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+% $Xorg: dbelib.tex,v 1.3 2000/08/17 19:42:31 cpqbld Exp $

+% edited for DP edits and code consistency w/ core protocol/xlib 3/30/96

+% split into separate library and protocol documentos 4/15/96

+\documentstyle{article}

+\pagestyle{myheadings}

+\markboth{Double Buffer Extension Specification}{Double Buffer Extension Specification}

+\setlength{\parindent}{0 pt}

+\setlength{\parskip}{6pt}

+\setlength{\topsep}{0 pt}

+

+% Request names are literal symbols; therefore, use the same font for both.

+\newcommand{\requestname}[1]{{\tt #1}}

+\newcommand{\literal}[1]{\mbox{\tt #1}}

+

+\newcommand{\encodingsection}[1]{{\bf #1}}

+\newcommand{\requestsection}[1]{{\bf #1}}

+

+% Font treatment of type names differs between protocol and library sections.

+\newcommand{\libtypename}[1]{\mbox{\tt #1}}

+\newcommand{\typename}[1]{\mbox{\rm #1}}  % default font

+\newcommand{\typeargname}[1]{\mbox{\rm #1}}  % default font

+\newcommand{\argname}[1]{\mbox{\it #1}}

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+\newcommand{\areplyargdecl}[2]{#1 & : \typename{#2}\\}

+

+\newenvironment{arequest}[1]{\requestsection{#1} \\ \begin{tabular}{ll}}{\end{tabular}}

+\newcommand{\areply}{$\Rightarrow$\\}

+

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+

+\newcommand{\eargdecl}[3]{\> #1 \> \typename{#2} \> #3 \\}

+

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+

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+

+\newenvironment{eerror}[1]{\begin{keeptogether} \encodingsection{#1} \begin{tabbing} \etabstops }{\end{tabbing} \end{keeptogether}}

+

+\newenvironment{etypedef}[1]{\begin{keeptogether} \typename{#1} \begin{tabbing} \etabstops }{\end{tabbing} \end{keeptogether}}

+

+\newcommand{\cfunctionname}[1]{\mbox{\tt #1}}

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+

+% make things easier with all the long names

+\spaceskip .3333em plus 5em

+\tolerance=2000

+

+\begin{document}

+

+\title{Double Buffer Extension Library\\Protocol Version 1.0\\X Consortium Standard}

+\author{Ian Elliott\\Hewlett-Packard Company \and David P. Wiggins\\X Consortium, Inc.}

+\maketitle

+\thispagestyle{empty}

+

+\eject

+

+Copyright \copyright 1989 X Consortium, Inc. and Digital Equipment Corporation.

+

+Copyright \copyright 1992 X Consortium, Inc. and Intergraph Corporation.

+

+Copyright \copyright 1993 X Consortium, Inc. and Silicon Graphics, Inc.

+

+Copyright \copyright 1994, 1995 X Consortium, Inc. and Hewlett-Packard Company.

+

+Permission to use, copy, modify, and distribute this documentation for

+any purpose and without fee is hereby granted, provided that the above

+copyright notice and this permission notice appear in all copies.

+Digital Equipment Corporation, Intergraph Corporation, Silicon

+Graphics, Hewlett-Packard, and the X Consortium make no

+representations about the suitability for any purpose of the

+information in this document.  This documentation is provided ``as is''

+without express or implied warranty.

+

+\eject

+

+\section{Introduction}

+

+The Double Buffer Extension (DBE) provides a standard way to utilize

+double-buffering within the framework of the X Window System.

+Double-buffering uses two buffers, called front and back, which hold

+images.  The front buffer is visible to the user; the back buffer is

+not.  Successive frames of an animation are rendered into the back

+buffer while the previously rendered frame is displayed in the front

+buffer.  When a new frame is ready, the back and front buffers swap

+roles, making the new frame visible.  Ideally, this exchange appears to

+happen instantaneously to the user and with no visual artifacts.  Thus,

+only completely rendered images are presented to the user, and they remain

+visible during the entire time it takes to render a new frame.  The

+result is a flicker-free animation.

+

+\section{Goals}

+

+This extension should enable clients to:

+\begin{itemize}

+

+\item Allocate and deallocate double-buffering for a window.

