178 lines
5.1 KiB
Plaintext
178 lines
5.1 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 60987 10 xgetconfig.gl
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.TH GLXGETCONFIG 3
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.SH NAME
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glXGetConfig
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\- return information about GLX visuals
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.SH C SPECIFICATION
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int \f3glXGetConfig\fP(
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Display \fI*dpy\fP,
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.nf
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.ta \w'\f3int \fPglXGetConfig( 'u
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XVisualInfo \fI*vis\fP,
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int \fIattrib\fP,
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int \fI*value\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'\fIattrib\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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\f2vis\fP
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Specifies the visual to be queried.
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It is a pointer to an \f3XVisualInfo\fP structure,
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not a visual ID or a pointer to a \f3Visual\fP.
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.TP
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\f2attrib\fP
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Specifies the visual attribute to be returned.
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.TP
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\f2value\fP
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Returns the requested value.
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.SH DESCRIPTION
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\f3glXGetConfig\fP sets \f2value\fP to the \f2attrib\fP value of windows or GLX pixmaps
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created with respect to \f2vis\fP.
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\f3glXGetConfig\fP returns an error code if it fails for any reason.
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Otherwise, zero is returned.
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.P
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\f2attrib\fP is one of the following:
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.P
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.TP 22
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\f3GLX_USE_GL\fP
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\f3True\fP if OpenGL rendering is supported by this visual,
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\f3False\fP otherwise.
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.TP
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\f3GLX_BUFFER_SIZE\fP
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Number of bits per color buffer.
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For RGBA visuals, \f3GLX_BUFFER_SIZE\fP is the sum of
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\f3GLX_RED_SIZE\fP,
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\f3GLX_GREEN_SIZE\fP,
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\f3GLX_BLUE_SIZE\fP, and
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\f3GLX_ALPHA_SIZE\fP.
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For color index visuals, \f3GLX_BUFFER_SIZE\fP is the size of the
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color indexes.
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.TP
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\f3GLX_LEVEL\fP
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Frame buffer level of the visual.
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Level zero is the default frame buffer.
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Positive levels correspond to frame buffers that overlay the default buffer,
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and negative levels correspond to frame buffers that underlay the default
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buffer.
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.TP
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\f3GLX_RGBA\fP
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\f3True\fP if color buffers store red, green, blue, and alpha values.
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\f3False\fP if they store color indexes.
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.TP
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\f3GLX_DOUBLEBUFFER\fP
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\f3True\fP if color buffers exist in front/back pairs that can be swapped,
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\f3False\fP otherwise.
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.TP
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\f3GLX_STEREO\fP
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\f3True\fP if color buffers exist in left/right pairs,
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\f3False\fP otherwise.
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.TP
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\f3GLX_AUX_BUFFERS\fP
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Number of auxiliary color buffers that are available.
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Zero indicates that no auxiliary color buffers exist.
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.TP
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\f3GLX_RED_SIZE\fP
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Number of bits of red stored in each color buffer.
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Undefined if \f3GLX_RGBA\fP is \f3False\fP.
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.TP
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\f3GLX_GREEN_SIZE\fP
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Number of bits of green stored in each color buffer.
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Undefined if \f3GLX_RGBA\fP is \f3False\fP.
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.TP
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\f3GLX_BLUE_SIZE\fP
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Number of bits of blue stored in each color buffer.
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Undefined if \f3GLX_RGBA\fP is \f3False\fP.
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.TP
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\f3GLX_ALPHA_SIZE\fP
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Number of bits of alpha stored in each color buffer.
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Undefined if \f3GLX_RGBA\fP is \f3False\fP.
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.TP
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\f3GLX_DEPTH_SIZE\fP
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Number of bits in the depth buffer.
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.TP
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\f3GLX_STENCIL_SIZE\fP
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Number of bits in the stencil buffer.
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.TP
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\f3GLX_ACCUM_RED_SIZE\fP
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Number of bits of red stored in the accumulation buffer.
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.TP
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\f3GLX_ACCUM_GREEN_SIZE\fP
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Number of bits of green stored in the accumulation buffer.
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.TP
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\f3GLX_ACCUM_BLUE_SIZE\fP
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Number of bits of blue stored in the accumulation buffer.
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.TP
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\f3GLX_ACCUM_ALPHA_SIZE\fP
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Number of bits of alpha stored in the accumulation buffer.
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.TE
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.P
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The X protocol allows a single visual ID to be instantiated with
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different numbers of bits per pixel.
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Windows or GLX pixmaps that will be rendered with OpenGL, however,
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must be instantiated with a color buffer depth of \f3GLX_BUFFER_SIZE\fP.
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.P
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Although a GLX implementation can export many visuals that support GL
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rendering,
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it must support
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at least one RGBA visual. This visual must have at
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least one color buffer,
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a stencil buffer of at least 1 bit,
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a depth buffer of at least 12 bits,
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and an accumulation buffer.
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Alpha bitplanes are optional in this visual.
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However,
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its color buffer size must be as great as that of the
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deepest \f3TrueColor\fP, \f3DirectColor\fP,
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\f3PseudoColor\fP, or \f3StaticColor\fP visual supported on level zero,
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and it must itself be made available on level zero.
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.P
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In addition, if the X server exports a \f3PseudoColor\fP
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or \f3StaticColor\fP visual on framebuffer level 0, a color index
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visual is also required on that level.
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It must have
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at least one color buffer,
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a stencil buffer of at least 1 bit,
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and a depth buffer of at least 12 bits.
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This visual must
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have as many
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color bitplanes as the deepest
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\f3PseudoColor\fP or \f3StaticColor\fP visual supported on level 0.
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.P
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Applications are best written to select the visual that most closely
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meets their requirements.
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Creating windows or GLX pixmaps with unnecessary buffers can result in
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reduced rendering performance as well as poor resource allocation.
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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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.SH ERRORS
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\f3GLX_NO_EXTENSION\fP is returned if \f2dpy\fP does not support the GLX
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extension.
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.P
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\f3GLX_BAD_SCREEN\fP is returned if the screen of \f2vis\fP does not correspond
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to a screen.
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.P
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\f3GLX_BAD_ATTRIBUTE\fP is returned if \f2attrib\fP is not a valid GLX attribute.
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.P
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\f3GLX_BAD_VISUAL\fP is returned if \f2vis\fP doesn't support GLX and an
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attribute other than \f3GLX_USE_GL\fP is requested.
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.SH SEE ALSO
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\f3glXChooseVisual\fP,
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\f3glXCreateContext\fP
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