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<div>
<h2 class="title"><a name="configtwinview" id=
"configtwinview"></a>Chapter&nbsp;12.&nbsp;Configuring Multiple
Display Devices on One X Screen</h2>
</div>
</div>
</div>
<p>Multiple display devices (digital flat panels, CRTs, and TVs)
can display the contents of a single X screen in any arbitrary
configuration. Configuring multiple display devices on a single X
screen has several distinct advantages over other techniques (such
as Xinerama):</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>A single X screen is used. The NVIDIA driver conceals all
information about multiple display devices from the X server; as
far as X is concerned, there is only one screen.</p>
</li>
<li>
<p>Both display devices share one frame buffer. Thus, all the
functionality present on a single display (e.g., accelerated
OpenGL) is available with multiple display devices.</p>
</li>
<li>
<p>No additional overhead is needed to emulate having a single
desktop.</p>
</li>
</ul>
</div>
<p>If you are interested in using each display device as a separate
X screen, see <a href="configmultxscreens.html" title=
"Chapter&nbsp;14.&nbsp;Configuring Multiple X Screens on One Card">Chapter&nbsp;14,
<i>Configuring Multiple X Screens on One Card</i></a>.</p>
<h3>Relevant X Configuration Options</h3>
<p>When the NVIDIA X driver starts, by default it will enable as
many display devices as are connected and as the GPU supports
driving simultaneously. Most NVIDIA GPUs based on the Kepler
architecture, or newer, support driving up to four display devices
simultaneously. Most NVIDIA GPUs older than Kepler support driving
up to two display devices simultaneously.</p>
<p>If multiple X screens are configured on the GPU, the NVIDIA X
driver will attempt to reserve display devices and GPU resources
for those other X screens (honoring the "UseDisplayDevice" and
"MetaModes" X configuration options of each X screen) and then
allocate all remaining resources to the first X screen configured
on the GPU.</p>
<p>There are several X configuration options that influence how
multiple display devices are used by an X screen:</p>
<pre class="screen">
    Option "MetaModes"                "&lt;list of MetaModes&gt;"

    Option "HorizSync"                "&lt;hsync range(s)&gt;"
    Option "VertRefresh"              "&lt;vrefresh range(s)&gt;"

    Option "MetaModeOrientation"      "&lt;relationship of head 1 to head 0&gt;"
    Option "ConnectedMonitor"         "&lt;list of connected display devices&gt;"
</pre>
<p>See detailed descriptions of each option below.</p>
<h3>Detailed Description of Options</h3>
<div class="variablelist">
<dl>
<dt><span class="term">HorizSync,</span> <span class=
"term">VertRefresh</span></dt>
<dd>
<p>With these options, you can specify a semicolon-separated list
of frequency ranges, each optionally prepended with a display
device name. In addition, if SLI Mosaic mode is enabled, a GPU
specifier can be used. For example:</p>
<pre class="screen">
    Option "HorizSync"   "CRT-0: 50-110; DFP-0: 40-70"
    Option "VertRefresh" "CRT-0: 60-120; GPU-0.DFP-0: 60"
</pre>
<p>See <a href="displaydevicenames.html" title=
"Appendix&nbsp;C.&nbsp;Display Device Names">Appendix&nbsp;C,
<i>Display Device Names</i></a> on Display Device Names for more
information.</p>
<p>These options are normally not needed: by default, the NVIDIA X
driver retrieves the valid frequency ranges from the display
device's EDID (see the <a href=
"xconfigoptions.html#UseEdidFreqs">UseEdidFreqs</a> option). The
"HorizSync" and "VertRefresh" options override any frequency ranges
retrieved from the EDID.</p>
</dd>
<dt><a name="metamodes" id="metamodes"></a><span class=
"term">MetaModes</span></dt>
<dd>
<p>MetaModes are "containers" that store information about what
mode should be used on each display device.</p>
<p>Multiple MetaModes list the combinations of modes and the
sequence in which they should be used. In MetaMode syntax, modes
within a MetaMode are comma separated, and multiple MetaModes are
separated by semicolons. For example:</p>
<pre class="screen">
    "&lt;mode name 0&gt;, &lt;mode name 1&gt;; &lt;mode name 2&gt;, &lt;mode name 3&gt;"
</pre>
<p>Where &lt;mode name 0&gt; is the name of the mode to be used on
display device 0 concurrently with &lt;mode name 1&gt; used on
display device 1. A mode switch will then cause &lt;mode name 2&gt;
to be used on display device 0 and &lt;mode name 3&gt; to be used
on display device 1. Here is an example MetaMode:</p>
<pre class="screen">
    Option "MetaModes" "1280x1024,1280x1024; 1024x768,1024x768"
</pre>
<p>If you want a display device to not be active for a certain
MetaMode, you can use the mode name "NULL", or simply omit the mode
name entirely:</p>
<pre class="screen">
    "1600x1200, NULL; NULL, 1024x768"
</pre>
<p>or</p>
<pre class="screen">
    "1600x1200; , 1024x768"
</pre>
<p>Optionally, mode names can be followed by offset information to
control the positioning of the display devices within the virtual
screen space; e.g.,</p>
<pre class="screen">
    "1600x1200 +0+0, 1024x768 +1600+0; ..."