+

+\item Draw to and read from the front and back buffers associated with

+a window.

+

+\item Swap the front and back buffers associated with a window.

+

+\item Specify a wide range of actions to be taken when a window is

+swapped.  This includes explicit, simple swap actions (defined

+below), and more complex actions (for example, clearing ancillary buffers)

+that can be put together within explicit ``begin'' and ``end''

+requests (defined below).

+

+\item Request that the front and back buffers associated with multiple

+double-buffered windows be swapped simultaneously.

+

+\end{itemize}

+

+In addition, the extension should:

+

+\begin{itemize}

+

+\item Allow multiple clients to use double-buffering on the same window.

+

+\item Support a range of implementation methods that can capitalize on

+existing hardware features.

+

+\item Add no new event types.

+

+\item Be reasonably easy to integrate with a variety of direct graphics

+hardware access (DGHA) architectures.

+\end{itemize}

+

+\section{Concepts}

+

+Normal windows are created using the core \requestname{CreateWindow}

+request, which allocates a set of window attributes and, for

+\literal{InputOutput} windows, a front buffer,

+into which an image can be drawn.

+The contents of this buffer will be displayed when the window is

+visible.

+

+This extension enables applications to use double-buffering with a

+window.  This involves creating a second buffer, called a back buffer,

+and associating one or more back buffer names (\typename{XID}s) with

+the window for use when referring to (that is, drawing to or reading

+from) the window's back buffer.  The back buffer name is a

+\typename{DRAWABLE} of type \typename{BACKBUFFER}.

+

+DBE provides a relative double-buffering model.  One XID, the window,

+always refers to the front buffer.  One or more other XIDs, the back buffer

+names, always refer to the back buffer.  After a buffer swap, the

+window continues to refer to the (new) front buffer, and the

+back buffer name continues to refer to the (new) back buffer.  Thus,

+applications and toolkits that want to just render to the back buffer

+always use the back buffer name for all drawing requests to the

+window.  Portions of an application that want to render to the front

+buffer always use the window XID for all drawing requests to the

+window.

+

+Multiple clients and toolkits can all use double-buffering on the same

+window.  DBE does not provide a request for querying whether a window

+has double-buffering support, and if so, what the back buffer name is.

+Given the asynchronous nature of the X Window System, this would cause

+race conditions.  Instead, DBE allows multiple back buffer names to

+exist for the same window; they all refer to the same physical back

+buffer.  The first time a back buffer name is allocated for a window,

+the window becomes double-buffered and the back buffer name is

+associated with the window.  Subsequently, the window already is a

+double-buffered window, and nothing about the window changes when a

+new back buffer name is allocated, except that the new back buffer

+name is associated with the window.  The window remains

+double-buffered until either the window is destroyed or until all of

+the back buffer names for the window are deallocated.

+

+In general, both the front and back buffers are treated the same.  In

+particular, here are some important characteristics:

+

+\begin{itemize}

+

+\item Only one buffer per window can be visible at a time (the

+front buffer).

+

+\item Both buffers associated with a window have the same visual type,

+depth, width, height, and shape as the window.

+

+\item Both buffers associated with a window are ``visible'' (or

+``obscured'') in the same way.  When an \literal{Expose} event is

+generated for

+a window, both buffers should be considered to be damaged in the

+exposed area.  Damage that occurs to either buffer will result in an

+\literal{Expose} event on the window.  When a double-buffered window is

+exposed,

+both buffers are tiled with the window background, exactly as stated

+by the core protocol.  Even though the back buffer is not visible,

+terms such as obscure apply to the back buffer as well as to the front

+buffer.

+

+\item It is acceptable at any time to pass a \typename{BACKBUFFER} in

+any request, notably any core or extension drawing request, that

+expects a \typename{DRAWABLE}.  This enables an application to draw

+directly into \typename{BACKBUFFER}s in the same fashion as it would

+draw into any other \typename{DRAWABLE}.

+

+\item It is an error (\literal{Window}) to pass a \typename{BACKBUFFER} in a

+core request that expects a Window.

+

+\item A \typename{BACKBUFFER} will never be sent by core X in a reply,

+event, or error where a Window is specified.

