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+<?xml version="1.0" encoding="UTF-8" ?>
+<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
+                   "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd"
+[
+<!ENTITY % defs SYSTEM "defs.ent"> %defs;
+]>
+
+
+<!-- lifted from troff+ms+XMan by doclifter -->
+<book id="multibuf">
+
+<bookinfo>
+   <title>Extending X for Double-Buffering, Multi-Buffering, and Stereo</title>
+   <authorgroup>
+      <othercredit>
+         <firstname>Jeffrey</firstname><surname>Friedberg</surname>
+      </othercredit>
+      <othercredit>
+         <firstname>Larry</firstname><surname>Seiler</surname>
+      </othercredit>
+      <othercredit>
+         <firstname>Jeff</firstname><surname>Vroom</surname>
+      </othercredit>
+   </authorgroup>
+   <copyright><year>1989</year><holder>Digital Equipment Corporation</holder></copyright>
+   <releaseinfo>X Version 11, Release &fullrelvers;</releaseinfo>
+   <releaseinfo>Version 3.3</releaseinfo>
+
+<legalnotice>
+<para>
+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 makes 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.  This document
+is subject to change.
+</para>
+</legalnotice>
+
+<legalnotice>
+<para role="multiLicensing">Copyright © 1989, 1994 X Consortium</para>
+<para>
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the ``Software''), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+</para>
+<para>
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+</para>
+<para>
+THE SOFTWARE IS PROVIDED &ldquo;AS IS&rdquo;, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL THE
+X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN
+AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+</para>
+<para>
+Except as contained in this notice, the name of the X Consortium shall not be
+used in advertising or otherwise to promote the sale, use or other dealings
+in this Software without prior written authorization from the X Consortium.
+</para>
+<para>X Window System is a trademark of The OpenGroup.</para>
+
+</legalnotice>
+</bookinfo>
+
+<preface><title>Warning</title>
+<warning><para>
+The <emphasis remap='I'>Multi-Buffering</emphasis> extension described here
+was a draft standard of the X Consortium prior to Release 6.1.  It has been
+superseded by the Double Buffer
+Extension (DBE).  DBE is an X Consortium Standard as of Release 6.1.
+</para></warning>
+</preface>
+
+<chapter id='Introduction'>
+<title>Introduction</title>
+
+<para>
+Several proposals have been written that address some of the
+issues surrounding the support of double-buffered, multi-buffered,
+and stereo windows in the X Window System:
+</para>
+
+<itemizedlist>
+  <listitem>
+    <para>
+<emphasis remap='I'>Extending X for Double-Buffering,</emphasis>
+Jeffrey Friedberg, Larry Seiler, Randi Rost.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+<emphasis remap='I'>(Proposal for) Double-Buffering Extensions</emphasis>,
+Jeff Vroom.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+<emphasis remap='I'>An Extension to X.11 for Displays with Multiple Buffers,</emphasis>
+David S.H. Rosenthal.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+<emphasis remap='I'>A Multiple Buffering/Stereo Proposal</emphasis>,
+Mark Patrick.
+    </para>
+  </listitem>
+</itemizedlist>
+
+<para>
+The authors of this proposal have tried to unify the above documents
+to yield a proposal that incorporates support for double-buffering,
+multi-buffering, and stereo in a way that is acceptable to all concerned.
+</para>
+</chapter>
+
+<chapter id='Goals'>
+<title>Goals</title>
+
+<para>
+Clients should be able to:
+</para>
+
+<itemizedlist>
+  <listitem>
+    <para>
+Associate multiple buffers with a window.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Paint in any buffer associated with a window.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Display any buffer associated with a window.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Display a series of buffers in a window in rapid succession
+to achieve a <emphasis remap='I'>smooth</emphasis> animation.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Request simultaneous display of different buffers in different windows.
+    </para>
+  </listitem>
+</itemizedlist>
+
+<para>
+In addition, the extension should:
+</para>
+
+<itemizedlist>
+  <listitem>
+    <para>
+Allow existing X applications to run unchanged.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Support a range of implementation methods that can capitalize on
+existing hardware features.
+    </para>
+  </listitem>
+</itemizedlist>
+
+</chapter>
+
+<chapter id='Image_Buffers'>
+<title>Image Buffers</title>
+
+<para>
+Normal windows are created using the standard
+<function>CreateWindow</function> request:
+</para>
+
+<literallayout class="monospaced">
+CreateWindow
+     parent          : WINDOW
+     w_id            : WINDOW
+     depth           : CARD8
+     visual          : VISUALID or CopyFromParent
+     x, y            : INT16
+     width, height   : INT16
+     border_width    : INT16
+     value_mask      : BITMASK
+     value_list      : LISTofVALUE
+</literallayout>
+
+<para>
+This request allocates a set of window attributes and
+a buffer into which an image can be drawn.
+The contents of this <emphasis remap='I'>image buffer</emphasis> will
+be displayed when the window is mapped to the screen.
+</para>
+
+<para>
+To support double-buffering and multi-buffering,
+we introduce the notion that additional image buffers can
+be created and bound together to form groups.
+The following rules will apply:
+</para>
+
+<itemizedlist>
+  <listitem>
+    <para>
+All image buffers in a group will have the same
+visual type, depth, and geometry (ie: width and height).
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Only one image buffer per group can be displayed
+at a time.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Draw operations can occur to any image buffer at
+any time.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Window management requests (<function>MapWindow</function>, <function>DestroyWindow</function>,
+<function>ConfigureWindow</function>, etc...)
+affect all image buffers associated with a window.
+    </para>
+  </listitem>
+  <listitem>
+    <para>
+Appropriate resize and exposure events will be generated
+for every image buffer that is affected by a window
+management operation.
+    </para>
+  </listitem>
+</itemizedlist>
+
+<para>
+By allowing draw operations to occur on any image buffer at any time,
+a client could, on a multi-threaded multi-processor server,
+simultaneously build up images for display.
+To support this, each buffer must have its own resource ID.
