Add Distributed Multihead X (DMX) support

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+<!DOCTYPE linuxdoc PUBLIC "-//XFree86//DTD linuxdoc//EN">
+  <article>
+
+    <!-- Title information -->
+      <title>Distributed Multihead X design
+      <author>Kevin E. Martin, David H. Dawes, and Rickard E. Faith
+      <date>29 June 2004 (created 25 July 2001)
+      <abstract>
+        This document covers the motivation, background, design, and
+        implementation of the distributed multihead X (DMX) system.  It
+        is a living document and describes the current design and
+        implementation details of the DMX system.  As the project
+        progresses, this document will be continually updated to reflect
+        the changes in the code and/or design.  <it>Copyright 2001 by VA
+        Linux Systems, Inc., Fremont, California.  Copyright 2001-2004
+        by Red Hat, Inc., Raleigh, North Carolina</it>
+      </abstract>
+
+      <!-- Table of contents -->
+    <toc>
+
+<!-- Begin the document -->
+<sect>Introduction
+
+<sect1>The Distributed Multihead X Server
+
+<p>Current Open Source multihead solutions are limited to a single
+physical machine.  A single X server controls multiple display devices,
+which can be arranged as independent heads or unified into a single
+desktop (with Xinerama).  These solutions are limited to the number of
+physical devices that can co-exist in a single machine (e.g., due to the
+number of AGP/PCI slots available for graphics cards).  Thus, large
+tiled displays are not currently possible.  The work described in this
+paper will eliminate the requirement that the display devices reside in
+the same physical machine.  This will be accomplished by developing a
+front-end proxy X server that will control multiple back-end X servers
+that make up the large display.
+
+<p>The overall structure of the distributed multihead X (DMX) project is
+as follows: A single front-end X server will act as a proxy to a set of
+back-end X servers, which handle all of the visible rendering.  X
+clients will connect to the front-end server just as they normally would
+to a regular X server.  The front-end server will present an abstracted
+view to the client of a single large display.  This will ensure that all
+standard X clients will continue to operate without modification
+(limited, as always, by the visuals and extensions provided by the X
+server).  Clients that are DMX-aware will be able to use an extension to
+obtain information about the back-end servers (e.g., for placement of
+pop-up windows, window alignments by the window manager, etc.).
+
+<p>The architecture of the DMX server is divided into two main sections:
+input (e.g., mouse and keyboard events) and output (e.g., rendering and
+windowing requests).  Each of these are describe briefly below, and the
+rest of this design document will describe them in greater detail.
+
+<p>The DMX server can receive input from three general types of input
+devices: "local" devices that are physically attached to the machine on
+which DMX is running, "backend" devices that are physically attached to
+one or more of the back-end X servers (and that generate events via the
+X protocol stream from the backend), and "console" devices that can be
+abstracted from any non-back-end X server.  Backend and console devices
+are treated differently because the pointer device on the back-end X
+server also controls the location of the hardware X cursor.  Full
+support for XInput extension devices is provided.
+
+<p>Rendering requests will be accepted by the front-end server; however,
+rendering to visible windows will be broken down as needed and sent to
+the appropriate back-end server(s) via X11 library calls for actual
+rendering.  The basic framework will follow a Xnest-style approach.  GC
+state will be managed in the front-end server and sent to the
+appropriate back-end server(s) as required.  Pixmap rendering will (at
+least initially) be handled by the front-end X server.  Windowing
+requests (e.g., ordering, mapping, moving, etc.) will handled in the
+front-end server.  If the request requires a visible change, the
+windowing operation will be translated into requests for the appropriate
+back-end server(s).  Window state will be mirrored in the back-end
+server(s) as needed.
+
+<sect1>Layout of Paper
+
+<p>The next section describes the general development plan that was
+actually used for implementation.  The final section discusses
+outstanding issues at the conclusion of development.  The first appendix
+provides low-level technical detail that may be of interest to those
+intimately familiar with the X server architecture.  The final appendix
+describes the four phases of development that were performed during the
+first two years of development.
+
+<p>The final year of work was divided into 9 tasks that are not
+described in specific sections of this document.  The major tasks during
+that time were the enhancement of the reconfiguration ability added in
+Phase IV, addition of support for a dynamic number of back-end displays
+(instead of a hard-coded limit), and the support for back-end display
+and input removal and addition.  This work is mentioned in this paper,
+but is not covered in detail.
+
+<!-- ============================================================ -->
+<sect>Development plan
+
+<p>This section describes the development plan from approximately June
+2001 through July 2003.
+
+<sect1>Bootstrap code
+
+<p>To allow for rapid development of the DMX server by multiple
+developers during the first development stage, the problem will be
+broken down into three tasks: the overall DMX framework, back-end
+rendering services and input device handling services.  However, before
+the work begins on these tasks, a simple framework that each developer
+could use was implemented to bootstrap the development effort.  This
+framework renders to a single back-end server and provides dummy input
+devices (i.e., the keyboard and mouse).  The simple back-end rendering
+service was implemented using the shadow framebuffer support currently
+available in the XFree86 environment.
+
+<p>Using this bootstrapping framework, each developer has been able to
+work on each of the tasks listed above independently as follows: the
+framework will be extended to handle arbitrary back-end server
+configurations; the back-end rendering services will be transitioned to
+the more efficient Xnest-style implementation; and, an input device
+framework to handle various input devices via the input extension will
+be developed.
+
+<p>Status: The boot strap code is complete.  <!-- August 2001 -->
+
+
+<sect1>Input device handling
+
+<p>An X server (including the front-end X server) requires two core
+input devices -- a keyboard and a pointer (mouse).  These core devices
+are handled and required by the core X11 protocol.  Additional types of
+input devices may be attached and utilized via the XInput extension.
+These are usually referred to as ``XInput extension devices'',
+
+<p>There are some options as to how the front-end X server gets its core
+input devices:
+
+<enum>
+    <item>Local Input. The physical input devices (e.g., keyboard and
+    mouse) can be attached directly to the front-end X server.  In this
+    case, the keyboard and mouse on the machine running the front-end X
+    server will be used.  The front-end will have drivers to read the
+    raw input from those devices and convert it into the required X
+    input events (e.g., key press/release, pointer button press/release,
+    pointer motion).  The front-end keyboard driver will keep track of
+    keyboard properties such as key and modifier mappings, autorepeat
+    state, keyboard sound and led state.  Similarly the front-end
+    pointer driver will keep track if pointer properties such as the
+    button mapping and movement acceleration parameters.  With this
+    option, input is handled fully in the front-end X server, and the
+    back-end X servers are used in a display-only mode.  This option was
+    implemented and works for a limited number of Linux-specific
+    devices.  Adding additional local input devices for other
+    architectures is expected to be relatively simple.
+
+    <p>The following options are available for implementing local input
+    devices:
+
+    <enum>
+        <item>The XFree86 X server has modular input drivers that could
+        be adapted for this purpose.  The mouse driver supports a wide
+        range of mouse types and interfaces, as well as a range of
+        Operating System platforms.  The keyboard driver in XFree86 is
+        not currently as modular as the mouse driver, but could be made
+        so.  The XFree86 X server also has a range of other input
+        drivers for extended input devices such as tablets and touch
+        screens.  Unfortunately, the XFree86 drivers are generally
+        complex, often simultaneously providing support for multiple
+        devices across multiple architectures; and rely so heavily on
+        XFree86-specific helper-functions, that this option was not
+        pursued.
+
+
+        <item>The <tt/kdrive/ X server in XFree86 has built-in drivers that
+        support PS/2 mice and keyboard under Linux.  The mouse driver
+        can indirectly handle other mouse types if the Linux utility
+        <tt/gpm/ is used as to translate the native mouse protocol into
+        PS/2 mouse format.  These drivers could be adapted and built in
+        to the front-end X server if this range of hardware and OS
+        support is sufficient.  While much simpler than the XFree86
+        drivers, the <tt/kdrive/ drivers were not used for the DMX
+        implementation.
+
+        <item>Reimplementation of keyboard and mouse drivers from
+        scratch for the DMX framework.  Because keyboard and mouse
+        drivers are relatively trivial to implement, this pathway was
+        selected.  Other drivers in the X source tree were referenced,
+        and significant contributions from other drivers are noted in
+        the DMX source code.
+    </enum>
+
+    <item>Backend Input.  The front-end can make use of the core input
+    devices attached to one or more of the back-end X servers.  Core
+    input events from multiple back-ends are merged into a single input
+    event stream.  This can work sanely when only a single set of input
+    devices is used at any given time.  The keyboard and pointer state
+    will be handled in the front-end, with changes propagated to the
+    back-end servers as needed.  This option was implemented and works
+    well.  Because the core pointer on a back-end controls the hardware
+    mouse on that back-end, core pointers cannot be treated as XInput
+    extension devices.  However, all back-end XInput extensions devices
+    can be mapped to either DMX core or DMX XInput extension devices.
+
+    <item>Console Input.  The front-end server could create a console
+    window that is displayed on an X server independent of the back-end
+    X servers.  This console window could display things like the
+    physical screen layout, and the front-end could get its core input
+    events from events delivered to the console window.  This option was
+    implemented and works well.  To help the human navigate, window
+    outlines are also displayed in the console window.  Further, console
+    windows can be used as either core or XInput extension devices.
+
+    <item>Other options were initially explored, but they were all
+    partial subsets of the options listed above and, hence, are
+    irrelevant.
+
+</enum>
+
+<p>Although extended input devices are not specifically mentioned in the
+Distributed X requirements, the options above were all implemented so
+that XInput extension devices were supported.
+
+<p>The bootstrap code (Xdmx) had dummy input devices, and these are
+still supported in the final version.  These do the necessary
+initialization to satisfy the X server's requirements for core pointer
+and keyboard devices, but no input events are ever generated.
+
+<p>Status: The input code is complete.  Because of the complexity of the
+XFree86 input device drivers (and their heavy reliance on XFree86
+infrastructure), separate low-level device drivers were implemented for
+Xdmx.  The following kinds of drivers are supported (in general, the
+devices can be treated arbitrarily as "core" input devices or as XInput
+"extension" devices; and multiple instances of different kinds of
+devices can be simultaneously available):
+    <enum>
+        <item> A "dummy" device drive that never generates events.
+
+        <item> "Local" input is from the low-level hardware on which the
+        Xdmx binary is running.  This is the only area where using the
+        XFree86 driver infrastructure would have been helpful, and then
+        only partially, since good support for generic USB devices does
+        not yet exist in XFree86 (in any case, XFree86 and kdrive driver
+        code was used where possible).  Currently, the following local
+        devices are supported under Linux (porting to other operating
+        systems should be fairly straightforward):
+        <itemize>
+            <item>Linux keyboard
+            <item>Linux serial mouse (MS)
+            <item>Linux PS/2 mouse
+            <item>USB keyboard
+            <item>USB mouse
+            <item>USB generic device (e.g., joystick, gamepad, etc.)
+        </itemize>
+
+        <item> "Backend" input is taken from one or more of the back-end
+        displays.  In this case, events are taken from the back-end X
+        server and are converted to Xdmx events.  Care must be taken so
+        that the sprite moves properly on the display from which input
+        is being taken.
+
+        <item> "Console" input is taken from an X window that Xdmx
+        creates on the operator's display (i.e., on the machine running
+        the Xdmx binary).  When the operator's mouse is inside the
+        console window, then those events are converted to Xdmx events.
+        Several special features are available: the console can display
+        outlines of windows that are on the Xdmx display (to facilitate
+        navigation), the cursor can be confined to the console, and a
+        "fine" mode can be activated to allow very precise cursor
+        positioning.
+    </enum>
+
+
+<!-- May 2002; July 2003 -->
+
+<sect1>Output device handling
+
+<p>The output of the DMX system displays rendering and windowing
+requests across multiple screens.  The screens are typically arranged in
+a grid such that together they represent a single large display.
+
+<p>The output section of the DMX code consists of two parts.  The first
+is in the front-end proxy X server (Xdmx), which accepts client
+connections, manages the windows, and potentially renders primitives but
+does not actually display any of the drawing primitives.  The second
+part is the back-end X server(s), which accept commands from the
+front-end server and display the results on their screens.
+
+<sect2>Initialization
+
+<p>The DMX front-end must first initialize its screens by connecting to
+each of the back-end X servers and collecting information about each of
+these screens.  However, the information collected from the back-end X
+servers might be inconsistent.  Handling these cases can be difficult
+and/or inefficient.  For example, a two screen system has one back-end X
+server running at 16bpp while the second is running at 32bpp.
+Converting rendering requests (e.g., XPutImage() or XGetImage()
+requests) to the appropriate bit depth can be very time consuming.
+Analyzing these cases to determine how or even if it is possible to
+handle them is required.  The current Xinerama code handles many of
+these cases (e.g., in PanoramiXConsolidate()) and will be used as a
+starting point.  In general, the best solution is to use homogeneous X
+servers and display devices.  Using back-end servers with the same depth
+is a requirement of the final DMX implementation.
+
+<p>Once this screen consolidation is finished, the relative position of
+each back-end X server's screen in the unified screen is initialized.  A
+full-screen window is opened on each of the back-end X servers, and the
+cursor on each screen is turned off.  The final DMX implementation can
+also make use of a partial-screen window, or multiple windows per
+back-end screen.
+
+<sect2>Handling rendering requests
+
+<p>After initialization, X applications connect to the front-end server.
+There are two possible implementations of how rendering and windowing
+requests are handled in the DMX system:
+
+<enum>
+    <item>A shadow framebuffer is used in the front-end server as the
+    render target.  In this option, all protocol requests are completely
+    handled in the front-end server.  All state and resources are
+    maintained in the front-end including a shadow copy of the entire
+    framebuffer.  The framebuffers attached to the back-end servers are
+    updated by XPutImage() calls with data taken directly from the
+    shadow framebuffer.
+
+    <p>This solution suffers from two main problems.  First, it does not
+    take advantage of any accelerated hardware available in the system.
+    Second, the size of the XPutImage() calls can be quite large and
+    thus will be limited by the bandwidth available.
+
+    <p>The initial DMX implementation used a shadow framebuffer by
+    default.
+
+    <item>Rendering requests are sent to each back-end server for
+    handling (as is done in the Xnest server described above).  In this
+    option, certain protocol requests are handled in the front-end
+    server and certain requests are repackaged and then sent to the
+    back-end servers.  The framebuffer is distributed across the
+    multiple back-end servers.  Rendering to the framebuffer is handled
+    on each back-end and can take advantage of any acceleration
+    available on the back-end servers' graphics display device.  State
+    is maintained both in the front and back-end servers.
+
+    <p>This solution suffers from two main drawbacks.  First, protocol
+    requests are sent to all back-end servers -- even those that will
+    completely clip the rendering primitive -- which wastes bandwidth
+    and processing time.  Second, state is maintained both in the front-
+    and back-end servers.  These drawbacks are not as severe as in
+    option 1 (above) and can either be overcome through optimizations or
+    are acceptable.  Therefore, this option will be used in the final
+    implementation.
+
+    <p>The final DMX implementation defaults to this mechanism, but also
+    supports the shadow framebuffer mechanism.  Several optimizations
+    were implemented to eliminate the drawbacks of the default
+    mechanism.  These optimizations are described the section below and
+    in Phase II of the Development Results (see appendix).
+
+</enum>
+
+<p>Status: Both the shadow framebuffer and Xnest-style code is complete.
+<!-- May 2002 -->
+
+
+<sect1>Optimizing DMX
+
+<p>Initially, the Xnest-style solution's performance will be measured
+and analyzed to determine where the performance bottlenecks exist.
+There are four main areas that will be addressed.
+
+<p>First, to obtain reasonable interactivity with the first development
+phase, XSync() was called after each protocol request.  The XSync()
+function flushes any pending protocol requests.  It then waits for the
+back-end to process the request and send a reply that the request has
+completed.  This happens with each back-end server and performance
+greatly suffers.  As a result of the way XSync() is called in the first
+development phase, the batching that the X11 library performs is
+effectively defeated.  The XSync() call usage will be analyzed and
+optimized by batching calls and performing them at regular intervals,
+except where interactivity will suffer (e.g., on cursor movements).
+
+<p>Second, the initial Xnest-style solution described above sends the
+repackaged protocol requests to all back-end servers regardless of
+whether or not they would be completely clipped out.  The requests that
+are trivially rejected on the back-end server wastes the limited
+bandwidth available.  By tracking clipping changes in the DMX X server's
+windowing code (e.g., by opening, closing, moving or resizing windows),
+we can determine whether or not back-end windows are visible so that
+trivial tests in the front-end server's GC ops drawing functions can
+eliminate these unnecessary protocol requests.
