graphic Context, we may need to - change its attributes (for example, changing the foreground - color we use to draw a line, or changing the attributes of the - font we use to display strings. See Subsections Drawing with a - color and - <a href="#assigningfont">Assigning a Font to a Graphic Context</a>). - This is done by using this function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_change_gc (xcb_connection_t *c, /* The XCB Connection */ - xcb_gcontext_t gc, /* The Graphic Context */ - uint32_t value_mask, /* Components of the Graphic Context that have to be set */ - const uint32_t *value_list); /* Value as specified by value_mask */ -</pre> - <p> - The <span class="code">value_mask</span> parameter could take - any combination of these masks from the xcb_gc_t enumeration: - </p> - <ul> - <li>XCB_GC_FUNCTION - <li>XCB_GC_PLANE_MASK - <li>XCB_GC_FOREGROUND - <li>XCB_GC_BACKGROUND - <li>XCB_GC_LINE_WIDTH - <li>XCB_GC_LINE_STYLE - <li>XCB_GC_CAP_STYLE - <li>XCB_GC_JOIN_STYLE - <li>XCB_GC_FILL_STYLE - <li>XCB_GC_FILL_RULE - <li>XCB_GC_TILE - <li>XCB_GC_STIPPLE - <li>XCB_GC_TILE_STIPPLE_ORIGIN_X - <li>XCB_GC_TILE_STIPPLE_ORIGIN_Y - <li>XCB_GC_FONT - <li>XCB_GC_SUBWINDOW_MODE - <li>XCB_GC_GRAPHICS_EXPOSURES - <li>XCB_GC_CLIP_ORIGIN_X - <li>XCB_GC_CLIP_ORIGIN_Y - <li>XCB_GC_CLIP_MASK - <li>XCB_GC_DASH_OFFSET - <li>XCB_GC_DASH_LIST - <li>XCB_GC_ARC_MODE - </ul> - <p> - It is possible to set several attributes at the same - time (for example setting the attributes of a font and the - color which will be used to display a string), by OR'ing these - values in <span class="code">value_mask</span>. Then - <span class="code">value_list</span> has to be an array which - lists the value for the respective attributes. <b>These values - must be in the same order as masks listed above.</b> See Subsection - Drawing with a color to have an example. - </p> - <p> - <b>TODO</b>: set the links of the 3 subsections, once they will - be written :) - </p> - <p> - <b>TODO</b>: give an example which sets several attributes. - </p> - <li class="subtitle"><a name="drawingprim">Drawing primitives: point, line, box, circle,...</a> - <p> - After we have created a Graphic Context, we can draw on a - window using this Graphic Context, with a set of XCB - functions, collectively called "drawing primitives". Let see - how they are used. - </p> - <p> - To draw a point, or several points, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_point (xcb_connection_t *c, /* The connection to the X server */ - uint8_t coordinate_mode, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */ - xcb_drawable_t drawable, /* The drawable on which we want to draw the point(s) */ - xcb_gcontext_t gc, /* The Graphic Context we use to draw the point(s) */ - uint32_t points_len, /* The number of points */ - const xcb_point_t *points); /* An array of points */ -</pre> - <p> - The <span class="code">coordinate_mode</span> parameter - specifies the coordinate mode. Available values are - </p> - <ul> - <li><span class="code">XCB_COORD_MODE_ORIGIN</span> - <li><span class="code">XCB_COORD_MODE_PREVIOUS</span> - </ul> - <p> - If XCB_COORD_MODE_PREVIOUS is used, then all points but the first one - are relative to the immediately previous point. - </p> - <p> - The <span class="code">xcb_point_t</span> type is just a - structure with two fields (the coordinates of the point): - </p> - <pre class="code"> -typedef struct { - int16_t x; - int16_t y; -} xcb_point_t; -</pre> - <p> - You could see an example in xpoints.c. <b>TODO</b> Set the link. - </p> - <p> - To draw a line, or a polygonal line, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_line (xcb_connection_t *c, /* The connection to the X server */ - uint8_t coordinate_mode, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */ - xcb_drawable_t drawable, /* The drawable on which we want to draw the line(s) */ - xcb_gcontext_t gc, /* The Graphic Context we use to draw the line(s) */ - uint32_t points_len, /* The number of points in the polygonal line */ - const xcb_point_t *points); /* An array of points */ -</pre> - <p> - This function will draw the line between the first and the - second points, then the line between the second and the third - points, and so on. - </p> - <p> - To draw a segment, or several segments, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_segment (xcb_connection_t *c, /* The connection to the X server */ - xcb_drawable_t drawable, /* The drawable on which we want to draw the segment(s) */ - xcb_gcontext_t gc, /* The Graphic Context we use to draw the segment(s) */ - uint32_t segments_len, /* The number of segments */ - const xcb_segment_t *segments); /* An array of segments */ -</pre> - <p> - The <span class="code">xcb_segment_t</span> type is just a - structure with four fields (the coordinates of the two points - that define the segment): - </p> - <pre class="code"> -typedef struct { - int16_t x1; - int16_t y1; - int16_t x2; - int16_t y2; -} xcb_segment_t; -</pre> - <p> - To draw a rectangle, or several rectangles, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_rectangle (xcb_connection_t *c, /* The connection to the X server */ - xcb_drawable_t drawable, /* The drawable on which we want to draw the rectangle(s) */ - xcb_gcontext_t gc, /* The Graphic Context we use to draw the rectangle(s) */ - uint32_t rectangles_len, /* The number of rectangles */ - const xcb_rectangle_t *rectangles); /* An array of rectangles */ -</pre> - <p> - The <span class="code">xcb_rectangle_t</span> type is just a - structure with four fields (the coordinates of the top-left - corner of the rectangle, and its width and height): - </p> - <pre class="code"> -typedef struct { - int16_t x; - int16_t y; - uint16_t width; - uint16_t height; -} xcb_rectangle_t; -</pre> - <!-- There's no coordinate_mode. Is it normal? --> - <!-- [iano] Yes, it's not in the protocol. --> - <p> - To draw an elliptical arc, or several elliptical arcs, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_arc (xcb_connection_t *c, /* The connection to the X server */ - xcb_drawable_t drawable, /* The drawable on which we want to draw the arc(s) */ - xcb_gcontext_t gc, /* The Graphic Context we use to draw the arc(s) */ - uint32_t arcs_len, /* The number of arcs */ - const xcb_arc_t *arcs); /* An array of arcs */ -</pre> - <p> - The <span class="code">xcb_arc_t</span> type is a structure with - six fields: - </p> - <pre class="code"> -typedef struct { - int16_t x; /* Top left x coordinate of the rectangle surrounding the ellipse */ - int16_t y; /* Top left y coordinate of the rectangle surrounding the ellipse */ - uint16_t width; /* Width of the rectangle surrounding the ellipse */ - uint16_t height; /* Height of the rectangle surrounding the ellipse */ - int16_t angle1; /* Angle at which the arc begins */ - int16_t angle2; /* Angle at which the arc ends */ -} xcb_arc_t; -</pre> - <div class="emph"> - <p> - Note: the angles are expressed in units of 1/64 of a degree, - so to have an angle of 90 degrees, starting at 0, - <span class="code">angle1 = 0</span> and - <span class="code">angle2 = 90 << 6</span>. Positive angles - indicate counterclockwise motion, while negative angles - indicate clockwise motion. - </p> - </div> - <!-- I think that (x,y) should be the center of the - ellipse, and (width, height) the radius. It's more logical. --> - <!-- iano: Yes, and I bet some toolkits do that. - But the protocol (and many other graphics APIs) define arcs - by bounding rectangles. --> - <p> - The corresponding function which fill inside the geometrical - object are listed below, without further explanation, as they - are used as the above functions. - </p> - <p> - To Fill a polygon defined by the points given as arguments , - we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_fill_poly (xcb_connection_t *c, - xcb_drawable_t drawable, - xcb_gcontext_t gc, - uint8_t shape, - uint8_t coordinate_mode, - uint32_t points_len, - const xcb_point_t *points); -</pre> - <p> - The <span class="code">shape</span> parameter specifies a - shape that helps the server to improve performance. Available - values are - </p> - <ul> - <li><span class="code">XCB_POLY_SHAPE_COMPLEX</span> - <li><span class="code">XCB_POLY_SHAPE_NONCONVEX</span> - <li><span class="code">XCB_POLY_SHAPE_CONVEX</span> - </ul> - <p> - To fill one or several rectangles, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_fill_rectangle (xcb_connection_t *c, - xcb_drawable_t drawable, - xcb_gcontext_t gc, - uint32_t rectangles_len, - const xcb_rectangle_t *rectangles); -</pre> - <p> - To fill one or several arcs, we use - </p> - <pre class="code"> -xcb_void_cookie_t xcb_poly_fill_arc (xcb_connection_t *c, - xcb_drawable_t drawable, - xcb_gcontext_t gc, - uint32_t arcs_len, - const xcb_arc_t *arcs); -</pre> - <br> - <a name="points.c"></a> - <p> - To illustrate these functions, here is an example that draws - four points, a polygonal line, two segments, two rectangles - and two arcs. Remark that we use events for the first time, as - an introduction to the next section. - </p> - <p> - <b>TODO:</b> Use screen->root_depth for depth parameter. - </p> - <pre class="code"> -#include <stdlib.h> -#include <stdio.h> - -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_drawable_t win; - xcb_gcontext_t foreground; - xcb_generic_event_t *e; - uint32_t mask = 0; - uint32_t values[2]; - - /* geometric objects */ - xcb_point_t points[] = { - {10, 10}, - {10, 20}, - {20, 10}, - {20, 20}}; - - xcb_point_t polyline[] = { - {50, 10}, - { 5, 20}, /* rest of points are relative */ - {25,-20}, - {10, 10}}; - - xcb_segment_t segments[] = { - {100, 10, 140, 30}, - {110, 25, 130, 60}}; - - xcb_rectangle_t rectangles[] = { - { 10, 50, 40, 20}, - { 80, 50, 10, 40}}; - - xcb_arc_t arcs[] = { - {10, 100, 60, 40, 0, 90 << 6}, - {90, 100, 55, 40, 0, 270 << 6}}; - - /* Open the connection to the X server */ - c = xcb_connect (NULL, NULL); - - /* Get the first screen */ - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* Create black (foreground) graphic context */ - win = screen->root; - - foreground = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES; - values[0] = screen->black_pixel; - values[1] = 0; - xcb_create_gc (c, foreground, win, mask, values); - - /* Ask for our window's Id */ - win = xcb_generate_id(c); - - /* Create the window */ - mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; - values[0] = screen->white_pixel; - values[1] = XCB_EVENT_MASK_EXPOSURE; - xcb_create_window (c, /* Connection */ - XCB_COPY_FROM_PARENT, /* depth */ - win, /* window Id */ - screen->root, /* parent window */ - 0, 0, /* x, y */ - 150, 150, /* width, height */ - 10, /* border_width */ - XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */ - screen->root_visual, /* visual */ - mask, values); /* masks */ - - /* Map the window on the screen */ - xcb_map_window (c, win); - - - /* We flush the request */ - xcb_flush (c); - - while ((e = xcb_wait_for_event (c))) { - switch (e->response_type & ~0x80) { - case XCB_EXPOSE: { - /* We draw the points */ - xcb_poly_point (c, XCB_COORD_MODE_ORIGIN, win, foreground, 4, points); - - /* We draw the polygonal line */ - xcb_poly_line (c, XCB_COORD_MODE_PREVIOUS, win, foreground, 4, polyline); - - /* We draw the segements */ - xcb_poly_segment (c, win, foreground, 2, segments); - - /* We draw the rectangles */ - xcb_poly_rectangle (c, win, foreground, 2, rectangles); - - /* We draw the arcs */ - xcb_poly_arc (c, win, foreground, 2, arcs); - - /* We flush the request */ - xcb_flush (c); - - break; - } - default: { - /* Unknown event type, ignore it */ - break; - } - } - /* Free the Generic Event */ - free (e); - } - - return 0; -} -</pre> - </ol> - <li class="title"><a name="xevents">X Events</a> - <p> - In an X program, everything is driven by events. Event painting - on the screen is sometimes done as a response to an event (an - <span class="code">Expose</span> event). If part of a program's - window that was hidden, gets exposed (e.g. the window was raised - above other widows), the X server will send an "expose" event to - let the program know it should repaint that part of the - window. User input (key presses, mouse movement, etc) is also - received as a set of events. - </p> - <ol> - <li class="subtitle"><a name="register">Registering for event types using event masks</a> - <p> - During the creation of a window, you should give it what kind - of events it wishes to receive. Thus, you may register for - various mouse (also called pointer) events, keyboard events, - expose events, and so on. This is done for optimizing the - server-to-client connection (i.e. why send a program (that - might even be running at the other side of the globe) an event - it is not interested in ?) - </p> - <p> - In XCB, you use the "value_mask" and "value_list" data in the - <span class="code">xcb_create_window()</span> function to - register for events. Here is how we register for - <span class="code">Expose</span> event when creating a window: - </p> - <pre class="code"> - mask = XCB_CW_EVENT_MASK; - valwin[0] = XCB_EVENT_MASK_EXPOSURE; - win = xcb_generate_id (c); - xcb_create_window (c, depth, win, root->root, - 0, 0, 150, 150, 10, - XCB_WINDOW_CLASS_INPUT_OUTPUT, root->root_visual, - mask, valwin); -</pre> - <p> - <span class="code">XCB_EVENT_MASK_EXPOSURE</span> is a constant defined - in the xcb_event_mask_t enumeration in the "xproto.h" header file. If we wanted to register for several - event types, we can logically "or" them, as follows: - </p> - <pre class="code"> - mask = XCB_CW_EVENT_MASK; - valwin[0] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS; - win = xcb_generate_id (c); - xcb_create_window (c, depth, win, root->root, - 0, 0, 150, 150, 10, - XCB_WINDOW_CLASS_INPUT_OUTPUT, root->root_visual, - mask, valwin); -</pre> - <p> - This registers for <span class="code">Expose</span> events as - well as for mouse button presses inside the created - window. You should note that a mask may represent several - event sub-types. - </p> - <p> - The values that a mask could take are given - by the <span class="code">xcb_cw_t</span> enumeration: - </p> - <pre class="code"> -typedef enum { - XCB_CW_BACK_PIXMAP = 1L<<0, - XCB_CW_BACK_PIXEL = 1L<<1, - XCB_CW_BORDER_PIXMAP = 1L<<2, - XCB_CW_BORDER_PIXEL = 1L<<3, - XCB_CW_BIT_GRAVITY = 1L<<4, - XCB_CW_WIN_GRAVITY = 1L<<5, - XCB_CW_BACKING_STORE = 1L<<6, - XCB_CW_BACKING_PLANES = 1L<<7, - XCB_CW_BACKING_PIXEL = 1L<<8, - XCB_CW_OVERRIDE_REDIRECT = 1L<<9, - XCB_CW_SAVE_UNDER = 1L<<10, - XCB_CW_EVENT_MASK = 1L<<11, - XCB_CW_DONT_PROPAGATE = 1L<<12, - XCB_CW_COLORMAP = 1L<<13, - XCB_CW_CURSOR = 1L<<14 -} xcb_cw_t; -</pre> - <div class="emph"> - <p>Note: we must be careful when setting the values of the valwin - parameter, as they have to follow the order the - <span class="code">xcb_cw_t</span> enumeration. Here is an - example: - </p> - </div> - <pre class="code"> - mask = XCB_CW_EVENT_MASK | XCB_CW_BACK_PIXMAP; - valwin[0] = XCB_NONE; /* for XCB_CW_BACK_PIXMAP (whose value is 1) */ - valwin[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS; /* for XCB_CW_EVENT_MASK, whose value (2048) */ - /* is greater than the one of XCB_CW_BACK_PIXMAP */ -</pre> - <p> - If the window has already been created, we can use the - <span class="code">xcb_configure_window()</span> function to set - the events that the window will receive. The subsection - <a href="#winconf">Configuring a window</a> shows its - prototype. As an example, here is a piece of code that - configures the window to receive the - <span class="code">Expose</span> and - <span class="code">ButtonPress</span> events: - </p> - <pre class="code"> -const static uint32_t values[] = { XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS }; - -/* The connection c and the window win are supposed to be defined */ - -xcb_configure_window (c, win, XCB_CW_EVENT_MASK, values); -</pre> - <div class="emph"> - <p> - Note: A common bug programmers do is adding code to handle new - event types in their program, while forgetting to add the - masks for these events in the creation of the window. Such a - programmer then should sit down for hours debugging his - program, wondering "Why doesn't my program notice that I - released the button?", only to find that they registered for - button press events but not for button release events. - </p> - </div> - <li class="subtitle"><a name="loop">Receiving events: writing the events loop</a> - <p> - After we have registered for the event types we are interested - in, we need to enter a loop of receiving events and handling - them. There are two ways to receive events: a blocking way and - a non-blocking way: - </p> - <ul> - <li> - <span class="code">xcb_wait_for_event (xcb_connection_t *c)</span> - is the blocking way. It waits (so blocks...) until an event is - queued in the X server. Then it retrieves it into a newly - allocated structure (it dequeues it from the queue) and returns - it. This structure has to be freed. The function returns - <span class="code">NULL</span> if an error occurs. - - <br> - <li> - <span class="code">xcb_poll_for_event (xcb_connection_t *c, int - *error)</span> is the non-blocking way. It looks at the event - queue and returns (and dequeues too) an existing event into - a newly allocated structure. This structure has to be - freed. It returns <span class="code">NULL</span> if there is - no event. If an error occurs, the parameter <span - class="code">error</span> will be filled with the error - status. - </ul> - <p> - There are various ways to write such a loop. We present two - ways to write such a loop, with the two functions above. The - first one uses <span class="code">xcb_wait_for_event_t</span>, which - is similar to an event Xlib loop using only <span - class="code">XNextEvent</span>: - </p> - <pre class="code"> - xcb_generic_event_t *e; - - while ((e = xcb_wait_for_event (c))) { - switch (e->response_type & ~0x80) { - case XCB_EXPOSE: { - /* Handle the Expose event type */ - xcb_expose_event_t *ev = (xcb_expose_event_t *)e; - - /* ... */ - - break; - } - case XCB_BUTTON_PRESS: { - /* Handle the ButtonPress event type */ - xcb_button_press_event_t *ev = (xcb_button_press_event_t *)e; - - /* ... */ - - break; - } - default: { - /* Unknown event type, ignore it */ - break; - } - } - /* Free the Generic Event */ - free (e); - } -</pre> - <p> - You will certainly want to use <span - class="code">xcb_poll_for_event(xcb_connection_t *c, int - *error)</span> if, in Xlib, you use <span - class="code">XPending</span> or - <span class="code">XCheckMaskEvent</span>: - </p> - <pre class="code"> - while (XPending (display)) { - XEvent ev; - - XNextEvent(d, &ev); - - /* Manage your event */ - } -</pre> - <p> - Such a loop in XCB looks like: - </p> - <pre class="code"> - xcb_generic_event_t *ev; - - while ((ev = xcb_poll_for_event (conn, 0))) { - /* Manage your event */ - } -</pre> - <p> - The events are managed in the same way as with <span - class="code">xcb_wait_for_event_t</span>. - Obviously, we will need to give the user some way of - terminating the program. This is usually done by handling a - special "quit" event, as we will soon see. - </p> - <div class="comp"> - <div class="title"> - Comparison Xlib/XCB - </div> - <div class="xlib"> - <ul> - <li>XNextEvent () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_wait_for_event () - </ul> - </div> - <div class="xlib"> - <ul> - <li>XPending () - <li>XCheckMaskEvent () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_poll_for_event () - </ul> - </div> - </div> - <br> - <li class="subtitle"><a name="expose">Expose events</a> - <p> - The <span class="code">Expose</span> event is one of the most - basic (and most used) events an application may receive. It - will be sent to us in one of several cases: - </p> - <ul> - <li>A window that covered part of our window has moved - away, exposing part (or all) of our window. - <li>Our window was raised above other windows. - <li>Our window mapped for the first time. - <li>Our window was de-iconified. - </ul> - <p> - You should note the implicit assumption hidden here: the - contents of our window is lost when it is being obscured - (covered) by either windows. One may wonder why the X server - does not save this contents. The answer is: to save - memory. After all, the number of windows on a display at a - given time may be very large, and storing the contents of all - of them might require a lot of memory. Actually, there is a - way to tell the X server to store the contents of a window in - special cases, as we will see later. - </p> - <p> - When we get an <span class="code">Expose</span> event, we - should take the event's data from the members of the following - structure: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; /* The type of the event, here it is XCB_EXPOSE */ - uint8_t pad0; - uint16_t sequence; - xcb_window_t window; /* The Id of the window that receives the event (in case */ - /* our application registered for events on several windows */ - uint16_t x; /* The x coordinate of the top-left part of the window that needs to be redrawn */ - uint16_t y; /* The y coordinate of the top-left part of the window that needs to be redrawn */ - uint16_t width; /* The width of the part of the window that needs to be redrawn */ - uint16_t height; /* The height of the part of the window that needs to be redrawn */ - uint16_t count; -} xcb_expose_event_t; -</pre> - <li class="subtitle"><a name="userinput">Getting user input</a> - <p> - User input traditionally comes from two sources: the mouse - and the keyboard. Various event types exist to notify us of - user input (a key being presses on the keyboard, a key being - released on the keyboard, the mouse moving over our window, - the mouse entering (or leaving) our window, and so on. - </p> - <ol> - <li class="subsubtitle"><a name="mousepressrelease">Mouse button press and release events</a> - <p> - The first event type we will deal with is a mouse - button-press (or button-release) event in our window. In - order to register to such an event type, we should add one - (or more) of the following masks when we create our window: - </p> - <ul> - <li><span class="code">XCB_EVENT_MASK_BUTTON_PRESS</span>: notify us - of any button that was pressed in one of our windows. - <li><span class="code">XCB_EVENT_MASK_BUTTON_RELEASE</span>: notify us - of any button that was released in one of our windows. - </ul> - <p> - The structure to be checked for in our events loop is the - same for these two events, and is the following: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; /* The type of the event, here it is xcb_button_press_event_t or xcb_button_release_event_t */ - xcb_button_t detail; - uint16_t sequence; - xcb_timestamp_t time; /* Time, in milliseconds the event took place in */ - xcb_window_t root; - xcb_window_t event; - xcb_window_t child; - int16_t root_x; - int16_t root_y; - int16_t event_x; /* The x coordinate where the mouse has been pressed in the window */ - int16_t event_y; /* The y coordinate where the mouse has been pressed in the window */ - uint16_t state; /* A mask of the buttons (or keys) during the event */ - uint8_t same_screen; -} xcb_button_press_event_t; - -typedef xcb_button_press_event_t xcb_button_release_event_t; -</pre> - <p> - The <span class="code">time</span> field may be used to calculate "double-click" - situations by an application (e.g. if the mouse button was - clicked two times in a duration shorter than a given amount - of time, assume this was a double click). - </p> - <p> - The <span class="code">state</span> field is a mask of the buttons held down during - the event. It is a bitwise OR of any of the following (from the xcb_button_mask_t and - xcb_mod_mask_t enumerations): - </p> - <ul> - <li><span class="code">XCB_BUTTON_MASK_1</span> - <li><span class="code">XCB_BUTTON_MASK_2</span> - <li><span class="code">XCB_BUTTON_MASK_3</span> - <li><span class="code">XCB_BUTTON_MASK_4</span> - <li><span class="code">XCB_BUTTON_MASK_5</span> - <li><span class="code">XCB_MOD_MASK_SHIFT</span> - <li><span class="code">XCB_MOD_MASK_LOCK</span> - <li><span class="code">XCB_MOD_MASK_CONTROL</span> - <li><span class="code">XCB_MOD_MASK_1</span> - <li><span class="code">XCB_MOD_MASK_2</span> - <li><span class="code">XCB_MOD_MASK_3</span> - <li><span class="code">XCB_MOD_MASK_4</span> - <li><span class="code">XCB_MOD_MASK_5</span> - </ul> - <p> - Their names are self explanatory, where the first 5 refer to - the mouse buttons that are being pressed, while the rest - refer to various "special keys" that are being pressed (Mod1 - is usually the 'Alt' key or the 'Meta' key). - </p> - <p> - <b>TODO:</b> Problem: it seems that the state does not - change when clicking with various buttons. - </p> - <li class="subsubtitle"><a name="mousemvnt">Mouse movement events</a> - <p> - Similar to mouse button press and release events, we also - can be notified of various mouse movement events. These can - be split into two families. One is of mouse pointer - movement while no buttons are pressed, and the second is a - mouse pointer motion while one (or more) of the buttons are - pressed (this is sometimes called "a mouse drag operation", - or just "dragging"). The following event masks may be added - during the creation of our window: - </p> - <ul> - <li><span class="code">XCB_EVENT_MASK_POINTER_MOTION</span>: events of - the pointer moving in one of the windows controlled by our - application, while no mouse button is held pressed. - <li><span class="code">XCB_EVENT_MASK_BUTTON_MOTION</span>: Events of - the pointer moving while one or more of the mouse buttons - is held pressed. - <li><span class="code">XCB_EVENT_MASK_BUTTON_1_MOTION</span>: same as - <span class="code">XCB_EVENT_MASK_BUTTON_MOTION</span>, but only when - the 1st mouse button is held pressed. - <li><span class="code">XCB_EVENT_MASK_BUTTON_2_MOTION</span>, - <span class="code">XCB_EVENT_MASK_BUTTON_3_MOTION</span>, - <span class="code">XCB_EVENT_MASK_BUTTON_4_MOTION</span>, - <span class="code">XCB_EVENT_MASK_BUTTON_5_MOTION</span>: same as - <span class="code">XCB_EVENT_MASK_BUTTON_1_MOTION</span>, but - respectively for 2nd, 3rd, 4th and 5th mouse button. - </ul> - <p> - The structure to be checked for in our events loop is the - same for these events, and is the following: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; /* The type of the event */ - uint8_t detail; - uint16_t sequence; - xcb_timestamp_t time; /* Time, in milliseconds the event took place in */ - xcb_window_t root; - xcb_window_t event; - xcb_window_t child; - int16_t root_x; - int16_t root_y; - int16_t event_x; /* The x coordinate of the mouse when the event was generated */ - int16_t event_y; /* The y coordinate of the mouse when the event was generated */ - uint16_t state; /* A mask of the buttons (or keys) during the event */ - uint8_t same_screen; -} xcb_motion_notify_event_t; -</pre> - <li class="subsubtitle"><a name="mouseenter">Mouse pointer enter and leave events</a> - <p> - Another type of event that applications might be interested - in, is a mouse pointer entering a window the program - controls, or leaving such a window. Some programs use these - events to show the user that the application is now in - focus. In order to register for such an event type, we - should add one (or more) of the following masks when we - create our window: - </p> - <ul> - <li><span class="code">xcb_event_enter_window_t</span>: notify us - when the mouse pointer enters any of our controlled - windows. - <li><span class="code">xcb_event_leave_window_t</span>: notify us - when the mouse pointer leaves any of our controlled - windows. - </ul> - <p> - The structure to be checked for in our events loop is the - same for these two events, and is the following: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; /* The type of the event */ - uint8_t detail; - uint16_t sequence; - xcb_timestamp_t time; /* Time, in milliseconds the event took place in */ - xcb_window_t root; - xcb_window_t event; - xcb_window_t child; - int16_t root_x; - int16_t root_y; - int16_t event_x; /* The x coordinate of the mouse when the event was generated */ - int16_t event_y; /* The y coordinate of the mouse when the event was generated */ - uint16_t state; /* A mask of the buttons (or keys) during the event */ - uint8_t mode; /* The number of mouse button that was clicked */ - uint8_t same_screen_focus; -} xcb_enter_notify_event_t; - -typedef xcb_enter_notify_event_t xcb_leave_notify_event_t; -</pre> - <li class="subsubtitle"><a name="focus">The keyboard focus</a> - <p> - There may be many windows on a screen, but only a single - keyboard attached to them. How does the X server then know - which window should be sent a given keyboard input ? This is - done using the keyboard focus. Only a single window on the - screen may have the keyboard focus at a given time. There - is a XCB function that allows a program to set the keyboard - focus to a given window. The user can usually set the - keyboard focus using the window manager (often by clicking - on the title bar of the desired window). Once our window - has the keyboard focus, every key press or key release will - cause an event to be sent to our program (if it regsitered - for these event types...). - </p> - <li class="subsubtitle"><a name="keypress">Keyboard press and release events</a> - <p> - If a window controlled by our program currently holds the - keyboard focus, it can receive key press and key release - events. So, we should add one (or more) of the following - masks when we create our window: - </p> - <ul> - <li><span class="code">XCB_EVENT_MASK_KEY_PRESS</span>: notify us when - a key was pressed while any of our controlled windows had - the keyboard focus. - <li><span class="code">XCB_EVENT_MASK_KEY_RELEASE</span>: notify us - when a key was released while any of our controlled - windows had the keyboard focus. - </ul> - <p> - The structure to be checked for in our events loop is the - same for these two events, and is the following: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; /* The type of the event */ - xcb_keycode_t detail; - uint16_t sequence; - xcb_timestamp_t time; /* Time, in milliseconds the event took place in */ - xcb_window_t root; - xcb_window_t event; - xcb_window_t child; - int16_t root_x; - int16_t root_y; - int16_t event_x; - int16_t event_y; - uint16_t state; - uint8_t same_screen; -} xcb_key_press_event_t; - -typedef xcb_key_press_event_t xcb_key_release_event_t; -</pre> - <p> - The <span class="code">detail</span> field refers to the - physical key on the keyboard. - </p> - <p> - <b>TODO:</b> Talk about getting the ASCII code from the key code. - </p> - </ol> - <li class="subtitle"><a name="eventex">X events: a complete example</a> - <p> - As an example for handling events, we show a program that - creates a window, enters an events loop and checks for all the - events described above, and writes on the terminal the relevant - characteristics of the event. With this code, it should be - easy to add drawing operations, like those which have been - described above. - </p> - <pre class="code"> -#include <stdlib.h> -#include <stdio.h> - -#include <xcb/xcb.h> - -void -print_modifiers (uint32_t mask) -{ - const char **mod, *mods[] = { - "Shift", "Lock", "Ctrl", "Alt", - "Mod2", "Mod3", "Mod4", "Mod5", - "Button1", "Button2", "Button3", "Button4", "Button5" - }; - printf ("Modifier mask: "); - for (mod = mods ; mask; mask >>= 1, mod++) - if (mask & 1) - printf(*mod); - putchar ('\n'); -} - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_window_t win; - xcb_generic_event_t *e; - uint32_t mask = 0; - uint32_t values[2]; - - /* Open the connection to the X server */ - c = xcb_connect (NULL, NULL); - - /* Get the first screen */ - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* Ask for our window's Id */ - win = xcb_generate_id (c); - - /* Create the window */ - mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; - values[0] = screen->white_pixel; - values[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS | - XCB_EVENT_MASK_BUTTON_RELEASE | XCB_EVENT_MASK_POINTER_MOTION | - XCB_EVENT_MASK_ENTER_WINDOW | XCB_EVENT_MASK_LEAVE_WINDOW | - XCB_EVENT_MASK_KEY_PRESS | XCB_EVENT_MASK_KEY_RELEASE; - xcb_create_window (c, /* Connection */ - 0, /* depth */ - win, /* window Id */ - screen->root, /* parent window */ - 0, 0, /* x, y */ - 150, 150, /* width, height */ - 10, /* border_width */ - XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */ - screen->root_visual, /* visual */ - mask, values); /* masks */ - - /* Map the window