+Since buffers are different than windows and pixmaps
+(buffers are not hierarchical and pixmaps cannot be displayed)
+a new resource, <function>Buffer</function>, is introduced.
+Furthermore, a <function>Buffer</function> is also a <function>Drawable</function>, thus
+draw operations may also be performed on buffers simply
+by passing a buffer ID to the existing pixmap/window
+interface.
+</para>
+
+<para>
+To allow existing X applications to work unchanged, we assume
+a window ID passed in a draw request, for a multi-buffered
+window, will be an <emphasis remap='I'>alias</emphasis> for the ID of the currently
+displayed image buffer.  Any draw requests (eq: <function>GetImage</function>) on
+the window will be relative to the displayed image buffer.
+</para>
+
+<para>
+In window management requests, only a window ID will be
+accepted.  Requests like <function>QueryTree</function>, will continue to
+return only window ID's.  Most events will return
+just the window ID.  Some new events, described in a subsequent
+section, will return a buffer ID.
+</para>
+
+<para>
+When a window has backing store the contents of the window
+are saved off-screen.  Likewise, when the contents of an image
+buffer of a multi-buffer window is saved off-screen, it is
+said to have backing store.  This applies to all image buffers,
+whether or not they are selected for display.
+</para>
+
+<para>
+In some multi-buffer implementations, undisplayed buffers might be
+implemented using pixmaps.  Since the contents of pixmaps exist
+off-screen and are not affected by occlusion, these image buffers
+in effect have backing store.
+</para>
+
+<para>
+On the other hand, both the displayed and undisplayed image buffers
+might be implemented using a subset of the on-screen pixels.
+In this case, unless the contents of an image buffer are saved
+off-screen, these image buffers in effect do not have backing store.
+</para>
+
+<para>
+Output to any image buffer of an unmapped multi-buffered window
+that does not have backing store is discarded.  Output to any
+image buffer of a mapped multi-buffer window will be performed;
+however, portions of an image buffer may be occluded or clipped.
+</para>
+
+<para>
+When an unmapped multi-buffered window becomes mapped, the contents
+of any image buffer buffer that did not have backing store is
+tiled with the background and zero or more exposure events are
+generated.  If no background is defined for the window, then
+the screen contents are not altered and the contents of any
+undisplayed image buffers are undefined.  If backing store was
+maintained for an image buffer, then no exposure events are generated.
+</para>
+</chapter>
+
+<chapter id='New_Requests'>
+<title>New Requests</title>
+
+<para>
+The new request, <function>CreateImageBuffers</function>, creates a group of
+image buffers and associates them with a normal X window:
+</para>
+
+<literallayout class="monospaced">
+CreateImageBuffers
+     w_id           : WINDOW
+     buffers        : LISTofBUFFER
+     update_action  : {Undefined,Background,Untouched,Copied}
+     update_hint    : {Frequent,Intermittent,Static}
+     =&gt;
+     number_buffers : CARD16
+
+     (Errors: Window, IDChoice, Value)
+</literallayout>
+
+<para>
+One image buffer will be associated with each ID passed in
+<emphasis remap='I'>buffers</emphasis>.
+The first buffer of the list is referred to as buffer[0], the next
+buffer[1], and so on.  Each buffer will have the same visual type
+and geometry as the window.
+Buffer[0] will refer to the image buffer already associated
+with the window ID and its contents will not be modified.
+The displayed image buffer attribute is set to buffer[0].
+</para>
+
+<para>
+Image buffers for the remaining ID's (buffer[1],...) are allocated.
+If the window is mapped, or if these image buffers have backing
+store, their contents will be tiled with the window background
+(if no background is defined, the buffer contents are undefined),
+and zero or more expose events will be generated for each of these
+buffers.  The contents of an image buffer is undefined when
+the window is unmapped and the buffer does not have backing store.
+</para>
+
+<para>
+If the window already has a group of image buffers
+associated with it (ie: from a previous <function>CreateImageBuffers</function> request)
+the actions described for <function>DestroyImageBuffers</function> are performed first
+(this will delete the association of the previous buffer ID's and
+their buffers as well as de-allocate all buffers except for the
+one already associated with the window ID).
+</para>
+
+<para>
+To allow a server implementation to efficiently allocate the
+buffers, the total number of buffers required and
+the update action (how they will behave during an update)
+is specified "up front" in the request.
+If the server cannot allocate all the buffers requested, the
+total number of buffers actually allocated will be returned.
+No <function>Alloc</function> errors will be generated \- buffer[0] can
+always be associated with the existing displayed image buffer.
+</para>
+
+<para>
+For example, an application that wants to animate a short movie
+loop may request 64 image buffers.  The server may only be able to
+support 16 image buffers of this type, size, and depth.
+The application can then decide 16 buffers is sufficient and may
+truncate the movie loop, or it may decide it really needs
+64 and will free the buffers and complain to the user.
+</para>
+
+<para>
+One might be tempted to provide a request that inquires whether
+<emphasis remap='I'>n</emphasis>
+buffers of a particular type, size, and depth
+<emphasis remap='I'>could</emphasis> be allocated.
+But if the query is decoupled from the actual allocation,
+another client could sneak in and take the buffers before the
+original client has allocated them.
+</para>
+
+<para>
+While any buffer of a group can be selected for display,
+some applications may display buffers in a predictable order
+(ie: the movie loop application).  The
+<emphasis remap='I'>list order</emphasis>
+(buffer[0], buffer[1], ...) will be used as a hint by the
+server as to which buffer will be displayed next.
+A client displaying buffers in this order may see a
+performance improvement.
+</para>
+
+<para>
+<emphasis remap='I'>update_action</emphasis> indicates what should happen to a previously
+displayed buffer when a different buffer becomes displayed.
+Possible actions are:
+</para>
+
+<variablelist>
+  <varlistentry>
+    <term>Undefined</term>
+    <listitem>
+      <para>
+The contents of the buffer that was
+last displayed will become undefined after the update.  This
+is the most efficient action since it allows the implementation
+to trash the contents of the buffer if it needs to.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>Background</term>
+    <listitem>
+      <para>
+The contents of the buffer that was
+last displayed will be set to the background of the window after the update.