+
+<p>Third, each protocol request will be analyzed to determine if it is
+possible to break the request into smaller pieces at display boundaries.
+The initial ones to be analyzed are put and get image requests since
+they will require the greatest bandwidth to transmit data between the
+front and back-end servers.  Other protocol requests will be analyzed
+and those that will benefit from breaking them into smaller requests
+will be implemented.
+
+<p>Fourth, an extension is being considered that will allow font glyphs to
+be transferred from the front-end DMX X server to each back-end server.
+This extension will permit the front-end to handle all font requests and
+eliminate the requirement that all back-end X servers share the exact
+same fonts as the front-end server.  We are investigating the
+feasibility of this extension during this development phase.
+
+<p>Other potential optimizations will be determined from the performance
+analysis.
+
+<p>Please note that in our initial design, we proposed optimizing BLT
+operations (e.g., XCopyArea() and window moves) by developing an
+extension that would allow individual back-end servers to directly copy
+pixel data to other back-end servers.  This potential optimization was
+in response to the simple image movement implementation that required
+potentially many calls to GetImage() and PutImage().  However, the
+current Xinerama implementation handles these BLT operations
+differently.  Instead of copying data to and from screens, they generate
+expose events -- just as happens in the case when a window is moved from
+off a screen to on screen.  This approach saves the limited bandwidth
+available between front and back-end servers and is being standardized
+with Xinerama.  It also eliminates the potential setup problems and
+security issues resulting from having each back-end server open
+connections to all other back-end servers.  Therefore, we suggest
+accepting Xinerama's expose event solution.
+
+<p>Also note that the approach proposed in the second and third
+optimizations might cause backing store algorithms in the back-end to be
+defeated, so a DMX X server configuration flag will be added to disable
+these optimizations.
+
+<p>Status: The optimizations proposed above are complete.  It was
+determined that the using the xfs font server was sufficient and
+creating a new mechanism to pass glyphs was redundant; therefore, the
+fourth optimization proposed above was not included in DMX.
+<!-- September 2002 -->
+
+
+<sect1>DMX X extension support
+
+<p>The DMX X server keeps track of all the windowing information on the
+back-end X servers, but does not currently export this information to
+any client applications.  An extension will be developed to pass the
+screen information and back-end window IDs to DMX-aware clients.  These
+clients can then use this information to directly connect to and render
+to the back-end windows.  Bypassing the DMX X server allows DMX-aware
+clients to break up complex rendering requests on their own and send
+them directly to the windows on the back-end server's screens.  An
+example of a client that can make effective use of this extension is
+Chromium.
+
+<p>Status: The extension, as implemented, is fully documented in
+"Client-to-Server DMX Extension to the X Protocol".  Future changes
+might be required based on feedback and other proposed enhancements to
+DMX.  Currently, the following facilities are supported:
+<enum>
+    <item>
+        Screen information (clipping rectangle for each screen relative
+        to the virtual screen)
+    <item>
+        Window information (window IDs and clipping information for each
+        back-end window that corresponds to each DMX window)
+    <item>
+        Input device information (mappings from DMX device IDs to
+        back-end device IDs)
+    <item>
+        Force window creation (so that a client can override the
+        server-side lazy window creation optimization)
+    <item>
+        Reconfiguration (so that a client can request that a screen
+        position be changed)
+    <item>
+        Addition and removal of back-end servers and back-end and
+        console inputs.
+</enum>
+<!-- September 2002; July 2003 -->
+
+
+<sect1>Common X extension support
+
+<p>The XInput, XKeyboard and Shape extensions are commonly used
+extensions to the base X11 protocol.  XInput allows multiple and
+non-standard input devices to be accessed simultaneously.  These input
+devices can be connected to either the front-end or back-end servers.
+XKeyboard allows much better keyboard mappings control.  Shape adds
+support for arbitrarily shaped windows and is used by various window
+managers.  Nearly all potential back-end X servers make these extensions
+available, and support for each one will be added to the DMX system.
+
+<p>In addition to the extensions listed above, support for the X
+Rendering extension (Render) is being developed.  Render adds digital
+image composition to the rendering model used by the X Window System.
+While this extension is still under development by Keith Packard of HP,
+support for the current version will be added to the DMX system.
+
+<p>Support for the XTest extension was added during the first
+development phase.
+
+<!-- WARNING: this list is duplicated in the Phase IV discussion -->
+<p>Status: The following extensions are supported and are discussed in
+more detail in Phase IV of the Development Results (see appendix):
+    BIG-REQUESTS,
+    DEC-XTRAP,
+    DMX,
+    DPMS,
+    Extended-Visual-Information,
+    GLX,
+    LBX,
+    RECORD,
+    RENDER,
+    SECURITY,
+    SHAPE,
+    SYNC,
+    X-Resource,
+    XC-APPGROUP,
+    XC-MISC,
+    XFree86-Bigfont,
+    XINERAMA,
+    XInputExtension,
+    XKEYBOARD, and
+    XTEST.
+<!-- November 2002; updated February 2003, July 2003 -->
+
+<sect1>OpenGL support
+
+<p>OpenGL support using the Mesa code base exists in XFree86 release 4
+and later.  Currently, the direct rendering infrastructure (DRI)
+provides accelerated OpenGL support for local clients and unaccelerated
+OpenGL support (i.e., software rendering) is provided for non-local
+clients.
+
+<p>The single head OpenGL support in XFree86 4.x will be extended to use
+the DMX system.  When the front and back-end servers are on the same
+physical hardware, it is possible to use the DRI to directly render to
+the back-end servers.  First, the existing DRI will be extended to
+support multiple display heads, and then to support the DMX system.
+OpenGL rendering requests will be direct rendering to each back-end X
+server.  The DRI will request the screen layout (either from the
+existing Xinerama extension or a DMX-specific extension).  Support for
+synchronized swap buffers will also be added (on hardware that supports
+it).  Note that a single front-end server with a single back-end server
+on the same physical machine can emulate accelerated indirect rendering.
+
+<p>When the front and back-end servers are on different physical
+hardware or are using non-XFree86 4.x X servers, a mechanism to render
+primitives across the back-end servers will be provided.  There are
+several options as to how this can be implemented.
+
+<enum>
+    <item>The existing OpenGL support in each back-end server can be
+    used by repackaging rendering primitives and sending them to each
+    back-end server.  This option is similar to the unoptimized
+    Xnest-style approach mentioned above.  Optimization of this solution
+    is beyond the scope of this project and is better suited to other
+    distributed rendering systems.
+
+    <item>Rendering to a pixmap in the front-end server using the
+    current XFree86 4.x code, and then displaying to the back-ends via
+    calls to XPutImage() is another option.  This option is similar to
+    the shadow frame buffer approach mentioned above.  It is slower and
+    bandwidth intensive, but has the advantage that the back-end servers
+    are not required to have OpenGL support.
+</enum>
+
+<p>These, and other, options will be investigated in this phase of the
+work.
+
+<p>Work by others have made Chromium DMX-aware.  Chromium will use the
+DMX X protocol extension to obtain information about the back-end
+servers and will render directly to those servers, bypassing DMX.
+
+<p>Status: OpenGL support by the glxProxy extension was implemented by
+SGI and has been integrated into the DMX code base.
+<!-- May 2003-->
+
+
+<!-- ============================================================ -->
+<sect>Current issues
+
+<p>In this sections the current issues are outlined that require further
+investigation.
+
+<sect1>Fonts
+
+<p>The font path and glyphs need to be the same for the front-end and
+each of the back-end servers.  Font glyphs could be sent to the back-end
+servers as necessary but this would consume a significant amount of
+available bandwidth during font rendering for clients that use many
+different fonts (e.g., Netscape).  Initially, the font server (xfs) will
+be used to provide the fonts to both the front-end and back-end servers.
+Other possibilities will be investigated during development.
+
+<sect1>Zero width rendering primitives
+
+<p>To allow pixmap and on-screen rendering to be pixel perfect, all
+back-end servers must render zero width primitives exactly the same as
+the front-end renders the primitives to pixmaps.  For those back-end
+servers that do not exactly match, zero width primitives will be
+automatically converted to one width primitives.  This can be handled in
+the front-end server via the GC state.
+
+<sect1>Output scaling
+
+<p>With very large tiled displays, it might be difficult to read the
+information on the standard X desktop.  In particular, the cursor can be
+easily lost and fonts could be difficult to read.  Automatic primitive
+scaling might prove to be very useful.  We will investigate the
+possibility of scaling the cursor and providing a set of alternate
+pre-scaled fonts to replace the standard fonts that many applications
+use (e.g., fixed).  Other options for automatic scaling will also be
+investigated.
+
+<sect1>Per-screen colormaps
+
+<p>Each screen's default colormap in the set of back-end X servers
+should be able to be adjusted via a configuration utility.  This support
+is would allow the back-end screens to be calibrated via custom gamma
+tables.  On 24-bit systems that support a DirectColor visual, this type
+of correction can be accommodated.  One possible implementation would be
+to advertise to X client of the DMX server a TrueColor visual while
+using DirectColor visuals on the back-end servers to implement this type
+of color correction.  Other options will be investigated.
+
+<!-- ============================================================ -->
+<appendix>
+
+<sect>Background
+
+<p>This section describes the existing Open Source architectures that
+can be used to handle multiple screens and upon which this development
+project is based.  This section was written before the implementation
+was finished, and may not reflect actual details of the implementation.
+It is left for historical interest only.
+
+<sect1>Core input device handling
+
+<p>The following is a description of how core input devices are handled
+by an X server.
+
+<sect2>InitInput()
+
+<p>InitInput() is a DDX function that is called at the start of each
+server generation from the X server's main() function.  Its purpose is
+to determine what input devices are connected to the X server, register
+them with the DIX and MI layers, and initialize the input event queue.
+InitInput() does not have a return value, but the X server will abort if
+either a core keyboard device or a core pointer device are not
+registered.  Extended input (XInput) devices can also be registered in
+InitInput().
+
+<p>InitInput() usually has implementation specific code to determine
+which input devices are available.  For each input device it will be
+using, it calls AddInputDevice():
+
+<descrip>
+<tag/AddInputDevice()/ This DIX function allocates the device structure,
+registers a callback function (which handles device init, close, on and
+off), and returns the input handle, which can be treated as opaque.  It
+is called once for each input device.
+</descrip>
+
+<p>Once input handles for core keyboard and core pointer devices have
+been obtained from AddInputDevice(), they are registered as core devices
+by calling RegisterPointerDevice() and RegisterKeyboardDevice().  Each
+of these should be called once.  If both core devices are not
+registered, then the X server will exit with a fatal error when it
+attempts to start the input devices in InitAndStartDevices(), which is
+called directly after InitInput() (see below).
+
+<descrip>
+<tag/Register{Pointer,Keyboard}Device()/ These DIX functions take a
+handle returned from AddInputDevice() and initialize the core input
+device fields in inputInfo, and initialize the input processing and grab
+functions for each core input device.
+</descrip>
+
+<p>The core pointer device is then registered with the miPointer code
+(which does the high level cursor handling).  While this registration
+is not necessary for correct miPointer operation in the current XFree86
+code, it is still done mostly for compatibility reasons.
+
+<descrip>
+<tag/miRegisterPointerDevice()/ This MI function registers the core
+pointer's input handle with with the miPointer code.
+</descrip>
+
+<p>The final part of InitInput() is the initialization of the input
+event queue handling.  In most cases, the event queue handling provided
+in the MI layer is used.  The primary XFree86 X server uses its own
+event queue handling to support some special cases related to the XInput
+extension and the XFree86-specific DGA extension.  For our purposes, the
+MI event queue handling should be suitable.  It is initialized by
+calling mieqInit():
+
+<descrip>
+<tag/mieqInit()/ This MI function initializes the MI event queue for the
+core devices, and is passed the public component of the input handles
+for the two core devices.
+</descrip>
+
+<p>If a wakeup handler is required to deliver synchronous input
+events, it can be registered here by calling the DIX function
+RegisterBlockAndWakeupHandlers().  (See the devReadInput() description
+below.)
+
+<sect2>InitAndStartDevices()
+
+<p>InitAndStartDevices() is a DIX function that is called immediately
+after InitInput() from the X server's main() function.  Its purpose is
+to initialize each input device that was registered with
+AddInputDevice(), enable each input device that was successfully
+initialized, and create the list of enabled input devices.  Once each
+registered device is processed in this way, the list of enabled input
+devices is checked to make sure that both a core keyboard device and
+core pointer device were registered and successfully enabled.  If not,
+InitAndStartDevices() returns failure, and results in the the X server
+exiting with a fatal error.
+
+<p>Each registered device is initialized by calling its callback
+(dev-&gt;deviceProc) with the DEVICE_INIT argument:
+
+<descrip>
+<tag/(*dev-&gt;deviceProc)(dev, DEVICE_INIT)/ This function initializes the
+device structs with core information relevant to the device.
+
+<p>For pointer devices, this means specifying the number of buttons,
+default button mapping, the function used to get motion events (usually
+miPointerGetMotionEvents()), the function used to change/control the
+core pointer motion parameters (acceleration and threshold), and the
+motion buffer size.
+
+<p>For keyboard devices, this means specifying the keycode range,
+default keycode to keysym mapping, default modifier mapping, and the
+functions used to sound the keyboard bell and modify/control the
+keyboard parameters (LEDs, bell pitch and duration, key click, which
+keys are auto-repeating, etc).
+</descrip>
+
+<p>Each initialized device is enabled by calling EnableDevice():
+
+<descrip>
+<tag/EnableDevice()/ EnableDevice() calls the device callback with
+DEVICE_ON:
+    <descrip>
+    <tag/(*dev-&gt;deviceProc)(dev, DEVICE_ON)/ This typically opens and
+    initializes the relevant physical device, and when appropriate,
+    registers the device's file descriptor (or equivalent) as a valid
+    input source.
+    </descrip>
+
+    <p>EnableDevice() then adds the device handle to the X server's
+    global list of enabled devices.
+</descrip>
+
+<p>InitAndStartDevices() then verifies that a valid core keyboard and
+pointer has been initialized and enabled.  It returns failure if either
+are missing.
+
+<sect2>devReadInput()
+
+<p>Each device will have some function that gets called to read its
+physical input.  These may be called in a number of different ways.  In
+the case of synchronous I/O, they will be called from a DDX
+wakeup-handler that gets called after the server detects that new input is
+available.  In the case of asynchronous I/O, they will be called from a
+(SIGIO) signal handler triggered when new input is available.  This
+function should do at least two things: make sure that input events get
+enqueued, and make sure that the cursor gets moved for motion events
+(except if these are handled later by the driver's own event queue
+processing function, which cannot be done when using the MI event queue
+handling).
+
+<p>Events are queued by calling mieqEnqueue():
+
+<descrip>
+<tag/mieqEnqueue()/ This MI function is used to add input events to the
+event queue.  It is simply passed the event to be queued.
+</descrip>
+
+<p>The cursor position should be updated when motion events are
+enqueued, by calling either miPointerAbsoluteCursor() or
+miPointerDeltaCursor():
+
+<descrip>
+<tag/miPointerAbsoluteCursor()/ This MI function is used to move the
+cursor to the absolute coordinates provided.
+<tag/miPointerDeltaCursor()/ This MI function is used to move the cursor
+relative to its current position.
+</descrip>
+
+<sect2>ProcessInputEvents()
+
+<p>ProcessInputEvents() is a DDX function that is called from the X
+server's main dispatch loop when new events are available in the input
+event queue.  It typically processes the enqueued events, and updates
+the cursor/pointer position.  It may also do other DDX-specific event
+processing.
+
+<p>Enqueued events are processed by mieqProcessInputEvents() and passed
+to the DIX layer for transmission to clients:
+
+<descrip>
+<tag/mieqProcessInputEvents()/ This function processes each event in the
+event queue, and passes it to the device's input processing function.
+The DIX layer provides default functions to do this processing, and they
+handle the task of getting the events passed back to the relevant
+clients.
+<tag/miPointerUpdate()/ This function resynchronized the cursor position
+with the new pointer position.  It also takes care of moving the cursor
+between screens when needed in multi-head configurations.
