path: root/libX11/specs/libX11/CH05

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.sp 1
.ce 3
\s+1\fBChapter 5\fP\s-1

\s+1\fBPixmap and Cursor Functions\fP\s-1
.sp 2
.nr H1 5
.nr H2 0
.nr H3 0
.nr H4 0
.nr H5 0
.na
.LP
.XS
Chapter 5: Pixmap and Cursor Functions 
.XE
Once you have connected to an X server,
you can use the Xlib functions to:
.IP \(bu 5
Create and free pixmaps
.IP \(bu 5
Create, recolor, and free cursors
.NH 2
Creating and Freeing Pixmaps
.XS
\*(SN Creating and Freeing Pixmaps
.XE
.LP
Pixmaps can only be used on the screen on which they were created.
Pixmaps are off-screen resources that are used for various operations,
such as defining cursors as tiling patterns 
or as the source for certain raster operations.
Most graphics requests can operate either on a window or on a pixmap.
A bitmap is a single bit-plane pixmap.
.LP
.sp
To create a pixmap of a given size, use
.PN XCreatePixmap .
.IN "XCreatePixmap" "" "@DEF@"
.sM
.FD 0
Pixmap XCreatePixmap\^(\^\fIdisplay\fP, \fId\fP\^, \fIwidth\fP\^, \fIheight\fP\^, \fIdepth\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Drawable \fId\fP\^;
.br
      unsigned int \fIwidth\fP\^, \fIheight\fP\^;
.br
      unsigned int \fIdepth\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fId\fP 1i
Specifies which screen the pixmap is created on. 
.ds Wh , which define the dimensions of the pixmap
.IP \fIwidth\fP 1i
.br
.ns
.IP \fIheight\fP 1i
Specify the width and height\*(Wh.
.IP \fIdepth\fP 1i
Specifies the depth of the pixmap.
.LP
.eM 
The
.PN XCreatePixmap
function creates a pixmap of the width, height, and depth you specified
and returns a pixmap ID that identifies it.
It is valid to pass an 
.PN InputOnly
window to the drawable argument.
The width and height arguments must be nonzero,
or a 
.PN BadValue
error results.
The depth argument must be one of the depths supported by the screen
of the specified drawable,
or a
.PN BadValue
error results.
.LP
The server uses the specified drawable to determine on which screen
to create the pixmap.
The pixmap can be used only on this screen
and only with other drawables of the same depth (see
.PN XCopyPlane
for an exception to this rule).
The initial contents of the pixmap are undefined.
.LP
.PN XCreatePixmap
can generate
.PN BadAlloc ,
.PN BadDrawable ,
and
.PN BadValue 
errors.
.LP
.sp
To free all storage associated with a specified pixmap, use
.PN XFreePixmap .
.IN "XFreePixmap" "" "@DEF@"
.sM
.FD 0
XFreePixmap\^(\^\fIdisplay\fP, \fIpixmap\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Pixmap \fIpixmap\fP\^;
.FN	
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIpixmap\fP 1i
Specifies the pixmap.
.LP
.eM 
The
.PN XFreePixmap
function first deletes the association between the pixmap ID and the pixmap.
Then, the X server frees the pixmap storage when there are no references to it.
The pixmap should never be referenced again.
.LP
.PN XFreePixmap
can generate a
.PN BadPixmap 
error.
.NH 2
Creating, Recoloring, and Freeing Cursors
.XS
\*(SN Creating, Recoloring, and Freeing Cursors 
.XE
.LP
Each window can have a different cursor defined for it.
Whenever the pointer is in a visible window, 
it is set to the cursor defined for that window.
If no cursor was defined for that window, 
the cursor is the one defined for the parent window.
.LP
From X's perspective, 
a cursor consists of a cursor source, mask, colors, and a hotspot. 
The mask pixmap determines the shape of the cursor and must be a depth
of one.
The source pixmap must have a depth of one,
and the colors determine the colors of the source.
The hotspot defines the point on the cursor that is reported
when a pointer event occurs.
There may be limitations imposed by the hardware on
cursors as to size and whether a mask is implemented. 
.IN "XQueryBestCursor"
.PN XQueryBestCursor
can be used to find out what sizes are possible.
There is a standard font for creating cursors, but
Xlib provides functions that you can use to create cursors
from an arbitrary font or from bitmaps.
.LP
.sp
To create a cursor from the standard cursor font, use
.PN XCreateFontCursor .