+\item If core X11 backing-store and save-under applies to a

+double-buffered window, it applies to both buffers equally.

+

+\item If the core \requestname{ClearArea} request is executed on a

+double-buffered window, the same area in both the front and back

+buffers is cleared.

+

+\end{itemize}

+

+The effect of passing a window to a request that accepts a

+\typename{DRAWABLE} is unchanged by this extension.  The window and

+front buffer are synonomous with each other.  This includes obeying

+the \requestname{GetImage} semantics and the subwindow-mode semantics

+if a core graphics context is involved.  Regardless of whether the

+window was explicitly passed in a \requestname{GetImage} request, or

+implicitly referenced (that is, one of the window's ancestors was passed

+in the request), the front (that is, visible) buffer is always referenced.

+Thus, DBE-na\"{\i}ve screen dump clients will always get the front buffer.

+\requestname{GetImage} on a back buffer returns undefined image

+contents for any obscured regions of the back buffer that fall within

+the image.

+

+Drawing to a back buffer always uses the clip region that would be

+used to draw to the front buffer with a GC subwindow-mode of

+\literal{ClipByChildren}.  If an ancestor of a double-buffered window is drawn

+to with a core GC having a subwindow-mode of \literal{IncludeInferiors}, the

+effect on the double-buffered window's back buffer depends on the

+depth of the double-buffered window and the ancestor.  If the depths

+are the same, the contents of the back buffer of the double-buffered

+window are not changed.  If the depths are different, the contents of

+the back buffer of the double-buffered window are undefined for the

+pixels that the \literal{IncludeInferiors} drawing touched.

+

+DBE adds no new events.  DBE does not extend the semantics of any

+existing events with the exception of adding a new \typename{DRAWABLE}

+type called \typename{BACKBUFFER}.  If events, replies, or errors that

+contain a \typename{DRAWABLE} (for example, \literal{GraphicsExpose}) are

+generated in

+response to a request, the \typename{DRAWABLE} returned will be the

+one specified in the request.

+

+DBE advertises which visuals support double-buffering.

+

+DBE does not include any timing or synchronization facilities.

+Applications that need such facilities (for example, to maintain a constant

+frame rate) should investigate the Synchronization Extension, an X

+Consortium standard.

+

+\subsection{Window Management Operations}

+

+The basic philosophy of DBE is that both buffers are treated the same by

+core X window management operations.

+

+When the core \requestname{DestroyWindow} is executed on a

+double-buffered window, both buffers associated with the window are

+destroyed, and all back buffer names associated with the window are

+freed.

+

+If the core \requestname{ConfigureWindow} request changes the size of

+a window, both buffers assume the new size.  If the window's size

+increases, the effect on the buffers depends on whether the

+implementation honors bit gravity for buffers.  If bit gravity is

+implemented, then the contents of both buffers are moved in accordance

+with the window's bit gravity (see the core

+\requestname{ConfigureWindow} request), and the remaining areas are

+tiled with the window background.  If bit gravity is not implemented,

+then the entire unobscured region of both buffers is tiled with the

+window background.  In either case, \literal{Expose} events are generated for

+the region that is tiled with the window background.

+

+If the core \requestname{GetGeometry} request is executed on a

+\typename{BACKBUFFER}, the returned x, y, and border-width will be

+zero.

+

+If the Shape extension \requestname{ShapeRectangles},

+\requestname{ShapeMask}, \requestname{ShapeCombine}, or

+\requestname{ShapeOffset} request is executed on a double-buffered

+window, both buffers are reshaped to match the new window shape.  The

+region difference is the following:

+

+\[ D = new shape - old shape \]

+

+It is tiled with the window background in both buffers,

+and \literal{Expose} events are generated for D.

+

+\subsection{Complex Swap Actions}

+

+DBE has no explicit knowledge of ancillary buffers (for example, depth buffers

+or alpha buffers), and only has a limited set of defined swap actions.