on the screen */ - xcb_map_window (c, win); - - xcb_flush (c); - - while ((e = xcb_wait_for_event (c))) { - switch (e->response_type & ~0x80) { - case XCB_EXPOSE: { - xcb_expose_event_t *ev = (xcb_expose_event_t *)e; - - printf ("Window %ld exposed. Region to be redrawn at location (%d,%d), with dimension (%d,%d)\n", - ev->window, ev->x, ev->y, ev->width, ev->height); - break; - } - case XCB_BUTTON_PRESS: { - xcb_button_press_event_t *ev = (xcb_button_press_event_t *)e; - print_modifiers(ev->state); - - switch (ev->detail) { - case 4: - printf ("Wheel Button up in window %ld, at coordinates (%d,%d)\n", - ev->event, ev->event_x, ev->event_y); - break; - case 5: - printf ("Wheel Button down in window %ld, at coordinates (%d,%d)\n", - ev->event, ev->event_x, ev->event_y); - break; - default: - printf ("Button %d pressed in window %ld, at coordinates (%d,%d)\n", - ev->detail, ev->event, ev->event_x, ev->event_y); - } - break; - } - case XCB_BUTTON_RELEASE: { - xcb_button_release_event_t *ev = (xcb_button_release_event_t *)e; - print_modifiers(ev->state); - - printf ("Button %d released in window %ld, at coordinates (%d,%d)\n", - ev->detail, ev->event, ev->event_x, ev->event_y); - break; - } - case XCB_MOTION_NOTIFY: { - xcb_motion_notify_event_t *ev = (xcb_motion_notify_event_t *)e; - - printf ("Mouse moved in window %ld, at coordinates (%d,%d)\n", - ev->event, ev->event_x, ev->event_y); - break; - } - case XCB_ENTER_NOTIFY: { - xcb_enter_notify_event_t *ev = (xcb_enter_notify_event_t *)e; - - printf ("Mouse entered window %ld, at coordinates (%d,%d)\n", - ev->event, ev->event_x, ev->event_y); - break; - } - case XCB_LEAVE_NOTIFY: { - xcb_leave_notify_event_t *ev = (xcb_leave_notify_event_t *)e; - - printf ("Mouse left window %ld, at coordinates (%d,%d)\n", - ev->event, ev->event_x, ev->event_y); - break; - } - case XCB_KEY_PRESS: { - xcb_key_press_event_t *ev = (xcb_key_press_event_t *)e; - print_modifiers(ev->state); - - printf ("Key pressed in window %ld\n", - ev->event); - break; - } - case XCB_KEY_RELEASE: { - xcb_key_release_event_t *ev = (xcb_key_release_event_t *)e; - print_modifiers(ev->state); - - printf ("Key released in window %ld\n", - ev->event); - break; - } - default: - /* Unknown event type, ignore it */ - printf("Unknown event: %d\n", e->response_type); - break; - } - /* Free the Generic Event */ - free (e); - } - - return 0; -} -</pre> - </ol> - <li class="title"><a name="font">Handling text and fonts</a> - <p> - Besides drawing graphics on a window, we often want to draw - text. Text strings have two major properties: the characters to - be drawn and the font with which they are drawn. In order to - draw text, we need to first request the X server to load a - font. We then assign a font to a Graphic Context, and finally, we - draw the text in a window, using the Graphic Context. - </p> - <ol> - <li class="subtitle"><a name="fontstruct">The Font structure</a> - <p> - In order to support flexible fonts, a font type is - defined. You know what ? It's an Id: - </p> - <pre class="code"> -typedef uint32_t xcb_font_t; -</pre> - <p> - It is used to contain information about a font, and is passed - to several functions that handle fonts selection and text drawing. - We ask the X server to attribute an Id to our font with the - function: - </p> - <pre class="code"> -xcb_font_t xcb_generate_id (xcb_connection_t *c); -</pre> - <br> - <li class="subtitle"><a name="openingfont">Opening a Font</a> - <p> - To open a font, we use the following function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_open_font (xcb_connection_t *c, - xcb_font_t fid, - uint16_t name_len, - const char *name); -</pre> - <p> - The <span class="code">fid</span> parameter is the font Id - defined by <span class="code">xcb_generate_id()</span> (see - above). The <span class="code">name</span> parameter is the - name of the font you want to open. Use the command - <span class="code">xlsfonts</span> in a terminal to know which - are the fonts available on your computer. The parameter - <span class="code">name_len</span> is the length of the name - of the font (given by <span class="code">strlen()</span>). - </p> - <li class="subtitle"><a name="assigningfont">Assigning a Font to a Graphic Context</a> - <p> - Once a font is opened, you have to create a Graphic Context - that will contain the informations about the color of the - foreground and the background used when you draw a text in a - Drawable. Here is an exemple of a Graphic Context that will - allow us to draw an opened font with a black foreground and a - white background: - </p> - <pre class="code"> - /* - * c is the connection - * screen is the screen where the window is displayed - * window is the window in which we will draw the text - * font is the opened font - */ - - uint32_t value_list[3]; - xcb_gcontext_t gc; - uint32_t mask; - - gc = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; - value_list[0] = screen->black_pixel; - value_list[1] = screen->white_pixel; - value_list[2] = font; - xcb_create_gc (c, gc, window, mask, value_list); - - /* The font is not needed anymore, so we close it */ - xcb_close_font (c, font); -</pre> - <li class="subtitle"><a name="drawingtext">Drawing text in a drawable</a> - <p> - To draw a text in a drawable, we use the following function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_image_text_8 (xcb_connection_t *c, - uint8_t string_len, - xcb_drawable_t drawable, - xcb_gcontext_t gc, - int16_t x, - int16_t y, - const char *string); -</pre> - <p> - The <span class="code">string</span> parameter is the text to - draw. The location of the drawing is given by the parameters - <span class="code">x</span> and <span class="code">y</span>. - The base line of the text is exactly the parameter - <span class="code">y</span>. - </p> - <li class="subtitle"><a name="fontcompleteexample">Complete example</a> - <p> - This example draw a text at 10 pixels (for the base line) of - the bottom of a window. Pressing the Esc key exits the program. - </p> - <pre class="code"> -#include <stdlib.h> -#include <stdio.h> -#include <string.h> - -#include <xcb/xcb.h> - -#define WIDTH 300 -#define HEIGHT 100 - - - -static xcb_gc_t gc_font_get (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - const char *font_name); - -static void text_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label); - -static void -text_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label) -{ - xcb_void_cookie_t cookie_gc; - xcb_void_cookie_t cookie_text; - xcb_generic_error_t *error; - xcb_gcontext_t gc; - uint8_t length; - - length = strlen (label); - - gc = gc_font_get(c, screen, window, "7x13"); - - cookie_text = xcb_image_text_8_checked (c, length, window, gc, - x1, - y1, label); - error = xcb_request_check (c, cookie_text); - if (error) { - fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_gc = xcb_free_gc (c, gc); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } -} - -static xcb_gc_t -gc_font_get (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - const char *font_name) -{ - uint32_t value_list[3]; - xcb_void_cookie_t cookie_font; - xcb_void_cookie_t cookie_gc; - xcb_generic_error_t *error; - xcb_font_t font; - xcb_gcontext_t gc; - uint32_t mask; - - font = xcb_generate_id (c); - cookie_font = xcb_open_font_checked (c, font, - strlen (font_name), - font_name); - - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - - gc = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; - value_list[0] = screen->black_pixel; - value_list[1] = screen->white_pixel; - value_list[2] = font; - cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_font = xcb_close_font_checked (c, font); - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - return gc; -} - -int main () -{ - xcb_screen_iterator_t screen_iter; - xcb_connection_t *c; - const xcb_setup_t *setup; - xcb_screen_t *screen; - xcb_generic_event_t *e; - xcb_generic_error_t *error; - xcb_void_cookie_t cookie_window; - xcb_void_cookie_t cookie_map; - xcb_window_t window; - uint32_t mask; - uint32_t values[2]; - int screen_number; - - /* getting the connection */ - c = xcb_connect (NULL, &screen_number); - if (!c) { - fprintf (stderr, "ERROR: can't connect to an X server\n"); - return -1; - } - - /* getting the current screen */ - setup = xcb_get_setup (c); - - screen = NULL; - screen_iter = xcb_setup_roots_iterator (setup); - for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter)) - if (screen_number == 0) - { - screen = screen_iter.data; - break; - } - if (!screen) { - fprintf (stderr, "ERROR: can't get the current screen\n"); - xcb_disconnect (c); - return -1; - } - - /* creating the window */ - window = xcb_generate_id (c); - mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; - values[0] = screen->white_pixel; - values[1] = - XCB_EVENT_MASK_KEY_RELEASE | - XCB_EVENT_MASK_BUTTON_PRESS | - XCB_EVENT_MASK_EXPOSURE | - XCB_EVENT_MASK_POINTER_MOTION; - cookie_window = xcb_create_window_checked (c, - screen->root_depth, - window, screen->root, - 20, 200, WIDTH, HEIGHT, - 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, - screen->root_visual, - mask, values); - cookie_map = xcb_map_window_checked (c, window); - - /* error managing */ - error = xcb_request_check (c, cookie_window); - if (error) { - fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - error = xcb_request_check (c, cookie_map); - if (error) { - fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - - xcb_flush(c); - - while (1) { - e = xcb_poll_for_event(c); - if (e) { - switch (e->response_type & ~0x80) { - case XCB_EXPOSE: { - char *text; - - text = "Press ESC key to exit..."; - text_draw (c, screen, window, 10, HEIGHT - 10, text); - break; - } - case XCB_KEY_RELEASE: { - xcb_key_release_event_t *ev; - - ev = (xcb_key_release_event_t *)e; - - switch (ev->detail) { - /* ESC */ - case 9: - free (e); - xcb_disconnect (c); - return 0; - } - } - } - free (e); - } - } - - return 0; -} -</pre> - </ol> - <li class="title"><a name="wm">Interacting with the window manager</a> - <p> - After we have seen how to create windows and draw on them, we - take one step back, and look at how our windows are interacting - with their environment (the full screen and the other - windows). First of all, our application needs to interact with - the window manager. The window manager is responsible to - decorating drawn windows (i.e. adding a frame, an iconify - button, a system menu, a title bar, etc), as well as handling - icons shown when windows are being iconified. It also handles - ordering of windows on the screen, and other administrative - tasks. We need to give it various hints as to how we want it to - treat our application's windows. - </p> - <ol> - <li class="subtitle"><a name="wmprop">Window properties</a> - <p> - Many of the parameters communicated to the window manager are - passed using data called "properties". These properties are - attached by the X server to different windows, and are stored - in a format that makes it possible to read them from different - machines that may use different architectures (remember that - an X client program may run on a remote machine). - </p> - <p> - The property and its type (a string, an integer, etc) are - Id. Their type are <span class="code">xcb_atom_t</span>: - </p> - <pre class="code"> -typedef uint32_t xcb_atom_t; -</pre> - <p> - To change the property of a window, we use the following - function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_change_property (xcb_connection_t *c, /* Connection to the X server */ - uint8_t mode, /* Property mode */ - xcb_window_t window, /* Window */ - xcb_atom_t property, /* Property to change */ - xcb_atom_t type, /* Type of the property */ - uint8_t format, /* Format of the property (8, 16, 32) */ - uint32_t data_len, /* Length of the data parameter */ - const void *data); /* Data */ -</pre> - <p> - The <span class="code">mode</span> parameter coud be one of - the following values (defined in enumeration xcb_prop_mode_t in - the xproto.h header file): - </p> - <ul> - <li>XCB_PROP_MODE_REPLACE - <li>XCB_PROP_MODE_PREPEND - <li>XCB_PROP_MODE_APPEND - </ul> - <br> - <li class="subtitle"><a name="wmname">Setting the window name and icon name</a> - <p> - The first thing we want to do would be to set the name for our - window. This is done using the - <span class="code">xcb_change_property()</span> function. This - name may be used by the window manager as the title of the - window (in the title bar), in a task list, etc. The property - atom to use to set the name of a window is - <span class="code">WM_NAME</span> (and - <span class="code">WM_ICON_NAME</span> for the iconified - window) and its type is <span class="code">STRING</span>. Here - is an example of utilization: - </p> - <pre class="code"> -#include <string.h> - -#include <xcb/xcb.h> -#include <xcb/xcb_atom.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_window_t win; - char *title = "Hello World !"; - char *title_icon = "Hello World ! (iconified)"; - - - - /* Open the connection to the X server */ - c = xcb_connect (NULL, NULL); - - /* Get the first screen */ - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* Ask for our window's Id */ - win = xcb_generate_id (c); - - /* Create the window */ - xcb_create_window (c, /* Connection */ - 0, /* depth */ - win, /* window Id */ - screen->root, /* parent window */ - 0, 0, /* x, y */ - 250, 150, /* width, height */ - 10, /* border_width */ - XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */ - screen->root_visual, /* visual */ - 0, NULL); /* masks, not used */ - - /* Set the title of the window */ - xcb_change_property (c, XCB_PROP_MODE_REPLACE, win, - WM_NAME, STRING, 8, - strlen (title), title); - - /* Set the title of the window icon */ - xcb_change_property (c, XCB_PROP_MODE_REPLACE, win, - WM_ICON_NAME, STRING, 8, - strlen(title_icon), title_icon); - - /* Map the window on the screen */ - xcb_map_window (c, win); - - xcb_flush (c); - - while (1) {} - - return 0; -} -</pre> - <div class="emph"> - <p>Note: the use of the atoms needs our program to be compiled - and linked against xcb_atom, so that we have to use - </p> - </div> - <pre class="text"> -gcc prog.c -o prog `pkg-config --cflags --libs xcb_atom` -</pre> - <div class="emph"> - <p> - for the program to compile fine. - </p> - </div> - </ol> - <li class="title"><a name="winop">Simple window operations</a> - <p> - One more thing we can do to our window is manipulate them on the - screen (resize them, move them, raise or lower them, iconify - them, and so on). Some window operations functions are supplied - by XCB for this purpose. - </p> - <ol> - <li class="subtitle"><a name="winmap">Mapping and un-mapping a window</a> - <p> - The first pair of operations we can apply on a window is - mapping it, or un-mapping it. Mapping a window causes the - window to appear on the screen, as we have seen in our simple - window program example. Un-mapping it causes it to be removed - from the screen (although the window as a logical entity still - exists). This gives the effect of making a window hidden - (unmapped) and shown again (mapped). For example, if we have a - dialog box window in our program, instead of creating it every - time the user asks to open it, we can create the window once, - in an un-mapped mode, and when the user asks to open it, we - simply map the window on the screen. When the user clicked the - 'OK' or 'Cancel' button, we simply un-map the window. This is - much faster than creating and destroying the window, however, - the cost is wasted resources, both on the client side, and on - the X server side. - </p> - <p> - To map a window, you use the following function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_map_window (xcb_connection_t *c, - xcb_window_t window); -</pre> - <p> - To have a simple example, see the <a href="#helloworld">example</a> - above. The mapping operation will cause an - <span class="code">Expose</span> event to be sent to our - application, unless the window is completely covered by other - windows. - </p> - <p> - Un-mapping a window is also simple. You use the function - </p> - <pre class="code"> -xcb_void_cookie_t xcb_unmap_window (xcb_connection_t *c, - xcb_window_t window); -</pre> - <p> - The utilization of this function is the same as - <span class="code">xcb_map_window()</span>. - </p> - <li class="subtitle"><a name="winconf">Configuring a window</a> - <p> - As we have seen when we have created our first window, in the - X Events subsection, we can set some attributes for the window - (that is, the position, the size, the events the window will - receive, etc). If we want to modify them, but the window is - already created, we can change them by using the following - function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_configure_window (xcb_connection_t *c, /* The connection to the X server*/ - xcb_window_t window, /* The window to configure */ - uint16_t value_mask, /* The mask */ - const uint32_t *value_list); /* The values to set */ -</pre> - <p> - We set the <span class="code">value_mask</span> to one or - several mask values that are in the xcb_config_window_t enumeration in the xproto.h header: - </p> - <ul> - <li><span class="code">XCB_CONFIG_WINDOW_X</span>: new x coordinate of the window's top left corner - <li><span class="code">XCB_CONFIG_WINDOW_Y</span>: new y coordinate of the window's top left corner - <li><span class="code">XCB_CONFIG_WINDOW_WIDTH</span>: new width of the window - <li><span class="code">XCB_CONFIG_WINDOW_HEIGHT</span>: new height of the window - <li><span class="code">XCB_CONFIG_WINDOW_BORDER_WIDTH</span>: new width of the border of the window - <li><span class="code">XCB_CONFIG_WINDOW_SIBLING</span> - <li><span class="code">XCB_CONFIG_WINDOW_STACK_MODE</span>: the new stacking order - </ul> - <p> - We then give to <span class="code">value_mask</span> the new - value. We now describe how to use - <span class="code">xcb_configure_window_t</span> in some useful - situations. - </p> - <li class="subtitle"><a name="winmove">Moving a window around the screen</a> - <p> - An operation we might want to do with windows is to move them - to a different location. This can be done like this: - </p> - <pre class="code"> -const static uint32_t values[] = { 10, 20 }; - -/* The connection c and the window win are supposed to be defined */ - -/* Move the window to coordinates x = 10 and y = 20 */ -xcb_configure_window (c, win, XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y, values); -</pre> - <p> - Note that when the window is moved, it might get partially - exposed or partially hidden by other windows, and thus we - might get <span class="code">Expose</span> events due to this - operation. - </p> - <li class="subtitle"><a name="winsize">Resizing a window</a> - <p> - Yet another operation we can do is to change the size of a - window. This is done using the following code: - </p> - <pre class="code"> -const static uint32_t values[] = { 200, 300 }; - -/* The connection c and the window win are supposed to be defined */ - -/* Resize the window to width = 10 and height = 20 */ -xcb_configure_window (c, win, XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT, values); -</pre> - <p> - We can also combine the move and resize operations using one - single call to <span class="code">xcb_configure_window_t</span>: - </p> - <pre class="code"> -const static uint32_t values[] = { 10, 20, 200, 300 }; - -/* The connection c and the window win are supposed to be defined */ - -/* Move the window to coordinates x = 10 and y = 20 */ -/* and resize the window to width = 10 and height = 20 */ -xcb_configure_window (c, win, XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y | XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT, values); -</pre> - <li class="subtitle"><a name="winstack">Changing windows stacking order: raise and lower</a> - <p> - Until now, we changed properties of a single window. We'll see - that there are properties that relate to the window and other - windows. One of them is the stacking order. That is, the order - in which the windows are layered on top of each other. The - front-most window is said to be on the top of the stack, while - the back-most window is at the bottom of the stack. Here is - how to manipulate our windows stack order: - </p> - <pre class="code"> -const static uint32_t values[] = { XCB_STACK_MODE_ABOVE }; - -/* The connection c and the window win are supposed to be defined */ - -/* Move the window on the top of the stack */ -xcb_configure_window (c, win, XCB_CONFIG_WINDOW_STACK_MODE, values); -</pre> - <pre class="code"> -const static uint32_t values[] = { XCB_STACK_MODE_BELOW }; - -/* The connection c and the window win are supposed to be defined */ - -/* Move the window on the bottom of the stack */ -xcb_configure_window (c, win, XCB_CONFIG_WINDOW_STACK_MODE, values); -</pre> - <li class="subtitle"><a name="wingetinfo">Getting information about a window</a> - <p> - Just like we can set various attributes of our windows, we can - also ask the X server supply the current values of these - attributes. For example, we can check where a window is - located on the screen, what is its current size, whether it is - mapped or not, etc. The structure that contains some of this - information is - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; - uint8_t depth; /* depth of the window */ - uint16_t sequence; - uint32_t length; - xcb_window_t root; /* Id of the root window *> - int16_t x; /* X coordinate of the window's location */ - int16_t y; /* Y coordinate of the window's location */ - uint16_t width; /* Width of the window */ - uint16_t height; /* Height of the window */ - uint16_t border_width; /* Width of the window's border */ -} xcb_get_geometry_reply_t; -</pre> - <p> - XCB fill this structure with two functions: - </p> - <pre class="code"> -xcb_get_geometry_cookie_t xcb_get_geometry (xcb_connection_t *c, - xcb_drawable_t drawable); -xcb_get_geometry_reply_t *xcb_get_geometry_reply (xcb_connection_t *c, - xcb_get_geometry_cookie_t cookie, - xcb_generic_error_t **e); -</pre> - <p> - You use them as follows: - </p> - <pre class="code"> - xcb_connection_t *c; - xcb_drawable_t win; - xcb_get_geometry_reply_t *geom; - - /* You initialize c and win */ - - geom = xcb_get_geometry_reply (c, xcb_get_geometry (c, win), NULL); - - /* Do something with the fields of geom */ - - free (geom); -</pre> - <p> - Remark that you have to free the structure, as - <span class="code">xcb_get_geometry_reply_t</span> allocates a - newly one. - </p> - <p> - One problem is that the returned location of the window is - relative to its parent window. This makes these coordinates - rather useless for any window manipulation functions, like - moving it on the screen. In order to overcome this problem, we - need to take a two-step operation. First, we find out the Id - of the parent window of our window. We then translate the - above relative coordinates to the screen coordinates. - </p> - <p> - To get the Id of the parent window, we need this structure: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; - uint8_t pad0; - uint16_t sequence; - uint32_t length; - xcb_window_t root; - xcb_window_t parent; /* Id of the parent window */ - uint16_t children_len; - uint8_t pad1[14]; -} xcb_query_tree_reply_t; -</pre> - <p> - To fill this structure, we use these two functions: - </p> - <pre class="code"> -xcb_query_tree_cookie_t xcb_query_tree (xcb_connection_t *c, - xcb_window_t window); -xcb_query_tree_reply_t *xcb_query_tree_reply (xcb_connection_t *c, - xcb_query_tree_cookie_t cookie, - xcb_generic_error_t **e); -</pre> - <p> - The translated coordinates will be found in this structure: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; - uint8_t same_screen; - uint16_t sequence; - uint32_t length; - xcb_window_t child; - uint16_t dst_x; /* Translated x coordinate */ - uint16_t dst_y; /* Translated y coordinate */ -} xcb_translate_coordinates_reply_t; -</pre> - <p> - As usual, we need two functions to fill this structure: - </p> - <pre class="code"> -xcb_translate_coordinates_cookie_t xcb_translate_coordinates (xcb_connection_t *c, - xcb_window_t src_window, - xcb_window_t dst_window, - int16_t src_x, - int16_t src_y); -xcb_translate_coordinates_reply_t *xcb_translate_coordinates_reply (xcb_connection_t *c, - xcb_translate_coordinates_cookie_t cookie, - xcb_generic_error_t **e); -</pre> - <p> - We use them as follows: - </p> - <pre class="code"> - xcb_connection_t *c; - xcb_drawable_t win; - xcb_get_geometry_reply_t *geom; - xcb_query_tree_reply_t *tree; - xcb_translate_coordinates_reply_t *trans; - - /* You initialize c and win */ - - geom = xcb_get_geometry_reply (c, xcb_get_geometry (c, win), NULL); - if (!geom) - return 0; - - tree = xcb_query_tree_reply (c, xcb_query_tree (c, win), NULL); - if (!tree) - return 0; - - trans = xcb_translate_coordinates_reply (c, - xcb_translate_coordinates (c, - win, - tree->parent, - geom->x, geom->y), - NULL); - if (!trans) - return 0; - - /* the translated coordinates are in trans->dst_x and trans->dst_y */ - - free (trans); - free (tree); - free (geom); -</pre> - <p> - Of course, as for <span class="code">geom</span>, - <span class="code">tree</span> and - <span class="code">trans</span> have to be freed. - </p> - <p> - The work is a bit hard, but XCB is a very low-level library. - </p> - <p> - <b>TODO:</b> the utilization of these functions should be a - prog, which displays the coordinates of the window. - </p> - <p> - There is another structure that gives informations about our window: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; - uint8_t backing_store; - uint16_t sequence; - uint32_t length; - xcb_visualid_t visual; /* Visual of the window */ - uint16_t _class; - uint8_t bit_gravity; - uint8_t win_gravity; - uint32_t backing_planes; - uint32_t backing_pixel; - uint8_t save_under; - uint8_t map_is_installed; - uint8_t map_state; /* Map state of the window */ - uint8_t override_redirect; - xcb_colormap_t colormap; /* Colormap of the window */ - uint32_t all_event_masks; - uint32_t your_event_mask; - uint16_t do_not_propagate_mask; -} xcb_get_window_attributes_reply_t; -</pre> - <p> - XCB supplies these two functions to fill it: - </p> - <pre class="code"> -xcb_get_window_attributes_cookie_t xcb_get_window_attributes (xcb_connection_t *c, - xcb_window_t window); -xcb_get_window_attributes_reply_t *xcb_get_window_attributes_reply (xcb_connection_t *c, - xcb_get_window_attributes_cookie_t cookie, - xcb_generic_error_t **e); -</pre> - <p> - You use them as follows: - </p> - <pre class="code"> - xcb_connection_t *c; - xcb_drawable_t win; - xcb_get_window_attributes_reply_t *attr; - - /* You initialize c and win */ - - attr = xcb_get_window_attributes_reply (c, xcb_get_window_attributes (c, win), NULL); - - if (!attr) - return 0; - - /* Do something with the fields of attr */ - - free (attr); -</pre> - <p> - As for <span class="code">geom</span>, - <span class="code">attr</span> has to be freed. - </p> - </ol> - <li class="title"><a name="usecolor">Using colors to paint the rainbow</a> - <p> - Up until now, all our painting operation were done using black - and white. We will (finally) see now how to draw using colors. - </p> - <ol> - <li class="subtitle"><a name="colormap">Color maps</a> - <p> - In the beginning, there were not enough colors. Screen - controllers could only support a limited number of colors - simultaneously (initially 2, then 4, 16 and 256). Because of - this, an application could not just ask to draw in a "light - purple-red" color, and expect that color to be available. Each - application allocated the colors it needed, and when all the - color entries (4, 16, 256 colors) were in use, the next color - allocation would fail. - </p> - <p> - Thus, the notion of "a color map" was introduced. A color map - is a table whose size is the same as the number of - simultaneous colors a given screen controller. Each entry - contained the RGB (Red, Green and Blue) values of a different - color (all colors can be drawn using some combination of red, - green and blue). When an application wants to draw on the - screen, it does not specify which color to use. Rather, it - specifies which color entry of some color map to be used - during this drawing. Change the value in this color map entry - and the drawing will use a different color. - </p> - <p> - In order to be able to draw using colors that got something to - do with what the programmer intended, color map allocation - functions are supplied. You could ask to allocate entry for a - color with a set of RGB values. If one already existed, you - would get its index in the table. If none existed, and the - table was not full, a new cell would be allocated to contain - the given RGB values, and its index returned. If the table was - full, the procedure would fail. You could then ask to get a - color map entry with a color that is closest to the one you - were asking for. This would mean that the actual drawing on - the screen would be done using colors similar to what you - wanted, but not the same. - </p> - <p> - On today's more modern screens where one runs an X server with - support for 16 million colors, this limitation looks a little - silly, but remember that there are still older computers with - older graphics cards out there. Using color map, support for - these screen becomes transparent to you. On a display - supporting 16 million colors, any color entry allocation - request would succeed. On a display supporting a limited - number of colors, some color allocation requests would return - similar colors. It won't look as good, but your application - would still work. - </p> - <li class="subtitle"><a name="colormapalloc">Allocating and freeing Color Maps</a> - <p> - When you draw using XCB, you can choose to use the standard - color map of the screen your window is displayed on, or you - can allocate a new color map and apply it to a window. In the - latter case, each time the mouse moves onto your window, the - screen color map will be replaced by your window's color map, - and you'll see all the other windows on screen change their - colors into something quite bizzare. In fact, this is the - effect you get with X applications that use the "-install" - command line option. - </p> - <p> - In XCB, a color map is (as often in X) an Id: - </p> - <pre class="code"> -typedef uint32_t xcb_colormap_t; -</pre> - <p> - In order to access the screen's default color map, you just - have to retrieve the <span class="code">default_colormap</span> - field of the <span class="code">xcb_screen_t</span> structure - (see Section - <a href="#screen">Checking basic information about a connection</a>): - </p> - <pre class="code"> -#include <stdio.h> - -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_colormap_t colormap; - - /* Open the connection to the X server and get the first screen */ - c = xcb_connect (NULL, NULL); - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - colormap = screen->default_colormap; - - return 0; -} -</pre> - <p> - This will return the color map used by default on the first - screen (again, remember that an X server may support several - different screens, each of which might have its own resources). - </p> - <p> - The other option, that of allocating a new colormap, works as - follows. We first ask the X server to give an Id to our color - map, with this function: - </p> - <pre class="code"> -xcb_colormap_t xcb_generate_id (xcb_connection_t *c); -</pre> - <p> - Then, we create the color map with - </p> - <pre class="code"> -xcb_void_cookie_t xcb_create_colormap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */ - uint8_t alloc, /* Colormap entries to be allocated (AllocNone or AllocAll) */ - xcb_colormap_t mid, /* Id of the color map */ - xcb_window_t window, /* Window on whose screen the colormap will be created */ - xcb_visualid_t visual); /* Id of the visual supported by the screen */ -</pre> - <p> - Here is an example of creation of a new color map: - </p> - <pre class="code"> -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_window_t win; - xcb_colormap_t cmap - - /* Open the connection to the X server and get the first screen */ - c = xcb_connect (NULL, NULL); - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* We create the window win here*/ - - cmap = xcb_generate_id (c); - xcb_create_colormap (c, XCB_COLORMAP_ALLOC_NONE, cmap, win, screen->root_visual); - - return 0; -} -</pre> - <p> - Note that the window parameter is only used to allow the X - server to create the color map for the given screen. We can - then use this color map for any window drawn on the same screen. - </p> - <p> - To free a color map, it suffices to use this function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_free_colormap (xcb_connection_t *c, /* The connection */ - xcb_colormap_t cmap); /* The color map */ -</pre> - <div class="comp"> - <div class="title"> - Comparison Xlib/XCB - </div> - <div class="xlib"> - <ul> - <li>XCreateColormap () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_generate_id () - <li>xcb_create_colormap () - </ul> - </div> - <div class="xlib"> - <ul> - <li>XFreeColormap () - </ul> - </div> - <div class="xcb"> - <ul> - <li>xcb_free_colormap () - </ul> - </div> - </div> - <br> - <li class="subtitle"><a name="alloccolor">Allocating and freeing a color entry</a> - <p> - Once we got access to some color map, we can start allocating - colors. The informations related to a color are stored in the - following structure: - </p> - <pre class="code"> -typedef struct { - uint8_t response_type; - uint8_t pad0; - uint16_t sequence; - uint32_t length; - uint16_t red; /* The red component */ - uint16_t green; /* The green component */ - uint16_t blue; /* The blue component */ - uint8_t pad1[2]; - uint32_t pixel; /* The entry in the color map, supplied by the X server */ -} xcb_alloc_color_reply_t; -</pre> - <p> - XCB supplies these two functions to fill it: - </p> - <pre class="code"> -xcb_alloc_color_cookie_t xcb_alloc_color (xcb_connection_t *c, - xcb_colormap_t cmap, - uint16_t red, - uint16_t green, - uint16_t blue); -xcb_alloc_color_reply_t *xcb_alloc_color_reply (xcb_connection_t *c, - xcb_alloc_color_cookie_t cookie, - xcb_generic_error_t **e); -</pre> - <p> - The fuction <span class="code">xcb_alloc_color()</span> takes the - 3 RGB components as parameters (red, green and blue). Here is an - example of using these functions: - </p> - <pre class="code"> -#include <malloc.h> - -#include <xcb/xcb.h> - -int -main () -{ - xcb_connection_t *c; - xcb_screen_t *screen; - xcb_window_t win; - xcb_colormap_t cmap; - xcb_alloc_color_reply_t *rep; - - /* Open the connection to the X server and get the first screen */ - c = xcb_connect (NULL, NULL); - screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data; - - /* We create the window win here*/ - - cmap = xcb_generate_id (c); - xcb_create_colormap (c, XCB_COLORMAP_ALLOC_NONE, cmap, win, screen->root_visual); - - rep = xcb_alloc_color_reply (c, xcb_alloc_color (c, cmap, 65535, 0, 0), NULL); - - if (!rep) - return 0; - - /* Do something with r->pixel or the components */ - - free (rep); - - return 0; -} -</pre> - <p> - As <span class="code">xcb_alloc_color_reply()</span> allocates - memory, you have to free <span class="code">rep</span>. - </p> - <p> - <b>TODO</b>: Talk about freeing colors. - </p> - </ol> - <li class="title"><a name="pixmaps">X Bitmaps and Pixmaps</a> - <p> - One thing many so-called "Multi-Media" applications need to do, - is display images. In the X world, this is done using bitmaps - and pixmaps. We have already seen some usage of them when - setting an icon for our application. Lets study them further, - and see how to draw these images inside a window, along side the - simple graphics and text we have seen so far. - </p> - <p> - One thing to note before delving further, is that XCB (nor Xlib) - supplies no means of manipulating popular image formats, such as - gif, png, jpeg or tiff. It is up to the programmer (or to higher - level graphics libraries) to translate these image formats into - formats that the X server is familiar with (x bitmaps and x - pixmaps). - </p> - <ol> - <li class="subtitle"><a name="pixmapswhat">What is a X Bitmap? An X Pixmap?