+The background action allows devices to use a fast clear
+capability during an update.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>Untouched</term>
+    <listitem>
+      <para>
+The contents of the buffer that was
+last displayed will be untouched after the update.  Used
+primarily when cycling through images that have already
+been drawn.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>Copied</term>
+    <listitem>
+      <para>
+The contents of the buffer that was
+last displayed will become the same as those that are being
+displayed after the update.  This is useful when incrementally
+adding to an image.
+      </para>
+    </listitem>
+  </varlistentry>
+</variablelist>
+
+
+
+<para>
+<emphasis remap='I'>update_hint</emphasis> indicates how often the client will
+request a different buffer to be displayed.
+This hint will allow smart server implementations to choose the
+most efficient means to support a multi-buffered window based
+on the current need of the application (dumb implementations
+may choose to ignore this hint).  Possible hints are:
+</para>
+
+<variablelist>
+  <varlistentry>
+    <term>Frequent</term>
+    <listitem>
+      <para>
+An animation or movie loop is
+being attempted and the fastest, most efficient means for
+multi-buffering should be employed.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>Intermittent</term>
+    <listitem>
+      <para>
+The displayed image will be
+changed every so often.  This is common for images that are
+displayed at a rate slower than a second.  For example, a
+clock that is updated only once a minute.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>Static</term>
+    <listitem>
+      <para>
+The displayed image buffer will
+not be changed any time soon.  Typically set by an application
+whenever there is a pause in the animation.
+      </para>
+    </listitem>
+  </varlistentry>
+</variablelist>
+
+<para>
+To display an image buffer the following request can be used:
+</para>
+
+<literallayout class="monospaced">
+DisplayImageBuffers
+     buffers         : LISTofBUFFER
+     min_delay       : CARD16
+     max_delay       : CARD16
+
+     (Errors: Buffer, Match)
+</literallayout>
+
+<para>
+The image buffers listed will become displayed as simultaneously
+as possible and the update action, bound at
+<function>CreateImageBuffers</function>
+time, will be performed.
+</para>
+
+<para>
+A list of buffers is specified to
+allow the server to efficiently change the display of more than one
+window at a time (ie: when a global screen swap method is used).
+Attempting to simultaneously display
+multiple image buffers from the same window is an error
+(<function>Match</function>) since it violates the rule that only one
+image buffer per group can be displayed at a time.
+</para>
+
+<para>
+If a specified buffer is already displayed,
+any delays and update action will still be
+performed for that buffer.  In this instance,
+only the update action of <emphasis remap='I'>Background</emphasis>
+(and possibly
+<emphasis remap='I'>Undefined</emphasis>) will have any affect on the
+contents of the displayed buffer.  These semantics allow
+an animation application to successfully execute
+even when there is only a single buffer available
+for a window.
+</para>
+<para>
+<!-- .LP -->
+When a <function>DisplayImageBuffers</function> request is made to an unmapped
+multi-buffered window, the effect of the update action depends
+on whether the image buffers involved have backing store.
+When the target of the update action is an image buffer that
+does not have backing store, output is discarded.  When the
+target image buffer does have backing store, the update is performed;
+however, when the source of the update is an image buffer does not
+have backing store (as in the case of update action
+<emphasis remap='I'>Copied</emphasis>), the
+contents of target image buffer will become undefined.
+</para>
+<para>
+<!-- .LP -->
+<emphasis remap='I'>min_delay</emphasis> and
+<emphasis remap='I'>max_delay</emphasis> put a bound on how long the
+server should wait before processing the display request.
+For each of the windows to be updated by this request, at least
+<emphasis remap='I'>min_delay</emphasis> milli-seconds should elapse since
+the last
+time any of the windows were updated; conversely, no window
+should have to wait more than <emphasis remap='I'>max_delay</emphasis>
+milli-seconds before being updated.
+</para>
+
+<para>
+<emphasis remap='I'>min_delay</emphasis> allows an application to
+<emphasis remap='I'>slow down</emphasis> an animation or movie loop so that
+it appears
+synchronized at a rate the server can support given the current load.
+For example, a <emphasis remap='I'>min_delay</emphasis> of 100 indicates the
+server should
+wait at least 1/10 of a second since the last time any of the
+windows were updated.  A <emphasis remap='I'>min_delay</emphasis> of zero
+indicates no waiting is necessary.
+</para>
+
+<para>
+<emphasis remap='I'>max_delay</emphasis> can be thought of as an additional
+delay beyond <emphasis remap='I'>min_delay</emphasis> the server is allowed
+to wait
+to facilitate such things as efficient update of multiple windows.
+If <emphasis remap='I'>max_delay</emphasis> would require an update before
+<emphasis remap='I'>min_delay</emphasis>
+is satisfied, then the server should process the display request as
+soon as the <emphasis remap='I'>min_delay</emphasis> requirement is met.  A
+typical value for <emphasis remap='I'>max_delay</emphasis> is zero.
+</para>
+
+<para>
+To implement the above functionality, the time since the last
+update by a <function>DisplayImageBuffers</function> request for each
+multi-buffered
+window needs to be saved as state by the server.
+The server may delay execution of the <function>DisplayImageBuffers</function>
+request until the appropriate time (e.g. by requeuing the
+request after computing the timeout);
+however, the entire request must be processed in one operation.
+Request execution indivisibility must be maintained.  When
+a server is implemented with internal concurrency, the
+extension must adhere to the same concurrency semantics
+as those defined for the core protocol.
+</para>
+
+<para>
+To explicitly clear a rectangular area of an image buffer to
+the window background, the following request can be used:
+</para>
+
+<literallayout class="monospaced">
+ClearImageBufferArea
+     buffer          : BUFFER
+     x, y            : INT16
+     w, h            : CARD16
+     exposures       : BOOL
+
+     (Errors: Buffer, Value)
+</literallayout>
+
+<para>
+Like the X <function>ClearArea</function> request,
+<emphasis remap='I'>x</emphasis> and <emphasis remap='I'>y</emphasis>
+are relative to
+the window's origin and specify the upper-left corner of the rectangle.