</pre>
<p>Offset descriptions follow the conventions used in the X
"-geometry" command line option; i.e., both positive and negative
offsets are valid, though negative offsets are only allowed when a
virtual screen size is explicitly given in the X config file.</p>
<p>When no offsets are given for a MetaMode, the offsets will be
computed following the value of the MetaModeOrientation option (see
below). Note that if offsets are given for any one of the modes in
a single MetaMode, then offsets will be expected for all modes
within that single MetaMode; in such a case offsets will be assumed
to be +0+0 when not given.</p>
<p>When not explicitly given, the virtual screen size will be
computed as the bounding box of all MetaMode bounding boxes.
MetaModes with a bounding box larger than an explicitly given
virtual screen size will be discarded.</p>
<p>A MetaMode string can be further modified with a "Panning
Domain" specification; e.g.,</p>
<pre class="screen">
    "1024x768 @1600x1200, 800x600 @1600x1200"
</pre>
<p>A panning domain is the area in which a display device's
viewport will be panned to follow the mouse. Panning actually
happens on two levels with MetaModes: first, an individual display
device's viewport will be panned within its panning domain, as long
as the viewport is contained by the bounding box of the MetaMode.
Once the mouse leaves the bounding box of the MetaMode, the entire
MetaMode (i.e., all display devices) will be panned to follow the
mouse within the virtual screen, unless the "PanAllDisplays" X
configuration option is disabled. Note that individual display
devices' panning domains default to being clamped to the position
of the display devices' viewports, thus the default behavior is
just that viewports remain "locked" together and only perform the
second type of panning.</p>
<p>The most beneficial use of panning domains is probably to
eliminate dead areas -- regions of the virtual screen that are
inaccessible due to display devices with different resolutions. For
example:</p>
<pre class="screen">
    "1600x1200, 1024x768"
</pre>
<p>produces an inaccessible region below the 1024x768 display.
Specifying a panning domain for the second display device:</p>
<pre class="screen">
    "1600x1200, 1024x768 @1024x1200"
</pre>
<p>provides access to that dead area by allowing you to pan the
1024x768 viewport up and down in the 1024x1200 panning domain.</p>
<p>Offsets can be used in conjunction with panning domains to
position the panning domains in the virtual screen space (note that
the offset describes the panning domain, and only affects the
viewport in that the viewport must be contained within the panning
domain). For example, the following describes two modes, each with
a panning domain width of 1900 pixels, and the second display is
positioned below the first:</p>
<pre class="screen">
    "1600x1200 @1900x1200 +0+0, 1024x768 @1900x768 +0+1200"
</pre>
<p>Because it is often unclear which mode within a MetaMode will be
used on each display device, mode descriptions within a MetaMode
can be prepended with a display device name. For example:</p>
<pre class="screen">
    "CRT-0: 1600x1200,  DFP-0: 1024x768"
</pre>
<p>If no MetaMode string is specified, then the X driver uses the
modes listed in the relevant "Display" subsection, attempting to
place matching modes on each display device.</p>
<p>Each mode of the MetaMode may also have extra attributes
associated with it, specified as a comma-separated list of
token=value pairs inside curly brackets. The value for each token
can optionally be enclosed in parentheses, to prevent commas within
the value from being interpreted as token=value pair separators.