</a> - <p> - An X bitmap is a two-color image stored in a format specific - to the X window system. When stored in a file, the bitmap data - looks like a C source file. It contains variables defining the - width and the height of the bitmap, an array containing the - bit values of the bitmap (the size of the array is - (width+7)/8*height and the bit and byte order are LSB), and - an optional hot-spot location (that will - be explained later, when discussing mouse cursors). - </p> - <p> - An X pixmap is a format used to stored images in the memory of - an X server. This format can store both black and white images - (such as x bitmaps) as well as color images. It is the only - image format supported by the X protocol, and any image to be - drawn on screen, should be first translated into this format. - </p> - <p> - In actuality, an X pixmap can be thought of as a window that - does not appear on the screen. Many graphics operations that - work on windows, will also work on pixmaps. Indeed, the type - of X pixmap in XCB is an Id like a window: - </p> - <pre class="code"> -typedef uint32_t xcb_pixmap_t; -</pre> - <p> - Like Xlib, there is no difference between a Drawable, a Window - or a Pixmap: - </p> - <pre class="code"> -typedef uint32_t xcb_drawable_t; -</pre> - <p> - in order to avoid confusion between a window and a pixmap. The - operations that will work the same on a window or a pixmap - will require a <span class="code">xcb_drawable_t</span> - </p> - <div class="emph"> - <p> - Remark: In Xlib, there is no specific difference between a - <span class="code">Drawable</span>, a - <span class="code">Pixmap</span> or a - <span class="code">Window</span>: all are 32 bit long - integer. XCB wraps all these different IDs in structures to - provide some measure of type-safety. - </p> - </div> - <li class="subtitle"><a name="pixmapscreate">Creating a pixmap</a> - <p> - Sometimes we want to create an un-initialized pixmap, so we - can later draw into it. This is useful for image drawing - programs (creating a new empty canvas will cause the creation - of a new pixmap on which the drawing can be stored). It is - also useful when reading various image formats: we load the - image data into memory, create a pixmap on the server, and - then draw the decoded image data onto that pixmap. - </p> - <p> - To create a new pixmap, we first ask the X server to give an - Id to our pixmap, with this function: - </p> - <pre class="code"> -xcb_pixmap_t xcb_generate_id (xcb_connection_t *c); -</pre> - <p> - Then, XCB supplies the following function to create new pixmaps: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_create_pixmap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */ - uint8_t depth, /* Depth of the screen */ - xcb_pixmap_t pid, /* Id of the pixmap */ - xcb_drawable_t drawable, - uint16_t width, /* Width of the window (in pixels) */ - uint16_t height); /* Height of the window (in pixels) */ -</pre> - <p> - <b>TODO</b>: Explain the drawable parameter, and give an - example (like <a href="xpoints.c">xpoints.c</a>) - </p> - <li class="subtitle"><a name="pixmapsdraw"></a>Drawing a pixmap in a window - <p> - Once we got a handle to a pixmap, we can draw it on some - window, using the following function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_copy_area (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */ - xcb_drawable_t src_drawable, /* The Drawable we want to paste */ - xcb_drawable_t dst_drawable, /* The Drawable on which we copy the previous Drawable */ - xcb_gcontext_t gc, /* A Graphic Context */ - int16_t src_x, /* Top left x coordinate of the region we want to copy */ - int16_t src_y, /* Top left y coordinate of the region we want to copy */ - int16_t dst_x, /* Top left x coordinate of the region where we want to copy */ - int16_t dst_y, /* Top left y coordinate of the region where we want to copy */ - uint16_t width, /* Width of the region we want to copy */ - uint16_t height); /* Height of the region we want to copy */ -</pre> - <p> - As you can see, we could copy the whole pixmap, as well as - only a given rectangle of the pixmap. This is useful to - optimize the drawing speed: we could copy only what we have - modified in the pixmap. - </p> - <p> - <b>One important note should be made</b>: it is possible to - create pixmaps with different depths on the same screen. When - we perform copy operations (a pixmap onto a window, etc), we - should make sure that both source and target have the same - depth. If they have a different depth, the operation would - fail. The exception to this is if we copy a specific bit plane - of the source pixmap using the - <span class="code">xcb_copy_plane_t</span> function. In such an - event, we can copy a specific plane to the target window (in - actuality, setting a specific bit in the color of each pixel - copied). This can be used to generate strange graphic effects - in a window, but that is beyond the scope of this tutorial. - </p> - <li class="subtitle"><a name="pixmapsfree"></a>Freeing a pixmap - <p> - Finally, when we are done using a given pixmap, we should free - it, in order to free resources of the X server. This is done - using this function: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_free_pixmap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */ - xcb_pixmap_t pixmap); /* A given pixmap */ -</pre> - <p> - Of course, after having freed it, we must not try accessing - the pixmap again. - </p> - <p> - <b>TODO</b>: Give an example, or a link to xpoints.c - </p> - </ol> - <li class="title"><a name="mousecursor">Messing with the mouse cursor</a> - <p> - It it possible to modify the shape of the mouse pointer (also - called the X pointer) when in certain states, as we otfen see in - programs. For example, a busy application would often display - the sand clock over its main window, to give the user a visual - hint that he should wait. Let's see how we can change the mouse - cursor of our windows. - </p> - <ol> - <li class="subtitle"><a name="mousecursorcreate">Creating and destroying a mouse cursor</a> - <p> - There are two methods for creating cursors. One of them is by - using a set of predefined cursors, that are supplied by the X - server, the other is by using a user-supplied bitmap. - </p> - <p> - In the first method, we use a special font named "cursor", and - the function <span class="code">xcb_create_glyph_cursor</span>: - </p> - <pre class="code"> -xcb_void_cookie_t xcb_create_glyph_cursor (xcb_connection_t *c, - xcb_cursor_t cid, - xcb_font_t source_font, /* font for the source glyph */ - xcb_font_t mask_font, /* font for the mask glyph or XCB_NONE */ - uint16_t source_char, /* character glyph for the source */ - uint16_t mask_char, /* character glyph for the mask */ - uint16_t fore_red, /* red value for the foreground of the source */ - uint16_t fore_green, /* green value for the foreground of the source */ - uint16_t fore_blue, /* blue value for the foreground of the source */ - uint16_t back_red, /* red value for the background of the source */ - uint16_t back_green, /* green value for the background of the source */ - uint16_t back_blue) /* blue value for the background of the source */ -</pre> - <p> - <b>TODO</b>: Describe <span class="code">source_char</span> - and <span class="code">mask_char</span>, for example by giving - an example on how to get the values. There is a list there: - <a href="http://tronche.com/gui/x/xlib/appendix/b/">X Font Cursors</a> - </p> - <p> - So we first open that font (see <a href="#loadfont">Loading a Font</a>) - and create the new cursor. As for every X ressource, we have to - ask for an X id with <span class="code">xcb_generate_id</span> - first: - </p> - <pre class="code"> -xcb_font_t font; -xcb_cursor_t cursor; - -/* The connection is set */ - -font = xcb_generate_id (conn); -xcb_open_font (conn, font, strlen ("cursor"), "cursor"); - -cursor = xcb_generate_id (conn); -xcb_create_glyph_cursor (conn, cursor, font, font, - 58, 58 + 1, - 0, 0, 0, - 0, 0, 0); -</pre> - <p> - We have created the cursor "right hand" by specifying 58 to - the <span class="code">source_fon</span>t argument and 58 + 1 - to the <span class="code">mask_font</span>. - </p> - <p> - The cursor is destroyed by using the function - </p> - <pre class="code"> -xcb_void_cookie_t xcb_free_cursor (xcb_connection_t *c, - xcb_cursor_t cursor); -</pre> - <p> - In the second method, we create a new cursor by using a pair - of pixmaps, with depth of one (that is, two colors - pixmaps). One pixmap defines the shape of the cursor, while - the other works as a mask, specifying which pixels of the - cursor will be actually drawn. The rest of the pixels will be - transparent. - </p> - <p> - <b>TODO</b>: give an example. - </p> - <li class="subtitle"><a name="mousecursorset">Setting a window's mouse cursor</a> - <p> - Once the cursor is created, we can modify the cursor of our - window by using <span class="code">xcb_change_window_attributes</span> - and using the <span class="code">XCB_CWCURSOR</span> attribute: - </p> - <pre class="code"> -uint32_t mask; -uint32_t value_list; - -/* The connection and window are set */ -/* The cursor is already created */ - -mask = XCB_CWCURSOR; -value_list = cursor; -xcb_change_window_attributes (conn, window, mask, &value_list); -</pre> - <p> - Of course, the cursor and the font must be freed. - </p> - <li class="subtitle"><a name="mousecursorexample">Complete example</a> - <p> - The following example displays a window with a - button. When entering the window, the window cursor is changed - to an arrow. When clicking once on the button, the cursor is - changed to a hand. When clicking again on the button, the - cursor window gets back to the arrow. The Esc key exits the - application. - </p> - <pre class="code"> -#include <stdlib.h> -#include <stdio.h> -#include <string.h> - -#include <xcb/xcb.h> - -#define WIDTH 300 -#define HEIGHT 150 - - - -static xcb_gc_t gc_font_get (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - const char *font_name); - -static void button_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label); - -static void text_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label); - -static void cursor_set (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int cursor_id); - - -static void -button_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label) -{ - xcb_point_t points[5]; - xcb_void_cookie_t cookie_gc; - xcb_void_cookie_t cookie_line; - xcb_void_cookie_t cookie_text; - xcb_generic_error_t *error; - xcb_gcontext_t gc; - int16_t width; - int16_t height; - uint8_t length; - int16_t inset; - - length = strlen (label); - inset = 2; - - gc = gc_font_get(c, screen, window, "7x13"); - - width = 7 * length + 2 * (inset + 1); - height = 13 + 2 * (inset + 1); - points[0].x = x1; - points[0].y = y1; - points[1].x = x1 + width; - points[1].y = y1; - points[2].x = x1 + width; - points[2].y = y1 - height; - points[3].x = x1; - points[3].y = y1 - height; - points[4].x = x1; - points[4].y = y1; - cookie_line = xcb_poly_line_checked (c, XCB_COORD_MODE_ORIGIN, - window, gc, 5, points); - - error = xcb_request_check (c, cookie_line); - if (error) { - fprintf (stderr, "ERROR: can't draw lines : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_text = xcb_image_text_8_checked (c, length, window, gc, - x1 + inset + 1, - y1 - inset - 1, label); - error = xcb_request_check (c, cookie_text); - if (error) { - fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_gc = xcb_free_gc (c, gc); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } -} - -static void -text_draw (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int16_t x1, - int16_t y1, - const char *label) -{ - xcb_void_cookie_t cookie_gc; - xcb_void_cookie_t cookie_text; - xcb_generic_error_t *error; - xcb_gcontext_t gc; - uint8_t length; - - length = strlen (label); - - gc = gc_font_get(c, screen, window, "7x13"); - - cookie_text = xcb_image_text_8_checked (c, length, window, gc, - x1, - y1, label); - error = xcb_request_check (c, cookie_text); - if (error) { - fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_gc = xcb_free_gc (c, gc); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } -} - -static xcb_gc_t -gc_font_get (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - const char *font_name) -{ - uint32_t value_list[3]; - xcb_void_cookie_t cookie_font; - xcb_void_cookie_t cookie_gc; - xcb_generic_error_t *error; - xcb_font_t font; - xcb_gcontext_t gc; - uint32_t mask; - - font = xcb_generate_id (c); - cookie_font = xcb_open_font_checked (c, font, - strlen (font_name), - font_name); - - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - - gc = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; - value_list[0] = screen->black_pixel; - value_list[1] = screen->white_pixel; - value_list[2] = font; - cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cookie_font = xcb_close_font_checked (c, font); - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - return gc; -} - -static void -cursor_set (xcb_connection_t *c, - xcb_screen_t *screen, - xcb_window_t window, - int cursor_id) -{ - uint32_t values_list[3]; - xcb_void_cookie_t cookie_font; - xcb_void_cookie_t cookie_gc; - xcb_generic_error_t *error; - xcb_font_t font; - xcb_cursor_t cursor; - xcb_gcontext_t gc; - uint32_t mask; - uint32_t value_list; - - font = xcb_generate_id (c); - cookie_font = xcb_open_font_checked (c, font, - strlen ("cursor"), - "cursor"); - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - cursor = xcb_generate_id (c); - xcb_create_glyph_cursor (c, cursor, font, font, - cursor_id, cursor_id + 1, - 0, 0, 0, - 0, 0, 0); - - gc = xcb_generate_id (c); - mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT; - values_list[0] = screen->black_pixel; - values_list[1] = screen->white_pixel; - values_list[2] = font; - cookie_gc = xcb_create_gc_checked (c, gc, window, mask, values_list); - error = xcb_request_check (c, cookie_gc); - if (error) { - fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } - - mask = XCB_CW_CURSOR; - value_list = cursor; - xcb_change_window_attributes (c, window, mask, &value_list); - - xcb_free_cursor (c, cursor); - - cookie_font = xcb_close_font_checked (c, font); - error = xcb_request_check (c, cookie_font); - if (error) { - fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code); - xcb_disconnect (c); - exit (-1); - } -} - -int main () -{ - xcb_screen_iterator_t screen_iter; - xcb_connection_t *c; - const xcb_setup_t *setup; - xcb_screen_t *screen; - xcb_generic_event_t *e; - xcb_generic_error_t *error; - xcb_void_cookie_t cookie_window; - xcb_void_cookie_t cookie_map; - xcb_window_t window; - uint32_t mask; - uint32_t values[2]; - int screen_number; - uint8_t is_hand = 0; - - /* getting the connection */ - c = xcb_connect (NULL, &screen_number); - if (!c) { - fprintf (stderr, "ERROR: can't connect to an X server\n"); - return -1; - } - - /* getting the current screen */ - setup = xcb_get_setup (c); - - screen = NULL; - screen_iter = xcb_setup_roots_iterator (setup); - for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter)) - if (screen_number == 0) - { - screen = screen_iter.data; - break; - } - if (!screen) { - fprintf (stderr, "ERROR: can't get the current screen\n"); - xcb_disconnect (c); - return -1; - } - - /* creating the window */ - window = xcb_generate_id (c); - mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK; - values[0] = screen->white_pixel; - values[1] = - XCB_EVENT_MASK_KEY_RELEASE | - XCB_EVENT_MASK_BUTTON_PRESS | - XCB_EVENT_MASK_EXPOSURE | - XCB_EVENT_MASK_POINTER_MOTION; - cookie_window = xcb_create_window_checked (c, - screen->root_depth, - window, screen->root, - 20, 200, WIDTH, HEIGHT, - 0, XCB_WINDOW_CLASS_INPUT_OUTPUT, - screen->root_visual, - mask, values); - cookie_map = xcb_map_window_checked (c, window); - - /* error managing */ - error = xcb_request_check (c, cookie_window); - if (error) { - fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - error = xcb_request_check (c, cookie_map); - if (error) { - fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code); - xcb_disconnect (c); - return -1; - } - - cursor_set (c, screen, window, 68); - - xcb_flush(c); - - while (1) { - e = xcb_poll_for_event(c); - if (e) { - switch (e->response_type & ~0x80) { - case XCB_EXPOSE: { - char *text; - - text = "click here to change cursor"; - button_draw (c, screen, window, - (WIDTH - 7 * strlen(text)) / 2, - (HEIGHT - 16) / 2, text); - - text = "Press ESC key to exit..."; - text_draw (c, screen, window, 10, HEIGHT - 10, text); - break; - } - case XCB_BUTTON_PRESS: { - xcb_button_press_event_t *ev; - int length; - - ev = (xcb_button_press_event_t *)e; - length = strlen ("click here to change cursor"); - - if ((ev->event_x >= (WIDTH - 7 * length) / 2) && - (ev->event_x <= ((WIDTH - 7 * length) / 2 + 7 * length + 6)) && - (ev->event_y >= (HEIGHT - 16) / 2 - 19) && - (ev->event_y <= ((HEIGHT - 16) / 2))) - is_hand = 1 - is_hand; - - is_hand ? cursor_set (c, screen, window, 58) : cursor_set (c, screen, window, 68); - } - case XCB_KEY_RELEASE: { - xcb_key_release_event_t *ev; - - ev = (xcb_key_release_event_t *)e; - - switch (ev->detail) { - /* ESC */ - case 9: - free (e); - xcb_disconnect (c); - return 0; - } - } - } - free (e); - } - } - - return 0; -} -</pre> - </ol> - <li class="title"><a name="translation">Translation of basic Xlib functions and macros</a> - <p> - The problem when you want to port an Xlib program to XCB is that - you don't know if the Xlib function that you want to "translate" - is a X Window one or an Xlib macro. In that section, we describe - a way to translate the usual functions or macros that Xlib - provides. It's usually just a member of a structure. - </p> - <ol> - <li class="subtitle"><a name="displaystructure">Members of the Display structure</a> - <p> - In this section, we look at how to translate the macros that - return some members of the <span class="code">Display</span> - structure. They are obtained by using a function that requires a - <span class="code">xcb_connection_t *</span> or a member of the - <span class="code">xcb_setup_t</span> structure - (via the function <span class="code">xcb_get_setup</span>), or - a function that requires that structure. - </p> - <ol> - <li class="subtitle"><a name="ConnectionNumber">ConnectionNumber</a> - <p> - This number is the file descriptor that connects the client - to the server. You just have to use that function: - </p> - <pre class="code"> -int xcb_get_file_descriptor (xcb_connection_t *c); -</pre> - <li class="subtitle"><a name="DefaultScreen"></a>DefaultScreen - <p> - That number is not stored by XCB. It is returned in the - second parameter of the function <span class="code"><a href="#openconn">xcb_connect</a></span>. - Hence, you have to store it yourself if you want to use - it. Then, to get the <span class="code">xcb_screen_t</span> - structure, you have to iterate on the screens. - The equivalent function of the Xlib's - <span class="code">ScreenOfDisplay</span> function can be - found <a href="#ScreenOfDisplay">below</a>. This is also provided in the - xcb_aux_t library as <span class="code">xcb_aux_get_screen()</span>. OK, here is the - small piece of code to get that number: - </p> - <pre class="code"> -xcb_connection_t *c; -int screen_default_nbr; - -/* you pass the name of the display you want to xcb_connect_t */ - -c = xcb_connect (display_name, &screen_default_nbr); - -/* screen_default_nbr contains now the number of the default screen */ -</pre> - <li class="subtitle"><a name="QLength"></a>QLength - <p> - Not documented yet. - </p> - <p> - However, this points out a basic difference in philosophy between - Xlib and XCB. Xlib has several functions for filtering and - manipulating the incoming and outgoing X message queues. XCB - wishes to hide this as much as possible from the user, which - allows for more freedom in implementation strategies. - </p> - <li class="subtitle"><a name="ScreenCount"></a>ScreenCount - <p> - You get the count of screens with the functions - <span class="code">xcb_get_setup</span> - and - <span class="code">xcb_setup_roots_iterator</span> - (if you need to iterate): - </p> - <pre class="code"> -xcb_connection_t *c; -int screen_count; - -/* you init the connection */ - -screen_count = xcb_setup_roots_iterator (xcb_get_setup (c)).rem; - -/* screen_count contains now the count of screens */ -</pre> - <p> - If you don't want to iterate over the screens, a better way - to get that number is to use - <span class="code">xcb_setup_roots_length_t</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -int screen_count; - -/* you init the connection */ - -screen_count = xcb_setup_roots_length (xcb_get_setup (c)); - -/* screen_count contains now the count of screens */ -</pre> - <li class="subtitle"><a name="ServerVendor"></a>ServerVendor - <p> - You get the name of the vendor of the server hardware with - the functions <span class="code">xcb_get_setup</span> - and - <span - class="code">xcb_setup_vendor</span>. Beware - that, unlike Xlib, the string returned by XCB is not - necessarily null-terminaled: - </p> - <pre class="code"> -xcb_connection_t *c; -char *vendor = NULL; -int length; - -/* you init the connection */ -length = xcb_setup_vendor_length (xcb_get_setup (c)); -vendor = (char *)malloc (length + 1); -if (vendor) -memcpy (vendor, xcb_setup_vendor (xcb_get_setup (c)), length); -vendor[length] = '\0'; - -/* vendor contains now the name of the vendor. Must be freed when not used anymore */ -</pre> - <li class="subtitle"><a name="ProtocolVersion"></a>ProtocolVersion - <p> - You get the major version of the protocol in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint16_t protocol_major_version; - -/* you init the connection */ - -protocol_major_version = xcb_get_setup (c)->protocol_major_version; - -/* protocol_major_version contains now the major version of the protocol */ -</pre> - <li class="subtitle"><a name="ProtocolRevision"></a>ProtocolRevision - <p> - You get the minor version of the protocol in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint16_t protocol_minor_version; - -/* you init the connection */ - -protocol_minor_version = xcb_get_setup (c)->protocol_minor_version; - -/* protocol_minor_version contains now the minor version of the protocol */ -</pre> - <li class="subtitle"><a name="VendorRelease"></a>VendorRelease - <p> - You get the number of the release of the server hardware in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint32_t release_number; - -/* you init the connection */ - -release_number = xcb_get_setup (c)->release_number; - -/* release_number contains now the number of the release of the server hardware */ -</pre> - <li class="subtitle"><a name="DisplayString"></a>DisplayString - <p> - The name of the display is not stored in XCB. You have to - store it by yourself. - </p> - <li class="subtitle"><a name="BitmapUnit"></a>BitmapUnit - <p> - You get the bitmap scanline unit in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint8_t bitmap_format_scanline_unit; - -/* you init the connection */ - -bitmap_format_scanline_unit = xcb_get_setup (c)->bitmap_format_scanline_unit; - -/* bitmap_format_scanline_unit contains now the bitmap scanline unit */ -</pre> - <li class="subtitle"><a name="BitmapBitOrder"></a>BitmapBitOrder - <p> - You get the bitmap bit order in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint8_t bitmap_format_bit_order; - -/* you init the connection */ - -bitmap_format_bit_order = xcb_get_setup (c)->bitmap_format_bit_order; - -/* bitmap_format_bit_order contains now the bitmap bit order */ -</pre> - <li class="subtitle"><a name="BitmapPad"></a>BitmapPad - <p> - You get the bitmap scanline pad in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint8_t bitmap_format_scanline_pad; - -/* you init the connection */ - -bitmap_format_scanline_pad = xcb_get_setup (c)->bitmap_format_scanline_pad; - -/* bitmap_format_scanline_pad contains now the bitmap scanline pad */ -</pre> - <li class="subtitle"><a name="ImageByteOrder"></a>ImageByteOrder - <p> - You get the image byte order in the - <span class="code">xcb_setup_t</span> - structure, with the function <span class="code">xcb_get_setup</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -uint8_t image_byte_order; - -/* you init the connection */ - -image_byte_order = xcb_get_setup (c)->image_byte_order; - -/* image_byte_order contains now the image byte order */ -</pre> - </ol> - <li class="subtitle"><a name="screenofdisplay">ScreenOfDisplay related functions</a> - <p> - in Xlib, <span class="code">ScreenOfDisplay</span> returns a - <span class="code">Screen</span> structure that contains - several characteristics of your screen. XCB has a similar - structure (<span class="code">xcb_screen_t</span>), - but the way to obtain it is a bit different. With - Xlib, you just provide the number of the screen and you grab it - from an array. With XCB, you iterate over all the screens to - obtain the one you want. The complexity of this operation is - O(n). So the best is to store this structure if you use - it often. See <a href="#ScreenOfDisplay">screen_of_display</a> just below. - </p> - <p> - Xlib provides generally two functions to obtain the characteristics - related to the screen. One with the display and the number of - the screen, which calls <span class="code">ScreenOfDisplay</span>, - and the other that uses the <span class="code">Screen</span> structure. - This might be a bit confusing. As mentioned above, with XCB, it - is better to store the <span class="code">xcb_screen_t</span> - structure. Then, you have to read the members of this - structure. That's why the Xlib functions are put by pairs (or - more) as, with XCB, you will use the same code. - </p> - <ol> - <li class="subtitle"><a name="ScreenOfDisplay">ScreenOfDisplay</a> - <p> - This function returns the Xlib <span class="code">Screen</span> - structure. With XCB, you iterate over all the screens and - once you get the one you want, you return it: - </p> - <pre class="code"><a name="ScreenOfDisplay"></a> -xcb_screen_t *screen_of_display (xcb_connection_t *c, - int screen) -{ - xcb_screen_iterator_t iter; - - iter = xcb_setup_roots_iterator (xcb_get_setup (c)); - for (; iter.rem; --screen, xcb_screen_next (&iter)) - if (screen == 0) - return iter.data; - - return NULL; -} -</pre> - <p> - As mentioned above, you might want to store the value - returned by this function. - </p> - <p> - All the functions below will use the result of that - function, as they just grab a specific member of the - <span class="code">xcb_screen_t</span> structure. - </p> - <li class="subtitle"><a name="DefaultScreenOfDisplay"></a>DefaultScreenOfDisplay - <p> - It is the default screen that you obtain when you connect to - the X server. It suffices to call the <a href="#ScreenOfDisplay">screen_of_display</a> - function above with the connection and the number of the - default screen. - </p> - <pre class="code"> -xcb_connection_t *c; -int screen_default_nbr; -xcb_screen_t *default_screen; /* the returned default screen */ - -/* you pass the name of the display you want to xcb_connect_t */ - -c = xcb_connect (display_name, &screen_default_nbr); -default_screen = screen_of_display (c, screen_default_nbr); - -/* default_screen contains now the default root window, or a NULL window if no screen is found */ -</pre> - <li class="subtitle"><a name="RootWindow">RootWindow / RootWindowOfScreen</a> - <br> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -xcb_window_t root_window = { 0 }; /* the returned window */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - root_window = screen->root; - -/* root_window contains now the root window, or a NULL window if no screen is found */ -</pre> - <li class="subtitle"><a name="DefaultRootWindow">DefaultRootWindow</a> - <p> - It is the root window of the default screen. So, you call - <a name="ScreenOfDisplay">ScreenOfDisplay</a> with the - default screen number and you get the - <a href="#RootWindow">root window</a> as above: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_default_nbr; -xcb_window_t root_window = { 0 }; /* the returned root window */ - -/* you pass the name of the display you want to xcb_connect_t */ - -c = xcb_connect (display_name, &screen_default_nbr); -screen = screen_of_display (c, screen_default_nbr); -if (screen) - root_window = screen->root; - -/* root_window contains now the default root window, or a NULL window if no screen is found */ -</pre> - <li class="subtitle"><a name="DefaultVisual">DefaultVisual / DefaultVisualOfScreen</a> - <p> - While a Visual is, in Xlib, a structure, in XCB, there are - two types: <span class="code">xcb_visualid_t</span>, which is - the Id of the visual, and <span class="code">xcb_visualtype_t</span>, - which corresponds to the Xlib Visual. To get the Id of the - visual of a screen, just get the - <span class="code">root_visual</span> - member of a <span