+Some applications may need a richer set of swap actions than DBE

+provides.  Some DBE implementations have knowledge of ancillary

+buffers, and/or can provide a rich set of swap actions.  Instead of

+continually extending DBE to increase its set of swap actions, DBE

+provides a flexible ``idiom'' mechanism.  If an application's needs

+are served by the defined swap actions, it should use them; otherwise,

+it should use the following method of expressing a complex swap action

+as an idiom.  Following this policy will ensure the best possible

+performance across a wide variety of implementations.

+

+As suggested by the term ``idiom,'' a complex swap action should be

+expressed as a group/series of requests.  Taken together, this group

+of requests may be combined into an atomic operation by the

+implementation, in order to maximize performance.  The set of idioms

+actually recognized for optimization is implementation dependent.  To

+help with idiom expression and interpretation, an idiom must be

+surrounded by two protocol requests: \requestname{DBEBeginIdiom} and

+\requestname{DBEEndIdiom}.  Unless this begin-end pair surrounds the

+idiom, it may not be recognized by a given implementation, and

+performance will suffer.

+

+For example, if an application wants to swap buffers for two windows,

+and use core X to clear only certain planes of the back buffers, the

+application would issue the following protocol requests as a group, and

+in the following order:

+

+\begin{itemize}

+\item \requestname{DBEBeginIdiom} request.

+\item \requestname{DBESwapBuffers} request with XIDs for two windows, each

+of which uses a swap action of \literal{Untouched}.

+\item Core X \requestname{PolyFillRectangle} request to the back buffer of one window.

+\item Core X \requestname{PolyFillRectangle} request to the back buffer of the other window.

+\item \requestname{DBEEndIdiom} request.

+\end{itemize}

+

+The \requestname{DBEBeginIdiom} and \requestname{DBEEndIdiom} requests

+do not perform any actions themselves.  They are treated as markers by

+implementations that can combine certain groups/series of requests as

+idioms, and are ignored by other implementations or for nonrecognized

+groups/series of requests.  If these requests are sent out of order,

+or are mismatched, no errors are sent, and the requests are executed

+as usual, though performance may suffer.

+

+An idiom need not include a \requestname{DBESwapBuffers} request.  For

+example, if a swap action of \literal{Copied} is desired, but only some of the

+planes should be copied, a core X \requestname{CopyArea} request may

+be used instead of \requestname{DBESwapBuffers}.  If

+\requestname{DBESwapBuffers} is included in an idiom, it should

+immediately follow the \requestname{DBEBeginIdiom} request.  Also,

+when the \requestname{DBESwapBuffers} is included in an idiom, that

+request's swap action will still be valid, and if the swap action

+might overlap with another request, then the final result of the idiom

+must be as if the separate requests were executed serially.  For

+example, if the specified swap action is \literal{Untouched}, and if a

+\requestname{PolyFillRectangle} using a client clip rectangle is done

+to the window's back buffer after the \requestname{DBESwapBuffers}

+request, then the contents of the new back buffer (after the idiom)

+will be the same as if the idiom was not recognized by the

+implementation.

+

+It is highly recommended that Application Programming Interface (API) 

+providers define, and application developers use, ``convenience'' functions 

+that allow client applications to call one procedure that encapsulates common idioms.

+These functions will generate the \requestname{DBEBeginIdiom} request,

+the idiom requests, and \requestname{DBEEndIdiom} request.  Usage of

+these functions will ensure best possible performance across a wide

+variety of implementations.

+

+\section{C Language Binding}

+

+The header for this extension is \verb|<X11/extensions/Xdbe.h>|.  All

+identifier names provided by this header begin with Xdbe.

+

+\subsection{Types}

+

+The type \libtypename{XdbeBackBuffer} is a \libtypename{Drawable}.

+

+The type \libtypename{XdbeSwapAction} can be one of the constants

+\literal{XdbeUndefined}, \literal{XdbeBackground},

+\literal{XdbeUntouched}, or \literal{XdbeCopied}.

+

+\subsection{C Functions}

+

+The C functions provide direct access to the protocol and add no

+additional semantics.  For complete details on the effects of these

+functions, refer to the appropriate protocol request, which can be

+derived by replacing Xdbe at the start of the function name with DBE\@.

+All functions that have return type \libtypename{Status} will return

+nonzero for success and zero for failure.