Currently, the only token that requires a parentheses-enclosed
value is "Transform".</p>
<p>The possible tokens within the curly bracket list are:</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>"Stereo": possible values are "PassiveLeft" or "PassiveRight".
When used in conjunction with stereo mode "4", this allows each
display to be configured independently to show any stereo eye. For
example:</p>
<pre class="screen">
    "CRT-0: 1600x1200 +0+0 { Stereo = PassiveLeft }, CRT-1: 1600x1200 +1600+0 { Stereo=PassiveRight }"
</pre>
<p>If the X screen is not configured for stereo mode "4", these
options are ignored. See the <a href=
"xconfigoptions.html#Stereo">Stereo</a> X configuration option for
more details about stereo configurations.</p>
</li>
<li>
<p>"Rotation": this rotates the content of an individual display
device. Possible values are "0" (with synonyms "no", "off" and
"normal"), "90" (with synonyms "left" and "CCW"), "180" (with
synonyms "invert" and "inverted") and "270" (with synonyms "right"
and "CW"). For example:</p>
<pre class="screen">
    "DFP-0: nvidia-auto-select { Rotation=left }, DFP-1: nvidia-auto-select { Rotation=right }"
</pre>
<p>Independent rotation configurability of each display device is
also possible through RandR. See <a href="xrandrextension.html"
title=
"Chapter&nbsp;15.&nbsp;Support for the X Resize and Rotate Extension">
Chapter&nbsp;15, <i>Support for the X Resize and Rotate
Extension</i></a> for details.</p>
</li>
<li>
<p>"Reflection": this reflects the content of an individual display
device about either the X axis, the Y axis, or both the X and Y
axes. Possible values are "X", "Y" and "XY". For example:</p>
<pre class="screen">
    "DFP-0: nvidia-auto-select { Reflection=X }, DFP-1: nvidia-auto-select"
</pre>
<p>Independent reflection configurability of each display device is
also possible through RandR. See <a href="xrandrextension.html"
title=
"Chapter&nbsp;15.&nbsp;Support for the X Resize and Rotate Extension">
Chapter&nbsp;15, <i>Support for the X Resize and Rotate
Extension</i></a> for details.</p>
</li>
<li>
<p>"Transform": this is a 3x3 matrix of floating point values that
defines a transformation from the ViewPortOut for a display device
to a region within the X screen. This is equivalent to the
transformation matrix specified through the RandR 1.3
RRSetCrtcTransform request. As in RandR, the transform is applied
before any specified rotation and reflection values to compute the
complete transform.</p>
<p>The 3x3 matrix is represented in the MetaMode syntax as a
comma-separated list of nine floating point values, stored in
row-major order. This is the same as the value passed to the
xrandr(1) '--transform' command line option.</p>
<p>Note that the transform value must be enclosed in parentheses,
so that the commas separating the nine floating point values are
interpreted correctly.</p>
<p>For example:</p>
<pre class="screen">
    "DFP-0: nvidia-auto-select { Transform=(43.864288330078125, 21.333328247070312, -16384, 0, 43.864288330078125, 0, 0, 0.0321197509765625, 19.190628051757812) }"
</pre>
<p></p>
</li>
<li>
<p>"PixelShiftMode": This allows a display to be configured in
pixel shift mode, in which a display overlays multiple downscaled
images to simulate a higher effective resolution. This is used in
certain JVC e-shift projectors. All pixel shift modes require a
Quadro Kepler or later GPU. Possible values are "4kTopLeft",
"4kBottomRight", and "8k".</p>
<p>In 4K pixel shift mode, two cloned displays are configured in
pixel shift mode, and either display is configured to display
either the top left or bottom right pixels of every pixel quad.