+If <emphasis remap='I'>width</emphasis> is zero, it is replaced with the
+current window width
+minus <emphasis remap='I'>x</emphasis>.  If
+<emphasis remap='I'>height</emphasis> is zero it is replaced with the current
+window height minus <emphasis remap='I'>y</emphasis>.  If the window has a
+defined background tile, the rectangle is tiled with a plane mask of all ones,
+a function of <emphasis remap='I'>Copy</emphasis>, and a subwindow-mode of
+<emphasis remap='I'>ClipByChildren</emphasis>.
+If the window has background <emphasis remap='I'>None</emphasis>, the
+contents of the buffer
+are not changed.  In either case, if
+<emphasis remap='I'>exposures</emphasis> is true, then one or
+more exposure events are generated for regions of the rectangle that are
+either visible or are being retained in backing store.
+</para>
+
+<para>
+<!-- .LP -->
+The group of image buffers allocated by a
+<function>CreateImageBuffers</function>
+request can be destroyed with the following request:
+</para>
+
+<literallayout class="monospaced">
+DestroyImageBuffers
+     w_id          : WINDOW
+
+     (Error: Window)
+</literallayout>
+
+<para>
+The association between the buffer ID's and their corresponding
+image buffers are deleted.  Any image buffers not selected for
+display are de-allocated.  If the window is not multi-buffered,
+the request is ignored.
+</para>
+
+</chapter>
+
+<chapter id='Attributes'>
+<title>Attributes</title>
+
+<para>
+The following attributes will be associated with each window that
+is multi-buffered:
+</para>
+
+<literallayout class="monospaced">
+     displayed_buffer : CARD16
+     update_action    : {Undefined,Background,Untouched,Copied}
+     update_hint      : {Frequent,Intermittent,Static}
+     window_mode      : {Mono,Stereo}
+     buffers          : LISTofBUFFER
+</literallayout>
+
+<para>
+<emphasis remap='I'>displayed_buffer</emphasis> is set to the
+<emphasis remap='I'>index</emphasis> of the currently
+displayed image buffer (for stereo windows, this will be
+the index of the left buffer \- the index of the right buffer
+is simply <emphasis remap='I'>index</emphasis>+1).
+<emphasis remap='I'>window_mode</emphasis> indicates whether this window is
+<emphasis remap='I'>Mono</emphasis> or <emphasis remap='I'>Stereo</emphasis>.
+The ID for each buffer associated with the window is recorded
+in the <emphasis remap='I'>buffers</emphasis> list.
+The above attributes can be queried with the following request:
+</para>
+
+<literallayout class="monospaced">
+GetMultiBufferAttributes
+     w_id             : WINDOW
+     =&gt;
+     displayed_buffer : CARD16
+     update_action    : {Undefined,Background,Untouched,Copied}
+     update_hint      : {Frequent,Intermittent,Static}
+     window_mode      : {Mono,Stereo}
+     buffers          : LISTofBUFFER
+
+     (Errors: Window, Access, Value)
+</literallayout>
+
+<para>
+If the window is not multi-buffered, a <function>Access</function> error
+will be generated.
+The only multi-buffer attribute that can be explicitly set
+is <emphasis remap='I'>update_hint</emphasis>.  Rather than have a specific
+request to set this attribute, a generic set request is provided to
+allow for future expansion:
+</para>
+
+<literallayout class="monospaced">
+SetMultiBufferAttributes
+     w_id            : WINDOW
+     value_mask      : BITMASK
+     value_list      : LISTofVALUE
+
+     (Errors: Window, Match, Value)
+</literallayout>
+
+<para>
+If the window is not multi-buffered, a <function>Match</function> error
+will be generated.
+The following attributes are maintained for each buffer of a
+multi-buffered window:
+</para>
+
+<literallayout class="monospaced">
+     window           : WINDOW
+     event_mask       : SETofEVENT
+     index            : CARD16
+     side             : {Mono,Left,Right}
+</literallayout>
+
+<para>
+<emphasis remap='I'>window</emphasis> indicates the window this buffer is
+associated with.
+<emphasis remap='I'>event_mask</emphasis> specifies which events, relevant to
+buffers, will be sent back to the client via the associated buffer ID
+(initially no events are selected).
+<emphasis remap='I'>index</emphasis> is the list position (0, 1, ...) of the
+buffer.
+<emphasis remap='I'>side</emphasis> indicates whether this buffer is
+associated with
+the left side or right side of a stereo window.
+For non-stereo windows, this attribute will be set to
+<emphasis remap='I'>Mono</emphasis>.
+These attributes can be queried with the following request:
+</para>
+
+<literallayout class="monospaced">
+GetBufferAttributes
+     buffer          : BUFFER
+     =&gt;
+     window           : WINDOW
+     event_mask       : SETofEVENT
+     index            : CARD16
+     side             : {Mono,Left,Right}
+
+     (Errors: Buffer, Value)
+</literallayout>
+
+<para>
+The only buffer attribute that can be explicitly set
+is <emphasis remap='I'>event_mask</emphasis>.
+The only events that are valid are
+<function>Expose</function> and the new
+<function>ClobberNotify</function> and <function>UpdateNotify</function>
+event (see Events section below). <!-- xref -->
+A <function>Value</function> error will be generated if an event not
+selectable for a buffer is specified in an event mask.
