226 lines
7.2 KiB
Plaintext
226 lines
7.2 KiB
Plaintext
'\"! eqn | mmdoc
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'\"macro stdmacro
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.ds Vn Version 1.2
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.ds Dt 6 March 1997
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.ds Re Release 1.2.0
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.ds Dp Feb 16 02:56
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.ds Dm Feb 10 17:2
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.ds Xs 58988 14 xchoosevisual.gl
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.TH GLXCHOOSEVISUAL
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.SH NAME
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glXChooseVisual
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\- return a visual that matches specified attributes
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.SH C SPECIFICATION
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XVisualInfo* \f3glXChooseVisual\fP(
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Display \fI*dpy\fP,
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.nf
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.ta \w'\f3XVisualInfo* \fPglXChooseVisual( 'u
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int \fIscreen\fP,
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int \fI*attribList\fP )
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.fi
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.EQ
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delim $$
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.EN
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.SH PARAMETERS
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.TP \w'\fIattribList\fP\ \ 'u
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\f2dpy\fP
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Specifies the connection to the X server.
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.TP
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\f2screen\fP
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Specifies the screen number.
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.TP
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\f2attribList\fP
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Specifies a list of boolean attributes and integer attribute/value pairs.
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The last attribute must be \f3None\fP.
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.SH DESCRIPTION
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\f3glXChooseVisual\fP returns a pointer to an XVisualInfo structure describing the visual
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that best meets a minimum specification.
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The boolean GLX attributes of the visual that is returned will match the
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specified values,
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and the integer GLX attributes will meet or exceed the specified
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minimum values.
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If all other attributes are equivalent, then TrueColor and PseudoColor
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visuals have priority over DirectColor and StaticColor visuals,
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respectively.
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If no conforming visual exists, \f3NULL\fP is returned.
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To free the data returned by this function, use \f3XFree\fP.
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.P
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All boolean GLX attributes default to \f3False\fP
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except \f3GLX_USE_GL\fP,
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which defaults to \f3True\fP.
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All integer GLX attributes default to zero.
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Default specifications are superseded by attributes included in \f2attribList\fP.
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Boolean attributes included in \f2attribList\fP are understood to be \f3True\fP.
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Integer attributes and enumerated type attributes are followed immediately
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by the corresponding desired or
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minimum value.
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The list must be terminated with \f3None\fP.
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.P
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The interpretations of the various GLX visual attributes are as follows:
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.TP 22
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\f3GLX_USE_GL\fP
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Ignored.
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Only visuals that can be rendered with GLX are considered.
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.TP
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\f3GLX_BUFFER_SIZE\fP
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Must be followed by a nonnegative integer that indicates the desired
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color index buffer size.
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The smallest index buffer of at least the specified size is preferred.
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Ignored if \f3GLX_RGBA\fP is asserted.
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.BP
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.TP
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\f3GLX_LEVEL\fP
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Must be followed by an integer buffer-level specification.
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This specification is honored exactly.
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Buffer level zero corresponds to the main frame buffer of the display.
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Buffer level one is the first overlay frame buffer, level two the second
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overlay frame buffer, and so on.
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Negative buffer levels correspond to underlay frame buffers.
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.TP
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\f3GLX_RGBA\fP
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If present,
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only TrueColor and DirectColor visuals are considered.
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Otherwise,
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only PseudoColor and StaticColor visuals are considered.
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.TP
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\f3GLX_DOUBLEBUFFER\fP
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If present,
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only double-buffered visuals are considered.
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.BR
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Otherwise,
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only single-buffered visuals are considered.
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.TP
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\f3GLX_STEREO\fP
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If present,
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only stereo visuals are considered.
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Otherwise,
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only monoscopic visuals are considered.
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.TP
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\f3GLX_AUX_BUFFERS\fP
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Must be followed by a nonnegative integer that indicates the desired
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number of auxiliary buffers.
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Visuals with the
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.BR
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smallest number of auxiliary buffers that meets or exceeds
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the specified number are preferred.