+</descrip>
+
+
+<sect2>DisableDevice()
+
+<p>DisableDevice is a DIX function that removes an input device from the
+list of enabled devices.  The result of this is that the device no
+longer generates input events.  The device's data structures are kept in
+place, and disabling a device like this can be reversed by calling
+EnableDevice().  DisableDevice() may be called from the DDX when it is
+desirable to do so (e.g., the XFree86 server does this when VT
+switching).  Except for special cases, this is not normally called for
+core input devices.
+
+<p>DisableDevice() calls the device's callback function with
+<tt/DEVICE_OFF/:
+
+<descrip>
+<tag/(*dev-&gt;deviceProc)(dev, DEVICE_OFF)/ This typically closes the
+relevant physical device, and when appropriate, unregisters the device's
+file descriptor (or equivalent) as a valid input source.
+</descrip>
+
+<p>DisableDevice() then removes the device handle from the X server's
+global list of enabled devices.
+
+
+<sect2>CloseDevice()
+
+<p>CloseDevice is a DIX function that removes an input device from the
+list of available devices.  It disables input from the device and frees
+all data structures associated with the device.  This function is
+usually called from CloseDownDevices(), which is called from main() at
+the end of each server generation to close all input devices.
+
+<p>CloseDevice() calls the device's callback function with
+<tt/DEVICE_CLOSE/:
+
+<descrip>
+<tag/(*dev-&gt;deviceProc)(dev, DEVICE_CLOSE)/ This typically closes the
+relevant physical device, and when appropriate, unregisters the device's
+file descriptor (or equivalent) as a valid input source.  If any device
+specific data structures were allocated when the device was initialized,
+they are freed here.
+</descrip>
+
+<p>CloseDevice() then frees the data structures that were allocated
+for the device when it was registered/initialized.
+
+
+<sect2>LegalModifier()
+<!-- dmx/dmxinput.c - currently returns TRUE -->           
+<p>LegalModifier() is a required DDX function that can be used to
+restrict which keys may be modifier keys.  This seems to be present for
+historical reasons, so this function should simply return TRUE
+unconditionally.
+
+
+<sect1>Output handling
+
+<p>The following sections describe the main functions required to
+initialize, use and close the output device(s) for each screen in the X
+server.
+
+<sect2>InitOutput()
+
+<p>This DDX function is called near the start of each server generation
+from the X server's main() function.  InitOutput()'s main purpose is to
+initialize each screen and fill in the global screenInfo structure for
+each screen.  It is passed three arguments: a pointer to the screenInfo
+struct, which it is to initialize, and argc and argv from main(), which
+can be used to determine additional configuration information.
+
+<p>The primary tasks for this function are outlined below:
+
+<enum>
+    <item><bf/Parse configuration info:/ The first task of InitOutput()
+    is to parses any configuration information from the configuration
+    file.  In addition to the XF86Config file, other configuration
+    information can be taken from the command line.  The command line
+    options can be gathered either in InitOutput() or earlier in the
+    ddxProcessArgument() function, which is called by
+    ProcessCommandLine().  The configuration information determines the
+    characteristics of the screen(s).  For example, in the XFree86 X
+    server, the XF86Config file specifies the monitor information, the
+    screen resolution, the graphics devices and slots in which they are
+    located, and, for Xinerama, the screens' layout.
+
+    <item><bf/Initialize screen info:/ The next task is to initialize
+    the screen-dependent internal data structures.  For example, part of
+    what the XFree86 X server does is to allocate its screen and pixmap
+    private indices, probe for graphics devices, compare the probed
+    devices to the ones listed in the XF86Config file, and add the ones that
+    match to the internal xf86Screens&lsqb;&rsqb; structure.
+
+    <item><bf/Set pixmap formats:/ The next task is to initialize the
+    screenInfo's image byte order, bitmap bit order and bitmap scanline
+    unit/pad.  The screenInfo's pixmap format's depth, bits per pixel
+    and scanline padding is also initialized at this stage.
+
+    <item><bf/Unify screen info:/ An optional task that might be done at
+    this stage is to compare all of the information from the various
+    screens and determines if they are compatible (i.e., if the set of
+    screens can be unified into a single desktop).  This task has
+    potential to be useful to the DMX front-end server, if Xinerama's
+    PanoramiXConsolidate() function is not sufficient.
+</enum>
+
+<p>Once these tasks are complete, the valid screens are known and each
+of these screens can be initialized by calling AddScreen().
+
+<sect2>AddScreen()
+
+<p>This DIX function is called from InitOutput(), in the DDX layer, to
+add each new screen to the screenInfo structure.  The DDX screen
+initialization function and command line arguments (i.e., argc and argv)
+are passed to it as arguments.
+
+<p>This function first allocates a new Screen structure and any privates
+that are required.  It then initializes some of the fields in the Screen
+struct and sets up the pixmap padding information.  Finally, it calls
+the DDX screen initialization function ScreenInit(), which is described
+below.  It returns the number of the screen that were just added, or -1
+if there is insufficient memory to add the screen or if the DDX screen
+initialization fails.
+
+<sect2>ScreenInit()
+
+<p>This DDX function initializes the rest of the Screen structure with
+either generic or screen-specific functions (as necessary).  It also
+fills in various screen attributes (e.g., width and height in
+millimeters, black and white pixel values).
+
+<p>The screen init function usually calls several functions to perform
+certain screen initialization functions.  They are described below:
+
+<descrip>
+<tag/{mi,*fb}ScreenInit()/ The DDX layer's ScreenInit() function usually
+calls another layer's ScreenInit() function (e.g., miScreenInit() or
+fbScreenInit()) to initialize the fallbacks that the DDX driver does not
+specifically handle.
+
+<p>After calling another layer's ScreenInit() function, any
+screen-specific functions either wrap or replace the other layer's
+function pointers.  If a function is to be wrapped, each of the old
+function pointers from the other layer are stored in a screen private
+area.  Common functions to wrap are CloseScreen() and SaveScreen().
+
+<tag/miInitializeBackingStore()/ This MI function initializes the
+screen's backing storage functions, which are used to save areas of
+windows that are currently covered by other windows.
+
+<tag/miDCInitialize()/ This MI function initializes the MI cursor
+display structures and function pointers.  If a hardware cursor is used,
+the DDX layer's ScreenInit() function will wrap additional screen and
+the MI cursor display function pointers.
+</descrip>
+
+<p>Another common task for ScreenInit() function is to initialize the
+output device state.  For example, in the XFree86 X server, the
+ScreenInit() function saves the original state of the video card and
+then initializes the video mode of the graphics device.
+
+<sect2>CloseScreen()
+
+<p>This function restores any wrapped screen functions (and in
+particular the wrapped CloseScreen() function) and restores the state of
+the output device to its original state.  It should also free any
+private data it created during the screen initialization.
+
+<sect2>GC operations
+
+<p>When the X server is requested to render drawing primitives, it does
+so by calling drawing functions through the graphics context's operation
+function pointer table (i.e., the GCOps functions).  These functions
+render the basic graphics operations such as drawing rectangles, lines,
+text or copying pixmaps.  Default routines are provided either by the MI
+layer, which draws indirectly through a simple span interface, or by the
+framebuffer layers (e.g., CFB, MFB, FB), which draw directly to a
+linearly mapped frame buffer.
+
+<p>To take advantage of special hardware on the graphics device,
+specific GCOps functions can be replaced by device specific code.
+However, many times the graphics devices can handle only a subset of the
+possible states of the GC, so during graphics context validation,
+appropriate routines are selected based on the state and capabilities of
+the hardware.  For example, some graphics hardware can accelerate single
+pixel width lines with certain dash patterns.  Thus, for dash patterns
+that are not supported by hardware or for width 2 or greater lines, the
+default routine is chosen during GC validation.
+
+<p>Note that some pointers to functions that draw to the screen are
+stored in the Screen structure.  They include GetImage(), GetSpans(),
+PaintWindowBackground(), PaintWindowBorder(), CopyWindow() and
+RestoreAreas().
+
+<sect2>Xnest
+
+<p>The Xnest X server is a special proxy X server that relays the X
+protocol requests that it receives to a ``real'' X server that then
+processes the requests and displays the results, if applicable.  To the X
+applications, Xnest appears as if it is a regular X server.  However,
+Xnest is both server to the X application and client of the real X
+server, which will actually handle the requests.
+
+<p>The Xnest server implements all of the standard input and output
+initialization steps outlined above.
+
+<descrip>
+<tag/InitOutput()/ Xnest takes its configuration information from
+command line arguments via ddxProcessArguments().  This information
+includes the real X server display to connect to, its default visual
+class, the screen depth, the Xnest window's geometry, etc.  Xnest then
+connects to the real X server and gathers visual, colormap, depth and
+pixmap information about that server's display, creates a window on that
+server, which will be used as the root window for Xnest.
+
+<p>Next, Xnest initializes its internal data structures and uses the
+data from the real X server's pixmaps to initialize its own pixmap
+formats.  Finally, it calls AddScreen(xnestOpenScreen, argc, argv) to
+initialize each of its screens.
+
+<tag/ScreenInit()/ Xnest's ScreenInit() function is called
+xnestOpenScreen().  This function initializes its screen's depth and
+visual information, and then calls miScreenInit() to set up the default
+screen functions.  It then calls miInitializeBackingStore() and
+miDCInitialize() to initialize backing store and the software cursor.
+Finally, it replaces many of the screen functions with its own
+functions that repackage and send the requests to the real X server to
+which Xnest is attached.
+
+<tag/CloseScreen()/ This function frees its internal data structure
+allocations.  Since it replaces instead of wrapping screen functions,
+there are no function pointers to unwrap.  This can potentially lead to
+problems during server regeneration.
+
+<tag/GC operations/ The GC operations in Xnest are very simple since
+they leave all of the drawing to the real X server to which Xnest is
+attached.  Each of the GCOps takes the request and sends it to the
+real X server using standard Xlib calls.  For example, the X
+application issues a XDrawLines() call.  This function turns into a
+protocol request to Xnest, which calls the xnestPolylines() function
+through Xnest's GCOps function pointer table.  The xnestPolylines()
+function is only a single line, which calls XDrawLines() using the same
+arguments that were passed into it.  Other GCOps functions are very
+similar.  Two exceptions to the simple GCOps functions described above
+are the image functions and the BLT operations.
+
+<p>The image functions, GetImage() and PutImage(), must use a temporary
+image to hold the image to be put of the image that was just grabbed
+from the screen while it is in transit to the real X server or the
+client.  When the image has been transmitted, the temporary image is
+destroyed.
+
+<p>The BLT operations, CopyArea() and CopyPlane(), handle not only the
+copy function, which is the same as the simple cases described above,
+but also the graphics exposures that result when the GC's graphics
+exposure bit is set to True.  Graphics exposures are handled in a helper
+function, xnestBitBlitHelper().  This function collects the exposure
+events from the real X server and, if any resulting in regions being
+exposed, then those regions are passed back to the MI layer so that it
+can generate exposure events for the X application.
+</descrip>
+
+<p>The Xnest server takes its input from the X server to which it is
+connected.  When the mouse is in the Xnest server's window, keyboard and
+mouse events are received by the Xnest server, repackaged and sent back
+to any client that requests those events.
+
+<sect2>Shadow framebuffer
+
+<p>The most common type of framebuffer is a linear array memory that
+maps to the video memory on the graphics device.  However, accessing
+that video memory over an I/O bus (e.g., ISA or PCI) can be slow.  The
+shadow framebuffer layer allows the developer to keep the entire
+framebuffer in main memory and copy it back to video memory at regular
+intervals.  It also has been extended to handle planar video memory and
+rotated framebuffers.
+
+<p>There are two main entry points to the shadow framebuffer code:
+
+<descrip>
+<tag/shadowAlloc(width, height, bpp)/ This function allocates the in
+memory copy of the framebuffer of size width*height*bpp.  It returns a
+pointer to that memory, which will be used by the framebuffer
+ScreenInit() code during the screen's initialization.
+
+<tag/shadowInit(pScreen, updateProc, windowProc)/ This function
+initializes the shadow framebuffer layer.  It wraps several screen
+drawing functions, and registers a block handler that will update the
+screen.  The updateProc is a function that will copy the damaged regions
+to the screen, and the windowProc is a function that is used when the
+entire linear video memory range cannot be accessed simultaneously so
+that only a window into that memory is available (e.g., when using the
+VGA aperture).
+</descrip>
+
+<p>The shadow framebuffer code keeps track of the damaged area of each
+screen by calculating the bounding box of all drawing operations that
+have occurred since the last screen update.  Then, when the block handler
+is next called, only the damaged portion of the screen is updated.
+
+<p>Note that since the shadow framebuffer is kept in main memory, all
+drawing operations are performed by the CPU and, thus, no accelerated
+hardware drawing operations are possible.
+
+
+<sect1>Xinerama
+
+<p>Xinerama is an X extension that allows multiple physical screens
+controlled by a single X server to appear as a single screen.  Although
+the extension allows clients to find the physical screen layout via
+extension requests, it is completely transparent to clients at the core
+X11 protocol level.  The original public implementation of Xinerama came
+from Digital/Compaq.  XFree86 rewrote it, filling in some missing pieces
+and improving both X11 core protocol compliance and performance.  The
+Xinerama extension will be passing through X.Org's standardization
+process in the near future, and the sample implementation will be based
+on this rewritten version.
+
+<p>The current implementation of Xinerama is based primarily in the DIX
+(device independent) and MI (machine independent) layers of the X
+server.  With few exceptions the DDX layers do not need any changes to
+support Xinerama.  X server extensions often do need modifications to
+provide full Xinerama functionality.
+
+<p>The following is a code-level description of how Xinerama functions.
+
+<p>Note: Because the Xinerama extension was originally called the
+PanoramiX extension, many of the Xinerama functions still have the
+PanoramiX prefix.
+
+<descrip>
+    <tag/PanoramiXExtensionInit()/ PanoramiXExtensionInit() is a
+    device-independent extension function that is called at the start of
+    each server generation from InitExtensions(), which is called from
+    the X server's main() function after all output devices have been
+    initialized, but before any input devices have been initialized.
+
+    <p>PanoramiXNumScreens is set to the number of physical screens.  If
+    only one physical screen is present, the extension is disabled, and
+    PanoramiXExtensionInit() returns without doing anything else.
+
+    <p>The Xinerama extension is registered by calling AddExtension().
+    
+    <p>A local per-screen array of data structures
+    (panoramiXdataPtr&lsqb;&rsqb;)
+    is allocated for each physical screen, and GC and Screen private
+    indexes are allocated, and both GC and Screen private areas are
+    allocated for each physical screen.  These hold Xinerama-specific
+    per-GC and per-Screen data.  Each screen's CreateGC and CloseScreen
+    functions are wrapped by XineramaCreateGC() and
+    XineramaCloseScreen() respectively.  Some new resource classes are
+    created for Xinerama drawables and GCs, and resource types for
+    Xinerama windows, pixmaps and colormaps.
+
+    <p>A region (XineramaScreenRegions&lsqb;i&rsqb;) is initialized for each
+    physical screen, and single region (PanoramiXScreenRegion) is
+    initialized to be the union of the screen regions.  The
+    panoramiXdataPtr&lsqb;&rsqb; array is also initialized with the size and
+    origin of each screen.  The relative positioning information for the
+    physical screens is taken from the array
+    dixScreenOrigins&lsqb;&rsqb;, which
+    the DDX layer must initialize in InitOutput().  The bounds of the
+    combined screen is also calculated (PanoramiXPixWidth and
+    PanoramiXPixHeight).
+
+    <p>The DIX layer has a list of function pointers
+    (ProcVector&lsqb;&rsqb;) that
+    holds the entry points for the functions that process core protocol
+    requests.  The requests that Xinerama must intercept and break up
+    into physical screen-specific requests are wrapped.  The original
+    set is copied to SavedProcVector&lsqb;&rsqb;.  The types of requests
+    intercepted are Window requests, GC requests, colormap requests,
+    drawing requests, and some geometry-related requests.  This wrapping
+    allows the bulk of the protocol request processing to be handled
+    transparently to the DIX layer.  Some operations cannot be dealt with
+    in this way and are handled with Xinerama-specific code within the
+    DIX layer.
+
+    <tag/PanoramiXConsolidate()/ PanoramiXConsolidate() is a
+    device-independent extension function that is called directly from
+    the X server's main() function after extensions and input/output
+    devices have been initialized, and before the root windows are
+    defined and initialized.
+
+    <p>This function finds the set of depths (PanoramiXDepths&lsqb;&rsqb;) and
+    visuals (PanoramiXVisuals&lsqb;&rsqb;)
+    common to all of the physical screens.