Note that the mode timings used by each display are one quarter of
the resolution read from the X screen and one quarter of the
effective resolution displayed (e.g., "1920x1080" rather than
"3840x2160").</p>
<p>For example, here is the configuration of a 4K pixel shift mode,
with an effective desktop resolution of 3840x2160:</p>
<pre class="screen">
    "DFP-0: 1920x1080 +0+0 { PixelShiftMode = 4kTopLeft, ViewPortIn = 3840x2160 }, DFP-1: 1920x1080 +0+0 { PixelShiftMode = 4kBottomRight, ViewPortIn = 3840x2160 }"
</pre>
<p></p>
<p>In 8K pixel shift mode, the image is downscaled from the
ViewPortIn resolution to the mode timing resolution, to produce two
different images: one for the top left pixel of every pixel quad
and one for the bottom right of every pixel quad. The display
alternates between the two images each vblank. This requires a
Quadro graphics card with a 3-pin DIN stereo connector.</p>
<p>For example, here is the configuration for an 8K pixel shift
mode, with an effective desktop resolution and refresh rate of
8192x4800 @30Hz, split across 4 1024x2400@60Hz displays. Note that
the panning offsets of each display are in X screen (ViewPortIn)
coordinates:</p>
<pre class="screen">
    "DFP-0: 1024x2400 +0+0 { PixelShiftMode=8k, ViewPortIn = 2048x4800 }, DFP-1: 1024x2400 +2048+0 { PixelShiftMode=8k, ViewPortIn = 2048x4800 }, DFP-2: 1024x2400 +4096+0 { PixelShiftMode=8k, ViewPortIn = 2048x4800 }, DFP-4: 1024x2400 +6144+0 { PixelShiftMode=8k, ViewPortIn = 2048x4800 }"
</pre>
<p></p>
<p>In both examples above, the ViewPortIn is provided here for
illustrative purposes only. When PixelShiftMode is used, the
ViewPortIn and ViewPortOut are always inferred from the mode
timings: the ViewPortOut will match the mode timing resolution,
which is half the intended resolution. The ViewPortIn will be twice
the ViewPortOut, in order to achieve the pixel shift effect.</p>
</li>
<li>
<p>"ViewPortOut": this specifies the region within the mode sent to
the display device that will display pixels from the X screen. The
region of the mode outside the ViewPortOut will contain black. The
format is "WIDTH x HEIGHT +X +Y".</p>
<p>This is useful, for example, for configuring overscan
compensation. E.g., if the mode sent to the display device is
1920x1080, to configure a 10 pixel border on all four sides:</p>
<pre class="screen">
    "DFP-0: 1920x1080 { ViewPortOut=1900x1060+10+10 }"
</pre>
<p>Or, to only display an image in the lower right quarter of the
1920x1080 mode:</p>
<pre class="screen">
    "DFP-0: 1920x1080 { ViewPortOut=960x540+960+540 }"
</pre>
<p></p>
<p>When not specified, the ViewPortOut defaults to the size of the
mode.</p>
</li>
<li>
<p>"ViewPortIn": this defines the size of the region of the X
screen which will be displayed within the ViewPortOut. The format
is "WIDTH x HEIGHT".</p>
<p>ViewPortIn is useful for configuring scaling between the X
screen and the display device. For example, to display an 800x600
region from the X screen on a 1920x1200 mode:</p>
<pre class="screen">
    "DFP-0: 1920x1200 { ViewPortIn=800x600 }"
</pre>
<p>Or, to display a 2560x1600 region from the X screen on a
1920x1200 mode:</p>
<pre class="screen">
    "DFP-0: 1920x1200 { ViewPortIn=2560x1600 }"
</pre>
<p>Or, in conjunction with ViewPortOut, to scale an 800x600 region
of the X screen within a 1920x1200 mode while preserving the aspect
ratio:</p>
<pre class="screen">
    "DFP-0: 1920x1200 { ViewPortIn=800x600, ViewPortOut=1600x1200+160+0 }"
</pre>
<p></p>
<p>Scaling from ViewPortIn to ViewPortOut is also expressible
through the "Transform" attribute. In fact, ViewPortIn is just a
shortcut for populating the transformation matrix. If both
ViewPortIn and Transform are specified in the MetaMode for a
display device, ViewPortIn is ignored.</p>
<p>ViewPortIn is also ignored if PixelShiftMode is enabled, as
PixelShiftMode implies a transformation of double width and
height.</p>
</li>
<li>
<p>"PanningTrackingArea": this defines the region of the MetaMode
inside which cursor movement will influence panning of the display
device. The format is "WIDTH x HEIGHT + X + Y", to describe the
size and offset of the region within the X screen. E.g.,</p>
<pre class="screen">
    "DFP-0: 1920x1200 +0+0 { PanningTrackingArea = 1920x1200 +0+0 }"
</pre>
<p></p>
<p>If not specified in the MetaMode, this will default to the
entire X screen. If the <a href=
"xconfigoptions.html#PanAllDisplays">PanAllDisplays</a> X
configuration option is explicitly set to False, then
PanningTrackingArea will default to the panning domain of the
display device.</p>
<p>This is equivalent to the panning tracking_area region in the
RRSetPanning RandR 1.3 protocol request.</p>
</li>
<li>
<p>"PanningBorder": this defines the distances from the edges of
the ViewPortIn that will activate panning if the pointer hits them.