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.TP
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\f3GLX_RED_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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the smallest available red buffer is preferred.
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Otherwise, the largest available red buffer of at least the minimum size
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is preferred.
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.TP
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\f3GLX_GREEN_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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the smallest available green buffer is preferred.
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Otherwise, the largest available green buffer of at least the minimum size
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is preferred.
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.TP
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\f3GLX_BLUE_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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the smallest available blue buffer is preferred.
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Otherwise, the largest available blue buffer of at least the minimum size
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is preferred.
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.TP
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\f3GLX_ALPHA_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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the smallest available alpha buffer is preferred.
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Otherwise, the largest available alpha buffer of at least the minimum size
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is preferred.
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.TP
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\f3GLX_DEPTH_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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visuals with no depth buffer are preferred.
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Otherwise, the largest available depth buffer of at least the minimum size
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is preferred.
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.TP
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\f3GLX_STENCIL_SIZE\fP
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Must be followed by a nonnegative integer that indicates the desired
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number of stencil bitplanes.
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The smallest stencil buffer of at least the specified size is preferred.
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If the desired value is zero,
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visuals with no stencil buffer are preferred.
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.TP
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\f3GLX_ACCUM_RED_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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visuals with no red accumulation buffer are preferred.
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Otherwise, the largest possible red accumulation buffer
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of at least the minimum size is preferred.
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.TP
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\f3GLX_ACCUM_GREEN_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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visuals with no green accumulation buffer are preferred.
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Otherwise, the largest possible green accumulation buffer
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of at least the minimum size is preferred.
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.TP
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\f3GLX_ACCUM_BLUE_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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visuals with no blue accumulation buffer are preferred.
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Otherwise, the largest possible blue accumulation buffer
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of at least the minimum size is preferred.
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.TP
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\f3GLX_ACCUM_ALPHA_SIZE\fP
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Must be followed by a nonnegative minimum size specification.
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If this value is zero,
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visuals with no alpha accumulation buffer are preferred.
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Otherwise, the largest possible alpha accumulation buffer
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of at least the minimum size is preferred.
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.TE
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.SH EXAMPLES
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.TP 12
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\f2attribList\fP =
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{\f3GLX_RGBA\fP,
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\f3GLX_RED_SIZE\fP, 4,
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\f3GLX_GREEN_SIZE\fP, 4,
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\f3GLX_BLUE_SIZE\fP, 4,
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\f3None\fP};
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.P
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Specifies a single-buffered RGB visual in the normal frame buffer,
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not an overlay or underlay buffer.
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The returned visual supports at least four bits each of red,
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green, and blue,
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and possibly no bits of alpha.
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It does not support color index mode,
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double-buffering, or stereo display.
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It may or may not have one or more auxiliary color buffers,
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a depth buffer,
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a stencil buffer,
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or an accumulation buffer.
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.SH NOTES
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\f3XVisualInfo\fP is defined in \f2Xutil.h.\fP
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It is a structure that includes \f2visual\fP, \f2visualID\fP, \f2screen\fP, and
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\f2depth\fP elements.
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.P
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\f3glXChooseVisual\fP is implemented as a client-side utility using only \f3XGetVisualInfo\fP
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and \f3glXGetConfig\fP.
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Calls to these two routines can be used to implement selection algorithms
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other than the generic one implemented by \f3glXChooseVisual\fP.
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.P
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GLX implementers are strongly discouraged,
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but not proscribed,
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from changing the selection algorithm used by \f3glXChooseVisual\fP.
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Therefore, selections may change from release to release
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of the client-side library.
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.P
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There is no direct filter for picking only visuals that
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support GLXPixmaps.
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GLXPixmaps are supported for visuals whose
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\f3GLX_BUFFER_SIZE\fP
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is one of the pixmap depths supported by the X server.
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.SH ERRORS
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\f3NULL\fP is returned if an undefined GLX attribute is encountered in
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\f2attribList\fP.
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.SH SEE ALSO
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\f3glXCreateContext\fP,
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\f3glXGetConfig\fP
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