+Rather than have a specific request
+to set this attribute, a generic set request is provided to
+allow for future expansion:
+</para>
+
+<literallayout class="monospaced">
+SetBufferAttributes
+     buffer          : BUFFER
+     value_mask      : BITMASK
+     value_list      : LISTofVALUE
+
+     (Errors: Buffer, Value)
+</literallayout>
+
+<para>
+Clients may want to query the server about basic multi-buffer
+and stereo capability on a per screen basis.  The following request
+returns a large list of information
+that would most likely be read once by Xlib for each screen, and used as a
+data base for other Xlib queries:
+</para>
+
+<literallayout class="monospaced">
+GetBufferInfo
+     root            : WINDOW
+     =&gt;
+     info            : LISTofSCREEN_INFO
+</literallayout>
+
+<para>
+Where <function>SCREEN_INFO</function> and
+<function>BUFFER_INFO</function> are defined as:
+</para>
+
+<literallayout class="monospaced">
+     SCREEN_INFO     : [ normal_info : LISTofBUFFER_INFO,
+                         stereo_info : LISTofBUFFER_INFO ]
+
+     BUFFER_INFO     : [ visual      : VISUALID,
+                         max_buffers : CARD16,
+                         depth       : CARD8 ]
+</literallayout>
+
+<para>
+Information regarding multi-buffering of normal (mono) windows
+is returned in the <emphasis remap='I'>normal_info</emphasis> list.
+The <emphasis remap='I'>stereo_info</emphasis>
+list contains information about stereo windows.
+If the <emphasis remap='I'>stereo_info</emphasis> list is empty, stereo
+windows are
+not supported on the screen.  If
+<emphasis remap='I'>max_buffers</emphasis> is zero,
+the maximum number of buffers for the depth and visual is
+a function of the size of the created window and current
+memory limitations.
+</para>
+
+<para>
+The following request returns the major and minor version numbers
+of this extension:
+</para>
+
+<literallayout class="monospaced">
+GetBufferVersion
+     =&gt;
+     major_number    : CARD8
+     minor_number    : CARD8
+</literallayout>
+
+<para>
+The version numbers are an escape hatch in case future revisions of
+the protocol are necessary.  In general, the major version would
+increment for incompatible changes, and the minor version would
+increment for small upward compatible changes.  Barring changes, the
+major version will be 1, and the minor version will be 1.
+</para>
+</chapter>
+
+<chapter id='Events'>
+<title>Events</title>
+
+<para>
+All events normally generated for single-buffered
+windows are also generated for multi-buffered windows.
+Most of these events (ie: <function>ConfigureNotify</function>) will
+only be generated for the window and not for each buffer.
+These events will return a window ID.
+</para>
+
+<para>
+<function>Expose</function> events will be generated for both the window
+and any buffer affected.  When this event is generated for
+a buffer, the same event structure will be used
+but a buffer ID is returned instead of a window ID.
+Clients, when processing these events, will know whether an
+ID returned in an event structure is for a window or a buffer
+by comparing the returned ID to the ones returned when the
+window and buffer were created.
+</para>
+
+<para>
+<function>GraphicsExposure</function> and
+<function>NoExposure</function> are generated
+using whatever ID is specified in the graphics operation.
+If a window ID is specified, the event will contain the
+window ID.  If a buffer ID is specified, the event will
+contain the buffer ID.
+</para>
+<para>
+In some implementations, moving a window
+over a multi-buffered window may cause one or more of its buffers
+to get overwritten or become unwritable.  To allow a
+client drawing into one of these buffers the opportunity
+to stop drawing until some portion of the buffer is
+writable, the following event is added:
+</para>
+
+<literallayout class="monospaced">
+ClobberNotify
+     buffer         :  BUFFER
+     state          : {Unclobbered,PartiallyClobbered,FullyClobbered}
+</literallayout>
+
+<para>
+The <function>ClobberNotify</function> event is reported to clients selecting
+<emphasis remap='I'>ClobberNotify</emphasis> on a buffer.  When a buffer
+that was fully
+or partially clobbered becomes unclobbered, an event with
+<emphasis remap='I'>Unclobbered</emphasis>
+is generated.  When a buffer that was unclobbered becomes
+partially clobbered, an event with
+<emphasis remap='I'>PartiallyClobbered</emphasis>
+is generated.  When a buffer that was unclobbered or
+partially clobbered becomes fully clobbered, an event with
+<emphasis remap='I'>FullyClobbered</emphasis> is generated.
+</para>
+
+<para>
+<function>ClobberNotify</function> events on a given buffer are
+generated before any <function>Expose</function> events on that buffer,
+but it is not required that all <function>ClobberNotify</function>
+events on all buffers be generated before all
+<function>Expose</function> events on all buffers.
+</para>
+
+<para>
+The ordering of <function>ClobberNotify</function> events with respect
+to <function>VisibilityNotify</function> events is not constrained.
+</para>
+
+<para>
+If multiple buffers were used as an image FIFO between an image
+server and the X display server, then the FIFO manager would like
+to know when a buffer that was previously displayed, has been
+undisplayed and updated, as the side effect of a
+<function>DisplayImageBuffers</function>
+request.  This allows the FIFO manager to load up a future frame as
+soon as a buffer becomes available.  To support this,
+the following event is added:
+</para>
+
+<literallayout class="monospaced">
+UpdateNotify
+     buffer         :  BUFFER
+</literallayout>
+
+<para>
+The <function>UpdateNotify</function> event is reported to clients selecting
+<emphasis remap='I'>UpdateNotify</emphasis> on a buffer.  Whenever a buffer
+becomes <emphasis remap='I'>updated</emphasis>
+(e.g. its update action is performed as part of a
+<function>DisplayImageBuffers</function>
+request), an <function>UpdateNotify</function> event is generated.
+</para>
+</chapter>
+
+<chapter id='Errors'>
+<title>Errors</title>
+
+<para>
+The following error type has been added to support
+this extension:
+</para>
+
+<sect1 id='Buffer_2'>
+<title>Buffer</title>
+<para>
+A value for a BUFFER argument does not name a defined BUFFER.