+    PanoramiXNumDepths is set to the number of common depths, and
+    PanoramiXNumVisuals is set to the number of common visuals.
+    Resources are created for the single root window and the default
+    colormap.  Each of these resources has per-physical screen entries.
+
+    <tag/PanoramiXCreateConnectionBlock()/ PanoramiXConsolidate() is a
+    device-independent extension function that is called directly from
+    the X server's main() function after the per-physical screen root
+    windows are created.  It is called instead of the standard DIX
+    CreateConnectionBlock() function.  If this function returns FALSE,
+    the X server exits with a fatal error.  This function will return
+    FALSE if no common depths were found in PanoramiXConsolidate().
+    With no common depths, Xinerama mode is not possible.
+
+    <p>The connection block holds the information that clients get when
+    they open a connection to the X server.  It includes information
+    such as the supported pixmap formats, number of screens and the
+    sizes, depths, visuals, default colormap information, etc, for each
+    of the screens (much of information that <tt/xdpyinfo/ shows).  The
+    connection block is initialized with the combined single screen
+    values that were calculated in the above two functions.
+
+    <p>The Xinerama extension allows the registration of connection
+    block callback functions.  The purpose of these is to allow other
+    extensions to do processing at this point.  These callbacks can be
+    registered by calling XineramaRegisterConnectionBlockCallback() from
+    the other extension's ExtensionInit() function.  Each registered
+    connection block callback is called at the end of
+    PanoramiXCreateConnectionBlock().
+</descrip>
+
+<sect2>Xinerama-specific changes to the DIX code
+
+<p>There are a few types of Xinerama-specific changes within the DIX
+code.  The main ones are described here.
+
+<p>Functions that deal with colormap or GC -related operations outside of
+the intercepted protocol requests have a test added to only do the
+processing for screen numbers > 0.  This is because they are handled for
+the single Xinerama screen and the processing is done once for screen 0.
+
+<p>The handling of motion events does some coordinate translation between
+the physical screen's origin and screen zero's origin.  Also, motion
+events must be reported relative to the composite screen origin rather
+than the physical screen origins.
+
+<p>There is some special handling for cursor, window and event processing
+that cannot (either not at all or not conveniently) be done via the
+intercepted protocol requests.  A particular case is the handling of
+pointers moving between physical screens.
+
+<sect2>Xinerama-specific changes to the MI code
+
+<p>The only Xinerama-specific change to the MI code is in miSendExposures()
+to handle the coordinate (and window ID) translation for expose events.
+
+<sect2>Intercepted DIX core requests
+
+<p>Xinerama breaks up drawing requests for dispatch to each physical
+screen.  It also breaks up windows into pieces for each physical screen.
+GCs are translated into per-screen GCs.  Colormaps are replicated on
+each physical screen.  The functions handling the intercepted requests
+take care of breaking the requests and repackaging them so that they can
+be passed to the standard request handling functions for each screen in
+turn.  In addition, and to aid the repackaging, the information from
+many of the intercepted requests is used to keep up to date the
+necessary state information for the single composite screen.  Requests
+(usually those with replies) that can be satisfied completely from this
+stored state information do not call the standard request handling
+functions.
+
+<!-- ============================================================ -->
+
+<sect>Development Results
+
+<p>In this section the results of each phase of development are
+discussed.  This development took place between approximately June 2001
+and July 2003.
+
+<sect1>Phase I
+
+<p>The initial development phase dealt with the basic implementation
+including the bootstrap code, which used the shadow framebuffer, and the
+unoptimized implementation, based on an Xnest-style implementation.
+
+<sect2>Scope
+
+<p>The goal of Phase I is to provide fundamental functionality that can
+act as a foundation for ongoing work:
+<enum>
+    <item>Develop the proxy X server
+    <itemize>
+	<item>The proxy X server will operate on the X11 protocol and
+	relay requests as necessary to correctly perform the request.
+	<item>Work will be based on the existing work for Xinerama and
+	Xnest.
+	<item>Input events and windowing operations are handled in the
+	proxy server and rendering requests are repackaged and sent to
+	each of the back-end servers for display.
+	<item>The multiple screen layout (including support for
+	overlapping screens) will be user configurable via a
+	configuration file or through the configuration tool.
+    </itemize>
+    <item>Develop graphical configuration tool
+    <itemize>
+	<item>There will be potentially a large number of X servers to
+	configure into a single display.  The tool will allow the user
+	to specify which servers are involved in the configuration and
+	how they should be laid out.
+    </itemize>
+    <item>Pass the X Test Suite
+    <itemize>
+	<item>The X Test Suite covers the basic X11 operations.  All
+	tests known to succeed must correctly operate in the distributed
+	X environment.
+    </itemize>
+</enum>
+
+<p>For this phase, the back-end X servers are assumed to be unmodified X
+servers that do not support any DMX-related protocol extensions; future
+optimization pathways are considered, but are not implemented; and the
+configuration tool is assumed to rely only on libraries in the X source
+tree (e.g., Xt).
+
+<sect2>Results
+
+<p>The proxy X server, Xdmx, was developed to distribute X11 protocol
+requests to the set of back-end X servers.  It opens a window on each
+back-end server, which represents the part of the front-end's root
+window that is visible on that screen.  It mirrors window, pixmap and
+other state in each back-end server.  Drawing requests are sent to
+either windows or pixmaps on each back-end server.  This code is based
+on Xnest and uses the existing Xinerama extension.
+
+<p>Input events can be taken from (1) devices attached to the back-end
+server, (2) core devices attached directly to the Xdmx server, or (3)
+from a ``console'' window on another X server.  Events for these devices
+are gathered, processed and delivered to clients attached to the Xdmx
+server.
+
+<p>An intuitive configuration format was developed to help the user
+easily configure the multiple back-end X servers.  It was defined (see
+grammar in Xdmx man page) and a parser was implemented that is used by
+the Xdmx server and by a standalone xdmxconfig utility.  The parsing
+support was implemented such that it can be easily factored out of the X
+source tree for use with other tools (e.g., vdl).  Support for
+converting legacy vdl-format configuration files to the DMX format is
+provided by the vdltodmx utility.
+
+<p>Originally, the configuration file was going to be a subsection of
+XFree86's XF86Config file, but that was not possible since Xdmx is a
+completely separate X server.  Thus, a separate config file format was
+developed.  In addition, a graphical configuration
+tool, xdmxconfig, was developed to allow the user to create and arrange
+the screens in the configuration file.  The <bf/-configfile/ and <bf/-config/
+command-line options can be used to start Xdmx using a configuration
+file.
+
+<p>An extension that enables remote input testing is required for the X
+Test Suite to function.  During this phase, this extension (XTEST) was
+implemented in the Xdmx server.  The results from running the X Test
+Suite are described in detail below.
+
+<sect2>X Test Suite
+
+          <sect3> Introduction
+            <p>
+              The X Test Suite contains tests that verify Xlib functions
+              operate correctly.  The test suite is designed to run on a
+              single X server; however, since X applications will not be
+              able to tell the difference between the DMX server and a
+              standard X server, the X Test Suite should also run on the
+              DMX server.
+            <p>
+              The Xdmx server was tested with the X Test Suite, and the
+              existing failures are noted in this section.  To put these
+              results in perspective, we first discuss expected X Test
+              failures and how errors in underlying systems can impact
+              Xdmx test results.
+
+          <sect3>Expected Failures for a Single Head
+            <p>
+              A correctly implemented X server with a single screen is
+              expected to fail certain X Test tests.  The following
+              well-known errors occur because of rounding error in the X
+              server code:
+              <verb>
+XDrawArc: Tests 42, 63, 66, 73
+XDrawArcs: Tests 45, 66, 69, 76
+              </verb>
+            <p>
+              The following failures occur because of the high-level X
+              server implementation:
+              <verb>
+XLoadQueryFont: Test 1
+XListFontsWithInfo: Tests 3, 4
+XQueryFont: Tests 1, 2
+              </verb>
+            <p>
+              The following test fails when running the X server as root
+              under Linux because of the way directory modes are
+              interpreted:
+              <verb>
+XWriteBitmapFile: Test 3
+              </verb>
+            <p>
+              Depending on the video card used for the back-end, other
+              failures may also occur because of bugs in the low-level
+              driver implementation.  Over time, failures of this kind
+              are usually fixed by XFree86, but will show up in Xdmx
+              testing until then.
+
+          <sect3>Expected Failures for Xinerama
+            <p>
+              Xinerama fails several X Test Suite tests because of
+              design decisions made for the current implementation of
+              Xinerama.  Over time, many of these errors will be
+              corrected by XFree86 and the group working on a new
+              Xinerama implementation.  Therefore, Xdmx will also share
+              X Suite Test failures with Xinerama.
+            <p>
+              We may be able to fix or work-around some of these
+              failures at the Xdmx level, but this will require
+              additional exploration that was not part of Phase I.
+            <p>
+              Xinerama is constantly improving, and the list of
+              Xinerama-related failures depends on XFree86 version and
+              the underlying graphics hardware.  We tested with a
+              variety of hardware, including nVidia, S3, ATI Radeon,
+              and Matrox G400 (in dual-head mode).  The list below
+              includes only those failures that appear to be from the
+              Xinerama layer, and does not include failures listed in
+              the previous section, or failures that appear to be from
+              the low-level graphics driver itself:
+            <p>
+              These failures were noted with multiple Xinerama
+              configurations:
+              <verb>
+XCopyPlane: Tests 13, 22, 31 (well-known Xinerama implementation issue)
+XSetFontPath: Test 4
+XGetDefault: Test 5
+XMatchVisualInfo: Test 1
+              </verb>
+            <p>
+              These failures were noted only when using one dual-head
+              video card with a 4.2.99.x XFree86 server:
+              <verb>
+XListPixmapFormats: Test 1
+XDrawRectangles: Test 45
+              </verb>
+            <p>
+              These failures were noted only when using two video cards
+              from different vendors with a 4.1.99.x XFree86 server:
+              <verb>
+XChangeWindowAttributes: Test 32
+XCreateWindow: Test 30
+XDrawLine: Test 22
+XFillArc: Test 22
+XChangeKeyboardControl: Tests 9, 10
+XRebindKeysym: Test 1
+              </verb>
+
+          <sect3>Additional Failures from Xdmx
+            <p>
+              When running Xdmx, no unexpected failures were noted.
+              Since the Xdmx server is based on Xinerama, we expect to
+              have most of the Xinerama failures present in the Xdmx
+              server.  Similarly, since the Xdmx server must rely on the
+              low-level device drivers on each back-end server, we also
+              expect that Xdmx will exhibit most of the back-end
+              failures.  Here is a summary:
+              <verb>
+XListPixmapFormats: Test 1 (configuration dependent)
+XChangeWindowAttributes: Test 32
+XCreateWindow: Test 30
+XCopyPlane: Test 13, 22, 31
+XSetFontPath: Test 4
+XGetDefault: Test 5 (configuration dependent)
+XMatchVisualInfo: Test 1
+XRebindKeysym: Test 1 (configuration dependent)
+              </verb>
+            <p>
+              Note that this list is shorter than the combined list for
+              Xinerama because Xdmx uses different code paths to perform
+              some Xinerama operations.  Further, some Xinerama failures
+              have been fixed in the XFree86 4.2.99.x CVS repository.
+            
+          <sect3>Summary and Future Work
+            <p>
+              Running the X Test Suite on Xdmx does not produce any
+              failures that cannot be accounted for by the underlying
+              Xinerama subsystem used by the front-end or by the
+              low-level device-driver code running on the back-end X
+              servers.  The Xdmx server therefore is as ``correct'' as
+              possible with respect to the standard set of X Test Suite
+              tests.
+            <p>
+              During the following phases, we will continue to verify
+              Xdmx correctness using the X Test Suite.  We may also use
+              other tests suites or write additional tests that run
+              under the X Test Suite that specifically verify the
+              expected behavior of DMX.
+
+<sect2>Fonts
+
+<p>In Phase I, fonts are handled directly by both the front-end and the
+back-end servers, which is required since we must treat each back-end
+server during this phase as a ``black box''.  What this requires is that
+<bf/the front- and back-end servers must share the exact same font
+path/.  There are two ways to help make sure that all servers share the
+same font path:
+
+<enum>
+    <item>First, each server can be configured to use the same font
+    server.  The font server, xfs, can be configured to serve fonts to
+    multiple X servers via TCP.
+
+    <item>Second, each server can be configured to use the same font
+    path and either those font paths can be copied to each back-end
+    machine or they can be mounted (e.g., via NFS) on each back-end
+    machine.
+</enum>
+
+<p>One additional concern is that a client program can set its own font
+path, and if it does so, then that font path must be available on each
+back-end machine.
+
+<p>The -fontpath command line option was added to allow users to
+initialize the font path of the front end server.  This font path is
+propagated to each back-end server when the default font is loaded.  If
+there are any problems, an error message is printed, which will describe
+the problem and list the current font path.  For more information about
+setting the font path, see the -fontpath option description in the man
+page.
+
+<sect2>Performance
+
+<p>Phase I of development was not intended to optimize performance.  Its
+focus was on completely and correctly handling the base X11 protocol in
+the Xdmx server.  However, several insights were gained during Phase I,
+which are listed here for reference during the next phase of
+development.
+
+<enum>
+    <item>Calls to XSync() can slow down rendering since it requires a
+    complete round trip to and from a back-end server.  This is
+    especially problematic when communicating over long haul networks.
+    <item>Sending drawing requests to only the screens that they overlap
+    should improve performance.
+</enum>
+
+<sect2>Pixmaps
+
+<p>Pixmaps were originally expected to be handled entirely in the
+front-end X server; however, it was found that this overly complicated
+the rendering code and would have required sending potentially large
+images to each back server that required them when copying from pixmap
+to screen.  Thus, pixmap state is mirrored in the back-end server just
+as it is with regular window state.  With this implementation, the same
+rendering code that draws to windows can be used to draw to pixmaps on
+the back-end server, and no large image transfers are required to copy
+from pixmap to window.
+
+<!-- ============================================================ -->
+<sect1>Phase II
+
+<p>The second phase of development concentrates on performance
+optimizations.  These optimizations are documented here, with
+<tt/x11perf/ data to show how the optimizations improve performance.
+
+<p>All benchmarks were performed by running Xdmx on a dual processor
+1.4GHz AMD Athlon machine with 1GB of RAM connecting over 100baseT to
+two single-processor 1GHz Pentium III machines with 256MB of RAM and ATI
+Rage 128 (RF) video cards.  The front end was running Linux
+2.4.20-pre1-ac1 and the back ends were running Linux 2.4.7-10 and
+version 4.2.99.1 of XFree86 pulled from the XFree86 CVS repository on
+August 7, 2002.  All systems were running Red Hat Linux 7.2.
+
+<sect2>Moving from XFree86 4.1.99.1 to 4.2.0.0
+
+<p>For phase II, the working source tree was moved to the branch tagged
+with dmx-1-0-branch and was updated from version 4.1.99.1 (20 August
+2001) of the XFree86 sources to version 4.2.0.0 (18 January 2002).
+After this update, the following tests were noted to be more than 10%
+faster:
+            <verb>
+1.13   Fill 300x300 opaque stippled trapezoid (161x145 stipple) 
+1.16   Fill 1x1 tiled trapezoid (161x145 tile) 
+1.13   Fill 10x10 tiled trapezoid (161x145 tile) 
+1.17   Fill 100x100 tiled trapezoid (161x145 tile) 
+1.16   Fill 1x1 tiled trapezoid (216x208 tile) 
+1.20   Fill 10x10 tiled trapezoid (216x208 tile) 
+1.15   Fill 100x100 tiled trapezoid (216x208 tile) 
+1.37   Circulate Unmapped window (200 kids) 
+            </verb>
+And the following tests were noted to be more than 10% slower:
+            <verb>
+0.88   Unmap window via parent (25 kids) 
+0.75   Circulate Unmapped window (4 kids) 
+0.79   Circulate Unmapped window (16 kids) 
+0.80   Circulate Unmapped window (25 kids) 
+0.82   Circulate Unmapped window (50 kids) 
+0.85   Circulate Unmapped window (75 kids) 
+            </verb>
+<p>These changes were not caused by any changes in the DMX system, and
+may point to changes in the XFree86 tree or to tests that have more
+"jitter" than most other <tt/x11perf/ tests.