class="code">xcb_screen_t</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -xcb_visualid_t root_visual = { 0 }; /* the returned visual Id */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - root_visual = screen->root_visual; - -/* root_visual contains now the value of the Id of the visual, or a NULL visual if no screen is found */ -</pre> - <p> - To get the <span class="code">xcb_visualtype_t</span> - structure, it's a bit less easy. You have to get the - <span class="code">xcb_screen_t</span> structure that you want, - get its <span class="code">root_visual</span> member, - then iterate over the <span class="code">xcb_depth_t</span>s - and the <span class="code">xcb_visualtype_t</span>s, and compare - the <span class="code">xcb_visualid_t</span> of these <span class="code">xcb_visualtype_t</span>s: - with <span class="code">root_visual</span>: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -xcb_visualid_t root_visual = { 0 }; -xcb_visualtype_t *visual_type = NULL; /* the returned visual type */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) { - xcb_depth_iterator_t depth_iter; - - depth_iter = xcb_screen_allowed_depths_iterator (screen); - for (; depth_iter.rem; xcb_depth_next (&depth_iter)) { - xcb_visualtype_iterator_t visual_iter; - - visual_iter = xcb_depth_visuals_iterator (depth_iter.data); - for (; visual_iter.rem; xcb_visualtype_next (&visual_iter)) { - if (screen->root_visual == visual_iter.data->visual_id) { - visual_type = visual_iter.data; - break; - } - } - } -} - -/* visual_type contains now the visual structure, or a NULL visual structure if no screen is found */ -</pre> - <li class="subtitle"><a name="DefaultGC">DefaultGC / DefaultGCOfScreen</a> - <p> - This default Graphic Context is just a newly created Graphic - Context, associated to the root window of a - <span class="code">xcb_screen_t</span>, - using the black white pixels of that screen: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -xcb_gcontext_t gc = { 0 }; /* the returned default graphic context */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) { - xcb_drawable_t draw; - uint32_t mask; - uint32_t values[2]; - - gc = xcb_generate_id (c); - draw = screen->root; - mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND; - values[0] = screen->black_pixel; - values[1] = screen->white_pixel; - xcb_create_gc (c, gc, draw, mask, values); -} - -/* gc contains now the default graphic context */ -</pre> - <li class="subtitle"><a name="BlackPixel">BlackPixel / BlackPixelOfScreen</a> - <p> - It is the Id of the black pixel, which is in the structure - of an <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t black_pixel = 0; /* the returned black pixel */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - black_pixel = screen->black_pixel; - -/* black_pixel contains now the value of the black pixel, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="WhitePixel">WhitePixel / WhitePixelOfScreen</a> - <p> - It is the Id of the white pixel, which is in the structure - of an <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t white_pixel = 0; /* the returned white pixel */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - white_pixel = screen->white_pixel; - -/* white_pixel contains now the value of the white pixel, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DisplayWidth">DisplayWidth / WidthOfScreen</a> - <p> - It is the width in pixels of the screen that you want, and - which is in the structure of the corresponding - <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t width_in_pixels = 0; /* the returned width in pixels */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - width_in_pixels = screen->width_in_pixels; - -/* width_in_pixels contains now the width in pixels, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DisplayHeight">DisplayHeight / HeightOfScreen</a> - <p> - It is the height in pixels of the screen that you want, and - which is in the structure of the corresponding - <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t height_in_pixels = 0; /* the returned height in pixels */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - height_in_pixels = screen->height_in_pixels; - -/* height_in_pixels contains now the height in pixels, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DisplayWidthMM">DisplayWidthMM / WidthMMOfScreen</a> - <p> - It is the width in millimeters of the screen that you want, and - which is in the structure of the corresponding - <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t width_in_millimeters = 0; /* the returned width in millimeters */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - width_in_millimeters = screen->width_in_millimeters; - -/* width_in_millimeters contains now the width in millimeters, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DisplayHeightMM">DisplayHeightMM / HeightMMOfScreen</a> - <p> - It is the height in millimeters of the screen that you want, and - which is in the structure of the corresponding - <span class="code">xcb_screen_t</span>. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t height_in_millimeters = 0; /* the returned height in millimeters */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - height_in_millimeters = screen->height_in_millimeters; - -/* height_in_millimeters contains now the height in millimeters, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DisplayPlanes">DisplayPlanes / DefaultDepth / DefaultDepthOfScreen / PlanesOfScreen</a> - <p> - It is the depth (in bits) of the root window of the - screen. You get it from the <span class="code">xcb_screen_t</span> structure. - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint8_t root_depth = 0; /* the returned depth of the root window */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - root_depth = screen->root_depth; - -/* root_depth contains now the depth of the root window, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DefaultColormap">DefaultColormap / DefaultColormapOfScreen</a> - <p> - This is the default colormap of the screen (and not the - (default) colormap of the default screen !). As usual, you - get it from the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -xcb_colormap_t default_colormap = { 0 }; /* the returned default colormap */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - default_colormap = screen->default_colormap; - -/* default_colormap contains now the default colormap, or a NULL colormap if no screen is found */ -</pre> - <li class="subtitle"><a name="MinCmapsOfScreen"></a>MinCmapsOfScreen - <p> - You get the minimum installed colormaps in the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint16_t min_installed_maps = 0; /* the returned minimum installed colormaps */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - min_installed_maps = screen->min_installed_maps; - -/* min_installed_maps contains now the minimum installed colormaps, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="MaxCmapsOfScreen"></a>MaxCmapsOfScreen - <p> - You get the maximum installed colormaps in the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint16_t max_installed_maps = 0; /* the returned maximum installed colormaps */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - max_installed_maps = screen->max_installed_maps; - -/* max_installed_maps contains now the maximum installed colormaps, or 0 if no screen is found */ -</pre> - <li class="subtitle"><a name="DoesSaveUnders"></a>DoesSaveUnders - <p> - You know if <span class="code">save_unders</span> is set, - by looking in the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint8_t save_unders = 0; /* the returned value of save_unders */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - save_unders = screen->save_unders; - -/* save_unders contains now the value of save_unders, or FALSE if no screen is found */ -</pre> - <li class="subtitle"><a name="DoesBackingStore"></a>DoesBackingStore - <p> - You know the value of <span class="code">backing_stores</span>, - by looking in the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint8_t backing_stores = 0; /* the returned value of backing_stores */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - backing_stores = screen->backing_stores; - -/* backing_stores contains now the value of backing_stores, or FALSE if no screen is found */ -</pre> - <li class="subtitle"><a name="EventMaskOfScreen"></a>EventMaskOfScreen - <p> - To get the current input masks, - you look in the <span class="code">xcb_screen_t</span> structure: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_screen_t *screen; -int screen_nbr; -uint32_t current_input_masks = 0; /* the returned value of current input masks */ - -/* you init the connection and screen_nbr */ - -screen = screen_of_display (c, screen_nbr); -if (screen) - current_input_masks = screen->current_input_masks; - -/* current_input_masks contains now the value of the current input masks, or FALSE if no screen is found */ -</pre> - </ol> - <li class="subtitle"><a name="misc">Miscellaneous macros</a> - <ol> - <li class="subtitle"><a name="DisplayOfScreen"></a>DisplayOfScreen - <p> - in Xlib, the <span class="code">Screen</span> structure - stores its associated <span class="code">Display</span> - structure. This is not the case in the X Window protocol, - hence, it's also not the case in XCB. So you have to store - it by yourself. - </p> - <li class="subtitle"><a name="DisplayCells"></a>DisplayCells / CellsOfScreen - <p> - To get the colormap entries, - you look in the <span class="code">xcb_visualtype_t</span> - structure, that you grab like <a class="subsection" href="#DefaultVisual">here</a>: - </p> - <pre class="code"> -xcb_connection_t *c; -xcb_visualtype_t *visual_type; -uint16_t colormap_entries = 0; /* the returned value of the colormap entries */ - -/* you init the connection and visual_type */ - -if (visual_type) - colormap_entries = visual_type->colormap_entries; - -/* colormap_entries contains now the value of the colormap entries, or FALSE if no screen is found */ -</pre> - </ol> - </ol> - </ol> - </div> -</body> - -</html> +<!DOCTYPE html public "-//W3C//DTD HTML 4.01 Transitional//EN"
+"http://www.w3.org/TR/html4/loose.dtd">
+
+<html>
+
+<head>
+ <title>Basic Graphics Programming With The XCB Library</title>
+ <meta http-equiv="content-type" content="text/html; charset=iso-8859-1">
+ <link href="xcb.css" rel="stylesheet" type="text/css">
+</head>
+
+<body>
+ <div class="title">
+ Basic Graphics Programming With The XCB Library
+ </div>
+ <div class="toc">
+ <ol>
+ <li><a class="section" href="#intro">Introduction</a>
+ <li><a class="section" href="#Xmodel">The client and server model of the X window system</a>
+ <li><a class="section" href="#asynch">GUI programming: the asynchronous model</a>
+ <li><a class="section" href="#notions">Basic XCB notions</a>
+ <ol>
+ <li><a class="subsection" href="#conn">The X Connection</a>
+ <li><a class="subsection" href="#requestsreplies">Requests and replies: the Xlib killers</a>
+ <li><a class="subsection" href="#gc">The Graphics Context</a>
+ <li>Object handles
+ <li>Memory allocation for XCB structures
+ <li><a class="subsection" href="#events">Events</a>
+ </ol>
+ <li><a class="section" href="#use">Using XCB-based programs</a>
+ <ol>
+ <li><a class="subsection" href="#inst">Installation of XCB</a>
+ <li><a class="subsection" href="#comp">Compiling XCB-based programs</a>
+ </ol>
+ <li><a class="section" href="#openconn">Opening and closing the connection to an X server</a>
+ <li><a class="section" href="#screen">Checking basic information about a connection</a>
+ <li><a class="section" href="#helloworld">Creating a basic window - the "hello world" program</a>
+ <li><a class="section" href="#drawing">Drawing in a window</a>
+ <ol>
+ <li><a class="subsection" href="#allocgc">Allocating a Graphics Context</a>
+ <li><a class="subsection" href="#changegc">Changing the attributes of a Graphics Context</a>
+ <li><a class="subsection" href="#drawingprim">Drawing primitives: point, line, box, circle,...</a>
+ </ol>
+ <li><a class="section" href="#xevents">X Events</a>
+ <ol>
+ <li><a class="subsection" href="#register">Registering for event types using event masks</a>
+ <li><a class="subsection" href="#loop">Receiving events: writing the events loop</a>
+ <li><a class="subsection" href="#expose">Expose events</a>
+ <li><a class="subsection" href="#userinput">Getting user input</a>
+ <ol>
+ <li><a class="subsubsection" href="#mousepressrelease">Mouse button press and release events</a>
+ <li><a class="subsubsection" href="#mousemvnt">Mouse movement events</a>
+ <li><a class="subsubsection" href="#mouseenter">Mouse pointer enter and leave events</a>
+ <li><a class="subsubsection" href="#focus">The keyboard focus</a>
+ <li><a class="subsubsection" href="#keypress">Keyboard press and release events</a>
+ </ol>
+ <li><a class="subsection" href="#eventex">X events: a complete example</a>
+ </ol>
+ <li><a class="section" href="#font">Handling text and fonts</a>
+ <ol>
+ <li><a class="subsection" href="#fontstruct">The Font structure</a>
+ <li><a class="subsection" href="#openingfont">Opening a Font</a>
+ <li><a class="subsection" href="#assigningfont">Assigning a Font to a Graphic Context</a>
+ <li><a class="subsection" href="#drawingtext">Drawing text in a drawable</a>
+ <li><a class="subsection" href="#fontcompleteexample">Complete example</a>
+ </ol>
+ <li>Windows hierarchy
+ <ol>
+ <li>Root, parent and child windows
+ <li>Events propagation
+ </ol>
+ <li><a class="section" href="#wm">Interacting with the window manager</a>
+ <ol>
+ <li><a class="subsection" href="#wmprop">Window properties</a>
+ <li><a class="subsection" href="#wmname">Setting the window name and icon name</a>
+ <li>Setting preferred window size(s)
+ <li>Setting miscellaneous window manager hints
+ <li>Setting an application's icon
+ <li>Obeying the delete-window protocol
+ </ol>
+ <li><a class="section" href="#winop">Simple window operations</a>
+ <ol>
+ <li><a class="subsection" href="#winmap">Mapping and unmapping a window</a>
+ <li><a class="subsection" href="#winconf">Configuring a window</a>
+ <li><a class="subsection" href="#winmove">Moving a window around the screen</a>
+ <li><a class="subsection" href="#winsize">Resizing a window</a>
+ <li><a class="subsection" href="#winstack">Changing windows stacking order: raise and lower</a>
+ <li>Iconifying and de-iconifying a window
+ <li><a class="subsection" href="#wingetinfo">Getting informations about a window</a>
+ </ol>
+ <li><a class="section" href="#usecolor">Using colors to paint the rainbow</a>
+ <ol>
+ <li><a class="subsection" href="#colormap">Color maps</a>
+ <li><a class="subsection" href="#colormapalloc">Allocating and freeing Color Maps</a>
+ <li><a class="subsection" href="#alloccolor">Allocating and freeing a color entry</a>
+ <li>Drawing with a color
+ </ol>
+ <li><a class="section" href="#pixmaps">X Bitmaps and Pixmaps</a>
+ <ol>
+ <li><a class="subsection" href="#pixmapswhat">What is a X Bitmap ? An X Pixmap ?</a>
+ <li>Loading a bitmap from a file
+ <li>Drawing a bitmap in a window
+ <li><a class="subsection" href="#pixmapscreate">Creating a pixmap</a>
+ <li><a class="subsection" href="#pixmapsdraw">Drawing a pixmap in a window</a>
+ <li><a class="subsection" href="#pixmapsfree">Freeing a pixmap</a>
+ </ol>
+ <li><a class="subsection" href="#mousecursor">Messing with the mouse cursor</a>
+ <ol>
+ <li><a class="subsection" href="#mousecursorcreate">Creating and destroying a mouse cursor</a>
+ <li><a class="subsection" href="#mousecursorset">Setting a window's mouse cursor</a>
+ <li><a class="subsection" href="#mousecursorexample">Complete example</a>
+ </ol>
+ <li><a class="subsection" href="#translation">Translation of basic Xlib functions and macros</a>
+ <ol>
+ <li><a class="subsection" href="#displaystructure">Members of the Display structure</a>
+ <ol>
+ <li><a class="subsection" href="#ConnectionNumber">ConnectionNumber</a>
+ <li><a class="subsection" href="#DefaultScreen">DefaultScreen</a>
+ <li><a class="subsection" href="#QLength">QLength</a>
+ <li><a class="subsection" href="#ScreenCount">ScreenCount</a>
+ <li><a class="subsection" href="#ServerVendor">ServerVendor</a>
+ <li><a class="subsection" href="#ProtocolVersion">ProtocolVersion</a>
+ <li><a class="subsection" href="#ProtocolRevision">ProtocolRevision</a>
+ <li><a class="subsection" href="#VendorRelease">VendorRelease</a>
+ <li><a class="subsection" href="#DisplayString">DisplayString</a>
+ <li><a class="subsection" href="#BitmapUnit">BitmapUnit</a>
+ <li><a class="subsection" href="#BitmapBitOrder">BitmapBitOrder</a>
+ <li><a class="subsection" href="#BitmapPad">BitmapPad</a>
+ <li><a class="subsection" href="#ImageByteOrder">ImageByteOrder</a>
+ </ol>
+ <li><a class="subsection" href="#screenofdisplay">ScreenOfDisplay related functions</a>
+ <ol>
+ <li><a class="subsection" href="#ScreenOfDisplay">ScreenOfDisplay</a>
+ <li><a class="subsection" href="#DefaultScreenOfDisplay">DefaultScreenOfDisplay</a>
+ <li><a class="subsection" href="#RootWindow">RootWindow / RootWindowOfScreen</a>
+ <li><a class="subsection" href="#DefaultRootWindow">DefaultRootWindow</a>
+ <li><a class="subsection" href="#DefaultVisual">DefaultVisual / DefaultVisualOfScreen</a>
+ <li><a class="subsection" href="#DefaultGC">DefaultGC / DefaultGCOfScreen</a>
+ <li><a class="subsection" href="#BlackPixel">BlackPixel / BlackPixelOfScreen</a>
+ <li><a class="subsection" href="#WhitePixel">WhitePixel / WhitePixelOfScreen</a>
+ <li><a class="subsection" href="#DisplayWidth">DisplayWidth / WidthOfScreen</a>
+ <li><a class="subsection" href="#DisplayHeight">DisplayHeight / HeightOfScreen</a>
+ <li><a class="subsection" href="#DisplayWidthMM">DisplayWidthMM / WidthMMOfScreen</a>
+ <li><a class="subsection" href="#DisplayHeightMM">DisplayHeightMM / HeightMMOfScreen</a>
+ <li><a class="subsection" href="#DisplayPlanes">DisplayPlanes / DefaultDepth / DefaultDepthOfScreen / PlanesOfScreen</a>
+ <li><a class="subsection" href="#DefaultColormap">DefaultColormap / DefaultColormapOfScreen</a>
+ <li><a class="subsection" href="#MinCmapsOfScreen">MinCmapsOfScreen</a>
+ <li><a class="subsection" href="#MaxCmapsOfScreen">MaxCmapsOfScreen</a>
+ <li><a class="subsection" href="#DoesSaveUnders">DoesSaveUnders</a>
+ <li><a class="subsection" href="#DoesBackingStore">DoesBackingStore</a>
+ <li><a class="subsection" href="#EventMaskOfScreen">EventMaskOfScreen</a>
+ </ol>
+ <li><a class="subsection" href="#misc">Miscellaneaous macros</a>
+ <ol>
+ <li><a class="subsection" href="#DisplayOfScreen">DisplayOfScreen</a>
+ <li><a class="subsection" href="#DisplayCells">DisplayCells / CellsOfScreen</a>
+ </ol>
+ </ol>
+ </ol>
+ </div>
+ <div class="section">
+ <ol>
+ <li class="title"><a name="intro">Introduction</a>
+ <p>
+ This tutorial is based on the
+ <a href="http://users.actcom.co.il/~choo/lupg/tutorials/xlib-programming/xlib-programming.html">Xlib Tutorial</a>
+ written by <a href="mailto:choor at atcom dot co dot il">Guy Keren</a>. The
+ author allowed me to take some parts of his text, mainly the text which
+ deals with the X Windows generality.
+ </p>
+ <p>
+ This tutorial is intended for people who want to start to program
+ with the <a href="http://xcb.freedesktop.org">XCB</a>
+ library. keep in mind that XCB, like the
+ <a href="http://tronche.com/gui/x/xlib/introduction">Xlib</a>
+ library, isn't what most programmers wanting to write X
+ applications are looking for. They should use a much higher
+ level GUI toolkit like Motif,
+ <a href="http://www.lesstif.org">LessTiff</a>,
+ <a href="http://www.gtk.org">GTK</a>,
+ <a href="http://www.trolltech.com">QT</a>,
+ <a href="http://www.enlightenment.org">EWL</a>,
+ <a href="http://www.enlightenment.org">ETK</a>, or use
+ <a href="http://cairographics.org">Cairo</a>.
+ However,
+ we need to start somewhere. More than this, knowing how things
+ work down below is never a bad idea.
+ </p>
+ <p>
+ After reading this tutorial, one should be able to write very
+ simple graphical programs, but not programs with decent user
+ interfaces. For such programs, one of the previously mentioned
+ libraries should be used.
+ </p>
+ <p>
+ But what is XCB? Xlib has been
+ the standard C binding for the <a href="http://www.x.org">X
+ Window System</a> protocol for many years now. It is an
+ excellent piece of work, but there are applications for which it
+ is not ideal, for example:
+ </p>
+ <ul>
+ <li><b>Small platforms</b>: Xlib is a large piece of code, and
+ it's difficult to make it smaller
+ <li><b>Latency hiding</b>: Xlib requests requiring a reply are
+ effectively synchronous: they block until the reply appears,
+ whether the result is needed immediately or not.
+ <li><b>Direct access to the protocol</b>: Xlib does quite a
+ bit of caching, layering, and similar optimizations. While this
+ is normally a feature, it makes it difficult to simply emit
+ specified X protocol requests and process specific
+ responses.
+ <li><b>Threaded applications</b>: While Xlib does attempt to
+ support multithreading, the API makes this difficult and
+ error-prone.
+ <li><b>New extensions</b>: The Xlib infrastructure provides
+ limited support for the new creation of X extension client side
+ code.
+ </ul>
+ <p>
+ For these reasons, among others, XCB, an X C binding, has been
+ designed to solve the above problems and thus provide a base for
+ </p>
+ <ul>
+ <li>Toolkit implementation.
+ <li>Direct protocol-level programming.
+ <li>Lightweight emulation of commonly used portions of the
+ Xlib API.
+ </ul>
+ <br>
+ <li class="title"><a name="Xmodel">The client and server model of the X window system</a>
+ <p>
+ The X Window System was developed with one major goal:
+ flexibility. The idea was that the way things look is one thing,
+ but the way things work is another matter. Thus, the lower
+ levels provide the tools required to draw windows, handle user
+ input, allow drawing graphics using colors (or black and white
+ screens), etc. To this point, a decision was made to separate
+ the system into two parts. A client that decides what to do, and
+ a server that actually draws on the screen and reads user input
+ in order to send it to the client for processing.
+ </p>
+ <p>
+ This model is the complete opposite of what is used to when
+ dealing with clients and servers. In our case, the user sits
+ near the machine controlled by the server, while the client
+ might be running on a remote machine. The server controls the
+ screens, mouse and keyboard. A client may connect to the server,
+ request that it draws a window (or several windows), and ask the
+ server to send it any input the user sends to these
+ windows. Thus, several clients may connect to a single X server
+ (one might be running mail software, one running a WWW
+ browser, etc). When input is sent by the user to some window,
+ the server sends a message to the client controlling this window
+ for processing. The client decides what to do with this input,
+ and sends the server requests for drawing in the window.
+ </p>
+ <p>
+ The whole session is carried out using the X message
+ protocol. This protocol was originally carried over the TCP/IP
+ protocol suite, allowing the client to run on any machine
+ connected to the same network that the server is. Later on, the
+ X servers were extended to allow clients running on the local
+ machine with more optimized access to the server (note that an X
+ protocol message may be several hundreds of KB in size), such as
+ using shared memory, or using Unix domain sockets (a method for
+ creating a logical channel on a Unix system between two processes).
+ </p>
+ <li class="title"><a name="asynch">GUI programming: the asynchronous model</a>
+ <p>
+ Unlike conventional computer programs, that carry some serial
+ nature, a GUI program usually uses an asynchronous programming
+ model, also known as "event-driven programming". This means that
+ that program mostly sits idle, waiting for events sent by the X
+ server, and then acts upon these events. An event may say "The
+ user pressed the 1st button mouse in spot (x,y)", or "The window
+ you control needs to be redrawn". In order for the program to be
+ responsive to the user input, as well as to refresh requests, it
+ needs to handle each event in a rather short period of time
+ (e.g. less that 200 milliseconds, as a rule of thumb).
+ </p>
+ <p>
+ This also implies that the program may not perform operations
+ that might take a long time while handling an event (such as
+ opening a network connection to some remote server, or
+ connecting to a database server, or even performing a long file
+ copy operation). Instead, it needs to perform all these
+ operations in an asynchronous manner. This may be done by using
+ various asynchronous models to perform the longish operations,
+ or by performing them in a different process or thread.
+ </p>
+ <p>
+ So the way a GUI program looks is something like that:
+ </p>
+ <ol>
+ <li>Perform initialization routines.
+ <li>Connect to the X server.
+ <li>Perform X-related initialization.
+ <li>While not finished:
+ <ol>
+ <li>Receive the next event from the X server.
+ <li>Handle the event, possibly sending various drawing
+ requests to the X server.
+ <li>If the event was a quit message, exit the loop.
+ </ol>
+ <li>Close down the connection to the X server.
+ <li>Perform cleanup operations.
+ </ol>
+ <br>
+ <li class="title"><a name="notions">Basic XCB notions</a>
+ <p>
+ XCB has been created to eliminate the need for
+ programs to actually implement the X protocol layer. This
+ library gives a program a very low-level access to any X
+ server. Since the protocol is standardized, a client using any
+ implementation of XCB may talk with any X server (the same
+ occurs for Xlib, of course). We now give a brief description of
+ the basic XCB notions. They will be detailed later.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="conn">The X Connection</a>
+ <p>
+ The major notion of using XCB is the X Connection. This is a
+ structure representing the connection we have open with a
+ given X server. It hides a queue of messages coming from the
+ server, and a queue of pending requests that our client
+ intends to send to the server. In XCB, this structure is named
+ 'xcb_connection_t'. It is analogous to the Xlib Display.
+ When we open a connection to an X server, the
+ library returns a pointer to such a structure. Later, we
+ supply this pointer to any XCB function that should send
+ messages to the X server or receive messages from this server.
+ </p>
+ <li class="subtitle"><a name="requestsreplies">Requests and
+ replies: the Xlib killers</a>
+ <p>
+ To ask for information from the X server, we have to make a request
+ and ask for a reply. With Xlib, these two tasks are
+ automatically done: Xlib locks the system, sends a request,
+ waits for a reply from the X server and unlocks. This is
+ annoying, especially if one makes a lot of requests to the X
+ server. Indeed, Xlib has to wait for the end of a reply
+ before asking for the next request (because of the locks that
+ Xlib sends). For example, here is a time-line of N=4
+ requests/replies with Xlib, with a round-trip latency
+ <b>T_round_trip</b> that is 5 times long as the time required
+ to write or read a request/reply (<b>T_write/T_read</b>):
+ </p>
+ <pre class="text">
+ W-----RW-----RW-----RW-----R
+</pre>
+ <ul>
+ <li>W: Writing request
+ <li>-: Stalled, waiting for data
+ <li>R: Reading reply
+ </ul>
+ <p>
+ The total time is N * (T_write + T_round_trip + T_read).
+ </p>
+ <p>
+ With XCB, we can suppress most of the round-trips as the
+ requests and the replies are not locked. We usually send a
+ request, then XCB returns to us a <b>cookie</b>, which is an
+ identifier. Then, later, we ask for a reply using this
+ <b>cookie</b> and XCB returns a
+ pointer to that reply. Hence, with XCB, we can send a lot of
+ requests, and later in the program, ask for all the replies
+ when we need them. Here is the time-line for 4
+ requests/replies when we use this property of XCB:
+ </p>
+ <pre class="text">
+ WWWW--RRRR
+</pre>
+ <p>
+ The total time is N * T_write + max (0, T_round_trip - (N-1) *
+ T_write) + N * T_read. Which can be considerably faster than
+ all those Xlib round-trips.
+ </p>
+ <p>
+ Here is a program that computes the time to create 500 atoms
+ with Xlib and XCB. It shows the Xlib way, the bad XCB way
+ (which is similar to Xlib) and the good XCB way. On my
+ computer, XCB is 25 times faster than Xlib.
+ </p>
+ <pre class="code">
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <sys/time.h>
+
+#include <xcb/xcb.h>
+
+#include <X11/Xlib.h>
+
+double
+get_time(void)
+{
+ struct timeval timev;
+
+ gettimeofday(&timev, NULL);
+
+ return (double)timev.tv_sec + (((double)timev.tv_usec) / 1000000);
+}
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_atom_t *atoms;
+ xcb_intern_atom_cookie_t *cs;
+ char **names;
+ int count;
+ int i;
+ double start;
+ double end;
+ double diff;
+
+ /* Xlib */
+ Display *disp;
+ Atom *atoms_x;
+ double diff_x;
+
+ c = xcb_connect (NULL, NULL);
+
+ count = 500;
+ atoms = (xcb_atom_t *)malloc (count * sizeof (atoms));
+ names = (char **)malloc (count * sizeof (char *));
+
+ /* init names */
+ for (i = 0; i < count; ++i) {
+ char buf[100];
+
+ sprintf (buf, "NAME%d", i);
+ names[i] = strdup (buf);
+ }
+
+ /* bad use */
+ start = get_time ();
+
+ for (i = 0; i < count; ++i)
+ atoms[i] = xcb_intern_atom_reply (c,
+ xcb_intern_atom (c,
+ 0,
+ strlen(names[i]),
+ names[i]),
+ NULL)->atom;
+
+ end = get_time ();
+ diff = end - start;
+ printf ("bad use time : %f\n", diff);
+
+ /* good use */
+ start = get_time ();
+
+ cs = (xcb_intern_atom_cookie_t *) malloc (count * sizeof(xcb_intern_atom_cookie_t));
+ for(i = 0; i < count; ++i)
+ cs[i] = xcb_intern_atom (c, 0, strlen(names[i]), names[i]);
+
+ for(i = 0; i < count; ++i) {
+ xcb_intern_atom_reply_t *r;
+
+ r = xcb_intern_atom_reply(c, cs[i], 0);
+ if(r)
+ atoms[i] = r->atom;
+ free(r);
+ }
+
+ end = get_time ();
+ printf ("good use time : %f\n", end - start);
+ printf ("ratio : %f\n", diff / (end - start));
+ diff = end - start;
+
+ /* free var */
+ free (atoms);
+ free (cs);
+
+ xcb_disconnect (c);
+
+ /* Xlib */
+ disp = XOpenDisplay (getenv("DISPLAY"));
+
+ atoms_x = (Atom *)malloc (count * sizeof (atoms_x));
+
+ start = get_time ();
+
+ for (i = 0; i < count; ++i)
+ atoms_x[i] = XInternAtom(disp, names[i], 0);
+
+ end = get_time ();
+ diff_x = end - start;
+ printf ("Xlib use time : %f\n", diff_x);
+ printf ("ratio : %f\n", diff_x / diff);
+
+ free (atoms_x);
+ for (i = 0; i < count; ++i)
+ free (names[i]);
+ free (names);
+
+ XCloseDisplay (disp);
+
+ return 0;
+}
+</pre>
+ <li class="subtitle"><a name="gc">The Graphic Context</a>
+ <p>
+ When we perform various drawing operations (graphics, text,
+ etc), we may specify various options for controlling how the
+ data will be drawn (what foreground and background colors to
+ use, how line edges will be connected, what font to use when
+ drawing some text, etc). In order to avoid the need to supply
+ hundreds of parameters to each drawing function, a graphical
+ context structure is used. We set the various drawing options
+ in this structure, and then we pass a pointer to this
+ structure to any drawing routines. This is rather handy, as we
+ often need to perform several drawing requests with the same
+ options. Thus, we would initialize a graphical context, set
+ the desired options, and pass this structure to all drawing
+ functions.
+ </p>
+ <p>
+ Note that graphic contexts have no client-side structure in
+ XCB, they're just XIDs. Xlib has a client-side structure
+ because it caches the GC contents so it can avoid making
+ redundant requests, but of course XCB doesn't do that.
+ </p>
+ <li class="subtitle"><a name="events">Events</a>
+ <p>
+ A structure is used to pass events received from the X
+ server. XCB supports exactly the events specified in the
+ protocol (33 events). This structure contains the type
+ of event received (including a bit for whether it came
+ from the server or another client), as well as the data associated with the
+ event (e.g. position on the screen where the event was
+ generated, mouse button associated with the event, region of
+ the screen associated with a "redraw" event, etc). The way to
+ read the event's data depends on the event type.
+ </p>
+ </ol>
+ <br>
+ <li class="title"><a name="use">Using XCB-based programs</a>
+ <br>
+ <ol>
+ <li class="subtitle"><a name="inst">Installation of XCB</a>
+ <p>
+ <b>TODO:</b> These instructions are out of date.