+</para>
+</sect1>
+
+<sect1 id='Double_Buffering_Normal_Windows'>
+<title>Double-Buffering Normal Windows</title>
+
+<para>
+The following pseudo-code fragment illustrates how to create and display
+a double-buffered image:
+</para>
+
+<literallayout class="monospaced">
+/*
+ * Create a normal window
+ */
+CreateWindow( W, ... )
+
+/*
+ * Create two image buffers.  Assume after display, buffer
+ * contents become "undefined".  Assume we will "frequently"
+ * update the display.  Abort if we don't get two buffers,
+ */
+n = CreateImageBuffers( W, [B0,B1], Undefined, Frequent )
+if (n != 2) &lt;abort&gt;
+
+/*
+ * Map window to the screen
+ */
+MapWindow( W )
+
+/*
+ * Draw images using alternate buffers, display every
+ * 1/10 of a second.  Note we draw B1 first so it will
+ * "pop" on the screen
+ */
+while animating
+{
+     &lt;draw picture using B1&gt;
+     DisplayImageBuffers( [B1], 100, 0 )
+
+     &lt;draw picture using B0&gt;
+     DisplayImageBuffers( [B0], 100, 0 )
+}
+
+/*
+ * Strip image buffers and leave window with
+ * contents of last displayed image buffer.
+ */
+DestroyImageBuffers( W )
+</literallayout>
+
+</sect1>
+
+<sect1 id='Multi_Buffering_Normal_Windows'>
+<title>Multi-Buffering Normal Windows</title>
+
+<para>
+Multi-buffered images are also supported by these requests.
+The following pseudo-code fragment illustrates how to create a
+a multi-buffered image and cycle through the images to
+simulate a movie loop:
+</para>
+
+<literallayout class="monospaced">
+/*
+ * Create a normal window
+ */
+CreateWindow( W, ... )
+
+/*
+ * Create 'N' image buffers.  Assume after display, buffer
+ * contents are "untouched".  Assume we will "frequently"
+ * update the display.  Abort if we don't get all the buffers.
+ */
+n = CreateImageBuffers( W, [B0,B1,...,B(N-1)], Untouched, Frequent )
+if (n != N) &lt;abort&gt;
+
+/*
+ * Map window to screen
+ */
+MapWindow( W )
+
+/*
+ * Draw each frame of movie one per buffer
+ */
+foreach frame
+     &lt;draw frame using B(i)&gt;
+
+/*
+ * Cycle through frames, one frame every 1/10 of a second.
+ */
+while animating
+{
+     foreach frame
+          DisplayImageBuffers( [B(i)], 100, 0 )
+}
+</literallayout>
+
+</sect1>
+
+<sect1 id='Stereo_Windows'>
+<title>Stereo Windows</title>
+<para>
+<emphasis remap='I'>How</emphasis> stereo windows are supported on a server
+is implementation
+dependent.  A server may contain specialized hardware that allows
+left and right images to be toggled at field or frame rates.  The
+stereo affect may only be perceived with the aid of special
+viewing glasses.  The <emphasis remap='I'>display</emphasis> of a
+stereo picture should
+be independent of how often the contents of the picture are
+<emphasis remap='I'>updated</emphasis> by an application.  Double and
+multi-buffering
+of images should be possible regardless of whether the image
+is displayed normally or in stereo.
+</para>
+
+<para>
+To achieve this goal, a simple extension to normal windows
+is suggested.  Stereo windows are just like normal windows
+except the displayed image is made up of a left image
+buffer and a right image buffer.  To create a stereo window,
+a client makes the following request:
+</para>
+
+<literallayout class="monospaced">
+CreateStereoWindow
+     parent          : WINDOW
+     w_id            : WINDOW
+     left, right     : BUFFER
+     depth           : CARD8
+     visual          : VISUALID or CopyFromParent
+     x, y            : INT16
+     width, height   : INT16
+     border_width    : INT16
+     value_mask      : BITMASK
+     value_list      : LISTofVALUE
+
+     (Errors: Alloc, Color, Cursor, Match,
+              Pixmap, Value, Window)
+</literallayout>
+
+<para>
+This request, modeled after the <function>CreateWindow</function> request,
+adds just two new parameters: <emphasis remap='I'>left</emphasis> and
+<emphasis remap='I'>right</emphasis>.
+For stereo, it is essential that one can distinguish whether
+a draw operation is to occur on the left image or right image.
+While an internal mode could have been added to achieve this,
+using two buffer ID's allows clients to simultaneously build up
+the left and right components of a stereo image.  These
+ID's always refer to (are an alias for) the left and right
+image buffers that are currently <emphasis remap='I'>displayed</emphasis>.
+</para>
+
+<para>
+Like normal windows, the window ID is used whenever a window
+management operation is to be performed.  Window queries would
+also return this window ID (eg: <function>QueryTree</function>) as would most
+events.  Like the window ID, the left and right buffer ID's
+each have their own event mask.  They can be set and queried
+using the <function>Set/GetBufferAttributes</function> requests.
+</para>
+
+<para>
+Using the window ID of a stereo window in a draw request
+(eg: <function>GetImage</function>) results in pixels that are
+<emphasis remap='I'>undefined</emphasis>.
+Possible semantics are that both left and right images get
+drawn, or just a single side is operated on (existing applications
+will have to be re-written to explicitly use the left and right
+buffer ID's in order to successfully create, fetch, and store
+stereo images).
+</para>
+
+<para>
+Having an explicit <function>CreateStereoWindow</function> request is helpful
+in that a server implementation will know from the onset whether
+a stereo window is desired and can return appropriate status
+to the client if it cannot support this functionality.
+</para>
+
+<para>
+Some hardware may support separate stereo and non-stereo modes,
+perhaps with different vertical resolutions.  For example, the
+vertical resolution in stereo mode may be half that of non-stereo
+mode.  Selecting one mode or the other must be done through some
+means outside of this extension (eg: by providing a separate
+screen for each hardware display mode).  The screen attributes
+(ie: x/y resolution) for a screen that supports normal windows,
+may differ from a screen that supports stereo windows;
+however, all windows, regardless of type, displayed on the
+same screen must have the same screen attributes
+(ie: pixel aspect ratio).