If the borders are 0, the display device will pan when the pointer
hits the edge of the ViewPortIn (the default). If the borders are
positive, the display device will pan when the pointer gets close
to the edge of the ViewPortIn. If the borders are negative, the
display device will pan when the pointer is beyond the edge of the
ViewPortIn.</p>
<p>The format is "LeftBorder/TopBorder/RightBorder/BottomBorder".
E.g.,</p>
<pre class="screen">
    "DFP-0: 1920x1200 +0+0 { PanningBorder = 10/10/10/10 }"
</pre>
<p></p>
<p>This is equivalent to the panning border in the RRSetPanning
RandR 1.3 protocol request.</p>
</li>
<li>
<p>"ForceCompositionPipeline": possible values are "On" or "Off".
The NVIDIA X driver can use a composition pipeline to apply X
screen transformations and rotations. "ForceCompositionPipeline"
can be used to force the use of this pipeline, even when no
transformations or rotations are applied to the screen.</p>
</li>
<li>
<p>"ForceFullCompositionPipeline": possible values are "On" or
"Off". This option implicitly enables "ForceCompositionPipeline"
and additionally makes use of the composition pipeline to apply
ViewPortOut scaling.</p>
</li>
<li>
<p>"WarpMesh", "BlendTexture", "OffsetTexture": these string
attributes control the operation of Warp and Blend, an advanced
transformation feature available on select NVIDIA Quadro GPUs. Warp
and Blend can adjust a display's geometry (warp) with a greater
level of control than a simple matrix transformation: for example,
to facilitate projecting an image onto a non-planar surface, and
its intensity (blend) per pixel: for example, to seamlessly combine
images from multiple overlapping projectors into a single large
image. Each of the "WarpMesh", "BlendTexture", and "OffsetTexture"
MetaMode tokens can be set to the name of a pixmap which has
already been bound to a name via the XNVCtrlBindWarpPixmapName()
NV_CONTROL call. See the <code class=
"filename">nv-control-warpblend</code> sample application
distributed with the <span><strong class=
"command">nvidia-settings</strong></span> source code for a more
detailed description of the functionality of each of these pixmaps,
how to lay data out into the pixmaps, and an example implementation
of an X application that loads and binds pixmaps so that they are
ready to use in a MetaMode.</p>
<p>If driving the current mode in the RGB 4:4:4 color space would
require a pixel clock that exceeds the display's or GPU's
capabilities, and the display and GPU are capable of driving that
mode in the YCbCr 4:2:0 color space, then the color space will be
overridden to YCbCr 4:2:0 and Warp and Blend will be disabled.</p>
<p>Warp and Blend is not yet supported with the GLX_NV_swap_group
OpenGL extension.</p>
</li>
<li>
<p>"BlendOrder": Controls the order of warping and blending when
using Warp and Blend. By default, warping is performed first,
followed by blending; setting the "BlendOrder" MetaMode token to
"BlendAfterWarp" will reverse the default order.</p>
</li>
<li>
<p>"ResamplingMethod": Controls the filtering method used to smooth
the display image when scaling screen transformations (such as a
WarpMesh or scaling ViewPortOut) are in use. Possible values are
"Bilinear" (default), "BicubicTriangular", "BicubicBellShaped",
"BicubicBspline", "BicubicAdaptiveTriangular",
"BicubicAdaptiveBellShaped", "BicubicAdaptiveBspline", and
"Nearest".</p>
<p>Bicubic resampling is only available on NVIDIA Quadro GPUs, and
is unavailable when a mode requiring a YUV 4:2:0 color space is in
use. Bicubic resampling is not supported with the GLX_NV_swap_group
OpenGL extension.</p>
</li>
<li>
<p>"AllowGSYNC": Controls whether G-SYNC monitors are put into
G-SYNC mode or left in continuous refresh mode.</p>
<p>By default, G-SYNC monitors are put into G-SYNC mode when a mode
is set, and transition into and out of variable refresh mode
seamlessly. However, this prevents certain other features, such as
Ultra Low Motion Blur and Frame Lock, from working. Set this to
"Off" to use continuous refresh rates that are compatible with
these features.</p>
<p>Note: Disabling G-SYNC on any display in a MetaMode disables it
for the entire MetaMode.</p>
</li>
</ul>
</div>
<p>Note that the current MetaMode can also be configured through
the NV-CONTROL X extension and the nvidia-settings utility. For
example:</p>
<pre class="screen">
    nvidia-settings --assign CurrentMetaMode="DFP-0: 1920x1200 { ViewPortIn=800x600, ViewPortOut=1600x1200+160+0 }"
</pre>
<p></p>