.IN "XCreateFontCursor" "" "@DEF@"
.sM
.FD 0
#include <X11/cursorfont.h>
.sp 6p
Cursor XCreateFontCursor\^(\^\fIdisplay\fP, \fIshape\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      unsigned int \fIshape\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIshape\fP 1i
Specifies the shape of the cursor.
.LP
.eM
X provides a set of standard cursor shapes in a special font named
cursor.
Applications are encouraged to use this interface for their cursors
because the font can be customized for the individual display type.
The shape argument specifies which glyph of the standard fonts
to use.
.LP
The hotspot comes from the information stored in the cursor font.
The initial colors of a cursor are a black foreground and a white
background (see
.PN XRecolorCursor ).
For further information about cursor shapes,
see appendix B.
.LP
.PN XCreateFontCursor
can generate
.PN BadAlloc
and
.PN BadValue 
errors.
.LP
.sp
To create a cursor from font glyphs, use
.PN XCreateGlyphCursor .
.IN "XCreateGlyphCursor" "" "@DEF@"
.sM
.FD 0
Cursor XCreateGlyphCursor\^(\^\fIdisplay\fP, \fIsource_font\fP\^, \fImask_font\fP\^, \fIsource_char\fP\^, \fImask_char\fP\^,
.br
                           \fIforeground_color\fP\^, \fIbackground_color\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Font \fIsource_font\fP\^, \fImask_font\fP\^;
.br
      unsigned int \fIsource_char\fP\^, \fImask_char\fP\^;
.br
      XColor *\fIforeground_color\fP\^;
.br
      XColor *\fIbackground_color\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIsource_font\fP 1i
Specifies the font for the source glyph.
.IP \fImask_font\fP 1i
Specifies the font for the mask glyph or
.PN None .
.IP \fIsource_char\fP 1i
Specifies the character glyph for the source.
.IP \fImask_char\fP 1i
Specifies the glyph character for the mask. 
.IP \fIforeground_color\fP 1i
Specifies the RGB values for the foreground of the source. 
.IP \fIbackground_color\fP 1i
Specifies the RGB values for the background of the source.
.LP
.eM
The
.PN XCreateGlyphCursor
function is similar to
.PN XCreatePixmapCursor
except that the source and mask bitmaps are obtained from the specified 
font glyphs.
The source_char must be a defined glyph in source_font, 
or a
.PN BadValue
error results.
If mask_font is given, 
mask_char must be a defined glyph in mask_font,
or a
.PN BadValue
error results.
The mask_font and character are optional.
The origins of the source_char and mask_char (if defined) glyphs are
positioned coincidently and define the hotspot. 
The source_char and mask_char need not have the same bounding box metrics, 
and there is no restriction on the placement of the hotspot relative to the bounding
boxes. 
If no mask_char is given, all pixels of the source are displayed.
You can free the fonts immediately by calling
.PN XFreeFont
if no further explicit references to them are to be made. 
.LP
For 2-byte matrix fonts, 
the 16-bit value should be formed with the byte1
member in the most significant byte and the byte2 member in the 
least significant byte.
.LP
.PN XCreateGlyphCursor
can generate
.PN BadAlloc ,
.PN BadFont ,
and
.PN BadValue 
errors.
.LP
.sp
To create a cursor from two bitmaps,
use
.PN XCreatePixmapCursor .
.IN "XCreatePixmapCursor" "" "@DEF@"
.sM
.FD 0
Cursor XCreatePixmapCursor\^(\^\fIdisplay\fP, \fIsource\fP\^, \fImask\fP\^, \fIforeground_color\fP\^, \fIbackground_color\fP\^, \fIx\fP\^, \fIy\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Pixmap \fIsource\fP\^;
.br
      Pixmap \fImask\fP\^;
.br
      XColor *\fIforeground_color\fP\^;
.br
      XColor *\fIbackground_color\fP\^;
.br
      unsigned int \fIx\fP\^, \fIy\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIsource\fP 1i
Specifies the shape of the source cursor.
.\" *** JIM: NEED TO CHECK THIS. ***
.IP \fImask\fP 1i
Specifies the cursor's source bits to be displayed or
.PN None .
.IP \fIforeground_color\fP 1i
Specifies the RGB values for the foreground of the source. 
.IP \fIbackground_color\fP 1i
Specifies the RGB values for the background of the source.
.ds Xy , which indicate the hotspot relative to the source's origin
.IP \fIx\fP 1i
.br
.ns
.IP \fIy\fP 1i
Specify the x and y coordinates\*(Xy.