+
+<sect2>Global changes
+
+<p>During the development of the Phase II DMX server, several global
+changes were made.  These changes were also compared with the Phase I
+server.  The following tests were noted to be more than 10% faster:
+            <verb>
+1.13   Fill 300x300 opaque stippled trapezoid (161x145 stipple) 
+1.15   Fill 1x1 tiled trapezoid (161x145 tile) 
+1.13   Fill 10x10 tiled trapezoid (161x145 tile) 
+1.17   Fill 100x100 tiled trapezoid (161x145 tile) 
+1.16   Fill 1x1 tiled trapezoid (216x208 tile) 
+1.19   Fill 10x10 tiled trapezoid (216x208 tile) 
+1.15   Fill 100x100 tiled trapezoid (216x208 tile) 
+1.15   Circulate Unmapped window (4 kids) 
+            </verb>
+
+<p>The following tests were noted to be more than 10% slower:
+            <verb>
+0.69   Scroll 10x10 pixels 
+0.68   Scroll 100x100 pixels 
+0.68   Copy 10x10 from window to window 
+0.68   Copy 100x100 from window to window 
+0.76   Circulate Unmapped window (75 kids) 
+0.83   Circulate Unmapped window (100 kids) 
+            </verb>
+
+<p>For the remainder of this analysis, the baseline of comparison will
+be the Phase II deliverable with all optimizations disabled (unless
+otherwise noted).  This will highlight how the optimizations in
+isolation impact performance.
+
+<sect2>XSync() Batching
+
+<p>During the Phase I implementation, XSync() was called after every
+protocol request made by the DMX server.  This provided the DMX server
+with an interactive feel, but defeated X11's protocol buffering system
+and introduced round-trip wire latency into every operation.  During
+Phase II, DMX was changed so that protocol requests are no longer
+followed by calls to XSync().  Instead, the need for an XSync() is
+noted, and XSync() calls are only made every 100mS or when the DMX
+server specifically needs to make a call to guarantee interactivity.
+With this new system, X11 buffers protocol as much as possible during a
+100mS interval, and many unnecessary XSync() calls are avoided.
+
+<p>Out of more than 300 <tt/x11perf/ tests, 8 tests became more than 100
+times faster, with 68 more than 50X faster, 114 more than 10X faster,
+and 181 more than 2X faster.  See table below for summary.
+
+<p>The following tests were noted to be more than 10% slower with
+XSync() batching on:
+            <verb>
+0.88   500x500 tiled rectangle (161x145 tile) 
+0.89   Copy 500x500 from window to window 
+            </verb>
+
+<sect2>Offscreen Optimization
+
+<p>Windows span one or more of the back-end servers' screens; however,
+during Phase I development, windows were created on every back-end
+server and every rendering request was sent to every window regardless
+of whether or not that window was visible.  With the offscreen
+optimization, the DMX server tracks when a window is completely off of a
+back-end server's screen and, in that case, it does not send rendering
+requests to those back-end windows.  This optimization saves bandwidth
+between the front and back-end servers, and it reduces the number of
+XSync() calls.  The performance tests were run on a DMX system with only
+two back-end servers.  Greater performance gains will be had as the
+number of back-end servers increases.
+
+<p>Out of more than 300 <tt/x11perf/ tests, 3 tests were at least twice as
+fast, and 146 tests were at least 10% faster.  Two tests were more than
+10% slower with the offscreen optimization:
+            <verb>
+0.88   Hide/expose window via popup (4 kids) 
+0.89   Resize unmapped window (75 kids) 
+            </verb>
+
+<sect2>Lazy Window Creation Optimization
+
+<p>As mentioned above, during Phase I, windows were created on every
+back-end server even if they were not visible on that back-end.  With
+the lazy window creation optimization, the DMX server does not create
+windows on a back-end server until they are either visible or they
+become the parents of a visible window.  This optimization builds on the
+offscreen optimization (described above) and requires it to be enabled.
+
+<p>The lazy window creation optimization works by creating the window
+data structures in the front-end server when a client creates a window,
+but delays creation of the window on the back-end server(s).  A private
+window structure in the DMX server saves the relevant window data and
+tracks changes to the window's attributes and stacking order for later
+use.  The only times a window is created on a back-end server are (1)
+when it is mapped and is at least partially overlapping the back-end
+server's screen (tracked by the offscreen optimization), or (2) when the
+window becomes the parent of a previously visible window.  The first
+case occurs when a window is mapped or when a visible window is copied,
+moved or resized and now overlaps the back-end server's screen.  The
+second case occurs when starting a window manager after having created
+windows to which the window manager needs to add decorations.
+
+<p>When either case occurs, a window on the back-end server is created
+using the data saved in the DMX server's window private data structure.
+The stacking order is then adjusted to correctly place the window on the
+back-end and lastly the window is mapped.  From this time forward, the
+window is handled exactly as if the window had been created at the time
+of the client's request.
+
+<p>Note that when a window is no longer visible on a back-end server's
+screen (e.g., it is moved offscreen), the window is not destroyed;
+rather, it is kept and reused later if the window once again becomes
+visible on the back-end server's screen.  Originally with this
+optimization, destroying windows was implemented but was later rejected
+because it increased bandwidth when windows were opaquely moved or
+resized, which is common in many window managers.
+
+<p>The performance tests were run on a DMX system with only two back-end
+servers.  Greater performance gains will be had as the number of
+back-end servers increases.
+
+<p>This optimization improved the following <tt/x11perf/ tests by more
+than 10%:
+            <verb>
+1.10   500x500 rectangle outline 
+1.12   Fill 100x100 stippled trapezoid (161x145 stipple) 
+1.20   Circulate Unmapped window (50 kids) 
+1.19   Circulate Unmapped window (75 kids) 
+            </verb>
+            
+<sect2>Subdividing Rendering Primitives
+
+<p>X11 imaging requests transfer significant data between the client and
+the X server.  During Phase I, the DMX server would then transfer the
+image data to each back-end server.  Even with the offscreen
+optimization (above), these requests still required transferring
+significant data to each back-end server that contained a visible
+portion of the window.  For example, if the client uses XPutImage() to
+copy an image to a window that overlaps the entire DMX screen, then the
+entire image is copied by the DMX server to every back-end server.
+
+<p>To reduce the amount of data transferred between the DMX server and
+the back-end servers when XPutImage() is called, the image data is
+subdivided and only the data that will be visible on a back-end server's
+screen is sent to that back-end server.  Xinerama already implements a
+subdivision algorithm for XGetImage() and no further optimization was
+needed.
+
+<p>Other rendering primitives were analyzed, but the time required to
+subdivide these primitives was a significant proportion of the time
+required to send the entire rendering request to the back-end server, so
+this optimization was rejected for the other rendering primitives.
+
+<p>Again, the performance tests were run on a DMX system with only two
+back-end servers.  Greater performance gains will be had as the number
+of back-end servers increases.
+
+<p>This optimization improved the following <tt/x11perf/ tests by more
+than 10%:
+            <verb>
+1.12   Fill 100x100 stippled trapezoid (161x145 stipple) 
+1.26   PutImage 10x10 square 
+1.83   PutImage 100x100 square 
+1.91   PutImage 500x500 square 
+1.40   PutImage XY 10x10 square 
+1.48   PutImage XY 100x100 square 
+1.50   PutImage XY 500x500 square 
+1.45   Circulate Unmapped window (75 kids) 
+1.74   Circulate Unmapped window (100 kids) 
+            </verb>
+
+<p>The following test was noted to be more than 10% slower with this
+optimization:
+            <verb>
+0.88   10-pixel fill chord partial circle 
+            </verb>
+
+<sect2>Summary of x11perf Data
+
+<p>With all of the optimizations on, 53 <tt/x11perf/ tests are more than
+100X faster than the unoptimized Phase II deliverable, with 69 more than
+50X faster, 73 more than 10X faster, and 199 more than twice as fast.
+No tests were more than 10% slower than the unoptimized Phase II
+deliverable.  (Compared with the Phase I deliverable, only Circulate
+Unmapped window (100 kids) was more than 10% slower than the Phase II
+deliverable.  As noted above, this test seems to have wider variability
+than other <tt/x11perf/ tests.)
+
+<p>The following table summarizes relative <tt/x11perf/ test changes for
+all optimizations individually and collectively.  Note that some of the
+optimizations have a synergistic effect when used together.
+            <verb>
+
+1: XSync() batching only
+2: Off screen optimizations only
+3: Window optimizations only
+4: Subdivprims only
+5: All optimizations
+
+    1     2    3    4      5 Operation
+------ ---- ---- ---- ------ ---------
+  2.14 1.85 1.00 1.00   4.13 Dot 
+  1.67 1.80 1.00 1.00   3.31 1x1 rectangle 
+  2.38 1.43 1.00 1.00   2.44 10x10 rectangle 
+  1.00 1.00 0.92 0.98   1.00 100x100 rectangle 
+  1.00 1.00 1.00 1.00   1.00 500x500 rectangle 
+  1.83 1.85 1.05 1.06   3.54 1x1 stippled rectangle (8x8 stipple) 
+  2.43 1.43 1.00 1.00   2.41 10x10 stippled rectangle (8x8 stipple) 
+  0.98 1.00 1.00 1.00   1.00 100x100 stippled rectangle (8x8 stipple) 
+  1.00 1.00 1.00 1.00   0.98 500x500 stippled rectangle (8x8 stipple) 
+  1.75 1.75 1.00 1.00   3.40 1x1 opaque stippled rectangle (8x8 stipple) 
+  2.38 1.42 1.00 1.00   2.34 10x10 opaque stippled rectangle (8x8 stipple) 
+  1.00 1.00 0.97 0.97   1.00 100x100 opaque stippled rectangle (8x8 stipple) 
+  1.00 1.00 1.00 1.00   0.99 500x500 opaque stippled rectangle (8x8 stipple) 
+  1.82 1.82 1.04 1.04   3.56 1x1 tiled rectangle (4x4 tile) 
+  2.33 1.42 1.00 1.00   2.37 10x10 tiled rectangle (4x4 tile) 
+  1.00 0.92 1.00 1.00   1.00 100x100 tiled rectangle (4x4 tile) 
+  1.00 1.00 1.00 1.00   1.00 500x500 tiled rectangle (4x4 tile) 
+  1.94 1.62 1.00 1.00   3.66 1x1 stippled rectangle (17x15 stipple) 
+  1.74 1.28 1.00 1.00   1.73 10x10 stippled rectangle (17x15 stipple) 
+  1.00 1.00 1.00 0.89   0.98 100x100 stippled rectangle (17x15 stipple) 
+  1.00 1.00 1.00 1.00   0.98 500x500 stippled rectangle (17x15 stipple) 
+  1.94 1.62 1.00 1.00   3.67 1x1 opaque stippled rectangle (17x15 stipple) 
+  1.69 1.26 1.00 1.00   1.66 10x10 opaque stippled rectangle (17x15 stipple) 
+  1.00 0.95 1.00 1.00   1.00 100x100 opaque stippled rectangle (17x15 stipple) 
+  1.00 1.00 1.00 1.00   0.97 500x500 opaque stippled rectangle (17x15 stipple) 
+  1.93 1.61 0.99 0.99   3.69 1x1 tiled rectangle (17x15 tile) 
+  1.73 1.27 1.00 1.00   1.72 10x10 tiled rectangle (17x15 tile) 
+  1.00 1.00 1.00 1.00   0.98 100x100 tiled rectangle (17x15 tile) 
+  1.00 1.00 0.97 0.97   1.00 500x500 tiled rectangle (17x15 tile) 
+  1.95 1.63 1.00 1.00   3.83 1x1 stippled rectangle (161x145 stipple) 
+  1.80 1.30 1.00 1.00   1.83 10x10 stippled rectangle (161x145 stipple) 
+  0.97 1.00 1.00 1.00   1.01 100x100 stippled rectangle (161x145 stipple) 
+  1.00 1.00 1.00 1.00   0.98 500x500 stippled rectangle (161x145 stipple) 
+  1.95 1.63 1.00 1.00   3.56 1x1 opaque stippled rectangle (161x145 stipple) 
+  1.65 1.25 1.00 1.00   1.68 10x10 opaque stippled rectangle (161x145 stipple) 
+  1.00 1.00 1.00 1.00   1.01 100x100 opaque stippled rectangle (161x145...
+  1.00 1.00 1.00 1.00   0.97 500x500 opaque stippled rectangle (161x145...