+ Just reference the <a href="http://xcb.freedesktop.org/">main XCB page</a>
+ so we don't have to maintain these instructions in more than
+ one place.
+ </p>
+ <p>
+ To build XCB from source, you need to have installed at
+ least:
+ </p>
+ <ul>
+ <li>pkgconfig 0.15.0
+ <li><a href="http://www.gnu.org/software/automake/">automake 1.7</a>
+ <li><a href="http://www.gnu.org/software/autoconf/">autoconf 2.50</a>
+ <li><a href="http://www.check.org">check</a>
+ <li><a href="http://xmlsoft.org/XSLT/">xsltproc</a>
+ <li><a href="http://www.gnu.org/software/gperf/">gperf 3.0.1</a>
+ </ul>
+ <p>
+ You have to checkout in the git repository the following modules:
+ </p>
+ <ul>
+ <li>Xau from xlibs
+ <li>xcb-proto
+ <li>xcb
+ </ul>
+ <p>
+ Note that xcb-proto exists only to install header
+ files, so typing 'make' or 'make all' will produce the message
+ "Nothing to be done for 'all'". That's normal.
+ </p>
+ <li class="subtitle"><a name="comp">Compiling XCB-based programs</a>
+ <p>
+ Compiling XCB-based programs requires linking them with the XCB
+ library. This is easily done thanks to pkgconfig:
+ </p>
+ <pre class="text">
+gcc -Wall prog.c -o prog `pkg-config --cflags --libs xcb`
+</pre>
+ </ol>
+ <li class="title"><a name="openconn">Opening and closing the connection to an X server</a>
+ <p>
+ An X program first needs to open the connection to the X
+ server. There is a function that opens a connection. It requires
+ the display name, or NULL. In the latter case, the display name
+ will be the one in the environment variable DISPLAY.
+ </p>
+ <pre class="code">
+<span class="type">xcb_connection_t</span> *xcb_connect (<span class="keyword">const</span> <span class="type">char</span> *displayname,
+ <span class="type">int</span> *screenp);
+</pre>
+ <p>
+ The second parameter returns the screen number used for the
+ connection. The returned structure describes an XCB connection
+ and is opaque. Here is how the connection can be opened:
+ </p>
+ <pre class="code">
+#<span class="include">include</span> <span class="string"><xcb/xcb.h></span>
+
+<span class="type">int</span>
+<span class="function">main</span> ()
+{
+ <span class="type">xcb_connection_t</span> *c;
+
+ /* Open the connection to the X server. Use the DISPLAY environment variable as the default display name */
+ c = xcb_connect (NULL, NULL);
+
+ <span class="keyword">return</span> 0;
+}
+</pre>
+ <p>
+ To close a connection, it suffices to use:
+ </p>
+ <pre class="code">
+<span class="type">void</span> xcb_disconnect (<span class="type">xcb_connection_t</span> *c);
+</pre>
+ <div class="comp">
+ <div class="title">
+ Comparison Xlib/XCB
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XOpenDisplay ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_connect ()
+ </ul>
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XCloseDisplay ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_disconnect ()
+ </ul>
+ </div>
+ </div>
+ <br>
+ <li class="title"><a name="screen">Checking basic information about a connection</a>
+ <p>
+ Once we have opened a connection to an X server, we should check some
+ basic information about it: what screens it has, what is the
+ size (width and height) of the screen, how many colors it
+ supports (black and white ? grey scale ?, 256 colors ? more ?),
+ and so on. We get such information from the xcb_screen_t
+ structure:
+ </p>
+ <pre class="code">
+typedef struct {
+ xcb_window_t root;
+ xcb_colormap_t default_colormap;
+ uint32_t white_pixel;
+ uint32_t black_pixel;
+ uint32_t current_input_masks;
+ uint16_t width_in_pixels;
+ uint16_t height_in_pixels;
+ uint16_t width_in_millimeters;
+ uint16_t height_in_millimeters;
+ uint16_t min_installed_maps;
+ uint16_t max_installed_maps;
+ xcb_visualid_t root_visual;
+ uint8_t backing_stores;
+ uint8_t save_unders;
+ uint8_t root_depth;
+ uint8_t allowed_depths_len;
+} xcb_screen_t;
+</pre>
+ <p>
+ We could retrieve the first screen of the connection by using the
+ following function:
+ </p>
+ <pre class="code">
+xcb_screen_iterator_t xcb_setup_roots_iterator (xcb_setup_t *R);
+</pre>
+ <p>
+ Here is a small program that shows how to use this function:
+ </p>
+ <pre class="code">
+#include <stdio.h>
+
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ int screen_nbr;
+ xcb_screen_iterator_t iter;
+
+ /* Open the connection to the X server. Use the DISPLAY environment variable */
+ c = xcb_connect (NULL, &screen_nbr);
+
+ /* Get the screen #screen_nbr */
+ iter = xcb_setup_roots_iterator (xcb_get_setup (c));
+ for (; iter.rem; --screen_nbr, xcb_screen_next (&iter))
+ if (screen_nbr == 0) {
+ screen = iter.data;
+ break;
+ }
+
+ printf ("\n");
+ printf ("Informations of screen %ld:\n", screen->root);
+ printf (" width.........: %d\n", screen->width_in_pixels);
+ printf (" height........: %d\n", screen->height_in_pixels);
+ printf (" white pixel...: %ld\n", screen->white_pixel);
+ printf (" black pixel...: %ld\n", screen->black_pixel);
+ printf ("\n");
+
+ return 0;
+}
+</pre>
+ <li class="title"><a name="helloworld">Creating a basic window - the "hello world" program</a>
+ <p>
+ After we got some basic information about our screen, we can
+ create our first window. In the X Window System, a window is
+ characterized by an Id. So, in XCB, a window is of type:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_window_t;
+</pre>
+ <p>
+ We first ask for a new Id for our window, with this function:
+ </p>
+ <pre class="code">
+xcb_window_t xcb_generate_id(xcb_connection_t *c);
+</pre>
+ <p>
+ Then, XCB supplies the following function to create new windows:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_create_window (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */
+ uint8_t depth, /* Depth of the screen */
+ xcb_window_t wid, /* Id of the window */
+ xcb_window_t parent, /* Id of an existing window that should be the parent of the new window */
+ int16_t x, /* X position of the top-left corner of the window (in pixels) */
+ int16_t y, /* Y position of the top-left corner of the window (in pixels) */
+ uint16_t width, /* Width of the window (in pixels) */
+ uint16_t height, /* Height of the window (in pixels) */
+ uint16_t border_width, /* Width of the window's border (in pixels) */
+ uint16_t _class,
+ xcb_visualid_t visual,
+ uint32_t value_mask,
+ const uint32_t *value_list);
+</pre>
+ <p>
+ The fact that we created the window does not mean that it will
+ be drawn on screen. By default, newly created windows are not
+ mapped on the screen (they are invisible). In order to make our
+ window visible, we use the function <span class="code">xcb_map_window()</span>, whose
+ prototype is
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_map_window (xcb_connection_t *c,
+ xcb_window_t window);
+</pre>
+ <p>
+ Finally, here is a small program to create a window of size
+ 150x150 pixels, positioned at the top-left corner of the screen:
+ </p>
+ <pre class="code">
+#include <unistd.h> /* pause() */
+
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_window_t win;
+
+ /* Open the connection to the X server */
+ c = xcb_connect (NULL, NULL);
+
+ /* Get the first screen */
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* Ask for our window's Id */
+ win = xcb_generate_id(c);
+
+ /* Create the window */
+ xcb_create_window (c, /* Connection */
+ XCB_COPY_FROM_PARENT, /* depth (same as root)*/
+ win, /* window Id */
+ screen->root, /* parent window */
+ 0, 0, /* x, y */
+ 150, 150, /* width, height */
+ 10, /* border_width */
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */
+ screen->root_visual, /* visual */
+ 0, NULL); /* masks, not used yet */
+
+ /* Map the window on the screen */
+ xcb_map_window (c, win);
+
+ /* Make sure commands are sent before we pause, so window is shown */
+ xcb_flush (c);
+
+ pause (); /* hold client until Ctrl-C */
+
+ return 0;
+}
+</pre>
+ <p>
+ In this code, you see one more function - <span class="code">xcb_flush()</span>, not explained
+ yet. It is used to flush all the pending requests. More
+ precisely, there are 2 functions that do such things. The first
+ one is <span class="code">xcb_flush()</span>:
+ </p>
+ <pre class="code">
+int xcb_flush (xcb_connection_t *c);
+</pre>
+ <p>
+ This function flushes all pending requests to the X server (much
+ like the <span class="code">fflush()</span> function is used to
+ flush standard output). The second function is
+ <span class="code">xcb_aux_sync()</span>:
+ </p>
+ <pre class="code">
+int xcb_aux_sync (xcb_connection_t *c);
+</pre>
+ <p>
+ This functions also flushes all pending requests to the X
+ server, and then waits until the X server finishing processing
+ these requests. In a normal program, this will not be necessary
+ (we'll see why when we get to write a normal X program), but for
+ now, we put it there.
+ </p>
+ <p>
+ The window that is created by the above code has a non defined
+ background. This one can be set to a specific color,
+ thanks to the two last parameters of
+ <span class="code">xcb_create_window()</span>, which are not
+ described yet. See the subsections
+ <a href="#winconf">Configuring a window</a> or
+ <a href="#winconf">Registering for event types using event masks</a>
+ for examples on how to use these parameters. In addition, as no
+ events are handled, you have to make a Ctrl-C to interrupt the
+ program.
+ </p>
+ <p>
+ <b>TODO</b>: one should tell what these functions return and
+ about the generic error
+ </p>
+ <div class="comp">
+ <div class="title">
+ Comparison Xlib/XCB
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XCreateWindow ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_generate_id ()
+ <li>xcb_create_window ()
+ </ul>
+ </div>
+ </div>
+ <br>
+ <li class="title"><a name="drawing">Drawing in a window</a>
+ <p>
+ Drawing in a window can be done using various graphical
+ functions (drawing pixels, lines, rectangles, etc). In order to
+ draw in a window, we first need to define various general
+ drawing parameters (what line width to use, which color to draw
+ with, etc). This is done using a graphical context.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="allocgc">Allocating a Graphics Context</a>
+ <p>
+ As we said, a graphical context defines several attributes to
+ be used with the various drawing functions. For this, we
+ define a graphical context. We can use more than one graphical
+ context with a single window, in order to draw in multiple
+ styles (different colors, different line widths, etc). In XCB,
+ a Graphics Context is, as a window, characterized by an Id:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_gcontext_t;
+</pre>
+ <p>
+ We first ask the X server to attribute an Id to our graphic
+ context with this function:
+ </p>
+ <pre class="code">
+xcb_gcontext_t xcb_generate_id (xcb_connection_t *c);
+</pre>
+ <p>
+ Then, we set the attributes of the graphic context with this function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_create_gc (xcb_connection_t *c,
+ xcb_gcontext_t cid,
+ xcb_drawable_t drawable,
+ uint32_t value_mask,
+ const uint32_t *value_list);
+</pre>
+ <p>
+ We give now an example on how to allocate a graphic context
+ that specifies that each drawing function that uses it will
+ draw in foreground with a black color.
+ </p>
+ <pre class="code">
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_drawable_t win;
+ xcb_gcontext_t black;
+ uint32_t mask;
+ uint32_t value[1];
+
+ /* Open the connection to the X server and get the first screen */
+ c = xcb_connect (NULL, NULL);
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* Create a black graphic context for drawing in the foreground */
+ win = screen->root;
+ black = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND;
+ value[0] = screen->black_pixel;
+ xcb_create_gc (c, black, win, mask, value);
+
+ return 0;
+}
+</pre>
+ <p>
+ Note should be taken regarding the role of "value_mask" and
+ "value_list" in the prototype of <span class="code">xcb_create_gc()</span>. Since a
+ graphic context has many attributes, and since we often just
+ want to define a few of them, we need to be able to tell the
+ <span class="code">xcb_create_gc()</span> which attributes we
+ want to set. This is what the "value_mask" parameter is
+ for. We then use the "value_list" parameter to specify actual
+ values for the attribute we defined in "value_mask". Thus, for
+ each constant used in "value_list", we will use the matching
+ constant in "value_mask". In this case, we define a graphic
+ context with one attribute: when drawing (a point, a line,
+ etc), the foreground color will be black. The rest of the
+ attributes of this graphic context will be set to their
+ default values.
+ </p>
+ <p>
+ See the next Subsection for more details.
+ </p>
+ <div class="comp">
+ <div class="title">
+ Comparison Xlib/XCB
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XCreateGC ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_generate_id ()
+ <li>xcb_create_gc ()
+ </ul>
+ </div>
+ </div>
+ <br>
+ <li class="subtitle"><a name="changegc">Changing the attributes of a Graphics Context</a>
+ <p>
+ Once we have allocated a Graphic Context, we may need to
+ change its attributes (for example, changing the foreground
+ color we use to draw a line, or changing the attributes of the
+ font we use to display strings. See Subsections Drawing with a
+ color and
+ <a href="#assigningfont">Assigning a Font to a Graphic Context</a>).
+ This is done by using this function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_change_gc (xcb_connection_t *c, /* The XCB Connection */
+ xcb_gcontext_t gc, /* The Graphic Context */
+ uint32_t value_mask, /* Components of the Graphic Context that have to be set */
+ const uint32_t *value_list); /* Value as specified by value_mask */
+</pre>
+ <p>
+ The <span class="code">value_mask</span> parameter could take
+ any combination of these masks from the xcb_gc_t enumeration:
+ </p>
+ <ul>
+ <li>XCB_GC_FUNCTION
+ <li>XCB_GC_PLANE_MASK
+ <li>XCB_GC_FOREGROUND
+ <li>XCB_GC_BACKGROUND
+ <li>XCB_GC_LINE_WIDTH
+ <li>XCB_GC_LINE_STYLE
+ <li>XCB_GC_CAP_STYLE
+ <li>XCB_GC_JOIN_STYLE
+ <li>XCB_GC_FILL_STYLE
+ <li>XCB_GC_FILL_RULE
+ <li>XCB_GC_TILE
+ <li>XCB_GC_STIPPLE
+ <li>XCB_GC_TILE_STIPPLE_ORIGIN_X
+ <li>XCB_GC_TILE_STIPPLE_ORIGIN_Y
+ <li>XCB_GC_FONT
+ <li>XCB_GC_SUBWINDOW_MODE
+ <li>XCB_GC_GRAPHICS_EXPOSURES
+ <li>XCB_GC_CLIP_ORIGIN_X
+ <li>XCB_GC_CLIP_ORIGIN_Y
+ <li>XCB_GC_CLIP_MASK
+ <li>XCB_GC_DASH_OFFSET
+ <li>XCB_GC_DASH_LIST
+ <li>XCB_GC_ARC_MODE
+ </ul>
+ <p>
+ It is possible to set several attributes at the same
+ time (for example setting the attributes of a font and the
+ color which will be used to display a string), by OR'ing these
+ values in <span class="code">value_mask</span>. Then
+ <span class="code">value_list</span> has to be an array which
+ lists the value for the respective attributes. <b>These values
+ must be in the same order as masks listed above.</b> See Subsection
+ Drawing with a color to have an example.
+ </p>
+ <p>
+ <b>TODO</b>: set the links of the 3 subsections, once they will
+ be written :)
+ </p>
+ <p>
+ <b>TODO</b>: give an example which sets several attributes.
+ </p>
+ <li class="subtitle"><a name="drawingprim">Drawing primitives: point, line, box, circle,...</a>
+ <p>
+ After we have created a Graphic Context, we can draw on a
+ window using this Graphic Context, with a set of XCB
+ functions, collectively called "drawing primitives". Let see
+ how they are used.
+ </p>
+ <p>
+ To draw a point, or several points, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_point (xcb_connection_t *c, /* The connection to the X server */
+ uint8_t coordinate_mode, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */
+ xcb_drawable_t drawable, /* The drawable on which we want to draw the point(s) */
+ xcb_gcontext_t gc, /* The Graphic Context we use to draw the point(s) */
+ uint32_t points_len, /* The number of points */
+ const xcb_point_t *points); /* An array of points */
+</pre>
+ <p>
+ The <span class="code">coordinate_mode</span> parameter
+ specifies the coordinate mode. Available values are
+ </p>
+ <ul>
+ <li><span class="code">XCB_COORD_MODE_ORIGIN</span>
+ <li><span class="code">XCB_COORD_MODE_PREVIOUS</span>
+ </ul>
+ <p>
+ If XCB_COORD_MODE_PREVIOUS is used, then all points but the first one
+ are relative to the immediately previous point.
+ </p>
+ <p>
+ The <span class="code">xcb_point_t</span> type is just a
+ structure with two fields (the coordinates of the point):
+ </p>
+ <pre class="code">
+typedef struct {
+ int16_t x;
+ int16_t y;
+} xcb_point_t;
+</pre>
+ <p>
+ You could see an example in xpoints.c. <b>TODO</b> Set the link.
+ </p>
+ <p>
+ To draw a line, or a polygonal line, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_line (xcb_connection_t *c, /* The connection to the X server */
+ uint8_t coordinate_mode, /* Coordinate mode, usually set to XCB_COORD_MODE_ORIGIN */
+ xcb_drawable_t drawable, /* The drawable on which we want to draw the line(s) */
+ xcb_gcontext_t gc, /* The Graphic Context we use to draw the line(s) */
+ uint32_t points_len, /* The number of points in the polygonal line */
+ const xcb_point_t *points); /* An array of points */
+</pre>
+ <p>
+ This function will draw the line between the first and the
+ second points, then the line between the second and the third
+ points, and so on.
+ </p>
+ <p>
+ To draw a segment, or several segments, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_segment (xcb_connection_t *c, /* The connection to the X server */
+ xcb_drawable_t drawable, /* The drawable on which we want to draw the segment(s) */
+ xcb_gcontext_t gc, /* The Graphic Context we use to draw the segment(s) */
+ uint32_t segments_len, /* The number of segments */
+ const xcb_segment_t *segments); /* An array of segments */
+</pre>
+ <p>
+ The <span class="code">xcb_segment_t</span> type is just a
+ structure with four fields (the coordinates of the two points
+ that define the segment):
+ </p>
+ <pre class="code">
+typedef struct {
+ int16_t x1;
+ int16_t y1;
+ int16_t x2;
+ int16_t y2;
+} xcb_segment_t;
+</pre>
+ <p>
+ To draw a rectangle, or several rectangles, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_rectangle (xcb_connection_t *c, /* The connection to the X server */
+ xcb_drawable_t drawable, /* The drawable on which we want to draw the rectangle(s) */
+ xcb_gcontext_t gc, /* The Graphic Context we use to draw the rectangle(s) */
+ uint32_t rectangles_len, /* The number of rectangles */
+ const xcb_rectangle_t *rectangles); /* An array of rectangles */
+</pre>
+ <p>
+ The <span class="code">xcb_rectangle_t</span> type is just a
+ structure with four fields (the coordinates of the top-left
+ corner of the rectangle, and its width and height):
+ </p>
+ <pre class="code">
+typedef struct {
+ int16_t x;
+ int16_t y;
+ uint16_t width;
+ uint16_t height;
+} xcb_rectangle_t;
+</pre>
+ <!-- There's no coordinate_mode. Is it normal? -->
+ <!-- [iano] Yes, it's not in the protocol. -->
+ <p>
+ To draw an elliptical arc, or several elliptical arcs, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_arc (xcb_connection_t *c, /* The connection to the X server */
+ xcb_drawable_t drawable, /* The drawable on which we want to draw the arc(s) */
+ xcb_gcontext_t gc, /* The Graphic Context we use to draw the arc(s) */
+ uint32_t arcs_len, /* The number of arcs */
+ const xcb_arc_t *arcs); /* An array of arcs */
+</pre>
+ <p>
+ The <span class="code">xcb_arc_t</span> type is a structure with
+ six fields:
+ </p>
+ <pre class="code">
+typedef struct {
+ int16_t x; /* Top left x coordinate of the rectangle surrounding the ellipse */
+ int16_t y; /* Top left y coordinate of the rectangle surrounding the ellipse */
+ uint16_t width; /* Width of the rectangle surrounding the ellipse */
+ uint16_t height; /* Height of the rectangle surrounding the ellipse */
+ int16_t angle1; /* Angle at which the arc begins */
+ int16_t angle2; /* Angle at which the arc ends */
+} xcb_arc_t;
+</pre>
+ <div class="emph">
+ <p>
+ Note: the angles are expressed in units of 1/64 of a degree,
+ so to have an angle of 90 degrees, starting at 0,
+ <span class="code">angle1 = 0</span> and
+ <span class="code">angle2 = 90 << 6</span>. Positive angles
+ indicate counterclockwise motion, while negative angles
+ indicate clockwise motion.
+ </p>
+ </div>
+ <!-- I think that (x,y) should be the center of the
+ ellipse, and (width, height) the radius. It's more logical. -->
+ <!-- iano: Yes, and I bet some toolkits do that.
+ But the protocol (and many other graphics APIs) define arcs
+ by bounding rectangles. -->
+ <p>
+ The corresponding function which fill inside the geometrical
+ object are listed below, without further explanation, as they
+ are used as the above functions.
+ </p>
+ <p>
+ To Fill a polygon defined by the points given as arguments ,
+ we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_fill_poly (xcb_connection_t *c,
+ xcb_drawable_t drawable,
+ xcb_gcontext_t gc,
+ uint8_t shape,
+ uint8_t coordinate_mode,
+ uint32_t points_len,
+ const xcb_point_t *points);
+</pre>
+ <p>
+ The <span class="code">shape</span> parameter specifies a
+ shape that helps the server to improve performance. Available
+ values are
+ </p>
+ <ul>
+ <li><span class="code">XCB_POLY_SHAPE_COMPLEX</span>
+ <li><span class="code">XCB_POLY_SHAPE_NONCONVEX</span>
+ <li><span class="code">XCB_POLY_SHAPE_CONVEX</span>
+ </ul>
+ <p>
+ To fill one or several rectangles, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_fill_rectangle (xcb_connection_t *c,
+ xcb_drawable_t drawable,
+ xcb_gcontext_t gc,
+ uint32_t rectangles_len,
+ const xcb_rectangle_t *rectangles);
+</pre>
+ <p>
+ To fill one or several arcs, we use
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_poly_fill_arc (xcb_connection_t *c,
+ xcb_drawable_t drawable,
+ xcb_gcontext_t gc,
+ uint32_t arcs_len,
+ const xcb_arc_t *arcs);
+</pre>
+ <br>
+ <a name="points.c"></a>
+ <p>
+ To illustrate these functions, here is an example that draws
+ four points, a polygonal line, two segments, two rectangles
+ and two arcs. Remark that we use events for the first time, as
+ an introduction to the next section.
+ </p>
+ <p>
+ <b>TODO:</b> Use screen->root_depth for depth parameter.
+ </p>
+ <pre class="code">
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_drawable_t win;
+ xcb_gcontext_t foreground;
+ xcb_generic_event_t *e;
+ uint32_t mask = 0;
+ uint32_t values[2];
+
+ /* geometric objects */
+ xcb_point_t points[] = {
+ {10, 10},
+ {10, 20},
+ {20, 10},
+ {20, 20}};
+
+ xcb_point_t polyline[] = {
+ {50, 10},
+ { 5, 20}, /* rest of points are relative */
+ {25,-20},
+ {10, 10}};
+
+ xcb_segment_t segments[] = {
+ {100, 10, 140, 30},
+ {110, 25, 130, 60}};
+
+ xcb_rectangle_t rectangles[] = {
+ { 10, 50, 40, 20},
+ { 80, 50, 10, 40}};
+
+ xcb_arc_t arcs[] = {
+ {10, 100, 60, 40, 0, 90 << 6},
+ {90, 100, 55, 40, 0, 270 << 6}};
+
+ /* Open the connection to the X server */
+ c = xcb_connect (NULL, NULL);
+
+ /* Get the first screen */
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* Create black (foreground) graphic context */
+ win = screen->root;
+
+ foreground = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND | XCB_GC_GRAPHICS_EXPOSURES;
+ values[0] = screen->black_pixel;
+ values[1] = 0;
+ xcb_create_gc (c, foreground, win, mask, values);
+
+ /* Ask for our window's Id */
+ win = xcb_generate_id(c);
+
+ /* Create the window */
+ mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
+ values[0] = screen->white_pixel;
+ values[1] = XCB_EVENT_MASK_EXPOSURE;
+ xcb_create_window (c, /* Connection */
+ XCB_COPY_FROM_PARENT, /* depth */
+ win, /* window Id */
+ screen->root, /* parent window */
+ 0, 0, /* x, y */
+ 150, 150, /* width, height */
+ 10, /* border_width */
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */
+ screen->root_visual, /* visual */
+ mask, values); /* masks */
+
+ /* Map the window on the screen */
+ xcb_map_window (c, win);
+
+
+ /* We flush the request */
+ xcb_flush (c);
+
+ while ((e = xcb_wait_for_event (c))) {
+ switch (e->response_type & ~0x80) {
+ case XCB_EXPOSE: {
+ /* We draw the points */
+ xcb_poly_point (c, XCB_COORD_MODE_ORIGIN, win, foreground, 4, points);
+
+ /* We draw the polygonal line */
+ xcb_poly_line (c, XCB_COORD_MODE_PREVIOUS, win, foreground, 4, polyline);
+
+ /* We draw the segements */
+ xcb_poly_segment (c, win, foreground, 2, segments);
+
+ /* We draw the rectangles */
+ xcb_poly_rectangle (c, win, foreground, 2, rectangles);
+
+ /* We draw the arcs */
+ xcb_poly_arc (c, win, foreground, 2, arcs);
+
+ /* We flush the request */
+ xcb_flush (c);
+
+ break;
+ }
+ default: {
+ /* Unknown event type, ignore it */
+ break;
+ }
+ }
+ /* Free the Generic Event */
+ free (e);
+ }
+
+ return 0;
+}
+</pre>
+ </ol>
+ <li class="title"><a name="xevents">X Events</a>
+ <p>
+ In an X program, everything is driven by events. Event painting
+ on the screen is sometimes done as a response to an event (an
+ <span class="code">Expose</span> event). If part of a program's
+ window that was hidden, gets exposed (e.g. the window was raised
+ above other widows), the X server will send an "expose" event to
+ let the program know it should repaint that part of the
+ window. User input (key presses, mouse movement, etc) is also
+ received as a set of events.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="register">Registering for event types using event masks</a>
+ <p>
+ During the creation of a window, you should give it what kind
+ of events it wishes to receive. Thus, you may register for
+ various mouse (also called pointer) events, keyboard events,
+ expose events, and so on. This is done for optimizing the
+ server-to-client connection (i.e. why send a program (that
+ might even be running at the other side of the globe) an event
+ it is not interested in ?)
+ </p>
+ <p>
+ In XCB, you use the "value_mask" and "value_list" data in the
+ <span class="code">xcb_create_window()</span> function to
+ register for events. Here is how we register for
+ <span class="code">Expose</span> event when creating a window:
+ </p>
+ <pre class="code">
+ mask = XCB_CW_EVENT_MASK;
+ valwin[0] = XCB_EVENT_MASK_EXPOSURE;
+ win = xcb_generate_id (c);
+ xcb_create_window (c, depth, win, root->root,
+ 0, 0, 150, 150, 10,
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, root->root_visual,
+ mask, valwin);
+</pre>
+ <p>
+ <span class="code">XCB_EVENT_MASK_EXPOSURE</span> is a constant defined
+ in the xcb_event_mask_t enumeration in the "xproto.h" header file. If we wanted to register for several
+ event types, we can logically "or" them, as follows:
+ </p>
+ <pre class="code">
+ mask = XCB_CW_EVENT_MASK;
+ valwin[0] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS;
+ win = xcb_generate_id (c);
+ xcb_create_window (c, depth, win, root->root,
+ 0, 0, 150, 150, 10,
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, root->root_visual,
+ mask, valwin);
+</pre>
+ <p>
+ This registers for <span class="code">Expose</span> events as
+ well as for mouse button presses inside the created
+ window. You should note that a mask may represent several
+ event sub-types.
+ </p>
+ <p>
+ The values that a mask could take are given
+ by the <span class="code">xcb_cw_t</span> enumeration:
+ </p>
+ <pre class="code">
+typedef enum {
+ XCB_CW_BACK_PIXMAP = 1L<<0,
+ XCB_CW_BACK_PIXEL = 1L<<1,
+ XCB_CW_BORDER_PIXMAP = 1L<<2,
+ XCB_CW_BORDER_PIXEL = 1L<<3,
+ XCB_CW_BIT_GRAVITY = 1L<<4,
+ XCB_CW_WIN_GRAVITY = 1L<<5,
+ XCB_CW_BACKING_STORE = 1L<<6,
+ XCB_CW_BACKING_PLANES = 1L<<7,
+ XCB_CW_BACKING_PIXEL = 1L<<8,
+ XCB_CW_OVERRIDE_REDIRECT = 1L<<9,
+ XCB_CW_SAVE_UNDER = 1L<<10,
+ XCB_CW_EVENT_MASK = 1L<<11,
+ XCB_CW_DONT_PROPAGATE = 1L<<12,
+ XCB_CW_COLORMAP = 1L<<13,
+ XCB_CW_CURSOR = 1L<<14
+} xcb_cw_t;
+</pre>
+ <div class="emph">
+ <p>Note: we must be careful when setting the values of the valwin
+ parameter, as they have to follow the order the
+ <span class="code">xcb_cw_t</span> enumeration. Here is an
+ example:
+ </p>
+ </div>
+ <pre class="code">
+ mask = XCB_CW_EVENT_MASK | XCB_CW_BACK_PIXMAP;
+ valwin[0] = XCB_NONE; /* for XCB_CW_BACK_PIXMAP (whose value is 1) */
+ valwin[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS; /* for XCB_CW_EVENT_MASK, whose value (2048) */
+ /* is greater than the one of XCB_CW_BACK_PIXMAP */
+</pre>
+ <p>
+ If the window has already been created, we can use the
+ <span class="code">xcb_change_window_attributes()</span> function to set
+ the events that the window will receive. The subsection
+ <a href="#winconf">Configuring a window</a> shows its
+ prototype. As an example, here is a piece of code that
+ configures the window to receive the
+ <span class="code">Expose</span> and
+ <span class="code">ButtonPress</span> events:
+ </p>
+ <pre class="code">
+const static uint32_t values[] = { XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS };
+
+/* The connection c and the window win are supposed to be defined */
+
+xcb_change_window_attributes (c, win, XCB_CW_EVENT_MASK, values);
+</pre>
+ <div class="emph">
+ <p>
+ Note: A common bug programmers do is adding code to handle new
+ event types in their program, while forgetting to add the
+ masks for these events in the creation of the window. Such a
+ programmer then should sit down for hours debugging his
+ program, wondering "Why doesn't my program notice that I
+ released the button?", only to find that they registered for
+ button press events but not for button release events.