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{Status}{XdbeQueryExtension}

+\cargdecl{Display *}{dpy},

+\cargdecl{int *}{major\_version\_return},

+\cargdecl{int *}{minor\_version\_return}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeQueryExtension} sets major\_version\_return and

+minor\_version\_return to the major and minor DBE protocol

+version supported by the server.  If the DBE library is compatible

+with the version returned by the server, it returns

+nonzero.  If dpy does not support the DBE extension, or if

+there was an error during communication with the server, or if the

+server and library protocol versions are incompatible, it

+returns zero.  No other Xdbe functions may be called before this

+function.  If a client violates this rule, the effects of all

+subsequent Xdbe calls that it makes are undefined.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{XdbeScreenVisualInfo *}{XdbeGetVisualInfo}

+\cargdecl{Display *}{dpy},

+\cargdecl{Drawable *}{screen\_specifiers},

+\cargdecl{int *}{num\_screens}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeGetVisualInfo}  returns information about which visuals support

+double buffering.  The argument num\_screens specifies how many

+elements there are in the screen\_specifiers list.  Each

+drawable in screen\_specifiers designates a screen for which

+the supported visuals are being requested.  If num\_screens

+is zero, information for all screens is requested.  In this case, upon

+return from this function, num\_screens will be set to the

+number of screens that were found.  If an error occurs, this function

+returns NULL; otherwise, it returns a pointer to a list of

+\libtypename{XdbeScreenVisualInfo} structures of length num\_screens.

+The {\it n}th element in the returned list corresponds to the {\it n}th

+drawable in the screen\_specifiers list, unless

+num\_screens was passed in with the value zero, in which

+case the {\it n}th element in the returned list corresponds to the

+{\it n}th screen of the server, starting with screen zero.

+

+The \libtypename{XdbeScreenVisualInfo} structure has the following

+fields:

+

+\begin{tabular}{lll}

+\typename{int} & \argname{count} & number of items in visinfo \\

+\typename{XdbeVisualInfo *} & \argname{visinfo} & list of visuals and depths for this screen \\

+\end{tabular}

+

+The \libtypename{XdbeVisualInfo} structure has the following fields:

+

+\begin{tabular}{lll}

+\typename{VisualID} & \argname{visual} & one visual ID that supports double-buffering\\

+\typename{int} & \argname{depth} & depth of visual in bits \\

+\typename{int} & \argname{perflevel} & performance level of visual \\

+\end{tabular}

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{void }{XdbeFreeVisualInfo}

+\cargdecl{XdbeScreenVisualInfo *}{visual\_info}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeFreeVisualInfo} frees the list of \libtypename{XdbeScreenVisualInfo}

+returned by \cfunctionname{XdbeGetVisualInfo}.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{XdbeBackBuffer}{XdbeAllocateBackBufferName}

+\cargdecl{Display *}{dpy},

+\cargdecl{Window}{window},

+\cargdecl{XdbeSwapAction}{swap\_action}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeAllocateBackBufferName} returns a drawable ID used to refer

+to the back buffer of the specified window. 

+The swap\_action is a hint to indicate the swap action 

+that will likely be used in subsequent calls to

+\cfunctionname{XdbeSwapBuffers}. 

+The actual swap action used in calls to

+\cfunctionname{XdbeSwapBuffers} does not have

+to be the same as the swap\_action passed to this function,

+though clients are encouraged to provide accurate information whenever

+possible.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{Status}{XdbeDeallocateBackBufferName}

+\cargdecl{Display *}{dpy},

+\cargdecl{XdbeBackBuffer}{buffer}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeDeallocateBackBufferName} frees the specified

+drawable ID, buffer,

+that was obtained via \cfunctionname{XdbeAllocateBackBufferName}.  The buffer

+must be a valid name for the back buffer of a window, or an

+\literal{XdbeBadBuffer}

+error results.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{Status}{XdbeSwapBuffers}

+\cargdecl{Display *}{dpy},

+\cargdecl{XdbeSwapInfo *}{swap\_info},

+\cargdecl{int}{num\_windows}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeSwapBuffers} swaps the front and back buffers for a list of windows.