+  1.95 1.63 0.98 0.99   3.80 1x1 tiled rectangle (161x145 tile) 
+  1.67 1.26 1.00 1.00   1.67 10x10 tiled rectangle (161x145 tile) 
+  1.13 1.14 1.14 1.14   1.14 100x100 tiled rectangle (161x145 tile) 
+  0.88 1.00 1.00 1.00   0.99 500x500 tiled rectangle (161x145 tile) 
+  1.93 1.63 1.00 1.00   3.53 1x1 tiled rectangle (216x208 tile) 
+  1.69 1.26 1.00 1.00   1.66 10x10 tiled rectangle (216x208 tile) 
+  1.00 1.00 1.00 1.00   1.00 100x100 tiled rectangle (216x208 tile) 
+  1.00 1.00 1.00 1.00   1.00 500x500 tiled rectangle (216x208 tile) 
+  1.82 1.70 1.00 1.00   3.38 1-pixel line segment 
+  2.07 1.56 0.90 1.00   3.31 10-pixel line segment 
+  1.29 1.10 1.00 1.00   1.27 100-pixel line segment 
+  1.05 1.06 1.03 1.03   1.09 500-pixel line segment 
+  1.30 1.13 1.00 1.00   1.29 100-pixel line segment (1 kid) 
+  1.32 1.15 1.00 1.00   1.32 100-pixel line segment (2 kids) 
+  1.33 1.16 1.00 1.00   1.33 100-pixel line segment (3 kids) 
+  1.92 1.64 1.00 1.00   3.73 10-pixel dashed segment 
+  1.34 1.16 1.00 1.00   1.34 100-pixel dashed segment 
+  1.24 1.11 0.99 0.97   1.23 100-pixel double-dashed segment 
+  1.72 1.77 1.00 1.00   3.25 10-pixel horizontal line segment 
+  1.83 1.66 1.01 1.00   3.54 100-pixel horizontal line segment 
+  1.86 1.30 1.00 1.00   1.84 500-pixel horizontal line segment 
+  2.11 1.52 1.00 0.99   3.02 10-pixel vertical line segment 
+  1.21 1.10 1.00 1.00   1.20 100-pixel vertical line segment 
+  1.03 1.03 1.00 1.00   1.02 500-pixel vertical line segment 
+  4.42 1.68 1.00 1.01   4.64 10x1 wide horizontal line segment 
+  1.83 1.31 1.00 1.00   1.83 100x10 wide horizontal line segment 
+  1.07 1.00 0.96 1.00   1.07 500x50 wide horizontal line segment 
+  4.10 1.67 1.00 1.00   4.62 10x1 wide vertical line segment 
+  1.50 1.24 1.06 1.06   1.48 100x10 wide vertical line segment 
+  1.06 1.03 1.00 1.00   1.05 500x50 wide vertical line segment 
+  2.54 1.61 1.00 1.00   3.61 1-pixel line 
+  2.71 1.48 1.00 1.00   2.67 10-pixel line 
+  1.19 1.09 1.00 1.00   1.19 100-pixel line 
+  1.04 1.02 1.00 1.00   1.03 500-pixel line 
+  2.68 1.51 0.98 1.00   3.17 10-pixel dashed line 
+  1.23 1.11 0.99 0.99   1.23 100-pixel dashed line 
+  1.15 1.08 1.00 1.00   1.15 100-pixel double-dashed line 
+  2.27 1.39 1.00 1.00   2.23 10x1 wide line 
+  1.20 1.09 1.00 1.00   1.20 100x10 wide line 
+  1.04 1.02 1.00 1.00   1.04 500x50 wide line 
+  1.52 1.45 1.00 1.00   1.52 100x10 wide dashed line 
+  1.54 1.47 1.00 1.00   1.54 100x10 wide double-dashed line 
+  1.97 1.30 0.96 0.95   1.95 10x10 rectangle outline 
+  1.44 1.27 1.00 1.00   1.43 100x100 rectangle outline 
+  3.22 2.16 1.10 1.09   3.61 500x500 rectangle outline 
+  1.95 1.34 1.00 1.00   1.90 10x10 wide rectangle outline 
+  1.14 1.14 1.00 1.00   1.13 100x100 wide rectangle outline 
+  1.00 1.00 1.00 1.00   1.00 500x500 wide rectangle outline 
+  1.57 1.72 1.00 1.00   3.03 1-pixel circle 
+  1.96 1.35 1.00 1.00   1.92 10-pixel circle 
+  1.21 1.07 0.86 0.97   1.20 100-pixel circle 
+  1.08 1.04 1.00 1.00   1.08 500-pixel circle 
+  1.39 1.19 1.03 1.03   1.38 100-pixel dashed circle 
+  1.21 1.11 1.00 1.00   1.23 100-pixel double-dashed circle 
+  1.59 1.28 1.00 1.00   1.58 10-pixel wide circle 
+  1.22 1.12 0.99 1.00   1.22 100-pixel wide circle 
+  1.06 1.04 1.00 1.00   1.05 500-pixel wide circle 
+  1.87 1.84 1.00 1.00   1.85 100-pixel wide dashed circle 
+  1.90 1.93 1.01 1.01   1.90 100-pixel wide double-dashed circle 
+  2.13 1.43 1.00 1.00   2.32 10-pixel partial circle 
+  1.42 1.18 1.00 1.00   1.42 100-pixel partial circle 
+  1.92 1.85 1.01 1.01   1.89 10-pixel wide partial circle 
+  1.73 1.67 1.00 1.00   1.73 100-pixel wide partial circle 
+  1.36 1.95 1.00 1.00   2.64 1-pixel solid circle 
+  2.02 1.37 1.00 1.00   2.03 10-pixel solid circle 
+  1.19 1.09 1.00 1.00   1.19 100-pixel solid circle 
+  1.02 0.99 1.00 1.00   1.01 500-pixel solid circle 
+  1.74 1.28 1.00 0.88   1.73 10-pixel fill chord partial circle 
+  1.31 1.13 1.00 1.00   1.31 100-pixel fill chord partial circle 
+  1.67 1.31 1.03 1.03   1.72 10-pixel fill slice partial circle 
+  1.30 1.13 1.00 1.00   1.28 100-pixel fill slice partial circle 
+  2.45 1.49 1.01 1.00   2.71 10-pixel ellipse 
+  1.22 1.10 1.00 1.00   1.22 100-pixel ellipse 
+  1.09 1.04 1.00 1.00   1.09 500-pixel ellipse 
+  1.90 1.28 1.00 1.00   1.89 100-pixel dashed ellipse 
+  1.62 1.24 0.96 0.97   1.61 100-pixel double-dashed ellipse 
+  2.43 1.50 1.00 1.00   2.42 10-pixel wide ellipse 
+  1.61 1.28 1.03 1.03   1.60 100-pixel wide ellipse 
+  1.08 1.05 1.00 1.00   1.08 500-pixel wide ellipse 
+  1.93 1.88 1.00 1.00   1.88 100-pixel wide dashed ellipse 
+  1.94 1.89 1.01 1.00   1.94 100-pixel wide double-dashed ellipse 
+  2.31 1.48 1.00 1.00   2.67 10-pixel partial ellipse 
+  1.38 1.17 1.00 1.00   1.38 100-pixel partial ellipse 
+  2.00 1.85 0.98 0.97   1.98 10-pixel wide partial ellipse 
+  1.89 1.86 1.00 1.00   1.89 100-pixel wide partial ellipse 
+  3.49 1.60 1.00 1.00   3.65 10-pixel filled ellipse 
+  1.67 1.26 1.00 1.00   1.67 100-pixel filled ellipse 
+  1.06 1.04 1.00 1.00   1.06 500-pixel filled ellipse 
+  2.38 1.43 1.01 1.00   2.32 10-pixel fill chord partial ellipse 
+  2.06 1.30 1.00 1.00   2.05 100-pixel fill chord partial ellipse 
+  2.27 1.41 1.00 1.00   2.27 10-pixel fill slice partial ellipse 
+  1.98 1.33 1.00 0.97   1.97 100-pixel fill slice partial ellipse 
+ 57.46 1.99 1.01 1.00 114.92 Fill 1x1 equivalent triangle 
+ 56.94 1.98 1.01 1.00  73.89 Fill 10x10 equivalent triangle 
+  6.07 1.75 1.00 1.00   6.07 Fill 100x100 equivalent triangle 
+ 51.12 1.98 1.00 1.00 102.81 Fill 1x1 trapezoid 
+ 51.42 1.82 1.01 1.00  94.89 Fill 10x10 trapezoid 
+  6.47 1.80 1.00 1.00   6.44 Fill 100x100 trapezoid 
+  1.56 1.28 1.00 0.99   1.56 Fill 300x300 trapezoid 
+ 51.27 1.97 0.96 0.97 102.54 Fill 1x1 stippled trapezoid (8x8 stipple) 
+ 51.73 2.00 1.02 1.02  67.92 Fill 10x10 stippled trapezoid (8x8 stipple) 
+  5.36 1.72 1.00 1.00   5.36 Fill 100x100 stippled trapezoid (8x8 stipple) 
+  1.54 1.26 1.00 1.00   1.59 Fill 300x300 stippled trapezoid (8x8 stipple) 
+ 51.41 1.94 1.01 1.00 102.82 Fill 1x1 opaque stippled trapezoid (8x8 stipple) 
+ 50.71 1.95 0.99 1.00  65.44 Fill 10x10 opaque stippled trapezoid (8x8...
+  5.33 1.73 1.00 1.00   5.36 Fill 100x100 opaque stippled trapezoid (8x8...
+  1.58 1.25 1.00 1.00   1.58 Fill 300x300 opaque stippled trapezoid (8x8...
+ 51.56 1.96 0.99 0.90 103.68 Fill 1x1 tiled trapezoid (4x4 tile) 
+ 51.59 1.99 1.01 1.01  62.25 Fill 10x10 tiled trapezoid (4x4 tile) 
+  5.38 1.72 1.00 1.00   5.38 Fill 100x100 tiled trapezoid (4x4 tile) 
+  1.54 1.25 1.00 0.99   1.58 Fill 300x300 tiled trapezoid (4x4 tile) 
+ 51.70 1.98 1.01 1.01 103.98 Fill 1x1 stippled trapezoid (17x15 stipple) 
+ 44.86 1.97 1.00 1.00  44.86 Fill 10x10 stippled trapezoid (17x15 stipple) 
+  2.74 1.56 1.00 1.00   2.73 Fill 100x100 stippled trapezoid (17x15 stipple) 
+  1.29 1.14 1.00 1.00   1.27 Fill 300x300 stippled trapezoid (17x15 stipple) 
+ 51.41 1.96 0.96 0.95 103.39 Fill 1x1 opaque stippled trapezoid (17x15...
+ 45.14 1.96 1.01 1.00  45.14 Fill 10x10 opaque stippled trapezoid (17x15...
+  2.68 1.56 1.00 1.00   2.68 Fill 100x100 opaque stippled trapezoid (17x15...
+  1.26 1.10 1.00 1.00   1.28 Fill 300x300 opaque stippled trapezoid (17x15...
+ 51.13 1.97 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (17x15 tile) 
+ 47.58 1.96 1.00 1.00  47.86 Fill 10x10 tiled trapezoid (17x15 tile) 
+  2.74 1.56 1.00 1.00   2.74 Fill 100x100 tiled trapezoid (17x15 tile) 
+  1.29 1.14 1.00 1.00   1.28 Fill 300x300 tiled trapezoid (17x15 tile) 
+ 51.13 1.97 0.99 0.97 103.39 Fill 1x1 stippled trapezoid (161x145 stipple) 
+ 45.14 1.97 1.00 1.00  44.29 Fill 10x10 stippled trapezoid (161x145 stipple) 
+  3.02 1.77 1.12 1.12   3.38 Fill 100x100 stippled trapezoid (161x145 stipple) 
+  1.31 1.13 1.00 1.00   1.30 Fill 300x300 stippled trapezoid (161x145 stipple) 
+ 51.27 1.97 1.00 1.00 103.10 Fill 1x1 opaque stippled trapezoid (161x145...
+ 45.01 1.97 1.00 1.00  45.01 Fill 10x10 opaque stippled trapezoid (161x145...
+  2.67 1.56 1.00 1.00   2.69 Fill 100x100 opaque stippled trapezoid (161x145..
+  1.29 1.13 1.00 1.01   1.27 Fill 300x300 opaque stippled trapezoid (161x145..
+ 51.41 1.96 1.00 0.99 103.39 Fill 1x1 tiled trapezoid (161x145 tile) 
+ 45.01 1.96 0.98 1.00  45.01 Fill 10x10 tiled trapezoid (161x145 tile) 
+  2.62 1.36 1.00 1.00   2.69 Fill 100x100 tiled trapezoid (161x145 tile) 
+  1.27 1.13 1.00 1.00   1.22 Fill 300x300 tiled trapezoid (161x145 tile) 
+ 51.13 1.98 1.00 1.00 103.39 Fill 1x1 tiled trapezoid (216x208 tile) 
+ 45.14 1.97 1.01 0.99  45.14 Fill 10x10 tiled trapezoid (216x208 tile) 
+  2.62 1.55 1.00 1.00   2.71 Fill 100x100 tiled trapezoid (216x208 tile) 
+  1.28 1.13 1.00 1.00   1.20 Fill 300x300 tiled trapezoid (216x208 tile) 
+ 50.71 1.95 1.00 1.00  54.70 Fill 10x10 equivalent complex polygon 
+  5.51 1.71 0.96 0.98   5.47 Fill 100x100 equivalent complex polygons 
+  8.39 1.97 1.00 1.00  16.75 Fill 10x10 64-gon (Convex) 
+  8.38 1.83 1.00 1.00   8.43 Fill 100x100 64-gon (Convex) 
+  8.50 1.96 1.00 1.00  16.64 Fill 10x10 64-gon (Complex) 
+  8.26 1.83 1.00 1.00   8.35 Fill 100x100 64-gon (Complex) 
+ 14.09 1.87 1.00 1.00  14.05 Char in 80-char line (6x13) 
+ 11.91 1.87 1.00 1.00  11.95 Char in 70-char line (8x13) 
+ 11.16 1.85 1.01 1.00  11.10 Char in 60-char line (9x15) 
+ 10.09 1.78 1.00 1.00  10.09 Char16 in 40-char line (k14) 
+  6.15 1.75 1.00 1.00   6.31 Char16 in 23-char line (k24) 
+ 11.92 1.90 1.03 1.03  11.88 Char in 80-char line (TR 10) 
+  8.18 1.78 1.00 0.99   8.17 Char in 30-char line (TR 24) 
+ 42.83 1.44 1.01 1.00  42.11 Char in 20/40/20 line (6x13, TR 10) 
+ 27.45 1.43 1.01 1.01  27.45 Char16 in 7/14/7 line (k14, k24) 
+ 12.13 1.85 1.00 1.00  12.05 Char in 80-char image line (6x13) 
+ 10.00 1.84 1.00 1.00  10.00 Char in 70-char image line (8x13) 
+  9.18 1.83 1.00 1.00   9.12 Char in 60-char image line (9x15) 
+  9.66 1.82 0.98 0.95   9.66 Char16 in 40-char image line (k14) 
+  5.82 1.72 1.00 1.00   5.99 Char16 in 23-char image line (k24) 
+  8.70 1.80 1.00 1.00   8.65 Char in 80-char image line (TR 10) 
+  4.67 1.66 1.00 1.00   4.67 Char in 30-char image line (TR 24) 
+ 84.43 1.47 1.00 1.00 124.18 Scroll 10x10 pixels 
+  3.73 1.50 1.00 0.98   3.73 Scroll 100x100 pixels 
+  1.00 1.00 1.00 1.00   1.00 Scroll 500x500 pixels 
+ 84.43 1.51 1.00 1.00 134.02 Copy 10x10 from window to window 
+  3.62 1.51 0.98 0.98   3.62 Copy 100x100 from window to window 
+  0.89 1.00 1.00 1.00   1.00 Copy 500x500 from window to window 
+ 57.06 1.99 1.00 1.00  88.64 Copy 10x10 from pixmap to window 
+  2.49 2.00 1.00 1.00   2.48 Copy 100x100 from pixmap to window 
+  1.00 0.91 1.00 1.00   0.98 Copy 500x500 from pixmap to window 
+  2.04 1.01 1.00 1.00   2.03 Copy 10x10 from window to pixmap 
+  1.05 1.00 1.00 1.00   1.05 Copy 100x100 from window to pixmap 
+  1.00 1.00 0.93 1.00   1.04 Copy 500x500 from window to pixmap 
+ 58.52 1.03 1.03 1.02  57.95 Copy 10x10 from pixmap to pixmap 
+  2.40 1.00 1.00 1.00   2.45 Copy 100x100 from pixmap to pixmap 
+  1.00 1.00 1.00 1.00   1.00 Copy 500x500 from pixmap to pixmap 
+ 51.57 1.92 1.00 1.00  85.75 Copy 10x10 1-bit deep plane 
+  6.37 1.75 1.01 1.01   6.37 Copy 100x100 1-bit deep plane 
+  1.26 1.11 1.00 1.00   1.24 Copy 500x500 1-bit deep plane 
+  4.23 1.63 0.98 0.97   4.38 Copy 10x10 n-bit deep plane 
+  1.04 1.02 1.00 1.00   1.04 Copy 100x100 n-bit deep plane 
+  1.00 1.00 1.00 1.00   1.00 Copy 500x500 n-bit deep plane 
+  6.45 1.98 1.00 1.26  12.80 PutImage 10x10 square 
+  1.10 1.87 1.00 1.83   2.11 PutImage 100x100 square 
+  1.02 1.93 1.00 1.91   1.91 PutImage 500x500 square 
+  4.17 1.78 1.00 1.40   7.18 PutImage XY 10x10 square 
+  1.27 1.49 0.97 1.48   2.10 PutImage XY 100x100 square 
+  1.00 1.50 1.00 1.50   1.52 PutImage XY 500x500 square 
+  1.07 1.01 1.00 1.00   1.06 GetImage 10x10 square 
+  1.01 1.00 1.00 1.00   1.01 GetImage 100x100 square 
+  1.00 1.00 1.00 1.00   1.00 GetImage 500x500 square 
+  1.56 1.00 0.99 0.97   1.56 GetImage XY 10x10 square 
+  1.02 1.00 1.00 1.00   1.02 GetImage XY 100x100 square 
+  1.00 1.00 1.00 1.00   1.00 GetImage XY 500x500 square 
+  1.00 1.00 1.01 0.98   0.95 X protocol NoOperation 
+  1.02 1.03 1.04 1.03   1.00 QueryPointer 
+  1.03 1.02 1.04 1.03   1.00 GetProperty 
+100.41 1.51 1.00 1.00 198.76 Change graphics context 
+ 45.81 1.00 0.99 0.97  57.10 Create and map subwindows (4 kids) 
+ 78.45 1.01 1.02 1.02  63.07 Create and map subwindows (16 kids) 
+ 73.91 1.01 1.00 1.00  56.37 Create and map subwindows (25 kids) 
+ 73.22 1.00 1.00 1.00  49.07 Create and map subwindows (50 kids) 
+ 72.36 1.01 0.99 1.00  32.14 Create and map subwindows (75 kids) 
+ 70.34 1.00 1.00 1.00  30.12 Create and map subwindows (100 kids) 
+ 55.00 1.00 1.00 0.99  23.75 Create and map subwindows (200 kids) 
+ 55.30 1.01 1.00 1.00 141.03 Create unmapped window (4 kids) 
+ 55.38 1.01 1.01 1.00 163.25 Create unmapped window (16 kids) 
+ 54.75 0.96 1.00 0.99 166.95 Create unmapped window (25 kids) 
+ 54.83 1.00 1.00 0.99 178.81 Create unmapped window (50 kids) 
+ 55.38 1.01 1.01 1.00 181.20 Create unmapped window (75 kids) 
+ 55.38 1.01 1.01 1.00 181.20 Create unmapped window (100 kids) 
+ 54.87 1.01 1.01 1.00 182.05 Create unmapped window (200 kids) 
+ 28.13 1.00 1.00 1.00  30.75 Map window via parent (4 kids) 
+ 36.14 1.01 1.01 1.01  32.58 Map window via parent (16 kids) 
+ 26.13 1.00 0.98 0.95  29.85 Map window via parent (25 kids) 
+ 40.07 1.00 1.01 1.00  27.57 Map window via parent (50 kids) 
+ 23.26 0.99 1.00 1.00  18.23 Map window via parent (75 kids) 
+ 22.91 0.99 1.00 0.99  16.52 Map window via parent (100 kids) 
+ 27.79 1.00 1.00 0.99  12.50 Map window via parent (200 kids) 
+ 22.35 1.00 1.00 1.00  56.19 Unmap window via parent (4 kids) 
+  9.57 1.00 0.99 1.00  89.78 Unmap window via parent (16 kids) 