+ </p>
+ </div>
+ <li class="subtitle"><a name="loop">Receiving events: writing the events loop</a>
+ <p>
+ After we have registered for the event types we are interested
+ in, we need to enter a loop of receiving events and handling
+ them. There are two ways to receive events: a blocking way and
+ a non-blocking way:
+ </p>
+ <ul>
+ <li>
+ <span class="code">xcb_wait_for_event (xcb_connection_t *c)</span>
+ is the blocking way. It waits (so blocks...) until an event is
+ queued in the X server. Then it retrieves it into a newly
+ allocated structure (it dequeues it from the queue) and returns
+ it. This structure has to be freed. The function returns
+ <span class="code">NULL</span> if an error occurs.
+
+ <br>
+ <li>
+ <span class="code">xcb_poll_for_event (xcb_connection_t *c, int
+ *error)</span> is the non-blocking way. It looks at the event
+ queue and returns (and dequeues too) an existing event into
+ a newly allocated structure. This structure has to be
+ freed. It returns <span class="code">NULL</span> if there is
+ no event. If an error occurs, the parameter <span
+ class="code">error</span> will be filled with the error
+ status.
+ </ul>
+ <p>
+ There are various ways to write such a loop. We present two
+ ways to write such a loop, with the two functions above. The
+ first one uses <span class="code">xcb_wait_for_event_t</span>, which
+ is similar to an event Xlib loop using only <span
+ class="code">XNextEvent</span>:
+ </p>
+ <pre class="code">
+ xcb_generic_event_t *e;
+
+ while ((e = xcb_wait_for_event (c))) {
+ switch (e->response_type & ~0x80) {
+ case XCB_EXPOSE: {
+ /* Handle the Expose event type */
+ xcb_expose_event_t *ev = (xcb_expose_event_t *)e;
+
+ /* ... */
+
+ break;
+ }
+ case XCB_BUTTON_PRESS: {
+ /* Handle the ButtonPress event type */
+ xcb_button_press_event_t *ev = (xcb_button_press_event_t *)e;
+
+ /* ... */
+
+ break;
+ }
+ default: {
+ /* Unknown event type, ignore it */
+ break;
+ }
+ }
+ /* Free the Generic Event */
+ free (e);
+ }
+</pre>
+ <p>
+ You will certainly want to use <span
+ class="code">xcb_poll_for_event(xcb_connection_t *c, int
+ *error)</span> if, in Xlib, you use <span
+ class="code">XPending</span> or
+ <span class="code">XCheckMaskEvent</span>:
+ </p>
+ <pre class="code">
+ while (XPending (display)) {
+ XEvent ev;
+
+ XNextEvent(d, &ev);
+
+ /* Manage your event */
+ }
+</pre>
+ <p>
+ Such a loop in XCB looks like:
+ </p>
+ <pre class="code">
+ xcb_generic_event_t *ev;
+
+ while ((ev = xcb_poll_for_event (conn, 0))) {
+ /* Manage your event */
+ }
+</pre>
+ <p>
+ The events are managed in the same way as with <span
+ class="code">xcb_wait_for_event_t</span>.
+ Obviously, we will need to give the user some way of
+ terminating the program. This is usually done by handling a
+ special "quit" event, as we will soon see.
+ </p>
+ <div class="comp">
+ <div class="title">
+ Comparison Xlib/XCB
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XNextEvent ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_wait_for_event ()
+ </ul>
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XPending ()
+ <li>XCheckMaskEvent ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_poll_for_event ()
+ </ul>
+ </div>
+ </div>
+ <br>
+ <li class="subtitle"><a name="expose">Expose events</a>
+ <p>
+ The <span class="code">Expose</span> event is one of the most
+ basic (and most used) events an application may receive. It
+ will be sent to us in one of several cases:
+ </p>
+ <ul>
+ <li>A window that covered part of our window has moved
+ away, exposing part (or all) of our window.
+ <li>Our window was raised above other windows.
+ <li>Our window mapped for the first time.
+ <li>Our window was de-iconified.
+ </ul>
+ <p>
+ You should note the implicit assumption hidden here: the
+ contents of our window is lost when it is being obscured
+ (covered) by either windows. One may wonder why the X server
+ does not save this contents. The answer is: to save
+ memory. After all, the number of windows on a display at a
+ given time may be very large, and storing the contents of all
+ of them might require a lot of memory. Actually, there is a
+ way to tell the X server to store the contents of a window in
+ special cases, as we will see later.
+ </p>
+ <p>
+ When we get an <span class="code">Expose</span> event, we
+ should take the event's data from the members of the following
+ structure:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type; /* The type of the event, here it is XCB_EXPOSE */
+ uint8_t pad0;
+ uint16_t sequence;
+ xcb_window_t window; /* The Id of the window that receives the event (in case */
+ /* our application registered for events on several windows */
+ uint16_t x; /* The x coordinate of the top-left part of the window that needs to be redrawn */
+ uint16_t y; /* The y coordinate of the top-left part of the window that needs to be redrawn */
+ uint16_t width; /* The width of the part of the window that needs to be redrawn */
+ uint16_t height; /* The height of the part of the window that needs to be redrawn */
+ uint16_t count;
+} xcb_expose_event_t;
+</pre>
+ <li class="subtitle"><a name="userinput">Getting user input</a>
+ <p>
+ User input traditionally comes from two sources: the mouse
+ and the keyboard. Various event types exist to notify us of
+ user input (a key being presses on the keyboard, a key being
+ released on the keyboard, the mouse moving over our window,
+ the mouse entering (or leaving) our window, and so on.
+ </p>
+ <ol>
+ <li class="subsubtitle"><a name="mousepressrelease">Mouse button press and release events</a>
+ <p>
+ The first event type we will deal with is a mouse
+ button-press (or button-release) event in our window. In
+ order to register to such an event type, we should add one
+ (or more) of the following masks when we create our window:
+ </p>
+ <ul>
+ <li><span class="code">XCB_EVENT_MASK_BUTTON_PRESS</span>: notify us
+ of any button that was pressed in one of our windows.
+ <li><span class="code">XCB_EVENT_MASK_BUTTON_RELEASE</span>: notify us
+ of any button that was released in one of our windows.
+ </ul>
+ <p>
+ The structure to be checked for in our events loop is the
+ same for these two events, and is the following:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type; /* The type of the event, here it is xcb_button_press_event_t or xcb_button_release_event_t */
+ xcb_button_t detail;
+ uint16_t sequence;
+ xcb_timestamp_t time; /* Time, in milliseconds the event took place in */
+ xcb_window_t root;
+ xcb_window_t event;
+ xcb_window_t child;
+ int16_t root_x;
+ int16_t root_y;
+ int16_t event_x; /* The x coordinate where the mouse has been pressed in the window */
+ int16_t event_y; /* The y coordinate where the mouse has been pressed in the window */
+ uint16_t state; /* A mask of the buttons (or keys) during the event */
+ uint8_t same_screen;
+} xcb_button_press_event_t;
+
+typedef xcb_button_press_event_t xcb_button_release_event_t;
+</pre>
+ <p>
+ The <span class="code">time</span> field may be used to calculate "double-click"
+ situations by an application (e.g. if the mouse button was
+ clicked two times in a duration shorter than a given amount
+ of time, assume this was a double click).
+ </p>
+ <p>
+ The <span class="code">state</span> field is a mask of the buttons held down during
+ the event. It is a bitwise OR of any of the following (from the xcb_button_mask_t and
+ xcb_mod_mask_t enumerations):
+ </p>
+ <ul>
+ <li><span class="code">XCB_BUTTON_MASK_1</span>
+ <li><span class="code">XCB_BUTTON_MASK_2</span>
+ <li><span class="code">XCB_BUTTON_MASK_3</span>
+ <li><span class="code">XCB_BUTTON_MASK_4</span>
+ <li><span class="code">XCB_BUTTON_MASK_5</span>
+ <li><span class="code">XCB_MOD_MASK_SHIFT</span>
+ <li><span class="code">XCB_MOD_MASK_LOCK</span>
+ <li><span class="code">XCB_MOD_MASK_CONTROL</span>
+ <li><span class="code">XCB_MOD_MASK_1</span>
+ <li><span class="code">XCB_MOD_MASK_2</span>
+ <li><span class="code">XCB_MOD_MASK_3</span>
+ <li><span class="code">XCB_MOD_MASK_4</span>
+ <li><span class="code">XCB_MOD_MASK_5</span>
+ </ul>
+ <p>
+ Their names are self explanatory, where the first 5 refer to
+ the mouse buttons that are being pressed, while the rest
+ refer to various "special keys" that are being pressed (Mod1
+ is usually the 'Alt' key or the 'Meta' key).
+ </p>
+ <p>
+ <b>TODO:</b> Problem: it seems that the state does not
+ change when clicking with various buttons.
+ </p>
+ <li class="subsubtitle"><a name="mousemvnt">Mouse movement events</a>
+ <p>
+ Similar to mouse button press and release events, we also
+ can be notified of various mouse movement events. These can
+ be split into two families. One is of mouse pointer
+ movement while no buttons are pressed, and the second is a
+ mouse pointer motion while one (or more) of the buttons are
+ pressed (this is sometimes called "a mouse drag operation",
+ or just "dragging"). The following event masks may be added
+ during the creation of our window:
+ </p>
+ <ul>
+ <li><span class="code">XCB_EVENT_MASK_POINTER_MOTION</span>: events of
+ the pointer moving in one of the windows controlled by our
+ application, while no mouse button is held pressed.
+ <li><span class="code">XCB_EVENT_MASK_BUTTON_MOTION</span>: Events of
+ the pointer moving while one or more of the mouse buttons
+ is held pressed.
+ <li><span class="code">XCB_EVENT_MASK_BUTTON_1_MOTION</span>: same as
+ <span class="code">XCB_EVENT_MASK_BUTTON_MOTION</span>, but only when
+ the 1st mouse button is held pressed.
+ <li><span class="code">XCB_EVENT_MASK_BUTTON_2_MOTION</span>,
+ <span class="code">XCB_EVENT_MASK_BUTTON_3_MOTION</span>,
+ <span class="code">XCB_EVENT_MASK_BUTTON_4_MOTION</span>,
+ <span class="code">XCB_EVENT_MASK_BUTTON_5_MOTION</span>: same as
+ <span class="code">XCB_EVENT_MASK_BUTTON_1_MOTION</span>, but
+ respectively for 2nd, 3rd, 4th and 5th mouse button.
+ </ul>
+ <p>
+ The structure to be checked for in our events loop is the
+ same for these events, and is the following:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type; /* The type of the event */
+ uint8_t detail;
+ uint16_t sequence;
+ xcb_timestamp_t time; /* Time, in milliseconds the event took place in */
+ xcb_window_t root;
+ xcb_window_t event;
+ xcb_window_t child;
+ int16_t root_x;
+ int16_t root_y;
+ int16_t event_x; /* The x coordinate of the mouse when the event was generated */
+ int16_t event_y; /* The y coordinate of the mouse when the event was generated */
+ uint16_t state; /* A mask of the buttons (or keys) during the event */
+ uint8_t same_screen;
+} xcb_motion_notify_event_t;
+</pre>
+ <li class="subsubtitle"><a name="mouseenter">Mouse pointer enter and leave events</a>
+ <p>
+ Another type of event that applications might be interested
+ in, is a mouse pointer entering a window the program
+ controls, or leaving such a window. Some programs use these
+ events to show the user that the application is now in
+ focus. In order to register for such an event type, we
+ should add one (or more) of the following masks when we
+ create our window:
+ </p>
+ <ul>
+ <li><span class="code">xcb_event_enter_window_t</span>: notify us
+ when the mouse pointer enters any of our controlled
+ windows.
+ <li><span class="code">xcb_event_leave_window_t</span>: notify us
+ when the mouse pointer leaves any of our controlled
+ windows.
+ </ul>
+ <p>
+ The structure to be checked for in our events loop is the
+ same for these two events, and is the following:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type; /* The type of the event */
+ uint8_t detail;
+ uint16_t sequence;
+ xcb_timestamp_t time; /* Time, in milliseconds the event took place in */
+ xcb_window_t root;
+ xcb_window_t event;
+ xcb_window_t child;
+ int16_t root_x;
+ int16_t root_y;
+ int16_t event_x; /* The x coordinate of the mouse when the event was generated */
+ int16_t event_y; /* The y coordinate of the mouse when the event was generated */
+ uint16_t state; /* A mask of the buttons (or keys) during the event */
+ uint8_t mode; /* The number of mouse button that was clicked */
+ uint8_t same_screen_focus;
+} xcb_enter_notify_event_t;
+
+typedef xcb_enter_notify_event_t xcb_leave_notify_event_t;
+</pre>
+ <li class="subsubtitle"><a name="focus">The keyboard focus</a>
+ <p>
+ There may be many windows on a screen, but only a single
+ keyboard attached to them. How does the X server then know
+ which window should be sent a given keyboard input ? This is
+ done using the keyboard focus. Only a single window on the
+ screen may have the keyboard focus at a given time. There
+ is a XCB function that allows a program to set the keyboard
+ focus to a given window. The user can usually set the
+ keyboard focus using the window manager (often by clicking
+ on the title bar of the desired window). Once our window
+ has the keyboard focus, every key press or key release will
+ cause an event to be sent to our program (if it regsitered
+ for these event types...).
+ </p>
+ <li class="subsubtitle"><a name="keypress">Keyboard press and release events</a>
+ <p>
+ If a window controlled by our program currently holds the
+ keyboard focus, it can receive key press and key release
+ events. So, we should add one (or more) of the following
+ masks when we create our window:
+ </p>
+ <ul>
+ <li><span class="code">XCB_EVENT_MASK_KEY_PRESS</span>: notify us when
+ a key was pressed while any of our controlled windows had
+ the keyboard focus.
+ <li><span class="code">XCB_EVENT_MASK_KEY_RELEASE</span>: notify us
+ when a key was released while any of our controlled
+ windows had the keyboard focus.
+ </ul>
+ <p>
+ The structure to be checked for in our events loop is the
+ same for these two events, and is the following:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type; /* The type of the event */
+ xcb_keycode_t detail;
+ uint16_t sequence;
+ xcb_timestamp_t time; /* Time, in milliseconds the event took place in */
+ xcb_window_t root;
+ xcb_window_t event;
+ xcb_window_t child;
+ int16_t root_x;
+ int16_t root_y;
+ int16_t event_x;
+ int16_t event_y;
+ uint16_t state;
+ uint8_t same_screen;
+} xcb_key_press_event_t;
+
+typedef xcb_key_press_event_t xcb_key_release_event_t;
+</pre>
+ <p>
+ The <span class="code">detail</span> field refers to the
+ physical key on the keyboard.
+ </p>
+ <p>
+ <b>TODO:</b> Talk about getting the ASCII code from the key code.
+ </p>
+ </ol>
+ <li class="subtitle"><a name="eventex">X events: a complete example</a>
+ <p>
+ As an example for handling events, we show a program that
+ creates a window, enters an events loop and checks for all the
+ events described above, and writes on the terminal the relevant
+ characteristics of the event. With this code, it should be
+ easy to add drawing operations, like those which have been
+ described above.
+ </p>
+ <pre class="code">
+#include <stdlib.h>
+#include <stdio.h>
+
+#include <xcb/xcb.h>
+
+void
+print_modifiers (uint32_t mask)
+{
+ const char **mod, *mods[] = {
+ "Shift", "Lock", "Ctrl", "Alt",
+ "Mod2", "Mod3", "Mod4", "Mod5",
+ "Button1", "Button2", "Button3", "Button4", "Button5"
+ };
+ printf ("Modifier mask: ");
+ for (mod = mods ; mask; mask >>= 1, mod++)
+ if (mask & 1)
+ printf(*mod);
+ putchar ('\n');
+}
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_window_t win;
+ xcb_generic_event_t *e;
+ uint32_t mask = 0;
+ uint32_t values[2];
+
+ /* Open the connection to the X server */
+ c = xcb_connect (NULL, NULL);
+
+ /* Get the first screen */
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* Ask for our window's Id */
+ win = xcb_generate_id (c);
+
+ /* Create the window */
+ mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
+ values[0] = screen->white_pixel;
+ values[1] = XCB_EVENT_MASK_EXPOSURE | XCB_EVENT_MASK_BUTTON_PRESS |
+ XCB_EVENT_MASK_BUTTON_RELEASE | XCB_EVENT_MASK_POINTER_MOTION |
+ XCB_EVENT_MASK_ENTER_WINDOW | XCB_EVENT_MASK_LEAVE_WINDOW |
+ XCB_EVENT_MASK_KEY_PRESS | XCB_EVENT_MASK_KEY_RELEASE;
+ xcb_create_window (c, /* Connection */
+ 0, /* depth */
+ win, /* window Id */
+ screen->root, /* parent window */
+ 0, 0, /* x, y */
+ 150, 150, /* width, height */
+ 10, /* border_width */
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */
+ screen->root_visual, /* visual */
+ mask, values); /* masks */
+
+ /* Map the window on the screen */
+ xcb_map_window (c, win);
+
+ xcb_flush (c);
+
+ while ((e = xcb_wait_for_event (c))) {
+ switch (e->response_type & ~0x80) {
+ case XCB_EXPOSE: {
+ xcb_expose_event_t *ev = (xcb_expose_event_t *)e;
+
+ printf ("Window %ld exposed. Region to be redrawn at location (%d,%d), with dimension (%d,%d)\n",
+ ev->window, ev->x, ev->y, ev->width, ev->height);
+ break;
+ }
+ case XCB_BUTTON_PRESS: {
+ xcb_button_press_event_t *ev = (xcb_button_press_event_t *)e;
+ print_modifiers(ev->state);
+
+ switch (ev->detail) {
+ case 4:
+ printf ("Wheel Button up in window %ld, at coordinates (%d,%d)\n",
+ ev->event, ev->event_x, ev->event_y);
+ break;
+ case 5:
+ printf ("Wheel Button down in window %ld, at coordinates (%d,%d)\n",
+ ev->event, ev->event_x, ev->event_y);
+ break;
+ default:
+ printf ("Button %d pressed in window %ld, at coordinates (%d,%d)\n",
+ ev->detail, ev->event, ev->event_x, ev->event_y);
+ }
+ break;
+ }
+ case XCB_BUTTON_RELEASE: {
+ xcb_button_release_event_t *ev = (xcb_button_release_event_t *)e;
+ print_modifiers(ev->state);
+
+ printf ("Button %d released in window %ld, at coordinates (%d,%d)\n",
+ ev->detail, ev->event, ev->event_x, ev->event_y);
+ break;
+ }
+ case XCB_MOTION_NOTIFY: {
+ xcb_motion_notify_event_t *ev = (xcb_motion_notify_event_t *)e;
+
+ printf ("Mouse moved in window %ld, at coordinates (%d,%d)\n",
+ ev->event, ev->event_x, ev->event_y);
+ break;
+ }
+ case XCB_ENTER_NOTIFY: {
+ xcb_enter_notify_event_t *ev = (xcb_enter_notify_event_t *)e;
+
+ printf ("Mouse entered window %ld, at coordinates (%d,%d)\n",
+ ev->event, ev->event_x, ev->event_y);
+ break;
+ }
+ case XCB_LEAVE_NOTIFY: {
+ xcb_leave_notify_event_t *ev = (xcb_leave_notify_event_t *)e;
+
+ printf ("Mouse left window %ld, at coordinates (%d,%d)\n",
+ ev->event, ev->event_x, ev->event_y);
+ break;
+ }
+ case XCB_KEY_PRESS: {
+ xcb_key_press_event_t *ev = (xcb_key_press_event_t *)e;
+ print_modifiers(ev->state);
+
+ printf ("Key pressed in window %ld\n",
+ ev->event);
+ break;
+ }
+ case XCB_KEY_RELEASE: {
+ xcb_key_release_event_t *ev = (xcb_key_release_event_t *)e;
+ print_modifiers(ev->state);
+
+ printf ("Key released in window %ld\n",
+ ev->event);
+ break;
+ }
+ default:
+ /* Unknown event type, ignore it */
+ printf("Unknown event: %d\n", e->response_type);
+ break;
+ }
+ /* Free the Generic Event */
+ free (e);
+ }
+
+ return 0;
+}
+</pre>
+ </ol>
+ <li class="title"><a name="font">Handling text and fonts</a>
+ <p>
+ Besides drawing graphics on a window, we often want to draw
+ text. Text strings have two major properties: the characters to
+ be drawn and the font with which they are drawn. In order to
+ draw text, we need to first request the X server to load a
+ font. We then assign a font to a Graphic Context, and finally, we
+ draw the text in a window, using the Graphic Context.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="fontstruct">The Font structure</a>
+ <p>
+ In order to support flexible fonts, a font type is
+ defined. You know what ? It's an Id:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_font_t;
+</pre>
+ <p>
+ It is used to contain information about a font, and is passed
+ to several functions that handle fonts selection and text drawing.
+ We ask the X server to attribute an Id to our font with the
+ function:
+ </p>
+ <pre class="code">
+xcb_font_t xcb_generate_id (xcb_connection_t *c);
+</pre>
+ <br>
+ <li class="subtitle"><a name="openingfont">Opening a Font</a>
+ <p>
+ To open a font, we use the following function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_open_font (xcb_connection_t *c,
+ xcb_font_t fid,
+ uint16_t name_len,
+ const char *name);
+</pre>
+ <p>
+ The <span class="code">fid</span> parameter is the font Id
+ defined by <span class="code">xcb_generate_id()</span> (see
+ above). The <span class="code">name</span> parameter is the
+ name of the font you want to open. Use the command
+ <span class="code">xlsfonts</span> in a terminal to know which
+ are the fonts available on your computer. The parameter
+ <span class="code">name_len</span> is the length of the name
+ of the font (given by <span class="code">strlen()</span>).
+ </p>
+ <li class="subtitle"><a name="assigningfont">Assigning a Font to a Graphic Context</a>
+ <p>
+ Once a font is opened, you have to create a Graphic Context
+ that will contain the informations about the color of the
+ foreground and the background used when you draw a text in a
+ Drawable. Here is an exemple of a Graphic Context that will
+ allow us to draw an opened font with a black foreground and a
+ white background:
+ </p>
+ <pre class="code">
+ /*
+ * c is the connection
+ * screen is the screen where the window is displayed
+ * window is the window in which we will draw the text
+ * font is the opened font
+ */
+
+ uint32_t value_list[3];
+ xcb_gcontext_t gc;
+ uint32_t mask;
+
+ gc = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
+ value_list[0] = screen->black_pixel;
+ value_list[1] = screen->white_pixel;
+ value_list[2] = font;
+ xcb_create_gc (c, gc, window, mask, value_list);
+
+ /* The font is not needed anymore, so we close it */
+ xcb_close_font (c, font);
+</pre>
+ <li class="subtitle"><a name="drawingtext">Drawing text in a drawable</a>
+ <p>
+ To draw a text in a drawable, we use the following function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_image_text_8 (xcb_connection_t *c,
+ uint8_t string_len,
+ xcb_drawable_t drawable,
+ xcb_gcontext_t gc,
+ int16_t x,
+ int16_t y,
+ const char *string);
+</pre>
+ <p>
+ The <span class="code">string</span> parameter is the text to
+ draw. The location of the drawing is given by the parameters
+ <span class="code">x</span> and <span class="code">y</span>.
+ The base line of the text is exactly the parameter
+ <span class="code">y</span>.
+ </p>
+ <li class="subtitle"><a name="fontcompleteexample">Complete example</a>
+ <p>
+ This example draw a text at 10 pixels (for the base line) of
+ the bottom of a window. Pressing the Esc key exits the program.
+ </p>
+ <pre class="code">
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <xcb/xcb.h>
+
+#define WIDTH 300
+#define HEIGHT 100
+
+
+
+static xcb_gc_t gc_font_get (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ const char *font_name);
+
+static void text_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label);
+
+static void
+text_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label)
+{
+ xcb_void_cookie_t cookie_gc;
+ xcb_void_cookie_t cookie_text;
+ xcb_generic_error_t *error;
+ xcb_gcontext_t gc;
+ uint8_t length;
+
+ length = strlen (label);
+
+ gc = gc_font_get(c, screen, window, "7x13");
+
+ cookie_text = xcb_image_text_8_checked (c, length, window, gc,
+ x1,
+ y1, label);
+ error = xcb_request_check (c, cookie_text);
+ if (error) {
+ fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_gc = xcb_free_gc (c, gc);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+}
+
+static xcb_gc_t
+gc_font_get (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ const char *font_name)
+{
+ uint32_t value_list[3];
+ xcb_void_cookie_t cookie_font;
+ xcb_void_cookie_t cookie_gc;
+ xcb_generic_error_t *error;
+ xcb_font_t font;
+ xcb_gcontext_t gc;
+ uint32_t mask;
+
+ font = xcb_generate_id (c);
+ cookie_font = xcb_open_font_checked (c, font,
+ strlen (font_name),
+ font_name);
+
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ gc = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
+ value_list[0] = screen->black_pixel;
+ value_list[1] = screen->white_pixel;
+ value_list[2] = font;
+ cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_font = xcb_close_font_checked (c, font);
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ return gc;
+}
+
+int main ()
+{
+ xcb_screen_iterator_t screen_iter;
+ xcb_connection_t *c;
+ const xcb_setup_t *setup;
+ xcb_screen_t *screen;
+ xcb_generic_event_t *e;
+ xcb_generic_error_t *error;
+ xcb_void_cookie_t cookie_window;
+ xcb_void_cookie_t cookie_map;
+ xcb_window_t window;
+ uint32_t mask;
+ uint32_t values[2];
+ int screen_number;
+
+ /* getting the connection */
+ c = xcb_connect (NULL, &screen_number);
+ if (!c) {
+ fprintf (stderr, "ERROR: can't connect to an X server\n");
+ return -1;
+ }
+
+ /* getting the current screen */
+ setup = xcb_get_setup (c);
+
+ screen = NULL;
+ screen_iter = xcb_setup_roots_iterator (setup);
+ for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter))
+ if (screen_number == 0)
+ {
+ screen = screen_iter.data;
+ break;
+ }
+ if (!screen) {
+ fprintf (stderr, "ERROR: can't get the current screen\n");
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ /* creating the window */
+ window = xcb_generate_id (c);
+ mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
+ values[0] = screen->white_pixel;
+ values[1] =
+ XCB_EVENT_MASK_KEY_RELEASE |
+ XCB_EVENT_MASK_BUTTON_PRESS |
+ XCB_EVENT_MASK_EXPOSURE |
+ XCB_EVENT_MASK_POINTER_MOTION;
+ cookie_window = xcb_create_window_checked (c,
+ screen->root_depth,
+ window, screen->root,
+ 20, 200, WIDTH, HEIGHT,
+ 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
+ screen->root_visual,
+ mask, values);
+ cookie_map = xcb_map_window_checked (c, window);
+
+ /* error managing */
+ error = xcb_request_check (c, cookie_window);
+ if (error) {
+ fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+ error = xcb_request_check (c, cookie_map);
+ if (error) {
+ fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ xcb_flush(c);
+
+ while (1) {
+ e = xcb_poll_for_event(c);
+ if (e) {
+ switch (e->response_type & ~0x80) {
+ case XCB_EXPOSE: {
+ char *text;
+
+ text = "Press ESC key to exit...";
+ text_draw (c, screen, window, 10, HEIGHT - 10, text);
+ break;
+ }
+ case XCB_KEY_RELEASE: {
+ xcb_key_release_event_t *ev;
+
+ ev = (xcb_key_release_event_t *)e;
+
+ switch (ev->detail) {
+ /* ESC */
+ case 9:
+ free (e);
+ xcb_disconnect (c);
+ return 0;
+ }
+ }
+ }
+ free (e);
+ }
+ }
+
+ return 0;
+}
+</pre>
+ </ol>
+ <li class="title"><a name="wm">Interacting with the window manager</a>
+ <p>
+ After we have seen how to create windows and draw on them, we
+ take one step back, and look at how our windows are interacting
+ with their environment (the full screen and the other
+ windows). First of all, our application needs to interact with
+ the window manager. The window manager is responsible to
+ decorating drawn windows (i.e. adding a frame, an iconify
+ button, a system menu, a title bar, etc), as well as handling
+ icons shown when windows are being iconified. It also handles
+ ordering of windows on the screen, and other administrative
+ tasks. We need to give it various hints as to how we want it to
+ treat our application's windows.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="wmprop">Window properties</a>
+ <p>
+ Many of the parameters communicated to the window manager are
+ passed using data called "properties". These properties are
+ attached by the X server to different windows, and are stored
+ in a format that makes it possible to read them from different
+ machines that may use different architectures (remember that
+ an X client program may run on a remote machine).
+ </p>
+ <p>
+ The property and its type (a string, an integer, etc) are
+ Id. Their type are <span class="code">xcb_atom_t</span>:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_atom_t;
+</pre>
+ <p>
+ To change the property of a window, we use the following
+ function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_change_property (xcb_connection_t *c, /* Connection to the X server */
+ uint8_t mode, /* Property mode */
+ xcb_window_t window, /* Window */
+ xcb_atom_t property, /* Property to change */
+ xcb_atom_t type, /* Type of the property */
+ uint8_t format, /* Format of the property (8, 16, 32) */
+ uint32_t data_len, /* Length of the data parameter */
+ const void *data); /* Data */
+</pre>
+ <p>
+ The <span class="code">mode</span> parameter coud be one of
+ the following values (defined in enumeration xcb_prop_mode_t in
+ the xproto.h header file):
+ </p>
+ <ul>
+ <li>XCB_PROP_MODE_REPLACE
+ <li>XCB_PROP_MODE_PREPEND
+ <li>XCB_PROP_MODE_APPEND
+ </ul>
+ <br>
+ <li class="subtitle"><a name="wmname">Setting the window name and icon name</a>
+ <p>
+ The first thing we want to do would be to set the name for our
+ window. This is done using the
+ <span class="code">xcb_change_property()</span> function. This
+ name may be used by the window manager as the title of the
+ window (in the title bar), in a task list, etc. The property
+ atom to use to set the name of a window is
+ <span class="code">WM_NAME</span> (and
+ <span class="code">WM_ICON_NAME</span> for the iconified
+ window) and its type is <span class="code">STRING</span>. Here
+ is an example of utilization:
+ </p>
+ <pre class="code">
+#include <string.h>
+
+#include <xcb/xcb.h>
+#include <xcb/xcb_atom.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_window_t win;
+ char *title = "Hello World !";
+ char *title_icon = "Hello World ! (iconified)";
+
+
+
+ /* Open the connection to the X server */
+ c = xcb_connect (NULL, NULL);
+
+ /* Get the first screen */
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* Ask for our window's Id */
+ win = xcb_generate_id (c);
+
+ /* Create the window */
+ xcb_create_window (c, /* Connection */
+ 0, /* depth */
+ win, /* window Id */
+ screen->root, /* parent window */
+ 0, 0, /* x, y */
+ 250, 150, /* width, height */
+ 10, /* border_width */
+ XCB_WINDOW_CLASS_INPUT_OUTPUT, /* class */
+ screen->root_visual, /* visual */
+ 0, NULL); /* masks, not used */
+
+ /* Set the title of the window */
+ xcb_change_property (c, XCB_PROP_MODE_REPLACE, win,
+ WM_NAME, STRING, 8,
+ strlen (title), title);
+
+ /* Set the title of the window icon */
+ xcb_change_property (c, XCB_PROP_MODE_REPLACE, win,
+ WM_ICON_NAME, STRING, 8,
+ strlen(title_icon), title_icon);
+
+ /* Map the window on the screen */
+ xcb_map_window (c, win);
+
+ xcb_flush (c);
+
+ while (1) {}
+
+ return 0;
+}
+</pre>
+ <div class="emph">
+ <p>Note: the use of the atoms needs our program to be compiled
+ and linked against xcb_atom, so that we have to use
+ </p>
+ </div>
+ <pre class="text">
+gcc prog.c -o prog `pkg-config --cflags --libs xcb_atom`
+</pre>
+ <div class="emph">
+ <p>
+ for the program to compile fine.