+The argument num\_windows specifies how many windows are to

+have their buffers swapped; it is the number of elements in the

+swap\_info array.  The argument swap\_info

+specifies the information needed per window to do the swap.

+

+The \libtypename{XdbeSwapInfo} structure has the following fields:

+

+\begin{tabular}{lll}

+\typename{Window} & \argname{swap\_window} & window for which to swap buffers \\

+\typename{XdbeSwapAction} & \argname{swap\_action} & swap action to use for this swap\_window \\

+\end{tabular}

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{Status}{XdbeBeginIdiom}

+\cargdecl{Display *}{dpy}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeBeginIdiom} marks the beginning of an idiom sequence.

+See section 3.2

+for a complete discussion of idioms.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{Status}{XdbeEndIdiom}

+\cargdecl{Display *}{dpy}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeEndIdiom} marks the end of an idiom sequence.

+\end{keeptogether}

+

+% start marker

+\begin{keeptogether}

+\begin{cfunction}{XdbeBackBufferAttributes *}{XdbeGetBackBufferAttributes}

+\cargdecl{Display *}{dpy},

+\cargdecl{XdbeBackBuffer}{buffer}

+\end{cfunction}

+% end marker

+

+\cfunctionname{XdbeGetBackBufferAttributes} returns the attributes associated 

+with the specified buffer.

+

+The \libtypename{XdbeBackBufferAttributes} structure has the following fields:

+

+\begin{tabular}{lll}

+\typename{Window} & \argname{window} & window that buffer belongs to \\

+\end{tabular}

+

+If buffer is not a valid \libtypename{XdbeBackBuffer},

+window is set to \literal{None}.

+

+The returned \libtypename{XdbeBackBufferAttributes} structure can be

+freed with the Xlib function \cfunctionname{XFree}.

+\end{keeptogether}

+

+\begin{keeptogether}

+\subsection{Errors}

+

+The \libtypename{XdbeBufferError} structure has the following fields:

+

+\begin{tabular}{lll}

+\typename{int} & \argname{type} \\

+\typename{Display *} & \argname{display}& Display the event was read from\\

+\typename{XdbeBackBuffer} &  \argname{buffer}& resource id \\

+\typename{unsigned long} & \argname{serial}& serial number of failed request\\

+\typename{unsigned char} & \argname{error\_code}& error base + \literal{XdbeBadBuffer}\\

+\typename{unsigned char} & \argname{request\_code}& Major op-code of failed request\\

+\typename{unsigned char} & \argname{minor\_code}& Minor op-code of failed request\\

+\end{tabular}

+\end{keeptogether}

+

+\pagebreak[4]

+\section{Acknowledgements}

+

+We wish to thank the following individuals who have contributed their

+time and talent toward shaping the DBE specification:

+

+T. Alex Chen, IBM;

+Peter Daifuku, Silicon Graphics, Inc.; 

+Ian Elliott, Hewlett-Packard Company;

+Stephen Gildea, X Consortium, Inc.;

+Jim Graham, Sun;

+Larry Hare, AGE Logic;

+Jay Hersh, X Consortium, Inc.;

+Daryl Huff, Sun;

+Deron Dann Johnson, Sun;

+Louis Khouw, Sun;

+Mark Kilgard, Silicon Graphics, Inc.;

+Rob Lembree, Digital Equipment Corporation;

+Alan Ricker, Metheus;

+Michael Rosenblum, Digital Equipment Corporation;

+Bob Scheifler, X Consortium, Inc.;

+Larry Seiler, Digital Equipment Corporation;

+Jeanne Sparlin Smith, IBM;

+Jeff Stevenson, Hewlett-Packard Company;

+Walter Strand, Metheus;

+Ken Tidwell, Hewlett-Packard Company; and

+David P. Wiggins, X Consortium, Inc.

+

+Mark provided the impetus to start the DBE project.  Ian wrote the

+first draft of the specification.  David served as architect.

+

+\section{References}

+

+Jeffrey Friedberg, Larry Seiler, and Jeff Vroom, ``Multi-buffering Extension

+Specification Version 3.3.''

+

+Tim Glauert, Dave Carver, Jim Gettys, and David P. Wiggins,

+``X Synchronization Extension Version 3.0.'' 

+

+\end{document}