+ 80.77 1.01 1.00 1.00 103.85 Unmap window via parent (25 kids) 
+ 96.34 1.00 1.00 1.00 116.06 Unmap window via parent (50 kids) 
+ 99.72 1.00 1.00 1.00 124.93 Unmap window via parent (75 kids) 
+112.36 1.00 1.00 1.00 125.27 Unmap window via parent (100 kids) 
+105.41 1.00 1.00 0.99 120.00 Unmap window via parent (200 kids) 
+ 51.29 1.03 1.02 1.02  74.19 Destroy window via parent (4 kids) 
+ 86.75 0.99 0.99 0.99 116.87 Destroy window via parent (16 kids) 
+106.43 1.01 1.01 1.01 127.49 Destroy window via parent (25 kids) 
+120.34 1.01 1.01 1.00 140.11 Destroy window via parent (50 kids) 
+126.67 1.00 0.99 0.99 145.00 Destroy window via parent (75 kids) 
+126.11 1.01 1.01 1.00 140.56 Destroy window via parent (100 kids) 
+128.57 1.01 1.00 1.00 137.91 Destroy window via parent (200 kids) 
+ 16.04 0.88 1.00 1.00  20.36 Hide/expose window via popup (4 kids) 
+ 19.04 1.01 1.00 1.00  23.48 Hide/expose window via popup (16 kids) 
+ 19.22 1.00 1.00 1.00  20.44 Hide/expose window via popup (25 kids) 
+ 17.41 1.00 0.91 0.97  17.68 Hide/expose window via popup (50 kids) 
+ 17.29 1.01 1.00 1.01  17.07 Hide/expose window via popup (75 kids) 
+ 16.74 1.00 1.00 1.00  16.17 Hide/expose window via popup (100 kids) 
+ 10.30 1.00 1.00 1.00  10.51 Hide/expose window via popup (200 kids) 
+ 16.48 1.01 1.00 1.00  26.05 Move window (4 kids) 
+ 17.01 0.95 1.00 1.00  23.97 Move window (16 kids) 
+ 16.95 1.00 1.00 1.00  22.90 Move window (25 kids) 
+ 16.05 1.01 1.00 1.00  21.32 Move window (50 kids) 
+ 15.58 1.00 0.98 0.98  19.44 Move window (75 kids) 
+ 14.98 1.02 1.03 1.03  18.17 Move window (100 kids) 
+ 10.90 1.01 1.01 1.00  12.68 Move window (200 kids) 
+ 49.42 1.00 1.00 1.00 198.27 Moved unmapped window (4 kids) 
+ 50.72 0.97 1.00 1.00 193.66 Moved unmapped window (16 kids) 
+ 50.87 1.00 0.99 1.00 195.09 Moved unmapped window (25 kids) 
+ 50.72 1.00 1.00 1.00 189.34 Moved unmapped window (50 kids) 
+ 50.87 1.00 1.00 1.00 191.33 Moved unmapped window (75 kids) 
+ 50.87 1.00 1.00 0.90 186.71 Moved unmapped window (100 kids) 
+ 50.87 1.00 1.00 1.00 179.19 Moved unmapped window (200 kids) 
+ 41.04 1.00 1.00 1.00  56.61 Move window via parent (4 kids) 
+ 69.81 1.00 1.00 1.00 130.82 Move window via parent (16 kids) 
+ 95.81 1.00 1.00 1.00 141.92 Move window via parent (25 kids) 
+ 95.98 1.00 1.00 1.00 149.43 Move window via parent (50 kids) 
+ 96.59 1.01 1.01 1.00 153.98 Move window via parent (75 kids) 
+ 97.19 1.00 1.00 1.00 157.30 Move window via parent (100 kids) 
+ 96.67 1.00 0.99 0.96 159.44 Move window via parent (200 kids) 
+ 17.75 1.01 1.00 1.00  27.61 Resize window (4 kids) 
+ 17.94 1.00 1.00 0.99  25.42 Resize window (16 kids) 
+ 17.92 1.01 1.00 1.00  24.47 Resize window (25 kids) 
+ 17.24 0.97 1.00 1.00  24.14 Resize window (50 kids) 
+ 16.81 1.00 1.00 0.99  22.75 Resize window (75 kids) 
+ 16.08 1.00 1.00 1.00  21.20 Resize window (100 kids) 
+ 12.92 1.00 0.99 1.00  16.26 Resize window (200 kids) 
+ 52.94 1.01 1.00 1.00 327.12 Resize unmapped window (4 kids) 
+ 53.60 1.01 1.01 1.01 333.71 Resize unmapped window (16 kids) 
+ 52.99 1.00 1.00 1.00 337.29 Resize unmapped window (25 kids) 
+ 51.98 1.00 1.00 1.00 329.38 Resize unmapped window (50 kids) 
+ 53.05 0.89 1.00 1.00 322.60 Resize unmapped window (75 kids) 
+ 53.05 1.00 1.00 1.00 318.08 Resize unmapped window (100 kids) 
+ 53.11 1.00 1.00 0.99 306.21 Resize unmapped window (200 kids) 
+ 16.76 1.00 0.96 1.00  19.46 Circulate window (4 kids) 
+ 17.24 1.00 1.00 0.97  16.24 Circulate window (16 kids) 
+ 16.30 1.03 1.03 1.03  15.85 Circulate window (25 kids) 
+ 13.45 1.00 1.00 1.00  14.90 Circulate window (50 kids) 
+ 12.91 1.00 1.00 1.00  13.06 Circulate window (75 kids) 
+ 11.30 0.98 1.00 1.00  11.03 Circulate window (100 kids) 
+  7.58 1.01 1.01 0.99   7.47 Circulate window (200 kids) 
+  1.01 1.01 0.98 1.00   0.95 Circulate Unmapped window (4 kids) 
+  1.07 1.07 1.01 1.07   1.02 Circulate Unmapped window (16 kids) 
+  1.04 1.09 1.06 1.05   0.97 Circulate Unmapped window (25 kids) 
+  1.04 1.23 1.20 1.18   1.05 Circulate Unmapped window (50 kids) 
+  1.18 1.53 1.19 1.45   1.24 Circulate Unmapped window (75 kids) 
+  1.08 1.02 1.01 1.74   1.01 Circulate Unmapped window (100 kids) 
+  1.01 1.12 0.98 0.91   0.97 Circulate Unmapped window (200 kids) 
+            </verb>
+
+<sect2>Profiling with OProfile
+
+<p>OProfile (available from http://oprofile.sourceforge.net/) is a
+system-wide profiler for Linux systems that uses processor-level
+counters to collect sampling data.  OProfile can provide information
+that is similar to that provided by <tt/gprof/, but without the
+necessity of recompiling the program with special instrumentation (i.e.,
+OProfile can collect statistical profiling information about optimized
+programs).  A test harness was developed to collect OProfile data for
+each <tt/x11perf/ test individually.
+
+<p>Test runs were performed using the RETIRED_INSNS counter on the AMD
+Athlon and the CPU_CLK_HALTED counter on the Intel Pentium III (with a
+test configuration different from the one described above).  We have
+examined OProfile output and have compared it with <tt/gprof/ output.
+This investigation has not produced results that yield performance
+increases in <tt/x11perf/ numbers.
+
+<!--
+<sect3>Retired Instructions
+
+<p>The initial tests using OProfile were done using the RETIRED_INSNS
+counter with DMX running on the dual-processor AMD Athlon machine - the
+same test configuration that was described above and that was used for
+other tests.  The RETIRED_INSNS counter counts retired instructions and
+showed drawing, text, copying, and image tests to be dominated (&gt;
+30%) by calls to Hash(), SecurityLookupIDByClass(),
+SecurityLookupIDByType(), and StandardReadRequestFromClient().  Some of
+these tests also executed significant instructions in
+WaitForSomething().
+
+<p>In contrast, the window tests executed significant
+instructions in SecurityLookupIDByType(), Hash(),
+StandardReadRequestFromClient(), but also executed significant
+instructions in other routines, such as ConfigureWindow().  Some time
+was spent looking at Hash() function, but optimizations in this routine
+did not lead to a dramatic increase in <tt/x11perf/ performance.
+-->
+
+<!-- 
+<sect3>Clock Cycles
+
+<p>Retired instructions can be misleading because Intel/AMD instructions
+execute in variable amounts of time.  The OProfile tests were repeated
+using the Intel CPU_CLK_HALTED counter with DMX running on the second
+back-end machine.  Note that this is a different test configuration that
+the one described above.  However, these tests show the amount of time
+(as measured in CPU cycles) that are spent in each routine.  Because
+<tt/x11perf/ was running on the first back-end machine and because
+window optimizations were on, the load on the second back-end machine
+was not significant.
+
+<p>Using CPU_CLK_HALTED, DMX showed simple drawing
+tests spending more than 10% of their time in
+StandardReadRequestFromClient(), with significant time (&gt; 20% total)
+spent in SecurityLookupIDByClass(), WaitForSomething(), and Dispatch().
+For these tests, &lt; 5% of the time was spent in Hash(), which explains
+why optimizing the Hash() routine did not impact <tt/x11perf/ results.
+
+<p>The trapezoid, text, scrolling, copying, and image tests were
+dominated by time in ProcFillPoly(), PanoramiXFillPoly(), dmxFillPolygon(),
+SecurityLookupIDByClass(), SecurityLookupIDByType(), and
+StandardReadRequestFromClient().  Hash() time was generally above 5% but
+less than 10% of total time.
+-->
+
+<sect2>X Test Suite
+
+<p>The X Test Suite was run on the fully optimized DMX server using the
+configuration described above.  The following failures were noted:
+            <verb>
+XListPixmapFormats: Test 1              [1]
+XChangeWindowAttributes: Test 32        [1]
+XCreateWindow: Test 30                  [1]
+XFreeColors: Test 4                     [3]
+XCopyArea: Test 13, 17, 21, 25, 30      [2]
+XCopyPlane: Test 11, 15, 27, 31         [2]
+XSetFontPath: Test 4                    [1]
+XChangeKeyboardControl: Test 9, 10      [1]
+
+[1] Previously documented errors expected from the Xinerama
+    implementation (see Phase I discussion).
+[2] Newly noted errors that have been verified as expected
+    behavior of the Xinerama implementation.
+[3] Newly noted error that has been verified as a Xinerama
+    implementation bug.
+            </verb>
+          
+<!-- ============================================================ -->
+<sect1>Phase III
+
+<p>During the third phase of development, support was provided for the
+following extensions: SHAPE, RENDER, XKEYBOARD, XInput.
+
+<sect2>SHAPE
+
+<p>The SHAPE extension is supported.  Test applications (e.g., xeyes and
+oclock) and window managers that make use of the SHAPE extension will
+work as expected.
+
+<sect2>RENDER
+
+<p>The RENDER extension is supported.  The version included in the DMX
+CVS tree is version 0.2, and this version is fully supported by Xdmx.
+Applications using only version 0.2 functions will work correctly;
+however, some apps that make use of functions from later versions do not
+properly check the extension's major/minor version numbers.  These apps
+will fail with a Bad Implementation error when using post-version 0.2
+functions.  This is expected behavior.  When the DMX CVS tree is updated
+to include newer versions of RENDER, support for these newer functions
+will be added to the DMX X server.
+
+<sect2>XKEYBOARD
+
+<p>The XKEYBOARD extension is supported.  If present on the back-end X
+servers, the XKEYBOARD extension will be used to obtain information
+about the type of the keyboard for initialization.  Otherwise, the
+keyboard will be initialized using defaults.  Note that this departs
+from older behavior: when Xdmx is compiled without XKEYBOARD support,
+the map from the back-end X server will be preserved.  With XKEYBOARD
+support, the map is not preserved because better information and control
+of the keyboard is available.
+
+<sect2>XInput
+
+<p>The XInput extension is supported.  Any device can be used as a core
+device and be used as an XInput extension device, with the exception of
+core devices on the back-end servers.  This limitation is present
+because cursor handling on the back-end requires that the back-end
+cursor sometimes track the Xdmx core cursor -- behavior that is
+incompatible with using the back-end pointer as a non-core device.
+
+<p>Currently, back-end extension devices are not available as Xdmx
+extension devices, but this limitation should be removed in the future.
+
+<p>To demonstrate the XInput extension, and to provide more examples for
+low-level input device driver writers, USB device drivers have been
+written for mice (usb-mou), keyboards (usb-kbd), and
+non-mouse/non-keyboard USB devices (usb-oth).  Please see the man page
+for information on Linux kernel drivers that are required for using
+these Xdmx drivers.
+
+<sect2>DPMS
+
+<p>The DPMS extension is exported but does not do anything at this time.
+
+<sect2>Other Extensions
+
+<p>The LBX,
+       SECURITY,
+       XC-APPGROUP, and
+       XFree86-Bigfont
+extensions do not require any special Xdmx support and have been exported.
+
+<p>The
+    BIG-REQUESTS,
+    DEC-XTRAP,
+    DOUBLE-BUFFER,
+    Extended-Visual-Information,
+    FontCache,
+    GLX,
+    MIT-SCREEN-SAVER,
+    MIT-SHM,
+    MIT-SUNDRY-NONSTANDARD,
+    RECORD,
+    SECURITY,
+    SGI-GLX,
+    SYNC,
+    TOG-CUP,
+    X-Resource,
+    XC-MISC,
+    XFree86-DGA,
+    XFree86-DRI,
+    XFree86-Misc,
+    XFree86-VidModeExtension, and
+    XVideo
+extensions are <it/not/ supported at this time, but will be evaluated
+for inclusion in future DMX releases.  <bf>See below for additional work
+on extensions after Phase III.</bf>
+
+<sect1>Phase IV
+
+<sect2>Moving to XFree86 4.3.0
+
+<p>For Phase IV, the recent release of XFree86 4.3.0 (27 February 2003)
+was merged onto the dmx.sourceforge.net CVS trunk and all work is
+proceeding using this tree.
+
+<sect2>Extensions 
+
+<sect3>XC-MISC (supported)
+
+<p>XC-MISC is used internally by the X library to recycle XIDs from the
+X server.  This is important for long-running X server sessions.  Xdmx
+supports this extension.  The X Test Suite passed and failed the exact
+same tests before and after this extension was enabled.
+<!-- Tested February/March 2003 -->
+
+<sect3>Extended-Visual-Information (supported)
+
+<p>The Extended-Visual-Information extension provides a method for an X
+client to obtain detailed visual information.  Xdmx supports this
+extension.  It was tested using the <tt>hw/dmx/examples/evi</tt> example
+program.  <bf/Note that this extension is not Xinerama-aware/ -- it will
+return visual information for each screen even though Xinerama is
+causing the X server to export a single logical screen.
+<!-- Tested March 2003 -->
+
+<sect3>RES (supported)
+
+<p>The X-Resource extension provides a mechanism for a client to obtain
+detailed information about the resources used by other clients.  This
+extension was tested with the <tt>hw/dmx/examples/res</tt> program.  The
+X Test Suite passed and failed the exact same tests before and after
+this extension was enabled.
+<!-- Tested March 2003 -->
+
+<sect3>BIG-REQUESTS (supported)
+
+<p>This extension enables the X11 protocol to handle requests longer
+than 262140 bytes.  The X Test Suite passed and failed the exact same
+tests before and after this extension was enabled.
+<!-- Tested March 2003 -->
+
+<sect3>XSYNC (supported)
+
+<p>This extension provides facilities for two different X clients to
+synchronize their requests.  This extension was minimally tested with
+<tt/xdpyinfo/ and the X Test Suite passed and failed the exact same
+tests before and after this extension was enabled.