+ </p>
+ </div>
+ </ol>
+ <li class="title"><a name="winop">Simple window operations</a>
+ <p>
+ One more thing we can do to our window is manipulate them on the
+ screen (resize them, move them, raise or lower them, iconify
+ them, and so on). Some window operations functions are supplied
+ by XCB for this purpose.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="winmap">Mapping and un-mapping a window</a>
+ <p>
+ The first pair of operations we can apply on a window is
+ mapping it, or un-mapping it. Mapping a window causes the
+ window to appear on the screen, as we have seen in our simple
+ window program example. Un-mapping it causes it to be removed
+ from the screen (although the window as a logical entity still
+ exists). This gives the effect of making a window hidden
+ (unmapped) and shown again (mapped). For example, if we have a
+ dialog box window in our program, instead of creating it every
+ time the user asks to open it, we can create the window once,
+ in an un-mapped mode, and when the user asks to open it, we
+ simply map the window on the screen. When the user clicked the
+ 'OK' or 'Cancel' button, we simply un-map the window. This is
+ much faster than creating and destroying the window, however,
+ the cost is wasted resources, both on the client side, and on
+ the X server side.
+ </p>
+ <p>
+ To map a window, you use the following function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_map_window (xcb_connection_t *c,
+ xcb_window_t window);
+</pre>
+ <p>
+ To have a simple example, see the <a href="#helloworld">example</a>
+ above. The mapping operation will cause an
+ <span class="code">Expose</span> event to be sent to our
+ application, unless the window is completely covered by other
+ windows.
+ </p>
+ <p>
+ Un-mapping a window is also simple. You use the function
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_unmap_window (xcb_connection_t *c,
+ xcb_window_t window);
+</pre>
+ <p>
+ The utilization of this function is the same as
+ <span class="code">xcb_map_window()</span>.
+ </p>
+ <li class="subtitle"><a name="winconf">Configuring a window</a>
+ <p>
+ As we have seen when we have created our first window, in the
+ X Events subsection, we can set some attributes for the window
+ (that is, the position, the size, the events the window will
+ receive, etc). If we want to modify them, but the window is
+ already created, we can change them by using the following
+ function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_configure_window (xcb_connection_t *c, /* The connection to the X server*/
+ xcb_window_t window, /* The window to configure */
+ uint16_t value_mask, /* The mask */
+ const uint32_t *value_list); /* The values to set */
+</pre>
+ <p>
+ We set the <span class="code">value_mask</span> to one or
+ several mask values that are in the xcb_config_window_t enumeration in the xproto.h header:
+ </p>
+ <ul>
+ <li><span class="code">XCB_CONFIG_WINDOW_X</span>: new x coordinate of the window's top left corner
+ <li><span class="code">XCB_CONFIG_WINDOW_Y</span>: new y coordinate of the window's top left corner
+ <li><span class="code">XCB_CONFIG_WINDOW_WIDTH</span>: new width of the window
+ <li><span class="code">XCB_CONFIG_WINDOW_HEIGHT</span>: new height of the window
+ <li><span class="code">XCB_CONFIG_WINDOW_BORDER_WIDTH</span>: new width of the border of the window
+ <li><span class="code">XCB_CONFIG_WINDOW_SIBLING</span>
+ <li><span class="code">XCB_CONFIG_WINDOW_STACK_MODE</span>: the new stacking order
+ </ul>
+ <p>
+ We then give to <span class="code">value_mask</span> the new
+ value. We now describe how to use
+ <span class="code">xcb_configure_window_t</span> in some useful
+ situations.
+ </p>
+ <li class="subtitle"><a name="winmove">Moving a window around the screen</a>
+ <p>
+ An operation we might want to do with windows is to move them
+ to a different location. This can be done like this:
+ </p>
+ <pre class="code">
+const static uint32_t values[] = { 10, 20 };
+
+/* The connection c and the window win are supposed to be defined */
+
+/* Move the window to coordinates x = 10 and y = 20 */
+xcb_configure_window (c, win, XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y, values);
+</pre>
+ <p>
+ Note that when the window is moved, it might get partially
+ exposed or partially hidden by other windows, and thus we
+ might get <span class="code">Expose</span> events due to this
+ operation.
+ </p>
+ <li class="subtitle"><a name="winsize">Resizing a window</a>
+ <p>
+ Yet another operation we can do is to change the size of a
+ window. This is done using the following code:
+ </p>
+ <pre class="code">
+const static uint32_t values[] = { 200, 300 };
+
+/* The connection c and the window win are supposed to be defined */
+
+/* Resize the window to width = 10 and height = 20 */
+xcb_configure_window (c, win, XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT, values);
+</pre>
+ <p>
+ We can also combine the move and resize operations using one
+ single call to <span class="code">xcb_configure_window_t</span>:
+ </p>
+ <pre class="code">
+const static uint32_t values[] = { 10, 20, 200, 300 };
+
+/* The connection c and the window win are supposed to be defined */
+
+/* Move the window to coordinates x = 10 and y = 20 */
+/* and resize the window to width = 10 and height = 20 */
+xcb_configure_window (c, win, XCB_CONFIG_WINDOW_X | XCB_CONFIG_WINDOW_Y | XCB_CONFIG_WINDOW_WIDTH | XCB_CONFIG_WINDOW_HEIGHT, values);
+</pre>
+ <li class="subtitle"><a name="winstack">Changing windows stacking order: raise and lower</a>
+ <p>
+ Until now, we changed properties of a single window. We'll see
+ that there are properties that relate to the window and other
+ windows. One of them is the stacking order. That is, the order
+ in which the windows are layered on top of each other. The
+ front-most window is said to be on the top of the stack, while
+ the back-most window is at the bottom of the stack. Here is
+ how to manipulate our windows stack order:
+ </p>
+ <pre class="code">
+const static uint32_t values[] = { XCB_STACK_MODE_ABOVE };
+
+/* The connection c and the window win are supposed to be defined */
+
+/* Move the window on the top of the stack */
+xcb_configure_window (c, win, XCB_CONFIG_WINDOW_STACK_MODE, values);
+</pre>
+ <pre class="code">
+const static uint32_t values[] = { XCB_STACK_MODE_BELOW };
+
+/* The connection c and the window win are supposed to be defined */
+
+/* Move the window on the bottom of the stack */
+xcb_configure_window (c, win, XCB_CONFIG_WINDOW_STACK_MODE, values);
+</pre>
+ <li class="subtitle"><a name="wingetinfo">Getting information about a window</a>
+ <p>
+ Just like we can set various attributes of our windows, we can
+ also ask the X server supply the current values of these
+ attributes. For example, we can check where a window is
+ located on the screen, what is its current size, whether it is
+ mapped or not, etc. The structure that contains some of this
+ information is
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type;
+ uint8_t depth; /* depth of the window */
+ uint16_t sequence;
+ uint32_t length;
+ xcb_window_t root; /* Id of the root window *>
+ int16_t x; /* X coordinate of the window's location */
+ int16_t y; /* Y coordinate of the window's location */
+ uint16_t width; /* Width of the window */
+ uint16_t height; /* Height of the window */
+ uint16_t border_width; /* Width of the window's border */
+} xcb_get_geometry_reply_t;
+</pre>
+ <p>
+ XCB fill this structure with two functions:
+ </p>
+ <pre class="code">
+xcb_get_geometry_cookie_t xcb_get_geometry (xcb_connection_t *c,
+ xcb_drawable_t drawable);
+xcb_get_geometry_reply_t *xcb_get_geometry_reply (xcb_connection_t *c,
+ xcb_get_geometry_cookie_t cookie,
+ xcb_generic_error_t **e);
+</pre>
+ <p>
+ You use them as follows:
+ </p>
+ <pre class="code">
+ xcb_connection_t *c;
+ xcb_drawable_t win;
+ xcb_get_geometry_reply_t *geom;
+
+ /* You initialize c and win */
+
+ geom = xcb_get_geometry_reply (c, xcb_get_geometry (c, win), NULL);
+
+ /* Do something with the fields of geom */
+
+ free (geom);
+</pre>
+ <p>
+ Remark that you have to free the structure, as
+ <span class="code">xcb_get_geometry_reply_t</span> allocates a
+ newly one.
+ </p>
+ <p>
+ One problem is that the returned location of the window is
+ relative to its parent window. This makes these coordinates
+ rather useless for any window manipulation functions, like
+ moving it on the screen. In order to overcome this problem, we
+ need to take a two-step operation. First, we find out the Id
+ of the parent window of our window. We then translate the
+ above relative coordinates to the screen coordinates.
+ </p>
+ <p>
+ To get the Id of the parent window, we need this structure:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type;
+ uint8_t pad0;
+ uint16_t sequence;
+ uint32_t length;
+ xcb_window_t root;
+ xcb_window_t parent; /* Id of the parent window */
+ uint16_t children_len;
+ uint8_t pad1[14];
+} xcb_query_tree_reply_t;
+</pre>
+ <p>
+ To fill this structure, we use these two functions:
+ </p>
+ <pre class="code">
+xcb_query_tree_cookie_t xcb_query_tree (xcb_connection_t *c,
+ xcb_window_t window);
+xcb_query_tree_reply_t *xcb_query_tree_reply (xcb_connection_t *c,
+ xcb_query_tree_cookie_t cookie,
+ xcb_generic_error_t **e);
+</pre>
+ <p>
+ The translated coordinates will be found in this structure:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type;
+ uint8_t same_screen;
+ uint16_t sequence;
+ uint32_t length;
+ xcb_window_t child;
+ uint16_t dst_x; /* Translated x coordinate */
+ uint16_t dst_y; /* Translated y coordinate */
+} xcb_translate_coordinates_reply_t;
+</pre>
+ <p>
+ As usual, we need two functions to fill this structure:
+ </p>
+ <pre class="code">
+xcb_translate_coordinates_cookie_t xcb_translate_coordinates (xcb_connection_t *c,
+ xcb_window_t src_window,
+ xcb_window_t dst_window,
+ int16_t src_x,
+ int16_t src_y);
+xcb_translate_coordinates_reply_t *xcb_translate_coordinates_reply (xcb_connection_t *c,
+ xcb_translate_coordinates_cookie_t cookie,
+ xcb_generic_error_t **e);
+</pre>
+ <p>
+ We use them as follows:
+ </p>
+ <pre class="code">
+ xcb_connection_t *c;
+ xcb_drawable_t win;
+ xcb_get_geometry_reply_t *geom;
+ xcb_query_tree_reply_t *tree;
+ xcb_translate_coordinates_reply_t *trans;
+
+ /* You initialize c and win */
+
+ geom = xcb_get_geometry_reply (c, xcb_get_geometry (c, win), NULL);
+ if (!geom)
+ return 0;
+
+ tree = xcb_query_tree_reply (c, xcb_query_tree (c, win), NULL);
+ if (!tree)
+ return 0;
+
+ trans = xcb_translate_coordinates_reply (c,
+ xcb_translate_coordinates (c,
+ win,
+ tree->parent,
+ geom->x, geom->y),
+ NULL);
+ if (!trans)
+ return 0;
+
+ /* the translated coordinates are in trans->dst_x and trans->dst_y */
+
+ free (trans);
+ free (tree);
+ free (geom);
+</pre>
+ <p>
+ Of course, as for <span class="code">geom</span>,
+ <span class="code">tree</span> and
+ <span class="code">trans</span> have to be freed.
+ </p>
+ <p>
+ The work is a bit hard, but XCB is a very low-level library.
+ </p>
+ <p>
+ <b>TODO:</b> the utilization of these functions should be a
+ prog, which displays the coordinates of the window.
+ </p>
+ <p>
+ There is another structure that gives informations about our window:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type;
+ uint8_t backing_store;
+ uint16_t sequence;
+ uint32_t length;
+ xcb_visualid_t visual; /* Visual of the window */
+ uint16_t _class;
+ uint8_t bit_gravity;
+ uint8_t win_gravity;
+ uint32_t backing_planes;
+ uint32_t backing_pixel;
+ uint8_t save_under;
+ uint8_t map_is_installed;
+ uint8_t map_state; /* Map state of the window */
+ uint8_t override_redirect;
+ xcb_colormap_t colormap; /* Colormap of the window */
+ uint32_t all_event_masks;
+ uint32_t your_event_mask;
+ uint16_t do_not_propagate_mask;
+} xcb_get_window_attributes_reply_t;
+</pre>
+ <p>
+ XCB supplies these two functions to fill it:
+ </p>
+ <pre class="code">
+xcb_get_window_attributes_cookie_t xcb_get_window_attributes (xcb_connection_t *c,
+ xcb_window_t window);
+xcb_get_window_attributes_reply_t *xcb_get_window_attributes_reply (xcb_connection_t *c,
+ xcb_get_window_attributes_cookie_t cookie,
+ xcb_generic_error_t **e);
+</pre>
+ <p>
+ You use them as follows:
+ </p>
+ <pre class="code">
+ xcb_connection_t *c;
+ xcb_drawable_t win;
+ xcb_get_window_attributes_reply_t *attr;
+
+ /* You initialize c and win */
+
+ attr = xcb_get_window_attributes_reply (c, xcb_get_window_attributes (c, win), NULL);
+
+ if (!attr)
+ return 0;
+
+ /* Do something with the fields of attr */
+
+ free (attr);
+</pre>
+ <p>
+ As for <span class="code">geom</span>,
+ <span class="code">attr</span> has to be freed.
+ </p>
+ </ol>
+ <li class="title"><a name="usecolor">Using colors to paint the rainbow</a>
+ <p>
+ Up until now, all our painting operation were done using black
+ and white. We will (finally) see now how to draw using colors.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="colormap">Color maps</a>
+ <p>
+ In the beginning, there were not enough colors. Screen
+ controllers could only support a limited number of colors
+ simultaneously (initially 2, then 4, 16 and 256). Because of
+ this, an application could not just ask to draw in a "light
+ purple-red" color, and expect that color to be available. Each
+ application allocated the colors it needed, and when all the
+ color entries (4, 16, 256 colors) were in use, the next color
+ allocation would fail.
+ </p>
+ <p>
+ Thus, the notion of "a color map" was introduced. A color map
+ is a table whose size is the same as the number of
+ simultaneous colors a given screen controller. Each entry
+ contained the RGB (Red, Green and Blue) values of a different
+ color (all colors can be drawn using some combination of red,
+ green and blue). When an application wants to draw on the
+ screen, it does not specify which color to use. Rather, it
+ specifies which color entry of some color map to be used
+ during this drawing. Change the value in this color map entry
+ and the drawing will use a different color.
+ </p>
+ <p>
+ In order to be able to draw using colors that got something to
+ do with what the programmer intended, color map allocation
+ functions are supplied. You could ask to allocate entry for a
+ color with a set of RGB values. If one already existed, you
+ would get its index in the table. If none existed, and the
+ table was not full, a new cell would be allocated to contain
+ the given RGB values, and its index returned. If the table was
+ full, the procedure would fail. You could then ask to get a
+ color map entry with a color that is closest to the one you
+ were asking for. This would mean that the actual drawing on
+ the screen would be done using colors similar to what you
+ wanted, but not the same.
+ </p>
+ <p>
+ On today's more modern screens where one runs an X server with
+ support for 16 million colors, this limitation looks a little
+ silly, but remember that there are still older computers with
+ older graphics cards out there. Using color map, support for
+ these screen becomes transparent to you. On a display
+ supporting 16 million colors, any color entry allocation
+ request would succeed. On a display supporting a limited
+ number of colors, some color allocation requests would return
+ similar colors. It won't look as good, but your application
+ would still work.
+ </p>
+ <li class="subtitle"><a name="colormapalloc">Allocating and freeing Color Maps</a>
+ <p>
+ When you draw using XCB, you can choose to use the standard
+ color map of the screen your window is displayed on, or you
+ can allocate a new color map and apply it to a window. In the
+ latter case, each time the mouse moves onto your window, the
+ screen color map will be replaced by your window's color map,
+ and you'll see all the other windows on screen change their
+ colors into something quite bizzare. In fact, this is the
+ effect you get with X applications that use the "-install"
+ command line option.
+ </p>
+ <p>
+ In XCB, a color map is (as often in X) an Id:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_colormap_t;
+</pre>
+ <p>
+ In order to access the screen's default color map, you just
+ have to retrieve the <span class="code">default_colormap</span>
+ field of the <span class="code">xcb_screen_t</span> structure
+ (see Section
+ <a href="#screen">Checking basic information about a connection</a>):
+ </p>
+ <pre class="code">
+#include <stdio.h>
+
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_colormap_t colormap;
+
+ /* Open the connection to the X server and get the first screen */
+ c = xcb_connect (NULL, NULL);
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ colormap = screen->default_colormap;
+
+ return 0;
+}
+</pre>
+ <p>
+ This will return the color map used by default on the first
+ screen (again, remember that an X server may support several
+ different screens, each of which might have its own resources).
+ </p>
+ <p>
+ The other option, that of allocating a new colormap, works as
+ follows. We first ask the X server to give an Id to our color
+ map, with this function:
+ </p>
+ <pre class="code">
+xcb_colormap_t xcb_generate_id (xcb_connection_t *c);
+</pre>
+ <p>
+ Then, we create the color map with
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_create_colormap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */
+ uint8_t alloc, /* Colormap entries to be allocated (AllocNone or AllocAll) */
+ xcb_colormap_t mid, /* Id of the color map */
+ xcb_window_t window, /* Window on whose screen the colormap will be created */
+ xcb_visualid_t visual); /* Id of the visual supported by the screen */
+</pre>
+ <p>
+ Here is an example of creation of a new color map:
+ </p>
+ <pre class="code">
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_window_t win;
+ xcb_colormap_t cmap
+
+ /* Open the connection to the X server and get the first screen */
+ c = xcb_connect (NULL, NULL);
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* We create the window win here*/
+
+ cmap = xcb_generate_id (c);
+ xcb_create_colormap (c, XCB_COLORMAP_ALLOC_NONE, cmap, win, screen->root_visual);
+
+ return 0;
+}
+</pre>
+ <p>
+ Note that the window parameter is only used to allow the X
+ server to create the color map for the given screen. We can
+ then use this color map for any window drawn on the same screen.
+ </p>
+ <p>
+ To free a color map, it suffices to use this function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_free_colormap (xcb_connection_t *c, /* The connection */
+ xcb_colormap_t cmap); /* The color map */
+</pre>
+ <div class="comp">
+ <div class="title">
+ Comparison Xlib/XCB
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XCreateColormap ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_generate_id ()
+ <li>xcb_create_colormap ()
+ </ul>
+ </div>
+ <div class="xlib">
+ <ul>
+ <li>XFreeColormap ()
+ </ul>
+ </div>
+ <div class="xcb">
+ <ul>
+ <li>xcb_free_colormap ()
+ </ul>
+ </div>
+ </div>
+ <br>
+ <li class="subtitle"><a name="alloccolor">Allocating and freeing a color entry</a>
+ <p>
+ Once we got access to some color map, we can start allocating
+ colors. The informations related to a color are stored in the
+ following structure:
+ </p>
+ <pre class="code">
+typedef struct {
+ uint8_t response_type;
+ uint8_t pad0;
+ uint16_t sequence;
+ uint32_t length;
+ uint16_t red; /* The red component */
+ uint16_t green; /* The green component */
+ uint16_t blue; /* The blue component */
+ uint8_t pad1[2];
+ uint32_t pixel; /* The entry in the color map, supplied by the X server */
+} xcb_alloc_color_reply_t;
+</pre>
+ <p>
+ XCB supplies these two functions to fill it:
+ </p>
+ <pre class="code">
+xcb_alloc_color_cookie_t xcb_alloc_color (xcb_connection_t *c,
+ xcb_colormap_t cmap,
+ uint16_t red,
+ uint16_t green,
+ uint16_t blue);
+xcb_alloc_color_reply_t *xcb_alloc_color_reply (xcb_connection_t *c,
+ xcb_alloc_color_cookie_t cookie,
+ xcb_generic_error_t **e);
+</pre>
+ <p>
+ The fuction <span class="code">xcb_alloc_color()</span> takes the
+ 3 RGB components as parameters (red, green and blue). Here is an
+ example of using these functions:
+ </p>
+ <pre class="code">
+#include <malloc.h>
+
+#include <xcb/xcb.h>
+
+int
+main ()
+{
+ xcb_connection_t *c;
+ xcb_screen_t *screen;
+ xcb_window_t win;
+ xcb_colormap_t cmap;
+ xcb_alloc_color_reply_t *rep;
+
+ /* Open the connection to the X server and get the first screen */
+ c = xcb_connect (NULL, NULL);
+ screen = xcb_setup_roots_iterator (xcb_get_setup (c)).data;
+
+ /* We create the window win here*/
+
+ cmap = xcb_generate_id (c);
+ xcb_create_colormap (c, XCB_COLORMAP_ALLOC_NONE, cmap, win, screen->root_visual);
+
+ rep = xcb_alloc_color_reply (c, xcb_alloc_color (c, cmap, 65535, 0, 0), NULL);
+
+ if (!rep)
+ return 0;
+
+ /* Do something with r->pixel or the components */
+
+ free (rep);
+
+ return 0;
+}
+</pre>
+ <p>
+ As <span class="code">xcb_alloc_color_reply()</span> allocates
+ memory, you have to free <span class="code">rep</span>.
+ </p>
+ <p>
+ <b>TODO</b>: Talk about freeing colors.
+ </p>
+ </ol>
+ <li class="title"><a name="pixmaps">X Bitmaps and Pixmaps</a>
+ <p>
+ One thing many so-called "Multi-Media" applications need to do,
+ is display images. In the X world, this is done using bitmaps
+ and pixmaps. We have already seen some usage of them when
+ setting an icon for our application. Lets study them further,
+ and see how to draw these images inside a window, along side the
+ simple graphics and text we have seen so far.
+ </p>
+ <p>
+ One thing to note before delving further, is that XCB (nor Xlib)
+ supplies no means of manipulating popular image formats, such as
+ gif, png, jpeg or tiff. It is up to the programmer (or to higher
+ level graphics libraries) to translate these image formats into
+ formats that the X server is familiar with (x bitmaps and x
+ pixmaps).
+ </p>
+ <ol>
+ <li class="subtitle"><a name="pixmapswhat">What is a X Bitmap? An X Pixmap?</a>
+ <p>
+ An X bitmap is a two-color image stored in a format specific
+ to the X window system. When stored in a file, the bitmap data
+ looks like a C source file. It contains variables defining the
+ width and the height of the bitmap, an array containing the
+ bit values of the bitmap (the size of the array is
+ (width+7)/8*height and the bit and byte order are LSB), and
+ an optional hot-spot location (that will
+ be explained later, when discussing mouse cursors).
+ </p>
+ <p>
+ An X pixmap is a format used to stored images in the memory of
+ an X server. This format can store both black and white images
+ (such as x bitmaps) as well as color images. It is the only
+ image format supported by the X protocol, and any image to be
+ drawn on screen, should be first translated into this format.
+ </p>
+ <p>
+ In actuality, an X pixmap can be thought of as a window that
+ does not appear on the screen. Many graphics operations that
+ work on windows, will also work on pixmaps. Indeed, the type
+ of X pixmap in XCB is an Id like a window:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_pixmap_t;
+</pre>
+ <p>
+ Like Xlib, there is no difference between a Drawable, a Window
+ or a Pixmap:
+ </p>
+ <pre class="code">
+typedef uint32_t xcb_drawable_t;
+</pre>
+ <p>
+ in order to avoid confusion between a window and a pixmap. The
+ operations that will work the same on a window or a pixmap
+ will require a <span class="code">xcb_drawable_t</span>
+ </p>
+ <div class="emph">
+ <p>
+ Remark: In Xlib, there is no specific difference between a
+ <span class="code">Drawable</span>, a
+ <span class="code">Pixmap</span> or a
+ <span class="code">Window</span>: all are 32 bit long
+ integer. XCB wraps all these different IDs in structures to
+ provide some measure of type-safety.
+ </p>
+ </div>
+ <li class="subtitle"><a name="pixmapscreate">Creating a pixmap</a>
+ <p>
+ Sometimes we want to create an un-initialized pixmap, so we
+ can later draw into it. This is useful for image drawing
+ programs (creating a new empty canvas will cause the creation
+ of a new pixmap on which the drawing can be stored). It is
+ also useful when reading various image formats: we load the
+ image data into memory, create a pixmap on the server, and
+ then draw the decoded image data onto that pixmap.
+ </p>
+ <p>
+ To create a new pixmap, we first ask the X server to give an
+ Id to our pixmap, with this function:
+ </p>
+ <pre class="code">
+xcb_pixmap_t xcb_generate_id (xcb_connection_t *c);
+</pre>
+ <p>
+ Then, XCB supplies the following function to create new pixmaps:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_create_pixmap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */
+ uint8_t depth, /* Depth of the screen */
+ xcb_pixmap_t pid, /* Id of the pixmap */
+ xcb_drawable_t drawable,
+ uint16_t width, /* Width of the window (in pixels) */
+ uint16_t height); /* Height of the window (in pixels) */
+</pre>
+ <p>
+ <b>TODO</b>: Explain the drawable parameter, and give an
+ example (like <a href="xpoints.c">xpoints.c</a>)
+ </p>
+ <li class="subtitle"><a name="pixmapsdraw"></a>Drawing a pixmap in a window
+ <p>
+ Once we got a handle to a pixmap, we can draw it on some
+ window, using the following function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_copy_area (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */
+ xcb_drawable_t src_drawable, /* The Drawable we want to paste */
+ xcb_drawable_t dst_drawable, /* The Drawable on which we copy the previous Drawable */
+ xcb_gcontext_t gc, /* A Graphic Context */
+ int16_t src_x, /* Top left x coordinate of the region we want to copy */
+ int16_t src_y, /* Top left y coordinate of the region we want to copy */
+ int16_t dst_x, /* Top left x coordinate of the region where we want to copy */
+ int16_t dst_y, /* Top left y coordinate of the region where we want to copy */
+ uint16_t width, /* Width of the region we want to copy */
+ uint16_t height); /* Height of the region we want to copy */
+</pre>
+ <p>
+ As you can see, we could copy the whole pixmap, as well as
+ only a given rectangle of the pixmap. This is useful to
+ optimize the drawing speed: we could copy only what we have
+ modified in the pixmap.
+ </p>
+ <p>
+ <b>One important note should be made</b>: it is possible to
+ create pixmaps with different depths on the same screen. When
+ we perform copy operations (a pixmap onto a window, etc), we
+ should make sure that both source and target have the same
+ depth. If they have a different depth, the operation would
+ fail. The exception to this is if we copy a specific bit plane
+ of the source pixmap using the
+ <span class="code">xcb_copy_plane_t</span> function. In such an
+ event, we can copy a specific plane to the target window (in
+ actuality, setting a specific bit in the color of each pixel
+ copied). This can be used to generate strange graphic effects
+ in a window, but that is beyond the scope of this tutorial.
+ </p>
+ <li class="subtitle"><a name="pixmapsfree"></a>Freeing a pixmap
+ <p>
+ Finally, when we are done using a given pixmap, we should free
+ it, in order to free resources of the X server. This is done
+ using this function:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_free_pixmap (xcb_connection_t *c, /* Pointer to the xcb_connection_t structure */
+ xcb_pixmap_t pixmap); /* A given pixmap */
+</pre>
+ <p>
+ Of course, after having freed it, we must not try accessing
+ the pixmap again.
+ </p>
+ <p>
+ <b>TODO</b>: Give an example, or a link to xpoints.c
+ </p>
+ </ol>
+ <li class="title"><a name="mousecursor">Messing with the mouse cursor</a>
+ <p>
+ It it possible to modify the shape of the mouse pointer (also
+ called the X pointer) when in certain states, as we otfen see in
+ programs. For example, a busy application would often display
+ the sand clock over its main window, to give the user a visual
+ hint that he should wait. Let's see how we can change the mouse
+ cursor of our windows.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="mousecursorcreate">Creating and destroying a mouse cursor</a>
+ <p>
+ There are two methods for creating cursors. One of them is by
+ using a set of predefined cursors, that are supplied by the X
+ server, the other is by using a user-supplied bitmap.
+ </p>
+ <p>
+ In the first method, we use a special font named "cursor", and
+ the function <span class="code">xcb_create_glyph_cursor</span>:
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_create_glyph_cursor (xcb_connection_t *c,
+ xcb_cursor_t cid,
+ xcb_font_t source_font, /* font for the source glyph */
+ xcb_font_t mask_font, /* font for the mask glyph or XCB_NONE */
+ uint16_t source_char, /* character glyph for the source */
+ uint16_t mask_char, /* character glyph for the mask */
+ uint16_t fore_red, /* red value for the foreground of the source */
+ uint16_t fore_green, /* green value for the foreground of the source */
+ uint16_t fore_blue, /* blue value for the foreground of the source */
+ uint16_t back_red, /* red value for the background of the source */
+ uint16_t back_green, /* green value for the background of the source */
+ uint16_t back_blue) /* blue value for the background of the source */
+</pre>
+ <p>
+ <b>TODO</b>: Describe <span class="code">source_char</span>
+ and <span class="code">mask_char</span>, for example by giving
+ an example on how to get the values. There is a list there:
+ <a href="http://tronche.com/gui/x/xlib/appendix/b/">X Font Cursors</a>
+ </p>
+ <p>
+ So we first open that font (see <a href="#loadfont">Loading a Font</a>)
+ and create the new cursor. As for every X ressource, we have to
+ ask for an X id with <span class="code">xcb_generate_id</span>
+ first:
+ </p>
+ <pre class="code">
+xcb_font_t font;
+xcb_cursor_t cursor;
+
+/* The connection is set */
+
+font = xcb_generate_id (conn);
+xcb_open_font (conn, font, strlen ("cursor"), "cursor");
+
+cursor = xcb_generate_id (conn);
+xcb_create_glyph_cursor (conn, cursor, font, font,
+ 58, 58 + 1,
+ 0, 0, 0,
+ 0, 0, 0);
+</pre>
+ <p>
+ We have created the cursor "right hand" by specifying 58 to
+ the <span class="code">source_fon</span>t argument and 58 + 1
+ to the <span class="code">mask_font</span>.