+</para>
+
+<para>
+If a screen that supports stereo windows also supports
+normal windows, then the images presented to the left and
+right eyes for normal windows should be the same
+(ie: have no stereo offset).
+</para>
+
+</sect1>
+
+<sect1 id='Single_Buffered_Stereo_Windows'>
+<title>Single-Buffered Stereo Windows</title>
+
+<para>
+The following shows how to create and display a single-buffered
+stereo image:
+</para>
+<literallayout class="monospaced">
+/*
+ * Create the stereo window, map it the screen,
+ * and draw the left and right images
+ */
+CreateStereoWindow( W, L, R, ... )
+
+MapWindow( W )
+
+&lt;draw picture using L,R&gt;
+</literallayout>
+</sect1>
+
+<sect1 id='Double_Buffering_Stereo_Windows'>
+<title>Double-Buffering Stereo Windows</title>
+
+<para>
+Additional image buffers may be added to a stereo window
+to allow double or multi-buffering of stereo images.
+Simply use the the <function>CreateImageBuffers</function> request.
+Even numbered buffers (0,2,...) will be left buffers.
+Odd numbered buffers (1,3,...) will be right buffers.
+Displayable stereo images are formed by consecutive
+left/right pairs of image buffers.  For example,
+(buffer[0],buffer[1]) form the first displayable
+stereo image; (buffer[2],buffer[3]) the next;
+and so on.
+</para>
+
+<para>
+The <function>CreateImageBuffers</function> request will only create
+pairs of left and right image buffers for stereo windows.
+By always pairing left and right image
+buffers together, implementations might be able to
+perform some type of optimization.  If an odd number
+of buffers is specified, a <function>Value</function> error is generated.
+All the rules mentioned at the start of this proposal
+still apply to the image buffers supported by a stereo window.
+</para>
+
+<para>
+To display a image buffer pair of a multi-buffered stereo image,
+either the left buffer ID or right buffer ID may be specified in a
+<function>DisplayImageBuffers</function> request, but not both.
+</para>
+
+<para>
+To double-buffer a stereo window:
+</para>
+
+<literallayout class="monospaced">
+/*
+ * Create stereo window and map it to the screen
+ */
+CreateStereoWindow( W, L, R, ... )
+
+/*
+ * Create two pairs of image buffers.  Assume after display,
+ * buffer contents become "undefined".  Assume we will "frequently"
+ * update the display.  Abort if we did get all the buffers.
+ */
+n = CreateImageBuffers( W, [L0,R0,L1,R1], Undefined, Frequently )
+if (n != 4) &lt;abort&gt;
+
+/*
+ * Map window to the screen
+ */
+MapWindow( W )
+
+/*
+ * Draw images using alternate buffers,
+ * display every 1/10 of a second.
+ */
+while animating
+{
+     &lt;draw picture using L1,R1&gt;
+     DisplayImageBuffers( [L1], 100, 0 )
+
+     &lt;draw picture using L0,R0&gt;
+     DisplayImageBuffers( [L0], 100, 0 )
+}
+</literallayout>
+
+</sect1>
+
+<sect1 id='Multi_Buffering_Stereo_Windows'>
+<title>Multi-Buffering Stereo Windows</title>
+
+<para>
+To cycle through <emphasis remap='I'>N</emphasis> stereo images:
+</para>
+
+<literallayout class="monospaced">
+/*
+ * Create stereo window
+ */
+CreateStereoWindow( W, L, R, ... )
+
+/*
+ * Create N pairs of image buffers.  Assume after display,
+ * buffer contents are "untouched".  Assume we will "frequently"
+ * update the display.  Abort if we don't get all the buffers.
+ */
+n = CreateImageBuffers( W, [L0,R0,...,L(N-1),R(N-1)], Untouched, Frequently )
+if (n != N*2) &lt;abort&gt;
+
+/*
+ * Map window to screen
+ */
+MapWindow( W )
+
+/*
+ * Draw the left and right halves of each image
+ */
+foreach stereo image
+     &lt;draw picture using L(i),R(i)&gt;
+
+/*
+ * Cycle through images every 1/10 of a second
+ */
+while animating
+{
+     foreach stereo image
+          DisplayImageBuffers( [L(i)], 100, 0 )
+}
+</literallayout>
+</sect1>
+
+<sect1 id='Protocol_Encoding'>
+<title>Protocol Encoding</title>
+
+<para>
+The official name of this extension is "Multi-Buffering".
+When this string passed to <function>QueryExtension</function> the
+information returned should be interpreted as follows:
+</para>
+
+<variablelist>
+  <varlistentry>
+    <term>major-opcode</term>
+    <listitem>
+      <para>
+Specifies the major opcode of this extension.
+The first byte of each extension request should
+specify this value.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>first-event</term>
+    <listitem>
+      <para>
+Specifies the code that will be returned when
+<function>ClobberNotify</function> events are generated.
+      </para>
+    </listitem>
+  </varlistentry>
+  <varlistentry>
+    <term>first-error</term>
+    <listitem>
+      <para>
+Specifies the code that will be returned when
+<function>Buffer</function> errors are generated.
+      </para>
+    </listitem>
+  </varlistentry>
+</variablelist>
+
+<para>
+The following sections describe the protocol
+encoding for this extension.