</dd>
<dt><span class="term">MetaModeOrientation</span></dt>
<dd>
<p>This option controls the positioning of the display devices
within the virtual X screen, when offsets are not explicitly given
in the MetaModes. The possible values are:</p>
<pre class="screen">
    "RightOf"  (the default)
    "LeftOf"
    "Above"
    "Below"
    "SamePositionAs"
</pre>
<p>When "SamePositionAs" is specified, all display devices will be
assigned an offset of 0,0. For backwards compatibility, "Clone" is
a synonym for "SamePositionAs".</p>
<p>Because it is often unclear which display device relates to
which, MetaModeOrientation can be confusing. You can further
clarify the MetaModeOrientation with display device names to
indicate which display device is positioned relative to which
display device. For example:</p>
<pre class="screen">
    "CRT-0 LeftOf DFP-0"
</pre>
<p></p>
</dd>
<dt><span class="term">ConnectedMonitor</span></dt>
<dd>
<p>With this option you can override what the NVIDIA kernel module
detects is connected to your graphics card. This may be useful, for
example, if any of your display devices do not support detection
using Display Data Channel (DDC) protocols. Valid values are a
comma-separated list of display device names; for example:</p>
<pre class="screen">
    "CRT-0, CRT-1"
    "CRT"
    "CRT-1, DFP-0"
</pre>
<p>WARNING: this option overrides what display devices are detected
by the NVIDIA kernel module, and is very seldom needed. You really
only need this if a display device is not detected, either because
it does not provide DDC information, or because it is on the other
side of a KVM (Keyboard-Video-Mouse) switch. In most other cases,
it is best not to specify this option.</p>
</dd>
</dl>
</div>
<p>Just as in all X config entries, spaces are ignored and all
entries are case insensitive.</p>
<div class="qandaset">
<table border="0" summary="Q and A Set">
<col align="left" width="1%">
<tbody>
<tr class="qandadiv">
<td align="left" valign="top" colspan="2"><a name=
"FrequentlyAsked7a5bb" id="FrequentlyAsked7a5bb"></a>
<h3 class="title">12.1. Frequently Asked TwinView Questions</h3>
</td>
</tr>
<tr class="question">
<td align="left" valign="top"><a name="NothingGetsDispcf9c6" id=
"NothingGetsDispcf9c6"></a></td>
<td align="left" valign="top">
<p><b>Nothing gets displayed on my second monitor; what is
wrong?</b></p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top">
<p>Monitors that do not support monitor detection using Display
Data Channel (DDC) protocols (this includes most older monitors)
are not detectable by your NVIDIA card. You need to explicitly tell
the NVIDIA X driver what you have connected using the
"ConnectedMonitor" option; e.g.,</p>
<pre class="screen">
    Option "ConnectedMonitor" "CRT, CRT"
</pre>
<p></p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top"><a name="WillWindowManag82696" id=
"WillWindowManag82696"></a></td>
<td align="left" valign="top">
<p><b>Will window managers be able to appropriately place windows
(e.g., avoiding placing windows across both display devices, or in
inaccessible regions of the virtual desktop)?</b></p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top">
<p>Yes. Window managers can query the layout of display devices
through either RandR 1.2 or Xinerama.</p>
<p>The NVIDIA X driver provides a Xinerama extension that X clients
(such as window managers) can use to discover the current layout of
display devices. Note that the Xinerama protocol provides no way to
notify clients when a configuration change occurs, so if you
modeswitch to a different MetaMode, your window manager may still
think you have the previous configuration. Using RandR 1.2, or the
Xinerama extension in conjunction with the XF86VidMode extension to
get modeswitch events, window managers should be able to determine
the display device configuration at any given time.</p>
<p>Unfortunately, the data provided by XineramaQueryScreens()
appears to confuse some window managers; to work around such broken
window managers, you can disable communication of the display
device layout with the <a href=
"xconfigoptions.html#nvidiaXineramaInfo">nvidiaXineramaInfo</a> X
configuration option.</p>
<p>The order that display devices are reported in via the NVIDIA
Xinerama information can be configured with the
nvidiaXineramaInfoOrder X configuration option.</p>
<p>Be aware that the NVIDIA driver cannot provide the Xinerama
extension if the X server's own Xinerama extension is being used.