.LP
.eM
The
.PN XCreatePixmapCursor
function creates a cursor and returns the cursor ID associated with it.
The foreground and background RGB values must be specified using
foreground_color and background_color,
even if the X server only has a
.PN StaticGray
or
.PN GrayScale
screen.
The foreground color is used for the pixels set to 1 in the
source, and the background color is used for the pixels set to 0.
Both source and mask, if specified, must have depth one (or a 
.PN BadMatch
error results) but can have any root.
The mask argument defines the shape of the cursor.
The pixels set to 1 in the mask define which source pixels are displayed,
and the pixels set to 0 define which pixels are ignored.
If no mask is given, 
all pixels of the source are displayed.
The mask, if present, must be the same size as the pixmap defined by the 
source argument, or a
.PN BadMatch
error results.
The hotspot must be a point within the source,
or a
.PN BadMatch
error results.
.LP
The components of the cursor can be transformed arbitrarily to meet
display limitations.
The pixmaps can be freed immediately if no further explicit references
to them are to be made.
Subsequent drawing in the source or mask pixmap has an undefined effect on the
cursor.
The X server might or might not make a copy of the pixmap.
.LP
.PN XCreatePixmapCursor
can generate
.PN BadAlloc
and
.PN BadPixmap
errors.
.LP
.sp
To determine useful cursor sizes, use
.PN XQueryBestCursor .
.IN "XQueryBestCursor" "" "@DEF@"
.sM
.FD 0
Status XQueryBestCursor\^(\^\fIdisplay\fP, \fId\fP, \fIwidth\fP\^, \fIheight\fP\^, \fIwidth_return\fP\^, \fIheight_return\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Drawable \fId\fP\^;
.br
      unsigned int \fIwidth\fP\^, \fIheight\fP\^;
.br
      unsigned int *\fIwidth_return\fP\^, *\fIheight_return\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.ds Dr , which indicates the screen
.IP \fId\fP 1i
Specifies the drawable\*(Dr. 
.ds Wh \ of the cursor that you want the size information for
.IP \fIwidth\fP 1i
.br
.ns
.IP \fIheight\fP 1i
Specify the width and height\*(Wh.
.IP \fIwidth_return\fP 1i
.br
.ns
.IP \fIheight_return\fP 1i
Return the best width and height that is closest to the specified width 
and height.
.LP
.eM
Some displays allow larger cursors than other displays.
The
.PN XQueryBestCursor
function provides a way to find out what size cursors are actually
possible on the display.
.IN "Cursor" "limitations" 
It returns the largest size that can be displayed.
Applications should be prepared to use smaller cursors on displays that
cannot support large ones.
.LP
.PN XQueryBestCursor
can generate a
.PN BadDrawable 
error.
.LP
.sp
To change the color of a given cursor, use
.PN XRecolorCursor .
.IN "XRecolorCursor" "" "@DEF@"
.sM
.FD 0
XRecolorCursor\^(\^\fIdisplay\fP, \fIcursor\fP\^, \fIforeground_color\fP\^, \fIbackground_color\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Cursor \fIcursor\fP\^;
.br
      XColor *\fIforeground_color\fP\^, *\fIbackground_color\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcursor\fP 1i
Specifies the cursor. 
.IP \fIforeground_color\fP 1i
Specifies the RGB values for the foreground of the source. 
.IP \fIbackground_color\fP 1i
Specifies the RGB values for the background of the source.
.LP
.eM
The
.PN XRecolorCursor
function changes the color of the specified cursor, and
if the cursor is being displayed on a screen,
the change is visible immediately.
The pixel members of the
.PN XColor
structures are ignored; only the RGB values are used.
.LP
.PN XRecolorCursor
can generate a
.PN BadCursor 
error.
.LP
.sp
To free (destroy) a given cursor, use
.PN XFreeCursor .
.IN "XFreeCursor" "" "@DEF@"
.sM
.FD 0
XFreeCursor\^(\^\fIdisplay\fP, \fIcursor\fP\^)
.br
      Display *\fIdisplay\fP\^;
.br
      Cursor \fIcursor\fP\^;
.FN
.IP \fIdisplay\fP 1i
Specifies the connection to the X server.
.IP \fIcursor\fP 1i
Specifies the cursor. 
.LP
.eM 
The
.PN XFreeCursor
function deletes the association between the cursor resource ID 
and the specified cursor.
The cursor storage is freed when no other resource references it.
The specified cursor ID should not be referred to again.
.LP
.PN XFreeCursor
can generate a
.PN BadCursor 
error.
.bp