+<!-- Tested March 2003 -->
+
+<sect3>XTEST, RECORD, DEC-XTRAP (supported) and XTestExtension1 (not supported)
+
+<p>The XTEST and RECORD extension were developed by the X Consortium for
+use in the X Test Suite and are supported as a standard in the X11R6
+tree.  They are also supported in Xdmx.  When X Test Suite tests that
+make use of the XTEST extension are run, Xdmx passes and fails exactly
+the same tests as does a standard XFree86 X server.  When the
+<tt/rcrdtest/ test (a part of the X Test Suite that verifies the RECORD
+extension) is run, Xdmx passes and fails exactly the same tests as does
+a standard XFree86 X server. <!-- Tested February/March 2003 -->
+
+<p>There are two older XTEST-like extensions: DEC-XTRAP and
+XTestExtension1.  The XTestExtension1 extension was developed for use by
+the X Testing Consortium for use with a test suite that eventually
+became (part of?) the X Test Suite.  Unlike XTEST, which only allows
+events to be sent to the server, the XTestExtension1 extension also
+allowed events to be recorded (similar to the RECORD extension).  The
+second is the DEC-XTRAP extension that was developed by the Digital
+Equipment Corporation.
+
+<p>The DEC-XTRAP extension is available from Xdmx and has been tested
+with the <tt/xtrap*/ tools which are distributed as standard X11R6
+clients. <!-- Tested March 2003 -->
+
+<p>The XTestExtension1 is <em/not/ supported because it does not appear
+to be used by any modern X clients (the few that support it also support
+XTEST) and because there are no good methods available for testing that
+it functions correctly (unlike XTEST and DEC-XTRAP, the code for
+XTestExtension1 is not part of the standard X server source tree, so
+additional testing is important). <!-- Tested March 2003 -->
+
+<p>Most of these extensions are documented in the X11R6 source tree.
+Further, several original papers exist that this author was unable to
+locate -- for completeness and historical interest, citations are
+provide:
+<descrip>
+<tag/XRECORD/ Martha Zimet. Extending X For Recording.  8th Annual X
+Technical Conference Boston, MA January 24-26, 1994.
+<tag/DEC-XTRAP/ Dick Annicchiarico, Robert Chesler, Alan Jamison. XTrap
+Architecture. Digital Equipment Corporation, July 1991.
+<tag/XTestExtension1/ Larry Woestman. X11 Input Synthesis Extension
+Proposal. Hewlett Packard, November 1991.
+</descrip>
+
+<sect3>MIT-MISC (not supported)
+
+<p>The MIT-MISC extension is used to control a bug-compatibility flag
+that provides compatibility with xterm programs from X11R1 and X11R2.
+There does not appear to be a single client available that makes use of
+this extension and there is not way to verify that it works correctly.
+The Xdmx server does <em/not/ support MIT-MISC.
+
+<sect3>SCREENSAVER (not supported)
+
+<p>This extension provides special support for the X screen saver.  It
+was tested with beforelight, which appears to be the only client that
+works with it.  When Xinerama was not active, <tt/beforelight/ behaved
+as expected.  However, when Xinerama was active, <tt/beforelight/ did
+not behave as expected.  Further, when this extension is not active,
+<tt/xscreensaver/ (a widely-used X screen saver program) did not behave
+as expected.  Since this extension is not Xinerama-aware and is not
+commonly used with expected results by clients, we have left this
+extension disabled at this time.
+
+<sect3>GLX (supported)
+
+<p>The GLX extension provides OpenGL and GLX windowing support.  In
+Xdmx, the extension is called glxProxy, and it is Xinerama aware.  It
+works by either feeding requests forward through Xdmx to each of the
+back-end servers or handling them locally.  All rendering requests are
+handled on the back-end X servers.  This code was donated to the DMX
+project by SGI.  For the X Test Suite results comparison, see below.
+
+<sect3>RENDER (supported)
+
+<p>The X Rendering Extension (RENDER) provides support for digital image
+composition.  Geometric and text rendering are supported.  RENDER is
+partially Xinerama-aware, with text and the most basic compositing
+operator; however, its higher level primitives (triangles, triangle
+strips, and triangle fans) are not yet Xinerama-aware.  The RENDER
+extension is still under development, and is currently at version 0.8.
+Additional support will be required in DMX as more primitives and/or
+requests are added to the extension.
+
+<p>There is currently no test suite for the X Rendering Extension;
+however, there has been discussion of developing a test suite as the
+extension matures.  When that test suite becomes available, additional
+testing can be performed with Xdmx.  The X Test Suite passed and failed
+the exact same tests before and after this extension was enabled.
+
+<sect3>Summary
+
+<!-- WARNING: this list is duplicated in the "Common X extension
+support" section -->
+<p>To summarize, the following extensions are currently supported:
+    BIG-REQUESTS,
+    DEC-XTRAP,
+    DMX,
+    DPMS,
+    Extended-Visual-Information,
+    GLX,
+    LBX,
+    RECORD,
+    RENDER,
+    SECURITY,
+    SHAPE,
+    SYNC,
+    X-Resource,
+    XC-APPGROUP,
+    XC-MISC,
+    XFree86-Bigfont,
+    XINERAMA,
+    XInputExtension,
+    XKEYBOARD, and
+    XTEST.
+
+<p>The following extensions are <em/not/ supported at this time:
+    DOUBLE-BUFFER,
+    FontCache,
+    MIT-SCREEN-SAVER,
+    MIT-SHM,
+    MIT-SUNDRY-NONSTANDARD,
+    TOG-CUP,
+    XFree86-DGA,
+    XFree86-Misc,
+    XFree86-VidModeExtension,
+    XTestExtensionExt1, and
+    XVideo.
+
+<sect2>Additional Testing with the X Test Suite
+
+<sect3>XFree86 without XTEST
+
+<p>After the release of XFree86 4.3.0, we retested the XFree86 X server
+with and without using the XTEST extension.  When the XTEST extension
+was <em/not/ used for testing, the XFree86 4.3.0 server running on our
+usual test system with a Radeon VE card reported unexpected failures in
+the following tests:
+<verb>
+XListPixmapFormats: Test 1
+XChangeKeyboardControl: Tests 9, 10
+XGetDefault: Test 5
+XRebindKeysym: Test 1
+</verb>
+
+<sect3>XFree86 with XTEST
+
+<p>When using the XTEST extension, the XFree86 4.3.0 server reported the
+following errors:
+<verb>
+XListPixmapFormats: Test 1
+XChangeKeyboardControl: Tests 9, 10
+XGetDefault: Test 5
+XRebindKeysym: Test 1
+
+XAllowEvents: Tests 20, 21, 24
+XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+XGrabKey: Test 8
+XSetPointerMapping: Test 3
+XUngrabButton: Test 4
+</verb>
+
+<p>While these errors may be important, they will probably be fixed
+eventually in the XFree86 source tree.  We are particularly interested
+in demonstrating that the Xdmx server does not introduce additional
+failures that are not known Xinerama failures.
+
+<sect3>Xdmx with XTEST, without Xinerama, without GLX
+
+<p>Without Xinerama, but using the XTEST extension, the following errors
+were reported from Xdmx (note that these are the same as for the XFree86
+4.3.0, except that XGetDefault no longer fails):
+<verb>
+XListPixmapFormats: Test 1
+XChangeKeyboardControl: Tests 9, 10
+XRebindKeysym: Test 1
+
+XAllowEvents: Tests  20, 21, 24
+XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+XGrabKey: Test 8
+XSetPointerMapping: Test 3
+XUngrabButton: Test 4
+</verb>
+
+<sect3>Xdmx with XTEST, with Xinerama, without GLX
+
+<p>With Xinerama, using the XTEST extension, the following errors
+were reported from Xdmx:
+<verb>
+XListPixmapFormats: Test 1
+XChangeKeyboardControl: Tests 9, 10
+XRebindKeysym: Test 1
+
+XAllowEvents: Tests 20, 21, 24
+XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+XGrabKey: Test 8
+XSetPointerMapping: Test 3
+XUngrabButton: Test 4
+
+XCopyPlane: Tests 13, 22, 31 (well-known XTEST/Xinerama interaction issue)
+XDrawLine: Test 67
+XDrawLines: Test 91
+XDrawSegments: Test 68
+</verb>
+Note that the first two sets of errors are the same as for the XFree86
+4.3.0 server, and that the XCopyPlane error is a well-known error
+resulting from an XTEST/Xinerama interaction when the request crosses a
+screen boundary.  The XDraw* errors are resolved when the tests are run
+individually and they do not cross a screen boundary.  We will
+investigate these errors further to determine their cause.
+
+<sect3>Xdmx with XTEST, with Xinerama, with GLX
+
+<p>With GLX enabled, using the XTEST extension, the following errors
+were reported from Xdmx (these results are from early during the Phase
+IV development, but were confirmed with a late Phase IV snapshot):
+<verb>
+XListPixmapFormats: Test 1
+XChangeKeyboardControl: Tests 9, 10
+XRebindKeysym: Test 1
+
+XAllowEvents: Tests 20, 21, 24
+XGrabButton: Tests 5, 9-12, 14, 16, 19, 21-25
+XGrabKey: Test 8
+XSetPointerMapping: Test 3
+XUngrabButton: Test 4
+
+XClearArea: Test 8
+XCopyArea: Tests 4, 5, 11, 14, 17, 23, 25, 27, 30
+XCopyPlane: Tests 6, 7, 10, 19, 22, 31
+XDrawArcs: Tests 89, 100, 102
+XDrawLine: Test 67
+XDrawSegments: Test 68
+</verb>
+Note that the first two sets of errors are the same as for the XFree86
+4.3.0 server, and that the third set has different failures than when
+Xdmx does not include GLX support.  Since the GLX extension adds new
+visuals to support GLX's visual configs and the X Test Suite runs tests
+over the entire set of visuals, additional rendering tests were run and
+presumably more of them crossed a screen boundary.  This conclusion is
+supported by the fact that nearly all of the rendering errors reported
+are resolved when the tests are run individually and they do no cross a
+screen boundary.
+
+<p>Further, when hardware rendering is disabled on the back-end displays,
+many of the errors in the third set are eliminated, leaving only:
+<verb>
+XClearArea: Test 8
+XCopyArea: Test 4, 5, 11, 14, 17, 23, 25, 27, 30
+XCopyPlane: Test 6, 7, 10, 19, 22, 31
+</verb>
+
+<sect3>Conclusion
+
+<p>We conclude that all of the X Test Suite errors reported for Xdmx are
+the result of errors in the back-end X server or the Xinerama
+implementation.  Further, all of these errors that can be reasonably
+fixed at the Xdmx layer have been.  (Where appropriate, we have
+submitted patches to the XFree86 and Xinerama upstream maintainers.)
+
+<sect2>Dynamic Reconfiguration
+
+<p>During this development phase, dynamic reconfiguration support was
+added to DMX.  This support allows an application to change the position
+and offset of a back-end server's screen.  For example, if the
+application would like to shift a screen slightly to the left, it could
+query Xdmx for the screen's &lt;x,y&gt; position and then dynamically
+reconfigure that screen to be at position &lt;x+10,y&gt;.  When a screen
+is dynamically reconfigured, input handling and a screen's root window
+dimensions are adjusted as needed.  These adjustments are transparent to
+the user.
+
+<sect3>Dynamic reconfiguration extension
+
+<p>The application interface to DMX's dynamic reconfiguration is through
+a function in the DMX extension library:
+<verb>
+Bool DMXReconfigureScreen(Display *dpy, int screen, int x, int y)
+</verb>
+where <it/dpy/ is DMX server's display, <it/screen/ is the number of the
+screen to be reconfigured, and <it/x/ and <it/y/ are the new upper,
+left-hand coordinates of the screen to be reconfigured.
+
+<p>The coordinates are not limited other than as required by the X
+protocol, which limits all coordinates to a signed 16 bit number.  In
+addition, all coordinates within a screen must also be legal values.
+Therefore, setting a screen's upper, left-hand coordinates such that the
+right or bottom edges of the screen is greater than 32,767 is illegal.
+
+<sect3>Bounding box
+
+<p>When the Xdmx server is started, a bounding box is calculated from
+the screens' layout given either on the command line or in the
+configuration file.  This bounding box is currently fixed for the
+lifetime of the Xdmx server.
+
+<p>While it is possible to move a screen outside of the bounding box, it
+is currently not possible to change the dimensions of the bounding box.
+For example, it is possible to specify coordinates of &lt;-100,-100&gt;
+for the upper, left-hand corner of the bounding box, which was
+previously at coordinates &lt;0,0&gt;.  As expected, the screen is moved
+down and to the right; however, since the bounding box is fixed, the
+left side and upper portions of the screen exposed by the
+reconfiguration are no longer accessible on that screen.  Those
+inaccessible regions are filled with black.
+
+<p>This fixed bounding box limitation will be addressed in a future
+development phase.
+
+<sect3>Sample applications
+
+<p>An example of where this extension is useful is in setting up a video
+wall.  It is not always possible to get everything perfectly aligned,
+and sometimes the positions are changed (e.g., someone might bump into a
+projector).  Instead of physically moving projectors or monitors, it is
+now possible to adjust the positions of the back-end server's screens
+using the dynamic reconfiguration support in DMX.
+
+<p>Other applications, such as automatic setup and calibration tools,
+can make use of dynamic reconfiguration to correct for projector
+alignment problems, as long as the projectors are still arranged
+rectilinearly.  Horizontal and vertical keystone correction could be
+applied to projectors to correct for non-rectilinear alignment problems;
+however, this must be done external to Xdmx.
+
+<p>A sample test program is included in the DMX server's examples
+directory to demonstrate the interface and how an application might use
+dynamic reconfiguration.  See <tt/dmxreconfig.c/ for details.
+
+<sect3>Additional notes
+
+<p>In the original development plan, Phase IV was primarily devoted to
+adding OpenGL support to DMX; however, SGI became interested in the DMX
+project and developed code to support OpenGL/GLX.  This code was later
+donated to the DMX project and integrated into the DMX code base, which
+freed the DMX developers to concentrate on dynamic reconfiguration (as
+described above).
+
+<sect2>Doxygen documentation
+
+<p>Doxygen is an open-source (GPL) documentation system for generating
+browseable documentation from stylized comments in the source code.  We
+have placed all of the Xdmx server and DMX protocol source code files
+under Doxygen so that comprehensive documentation for the Xdmx source
+code is available in an easily browseable format.
+
+<sect2>Valgrind
+
+<p>Valgrind, an open-source (GPL) memory debugger for Linux, was used to
+search for memory management errors.  Several memory leaks were detected
+and repaired.  The following errors were not addressed:
+<enum>
+    <item>
+        When the X11 transport layer sends a reply to the client, only
+        those fields that are required by the protocol are filled in --
+        unused fields are left as uninitialized memory and are therefore
+        noted by valgrind.  These instances are not errors and were not
+        repaired.
+    <item>
+        At each server generation, glxInitVisuals allocates memory that
+        is never freed.  The amount of memory lost each generation
+        approximately equal to 128 bytes for each back-end visual.
+        Because the code involved is automatically generated, this bug
+        has not been fixed and will be referred to SGI.
+    <item>
+        At each server generation, dmxRealizeFont calls XLoadQueryFont,
+        which allocates a font structure that is not freed.
+        dmxUnrealizeFont can free the font structure for the first
+        screen, but cannot free it for the other screens since they are
+        already closed by the time dmxUnrealizeFont could free them.
+        The amount of memory lost each generation is approximately equal
+        to 80 bytes per font per back-end.  When this bug is fixed in
+        the the X server's device-independent (dix) code, DMX will be
+        able to properly free the memory allocated by XLoadQueryFont.
+</enum>
+
+<sect2>RATS
+
+<p>RATS (Rough Auditing Tool for Security) is an open-source (GPL)
+security analysis tool that scans source code for common
+security-related programming errors (e.g., buffer overflows and TOCTOU
+races).  RATS was used to audit all of the code in the hw/dmx directory
+and all "High" notations were checked manually.  The code was either
+re-written to eliminate the warning, or a comment containing "RATS" was
+inserted on the line to indicate that a human had checked the code.
+Unrepaired warnings are as follows:
+<enum>
+    <item>
+        Fixed-size buffers are used in many areas, but code has been
+        added to protect against buffer overflows (e.g., XmuSnprint).
+        The only instances that have not yet been fixed are in
+        config/xdmxconfig.c (which is not part of the Xdmx server) and
+        input/usb-common.c.
+    <item>
+        vprintf and vfprintf are used in the logging routines.  In
+        general, all uses of these functions (e.g., dmxLog) provide a
+        constant format string from a trusted source, so the use is
+        relatively benign.
+    <item>
+        glxProxy/glxscreens.c uses getenv and strcat.  The use of these
+        functions is safe and will remain safe as long as
+        ExtensionsString is longer then GLXServerExtensions (ensuring
+        this may not be ovious to the casual programmer, but this is in
+        automatically generated code, so we hope that the generator
+        enforces this constraint).
+</enum>
+
+  </article>
+  
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