+</para>
+</sect1>
+</chapter>
+
+<chapter id='TYPES'>
+<title>TYPES</title>
+
+<literallayout class="monospaced">
+BUFFER_INFO
+
+4       VISUALID     visual
+2       CARD16       max-buffers
+1       CARD8        depth
+1                    unused
+</literallayout>
+
+<literallayout class="monospaced">
+SETofBUFFER_EVENT
+
+        #x00008000   Exposure
+        #x02000000   ClobberNotify
+        #x04000000   UpdateNotify
+</literallayout>
+
+</chapter>
+
+<chapter id='EVENTS_2'>
+<title>EVENTS</title>
+
+<literallayout class="monospaced">
+<function>ClobberNotify</function>
+1       see <emphasis remap='I'>first-event</emphasis> code
+1                                unused
+2       CARD16                   sequence number
+4       BUFFER                   buffer
+1                                state
+        0 Unclobbered
+        1 PartiallyClobbered
+        2 FullyClobbered
+23                                unused
+</literallayout>
+
+<literallayout class="monospaced">
+<function>UpdateNotify</function>
+1 <emphasis remap='I'>first-event</emphasis>+1 code
+1                       unused
+2      CARD16           sequence number
+4      BUFFER           buffer
+24                      unused
+</literallayout>
+
+</chapter>
+<chapter id='ERRORS_2'>
+<title>ERRORS</title>
+
+<literallayout class="monospaced">
+<function>Buffer</function>
+1     0                 Error
+1     see <emphasis remap='I'>first-error</emphasis> code
+2     CARD16                 sequence number
+4     CARD32                 bad resource id
+2     CARD16                 minor-opcode
+1     CARD8                  major-opcode
+21                           unused
+</literallayout>
+
+</chapter>
+
+<chapter id='Requests'>
+<title>REQUESTS</title>
+
+<literallayout class="monospaced">
+<function>GetBufferVersion</function>
+1       see <emphasis remap='I'>major-opcode</emphasis>         major-opcode
+1       0                  minor-opcode
+2       1                  request length
+-&gt;
+1       1                  Reply
+1                          unused
+2       CARD16             sequencenumber
+4       0                  reply length
+1       CARD8              majorversion number
+1       CARD8              minorversion number
+22                         unused
+
+
+<function>CreateImageBuffers</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        1                 minor-opcode
+2        3+n               requestlength
+4        WINDOW            wid
+1                          update-action
+         0 Undefined
+         1 Background
+         2 Untouched
+         3 Copied
+1                          update-hint
+         0 Frequent
+         1 Intermittent
+         2 Static
+2                          unused
+4n     LISTofBUFFER        buffer-list
+-&gt;
+1        1                 Reply
+1                          unused
+2      CARD16              sequencenumber
+4      0                   reply length
+2      CARD16              number-buffers
+22                         unused
+
+
+<function>DestroyImageBuffers</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1       2                  minor-opcode
+2       2                  request length
+4       WINDOW             wid
+
+
+<function>DisplayImageBuffers</function>
+
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+2        2+n               requestlength
+2        CARD16            min-delay
+2        CARD16            max-delay
+4n       LISTofBUFFER      buffer-list
+
+
+<function>SetMultiBufferAttributes</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        4                 minor-opcode
+2        3+n               requestlength
+4        WINDOW            wid
+4        BITMASK           value-mask (has n bits set to 1)
+         #x00000001        update-hint
+4n        LISTofVALUE      value-list
+VALUEs
+1                          update-hint
+         0 Frequent
+         1 Intermittent
+         2 Static
+
+
+<function>GetMultiBufferAttributes</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        5                 minor-opcode
+2        2                 request length
+4        WINDOW            wid
+®
+1        1                 Reply
+1                          unused
+2        CARD16            sequencenumber
+4        n                 reply length
+2        CARD16            displayed-buffer
+1                          update-action
+         0 Undefined
+         1 Background
+         2 Untouched
+         3 Copied
+1                          update-hint
+         0 Frequent
+         1 Intermittent
+         2 Static
+1                          window-mode
+         0 Mono
+         1 Stereo
+19                         unused
+4n       LISTofBUFFER      buffer list
+
+
+<function>SetBufferAttributes</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        6                 minor-opcode
+2        3+n               requestlength
+4        BUFFER            buffer
+4        BITMASK           value-mask (has n bits set to 1)
+         #x00000001        event-mask
+4n       LISTofVALUE       value-list
+VALUEs
+4        SETofBUFFER_EVENT event-mask
+
+<function>GetBufferAttributes</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        7                 minor-opcode
+2        2                 request length
+4        BUFFER            buffer
+-&gt;
+1        1                 Reply
+1                          unused
+2        CARD16            sequencenumber
+4        0                 reply length
+4        WINDOW            wid
+4        SETofBUFFER_EVENT event-mask
+2        CARD16            index
+         1 side
+         0 Mono
+         1 Left
+         2 Right
+13                         unused
+
+<function>GetBufferInfo</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        8                   minor-opcode
+2        2                   request length
+4        WINDOW              root
+®
+1        1                   Reply
+1                            unused
+2        CARD16              sequencenumber
+4        2(n+m)              replylength
+2        n                   number BUFFER_INFO in normal-info
+2        m                   number BUFFER_INFO in stereo-info
+20                           unused
+8n       LISTofBUFFER_INFO   normal-info
+8m       LISTofBUFFER_INFO   stereo-info
+
+<function>CreateStereoWindow</function>
+
+1        see <emphasis remap='I'>major-opcode</emphasis>  major-opcode
+1        9 minor-opcode
+2        11+n                    requestlength
+3                                unused
+1        CARD8                   depth
+4        WINDOW                  wid
+4        WINDOW                  parent
+4        BUFFER                  left
+4        BUFFER                  right
+2        INT16                   x
+2        INT16                   y
+2        CARD16                  width
+2        CARD16                  height
+2        CARD16                  border-width
+2                                class
+         0 CopyFromParent
+         1 InputOutput
+         2 InputOnly
+4        VISUALID                visual
+         0 CopyFromParent
+4        BITMASK                 value-mask (has n bits set to 1)
+         encodings are the same
+         as for CreateWindow
+4n       LISTofVALUE             value-list
+         encodings are the same
+         as for CreateWindow
+
+
+<function>ClearImageBufferArea</function>
+
+1 see major-opcode major-opcode
+1        10                      minor-opcode
+2        5                       request length
+4        WINDOW                  buffer
+2        INT16                   x
+2        INT16                   y
+2        CARD16                  width
+2        CARD16                  height
+3                                unused
+1        BOOL                    exposures
+
+</literallayout>
+
+</chapter>
+</book>