+ </p>
+ <p>
+ The cursor is destroyed by using the function
+ </p>
+ <pre class="code">
+xcb_void_cookie_t xcb_free_cursor (xcb_connection_t *c,
+ xcb_cursor_t cursor);
+</pre>
+ <p>
+ In the second method, we create a new cursor by using a pair
+ of pixmaps, with depth of one (that is, two colors
+ pixmaps). One pixmap defines the shape of the cursor, while
+ the other works as a mask, specifying which pixels of the
+ cursor will be actually drawn. The rest of the pixels will be
+ transparent.
+ </p>
+ <p>
+ <b>TODO</b>: give an example.
+ </p>
+ <li class="subtitle"><a name="mousecursorset">Setting a window's mouse cursor</a>
+ <p>
+ Once the cursor is created, we can modify the cursor of our
+ window by using <span class="code">xcb_change_window_attributes</span>
+ and using the <span class="code">XCB_CWCURSOR</span> attribute:
+ </p>
+ <pre class="code">
+uint32_t mask;
+uint32_t value_list;
+
+/* The connection and window are set */
+/* The cursor is already created */
+
+mask = XCB_CWCURSOR;
+value_list = cursor;
+xcb_change_window_attributes (conn, window, mask, &value_list);
+</pre>
+ <p>
+ Of course, the cursor and the font must be freed.
+ </p>
+ <li class="subtitle"><a name="mousecursorexample">Complete example</a>
+ <p>
+ The following example displays a window with a
+ button. When entering the window, the window cursor is changed
+ to an arrow. When clicking once on the button, the cursor is
+ changed to a hand. When clicking again on the button, the
+ cursor window gets back to the arrow. The Esc key exits the
+ application.
+ </p>
+ <pre class="code">
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <xcb/xcb.h>
+
+#define WIDTH 300
+#define HEIGHT 150
+
+
+
+static xcb_gc_t gc_font_get (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ const char *font_name);
+
+static void button_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label);
+
+static void text_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label);
+
+static void cursor_set (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int cursor_id);
+
+
+static void
+button_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label)
+{
+ xcb_point_t points[5];
+ xcb_void_cookie_t cookie_gc;
+ xcb_void_cookie_t cookie_line;
+ xcb_void_cookie_t cookie_text;
+ xcb_generic_error_t *error;
+ xcb_gcontext_t gc;
+ int16_t width;
+ int16_t height;
+ uint8_t length;
+ int16_t inset;
+
+ length = strlen (label);
+ inset = 2;
+
+ gc = gc_font_get(c, screen, window, "7x13");
+
+ width = 7 * length + 2 * (inset + 1);
+ height = 13 + 2 * (inset + 1);
+ points[0].x = x1;
+ points[0].y = y1;
+ points[1].x = x1 + width;
+ points[1].y = y1;
+ points[2].x = x1 + width;
+ points[2].y = y1 - height;
+ points[3].x = x1;
+ points[3].y = y1 - height;
+ points[4].x = x1;
+ points[4].y = y1;
+ cookie_line = xcb_poly_line_checked (c, XCB_COORD_MODE_ORIGIN,
+ window, gc, 5, points);
+
+ error = xcb_request_check (c, cookie_line);
+ if (error) {
+ fprintf (stderr, "ERROR: can't draw lines : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_text = xcb_image_text_8_checked (c, length, window, gc,
+ x1 + inset + 1,
+ y1 - inset - 1, label);
+ error = xcb_request_check (c, cookie_text);
+ if (error) {
+ fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_gc = xcb_free_gc (c, gc);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+}
+
+static void
+text_draw (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int16_t x1,
+ int16_t y1,
+ const char *label)
+{
+ xcb_void_cookie_t cookie_gc;
+ xcb_void_cookie_t cookie_text;
+ xcb_generic_error_t *error;
+ xcb_gcontext_t gc;
+ uint8_t length;
+
+ length = strlen (label);
+
+ gc = gc_font_get(c, screen, window, "7x13");
+
+ cookie_text = xcb_image_text_8_checked (c, length, window, gc,
+ x1,
+ y1, label);
+ error = xcb_request_check (c, cookie_text);
+ if (error) {
+ fprintf (stderr, "ERROR: can't paste text : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_gc = xcb_free_gc (c, gc);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't free gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+}
+
+static xcb_gc_t
+gc_font_get (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ const char *font_name)
+{
+ uint32_t value_list[3];
+ xcb_void_cookie_t cookie_font;
+ xcb_void_cookie_t cookie_gc;
+ xcb_generic_error_t *error;
+ xcb_font_t font;
+ xcb_gcontext_t gc;
+ uint32_t mask;
+
+ font = xcb_generate_id (c);
+ cookie_font = xcb_open_font_checked (c, font,
+ strlen (font_name),
+ font_name);
+
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ gc = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
+ value_list[0] = screen->black_pixel;
+ value_list[1] = screen->white_pixel;
+ value_list[2] = font;
+ cookie_gc = xcb_create_gc_checked (c, gc, window, mask, value_list);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cookie_font = xcb_close_font_checked (c, font);
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ return gc;
+}
+
+static void
+cursor_set (xcb_connection_t *c,
+ xcb_screen_t *screen,
+ xcb_window_t window,
+ int cursor_id)
+{
+ uint32_t values_list[3];
+ xcb_void_cookie_t cookie_font;
+ xcb_void_cookie_t cookie_gc;
+ xcb_generic_error_t *error;
+ xcb_font_t font;
+ xcb_cursor_t cursor;
+ xcb_gcontext_t gc;
+ uint32_t mask;
+ uint32_t value_list;
+
+ font = xcb_generate_id (c);
+ cookie_font = xcb_open_font_checked (c, font,
+ strlen ("cursor"),
+ "cursor");
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't open font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ cursor = xcb_generate_id (c);
+ xcb_create_glyph_cursor (c, cursor, font, font,
+ cursor_id, cursor_id + 1,
+ 0, 0, 0,
+ 0, 0, 0);
+
+ gc = xcb_generate_id (c);
+ mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND | XCB_GC_FONT;
+ values_list[0] = screen->black_pixel;
+ values_list[1] = screen->white_pixel;
+ values_list[2] = font;
+ cookie_gc = xcb_create_gc_checked (c, gc, window, mask, values_list);
+ error = xcb_request_check (c, cookie_gc);
+ if (error) {
+ fprintf (stderr, "ERROR: can't create gc : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+
+ mask = XCB_CW_CURSOR;
+ value_list = cursor;
+ xcb_change_window_attributes (c, window, mask, &value_list);
+
+ xcb_free_cursor (c, cursor);
+
+ cookie_font = xcb_close_font_checked (c, font);
+ error = xcb_request_check (c, cookie_font);
+ if (error) {
+ fprintf (stderr, "ERROR: can't close font : %d\n", error->error_code);
+ xcb_disconnect (c);
+ exit (-1);
+ }
+}
+
+int main ()
+{
+ xcb_screen_iterator_t screen_iter;
+ xcb_connection_t *c;
+ const xcb_setup_t *setup;
+ xcb_screen_t *screen;
+ xcb_generic_event_t *e;
+ xcb_generic_error_t *error;
+ xcb_void_cookie_t cookie_window;
+ xcb_void_cookie_t cookie_map;
+ xcb_window_t window;
+ uint32_t mask;
+ uint32_t values[2];
+ int screen_number;
+ uint8_t is_hand = 0;
+
+ /* getting the connection */
+ c = xcb_connect (NULL, &screen_number);
+ if (!c) {
+ fprintf (stderr, "ERROR: can't connect to an X server\n");
+ return -1;
+ }
+
+ /* getting the current screen */
+ setup = xcb_get_setup (c);
+
+ screen = NULL;
+ screen_iter = xcb_setup_roots_iterator (setup);
+ for (; screen_iter.rem != 0; --screen_number, xcb_screen_next (&screen_iter))
+ if (screen_number == 0)
+ {
+ screen = screen_iter.data;
+ break;
+ }
+ if (!screen) {
+ fprintf (stderr, "ERROR: can't get the current screen\n");
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ /* creating the window */
+ window = xcb_generate_id (c);
+ mask = XCB_CW_BACK_PIXEL | XCB_CW_EVENT_MASK;
+ values[0] = screen->white_pixel;
+ values[1] =
+ XCB_EVENT_MASK_KEY_RELEASE |
+ XCB_EVENT_MASK_BUTTON_PRESS |
+ XCB_EVENT_MASK_EXPOSURE |
+ XCB_EVENT_MASK_POINTER_MOTION;
+ cookie_window = xcb_create_window_checked (c,
+ screen->root_depth,
+ window, screen->root,
+ 20, 200, WIDTH, HEIGHT,
+ 0, XCB_WINDOW_CLASS_INPUT_OUTPUT,
+ screen->root_visual,
+ mask, values);
+ cookie_map = xcb_map_window_checked (c, window);
+
+ /* error managing */
+ error = xcb_request_check (c, cookie_window);
+ if (error) {
+ fprintf (stderr, "ERROR: can't create window : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+ error = xcb_request_check (c, cookie_map);
+ if (error) {
+ fprintf (stderr, "ERROR: can't map window : %d\n", error->error_code);
+ xcb_disconnect (c);
+ return -1;
+ }
+
+ cursor_set (c, screen, window, 68);
+
+ xcb_flush(c);
+
+ while (1) {
+ e = xcb_poll_for_event(c);
+ if (e) {
+ switch (e->response_type & ~0x80) {
+ case XCB_EXPOSE: {
+ char *text;
+
+ text = "click here to change cursor";
+ button_draw (c, screen, window,
+ (WIDTH - 7 * strlen(text)) / 2,
+ (HEIGHT - 16) / 2, text);
+
+ text = "Press ESC key to exit...";
+ text_draw (c, screen, window, 10, HEIGHT - 10, text);
+ break;
+ }
+ case XCB_BUTTON_PRESS: {
+ xcb_button_press_event_t *ev;
+ int length;
+
+ ev = (xcb_button_press_event_t *)e;
+ length = strlen ("click here to change cursor");
+
+ if ((ev->event_x >= (WIDTH - 7 * length) / 2) &&
+ (ev->event_x <= ((WIDTH - 7 * length) / 2 + 7 * length + 6)) &&
+ (ev->event_y >= (HEIGHT - 16) / 2 - 19) &&
+ (ev->event_y <= ((HEIGHT - 16) / 2)))
+ is_hand = 1 - is_hand;
+
+ is_hand ? cursor_set (c, screen, window, 58) : cursor_set (c, screen, window, 68);
+ }
+ case XCB_KEY_RELEASE: {
+ xcb_key_release_event_t *ev;
+
+ ev = (xcb_key_release_event_t *)e;
+
+ switch (ev->detail) {
+ /* ESC */
+ case 9:
+ free (e);
+ xcb_disconnect (c);
+ return 0;
+ }
+ }
+ }
+ free (e);
+ }
+ }
+
+ return 0;
+}
+</pre>
+ </ol>
+ <li class="title"><a name="translation">Translation of basic Xlib functions and macros</a>
+ <p>
+ The problem when you want to port an Xlib program to XCB is that
+ you don't know if the Xlib function that you want to "translate"
+ is a X Window one or an Xlib macro. In that section, we describe
+ a way to translate the usual functions or macros that Xlib
+ provides. It's usually just a member of a structure.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="displaystructure">Members of the Display structure</a>
+ <p>
+ In this section, we look at how to translate the macros that
+ return some members of the <span class="code">Display</span>
+ structure. They are obtained by using a function that requires a
+ <span class="code">xcb_connection_t *</span> or a member of the
+ <span class="code">xcb_setup_t</span> structure
+ (via the function <span class="code">xcb_get_setup</span>), or
+ a function that requires that structure.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="ConnectionNumber">ConnectionNumber</a>
+ <p>
+ This number is the file descriptor that connects the client
+ to the server. You just have to use that function:
+ </p>
+ <pre class="code">
+int xcb_get_file_descriptor (xcb_connection_t *c);
+</pre>
+ <li class="subtitle"><a name="DefaultScreen"></a>DefaultScreen
+ <p>
+ That number is not stored by XCB. It is returned in the
+ second parameter of the function <span class="code"><a href="#openconn">xcb_connect</a></span>.
+ Hence, you have to store it yourself if you want to use
+ it. Then, to get the <span class="code">xcb_screen_t</span>
+ structure, you have to iterate on the screens.
+ The equivalent function of the Xlib's
+ <span class="code">ScreenOfDisplay</span> function can be
+ found <a href="#ScreenOfDisplay">below</a>. This is also provided in the
+ xcb_aux_t library as <span class="code">xcb_aux_get_screen()</span>. OK, here is the
+ small piece of code to get that number:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+int screen_default_nbr;
+
+/* you pass the name of the display you want to xcb_connect_t */
+
+c = xcb_connect (display_name, &screen_default_nbr);
+
+/* screen_default_nbr contains now the number of the default screen */
+</pre>
+ <li class="subtitle"><a name="QLength"></a>QLength
+ <p>
+ Not documented yet.
+ </p>
+ <p>
+ However, this points out a basic difference in philosophy between
+ Xlib and XCB. Xlib has several functions for filtering and
+ manipulating the incoming and outgoing X message queues. XCB
+ wishes to hide this as much as possible from the user, which
+ allows for more freedom in implementation strategies.
+ </p>
+ <li class="subtitle"><a name="ScreenCount"></a>ScreenCount
+ <p>
+ You get the count of screens with the functions
+ <span class="code">xcb_get_setup</span>
+ and
+ <span class="code">xcb_setup_roots_iterator</span>
+ (if you need to iterate):
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+int screen_count;
+
+/* you init the connection */
+
+screen_count = xcb_setup_roots_iterator (xcb_get_setup (c)).rem;
+
+/* screen_count contains now the count of screens */
+</pre>
+ <p>
+ If you don't want to iterate over the screens, a better way
+ to get that number is to use
+ <span class="code">xcb_setup_roots_length_t</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+int screen_count;
+
+/* you init the connection */
+
+screen_count = xcb_setup_roots_length (xcb_get_setup (c));
+
+/* screen_count contains now the count of screens */
+</pre>
+ <li class="subtitle"><a name="ServerVendor"></a>ServerVendor
+ <p>
+ You get the name of the vendor of the server hardware with
+ the functions <span class="code">xcb_get_setup</span>
+ and
+ <span
+ class="code">xcb_setup_vendor</span>. Beware
+ that, unlike Xlib, the string returned by XCB is not
+ necessarily null-terminaled:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+char *vendor = NULL;
+int length;
+
+/* you init the connection */
+length = xcb_setup_vendor_length (xcb_get_setup (c));
+vendor = (char *)malloc (length + 1);
+if (vendor)
+memcpy (vendor, xcb_setup_vendor (xcb_get_setup (c)), length);
+vendor[length] = '\0';
+
+/* vendor contains now the name of the vendor. Must be freed when not used anymore */
+</pre>
+ <li class="subtitle"><a name="ProtocolVersion"></a>ProtocolVersion
+ <p>
+ You get the major version of the protocol in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint16_t protocol_major_version;
+
+/* you init the connection */
+
+protocol_major_version = xcb_get_setup (c)->protocol_major_version;
+
+/* protocol_major_version contains now the major version of the protocol */
+</pre>
+ <li class="subtitle"><a name="ProtocolRevision"></a>ProtocolRevision
+ <p>
+ You get the minor version of the protocol in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint16_t protocol_minor_version;
+
+/* you init the connection */
+
+protocol_minor_version = xcb_get_setup (c)->protocol_minor_version;
+
+/* protocol_minor_version contains now the minor version of the protocol */
+</pre>
+ <li class="subtitle"><a name="VendorRelease"></a>VendorRelease
+ <p>
+ You get the number of the release of the server hardware in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint32_t release_number;
+
+/* you init the connection */
+
+release_number = xcb_get_setup (c)->release_number;
+
+/* release_number contains now the number of the release of the server hardware */
+</pre>
+ <li class="subtitle"><a name="DisplayString"></a>DisplayString
+ <p>
+ The name of the display is not stored in XCB. You have to
+ store it by yourself.
+ </p>
+ <li class="subtitle"><a name="BitmapUnit"></a>BitmapUnit
+ <p>
+ You get the bitmap scanline unit in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint8_t bitmap_format_scanline_unit;
+
+/* you init the connection */
+
+bitmap_format_scanline_unit = xcb_get_setup (c)->bitmap_format_scanline_unit;
+
+/* bitmap_format_scanline_unit contains now the bitmap scanline unit */
+</pre>
+ <li class="subtitle"><a name="BitmapBitOrder"></a>BitmapBitOrder
+ <p>
+ You get the bitmap bit order in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint8_t bitmap_format_bit_order;
+
+/* you init the connection */
+
+bitmap_format_bit_order = xcb_get_setup (c)->bitmap_format_bit_order;
+
+/* bitmap_format_bit_order contains now the bitmap bit order */
+</pre>
+ <li class="subtitle"><a name="BitmapPad"></a>BitmapPad
+ <p>
+ You get the bitmap scanline pad in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint8_t bitmap_format_scanline_pad;
+
+/* you init the connection */
+
+bitmap_format_scanline_pad = xcb_get_setup (c)->bitmap_format_scanline_pad;
+
+/* bitmap_format_scanline_pad contains now the bitmap scanline pad */
+</pre>
+ <li class="subtitle"><a name="ImageByteOrder"></a>ImageByteOrder
+ <p>
+ You get the image byte order in the
+ <span class="code">xcb_setup_t</span>
+ structure, with the function <span class="code">xcb_get_setup</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+uint8_t image_byte_order;
+
+/* you init the connection */
+
+image_byte_order = xcb_get_setup (c)->image_byte_order;
+
+/* image_byte_order contains now the image byte order */
+</pre>
+ </ol>
+ <li class="subtitle"><a name="screenofdisplay">ScreenOfDisplay related functions</a>
+ <p>
+ in Xlib, <span class="code">ScreenOfDisplay</span> returns a
+ <span class="code">Screen</span> structure that contains
+ several characteristics of your screen. XCB has a similar
+ structure (<span class="code">xcb_screen_t</span>),
+ but the way to obtain it is a bit different. With
+ Xlib, you just provide the number of the screen and you grab it
+ from an array. With XCB, you iterate over all the screens to
+ obtain the one you want. The complexity of this operation is
+ O(n). So the best is to store this structure if you use
+ it often. See <a href="#ScreenOfDisplay">screen_of_display</a> just below.
+ </p>
+ <p>
+ Xlib provides generally two functions to obtain the characteristics
+ related to the screen. One with the display and the number of
+ the screen, which calls <span class="code">ScreenOfDisplay</span>,
+ and the other that uses the <span class="code">Screen</span> structure.
+ This might be a bit confusing. As mentioned above, with XCB, it
+ is better to store the <span class="code">xcb_screen_t</span>
+ structure. Then, you have to read the members of this
+ structure. That's why the Xlib functions are put by pairs (or
+ more) as, with XCB, you will use the same code.
+ </p>
+ <ol>
+ <li class="subtitle"><a name="ScreenOfDisplay">ScreenOfDisplay</a>
+ <p>
+ This function returns the Xlib <span class="code">Screen</span>
+ structure. With XCB, you iterate over all the screens and
+ once you get the one you want, you return it:
+ </p>
+ <pre class="code"><a name="ScreenOfDisplay"></a>
+xcb_screen_t *screen_of_display (xcb_connection_t *c,
+ int screen)
+{
+ xcb_screen_iterator_t iter;
+
+ iter = xcb_setup_roots_iterator (xcb_get_setup (c));
+ for (; iter.rem; --screen, xcb_screen_next (&iter))
+ if (screen == 0)
+ return iter.data;
+
+ return NULL;
+}
+</pre>
+ <p>
+ As mentioned above, you might want to store the value
+ returned by this function.
+ </p>
+ <p>
+ All the functions below will use the result of that
+ function, as they just grab a specific member of the
+ <span class="code">xcb_screen_t</span> structure.
+ </p>
+ <li class="subtitle"><a name="DefaultScreenOfDisplay"></a>DefaultScreenOfDisplay
+ <p>
+ It is the default screen that you obtain when you connect to
+ the X server. It suffices to call the <a href="#ScreenOfDisplay">screen_of_display</a>
+ function above with the connection and the number of the
+ default screen.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+int screen_default_nbr;
+xcb_screen_t *default_screen; /* the returned default screen */
+
+/* you pass the name of the display you want to xcb_connect_t */
+
+c = xcb_connect (display_name, &screen_default_nbr);
+default_screen = screen_of_display (c, screen_default_nbr);
+
+/* default_screen contains now the default root window, or a NULL window if no screen is found */
+</pre>
+ <li class="subtitle"><a name="RootWindow">RootWindow / RootWindowOfScreen</a>
+ <br>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+xcb_window_t root_window = { 0 }; /* the returned window */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ root_window = screen->root;
+
+/* root_window contains now the root window, or a NULL window if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DefaultRootWindow">DefaultRootWindow</a>
+ <p>
+ It is the root window of the default screen. So, you call
+ <a name="ScreenOfDisplay">ScreenOfDisplay</a> with the
+ default screen number and you get the
+ <a href="#RootWindow">root window</a> as above:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_default_nbr;
+xcb_window_t root_window = { 0 }; /* the returned root window */
+
+/* you pass the name of the display you want to xcb_connect_t */
+
+c = xcb_connect (display_name, &screen_default_nbr);
+screen = screen_of_display (c, screen_default_nbr);
+if (screen)
+ root_window = screen->root;
+
+/* root_window contains now the default root window, or a NULL window if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DefaultVisual">DefaultVisual / DefaultVisualOfScreen</a>
+ <p>
+ While a Visual is, in Xlib, a structure, in XCB, there are
+ two types: <span class="code">xcb_visualid_t</span>, which is
+ the Id of the visual, and <span class="code">xcb_visualtype_t</span>,
+ which corresponds to the Xlib Visual. To get the Id of the
+ visual of a screen, just get the
+ <span class="code">root_visual</span>
+ member of a <span class="code">xcb_screen_t</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+xcb_visualid_t root_visual = { 0 }; /* the returned visual Id */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ root_visual = screen->root_visual;
+
+/* root_visual contains now the value of the Id of the visual, or a NULL visual if no screen is found */
+</pre>
+ <p>
+ To get the <span class="code">xcb_visualtype_t</span>
+ structure, it's a bit less easy. You have to get the
+ <span class="code">xcb_screen_t</span> structure that you want,
+ get its <span class="code">root_visual</span> member,
+ then iterate over the <span class="code">xcb_depth_t</span>s
+ and the <span class="code">xcb_visualtype_t</span>s, and compare
+ the <span class="code">xcb_visualid_t</span> of these <span class="code">xcb_visualtype_t</span>s:
+ with <span class="code">root_visual</span>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+xcb_visualid_t root_visual = { 0 };
+xcb_visualtype_t *visual_type = NULL; /* the returned visual type */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen) {
+ xcb_depth_iterator_t depth_iter;
+
+ depth_iter = xcb_screen_allowed_depths_iterator (screen);
+ for (; depth_iter.rem; xcb_depth_next (&depth_iter)) {
+ xcb_visualtype_iterator_t visual_iter;
+
+ visual_iter = xcb_depth_visuals_iterator (depth_iter.data);
+ for (; visual_iter.rem; xcb_visualtype_next (&visual_iter)) {
+ if (screen->root_visual == visual_iter.data->visual_id) {
+ visual_type = visual_iter.data;
+ break;
+ }
+ }
+ }
+}
+
+/* visual_type contains now the visual structure, or a NULL visual structure if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DefaultGC">DefaultGC / DefaultGCOfScreen</a>
+ <p>
+ This default Graphic Context is just a newly created Graphic
+ Context, associated to the root window of a
+ <span class="code">xcb_screen_t</span>,
+ using the black white pixels of that screen:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+xcb_gcontext_t gc = { 0 }; /* the returned default graphic context */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen) {
+ xcb_drawable_t draw;
+ uint32_t mask;
+ uint32_t values[2];
+
+ gc = xcb_generate_id (c);
+ draw = screen->root;
+ mask = XCB_GC_FOREGROUND | XCB_GC_BACKGROUND;
+ values[0] = screen->black_pixel;
+ values[1] = screen->white_pixel;
+ xcb_create_gc (c, gc, draw, mask, values);
+}
+
+/* gc contains now the default graphic context */
+</pre>
+ <li class="subtitle"><a name="BlackPixel">BlackPixel / BlackPixelOfScreen</a>
+ <p>
+ It is the Id of the black pixel, which is in the structure
+ of an <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t black_pixel = 0; /* the returned black pixel */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ black_pixel = screen->black_pixel;
+
+/* black_pixel contains now the value of the black pixel, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="WhitePixel">WhitePixel / WhitePixelOfScreen</a>
+ <p>
+ It is the Id of the white pixel, which is in the structure
+ of an <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t white_pixel = 0; /* the returned white pixel */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ white_pixel = screen->white_pixel;
+
+/* white_pixel contains now the value of the white pixel, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DisplayWidth">DisplayWidth / WidthOfScreen</a>
+ <p>
+ It is the width in pixels of the screen that you want, and
+ which is in the structure of the corresponding
+ <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t width_in_pixels = 0; /* the returned width in pixels */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ width_in_pixels = screen->width_in_pixels;
+
+/* width_in_pixels contains now the width in pixels, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DisplayHeight">DisplayHeight / HeightOfScreen</a>
+ <p>
+ It is the height in pixels of the screen that you want, and
+ which is in the structure of the corresponding
+ <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t height_in_pixels = 0; /* the returned height in pixels */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ height_in_pixels = screen->height_in_pixels;
+
+/* height_in_pixels contains now the height in pixels, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DisplayWidthMM">DisplayWidthMM / WidthMMOfScreen</a>
+ <p>
+ It is the width in millimeters of the screen that you want, and
+ which is in the structure of the corresponding
+ <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t width_in_millimeters = 0; /* the returned width in millimeters */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ width_in_millimeters = screen->width_in_millimeters;
+
+/* width_in_millimeters contains now the width in millimeters, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DisplayHeightMM">DisplayHeightMM / HeightMMOfScreen</a>
+ <p>
+ It is the height in millimeters of the screen that you want, and
+ which is in the structure of the corresponding
+ <span class="code">xcb_screen_t</span>.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t height_in_millimeters = 0; /* the returned height in millimeters */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ height_in_millimeters = screen->height_in_millimeters;
+
+/* height_in_millimeters contains now the height in millimeters, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DisplayPlanes">DisplayPlanes / DefaultDepth / DefaultDepthOfScreen / PlanesOfScreen</a>
+ <p>
+ It is the depth (in bits) of the root window of the
+ screen. You get it from the <span class="code">xcb_screen_t</span> structure.
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint8_t root_depth = 0; /* the returned depth of the root window */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ root_depth = screen->root_depth;
+
+/* root_depth contains now the depth of the root window, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DefaultColormap">DefaultColormap / DefaultColormapOfScreen</a>
+ <p>
+ This is the default colormap of the screen (and not the
+ (default) colormap of the default screen !). As usual, you
+ get it from the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+xcb_colormap_t default_colormap = { 0 }; /* the returned default colormap */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ default_colormap = screen->default_colormap;
+
+/* default_colormap contains now the default colormap, or a NULL colormap if no screen is found */
+</pre>
+ <li class="subtitle"><a name="MinCmapsOfScreen"></a>MinCmapsOfScreen
+ <p>
+ You get the minimum installed colormaps in the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint16_t min_installed_maps = 0; /* the returned minimum installed colormaps */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ min_installed_maps = screen->min_installed_maps;
+
+/* min_installed_maps contains now the minimum installed colormaps, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="MaxCmapsOfScreen"></a>MaxCmapsOfScreen
+ <p>
+ You get the maximum installed colormaps in the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint16_t max_installed_maps = 0; /* the returned maximum installed colormaps */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ max_installed_maps = screen->max_installed_maps;
+
+/* max_installed_maps contains now the maximum installed colormaps, or 0 if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DoesSaveUnders"></a>DoesSaveUnders
+ <p>
+ You know if <span class="code">save_unders</span> is set,
+ by looking in the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint8_t save_unders = 0; /* the returned value of save_unders */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ save_unders = screen->save_unders;
+
+/* save_unders contains now the value of save_unders, or FALSE if no screen is found */
+</pre>
+ <li class="subtitle"><a name="DoesBackingStore"></a>DoesBackingStore
+ <p>
+ You know the value of <span class="code">backing_stores</span>,
+ by looking in the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint8_t backing_stores = 0; /* the returned value of backing_stores */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ backing_stores = screen->backing_stores;
+
+/* backing_stores contains now the value of backing_stores, or FALSE if no screen is found */
+</pre>
+ <li class="subtitle"><a name="EventMaskOfScreen"></a>EventMaskOfScreen
+ <p>
+ To get the current input masks,
+ you look in the <span class="code">xcb_screen_t</span> structure:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_screen_t *screen;
+int screen_nbr;
+uint32_t current_input_masks = 0; /* the returned value of current input masks */
+
+/* you init the connection and screen_nbr */
+
+screen = screen_of_display (c, screen_nbr);
+if (screen)
+ current_input_masks = screen->current_input_masks;
+
+/* current_input_masks contains now the value of the current input masks, or FALSE if no screen is found */
+</pre>
+ </ol>
+ <li class="subtitle"><a name="misc">Miscellaneous macros</a>
+ <ol>
+ <li class="subtitle"><a name="DisplayOfScreen"></a>DisplayOfScreen
+ <p>
+ in Xlib, the <span class="code">Screen</span> structure
+ stores its associated <span class="code">Display</span>
+ structure. This is not the case in the X Window protocol,
+ hence, it's also not the case in XCB. So you have to store
+ it by yourself.
+ </p>
+ <li class="subtitle"><a name="DisplayCells"></a>DisplayCells / CellsOfScreen
+ <p>
+ To get the colormap entries,
+ you look in the <span class="code">xcb_visualtype_t</span>
+ structure, that you grab like <a class="subsection" href="#DefaultVisual">here</a>:
+ </p>
+ <pre class="code">
+xcb_connection_t *c;
+xcb_visualtype_t *visual_type;
+uint16_t colormap_entries = 0; /* the returned value of the colormap entries */
+
+/* you init the connection and visual_type */
+
+if (visual_type)
+ colormap_entries = visual_type->colormap_entries;
+
+/* colormap_entries contains now the value of the colormap entries, or FALSE if no screen is found */
+</pre>
+ </ol>
+ </ol>
+ </ol>
+ </div>
+</body>
+
+</html>
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