Explicitly specifying Xinerama in the X config file or on the X
server commandline will prohibit NVIDIA's Xinerama extension from
installing, so make sure that the X server's log file does not
contain:</p>
<pre class="screen">
    (++) Xinerama: enabled
</pre>
<p>if you want the NVIDIA driver to be able to provide the Xinerama
extension while in TwinView.</p>
<p>Another solution is to use panning domains to eliminate
inaccessible regions of the virtual screen (see the MetaMode
description above).</p>
<p>A third solution is to use two separate X screens, rather than
use TwinView. See <a href="configmultxscreens.html" title=
"Chapter&nbsp;14.&nbsp;Configuring Multiple X Screens on One Card">Chapter&nbsp;14,
<i>Configuring Multiple X Screens on One Card</i></a>.</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top"><a name="HowAreVirtualScad03c" id=
"HowAreVirtualScad03c"></a></td>
<td align="left" valign="top">
<p><b>How are virtual screen dimensions determined in
TwinView?</b></p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top">
<p>After all requested modes have been validated, and the offsets
for each MetaMode's viewports have been computed, the NVIDIA driver
computes the bounding box of the panning domains for each MetaMode.
The maximum bounding box width and height is then found.</p>
<p>Note that one side effect of this is that the virtual width and
virtual height may come from different MetaModes. Given the
following MetaMode string:</p>
<pre class="screen">
    "1600x1200,NULL; 1024x768+0+0, 1024x768+0+768"
</pre>
<p>the resulting virtual screen size will be 1600 x 1536.</p>
</td>
</tr>
<tr class="question">
<td align="left" valign="top"><a name="CanIPlayFullScr76116" id=
"CanIPlayFullScr76116"></a></td>
<td align="left" valign="top">
<p><b>Can I play full screen games across both display
devices?</b></p>
</td>
</tr>
<tr class="answer">
<td align="left" valign="top"></td>
<td align="left" valign="top">
<p>Yes. While the details of configuration will vary from game to
game, the basic idea is that a MetaMode presents X with a mode
whose resolution is the bounding box of the viewports for that
MetaMode. For example, the following:</p>
<pre class="screen">
    Option "MetaModes" "1024x768,1024x768; 800x600,800x600"
    Option "MetaModeOrientation" "RightOf"
</pre>
<p>produce two modes: one whose resolution is 2048x768, and another
whose resolution is 1600x600. Games such as Quake 3 Arena use the
VidMode extension to discover the resolutions of the modes
currently available. To configure Quake 3 Arena to use the above
MetaMode string, add the following to your q3config.cfg file:</p>
<pre class="screen">
    seta r_customaspect "1"
    seta r_customheight "600"
    seta r_customwidth  "1600"
    seta r_fullscreen   "1"
    seta r_mode         "-1"
</pre>
<p>Note that, given the above configuration, there is no mode with
a resolution of 800x600 (remember that the MetaMode "800x600,
800x600" has a resolution of 1600x600"), so if you change Quake 3
Arena to use a resolution of 800x600, it will display in the lower
left corner of your screen, with the rest of the screen grayed out.
To have single head modes available as well, an appropriate
MetaMode string might be something like:</p>
<pre class="screen">
    "800x600,800x600; 1024x768,NULL; 800x600,NULL; 640x480,NULL"
</pre>
<p>More precise configuration information for specific games is
beyond the scope of this document, but the above examples coupled
with numerous online sources should be enough to point you in the
right direction.</p>
</td>
</tr>
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