glXChooseFBConfigSGIX(3G) OpenGL Reference - GLX glXChooseFBConfigSGIX(3G)NAME
glXChooseFBConfigSGIX - return a list of GLX frame buffer configurations
that match the specified attributes
C SPECIFICATION
GLXFBConfigSGIX * glXChooseFBConfigSGIX( Display *dpy,
int screen,
int *attrib_list,
int *nitems )
PARAMETERS
dpy Specifies the connection to the X server.
screen Specifies the screen number.
attrib_list Specifies a list of attribute/value pairs. The last
attribute must be None.
nitems Returns the number of elements in the list returned by
glXChooseFBConfigSGIX.
DESCRIPTION
If attrib_list is NULL then glXChooseFBConfigSGIX returns an array of GLX
frame buffer configurations that are available on the specified screen;
otherwise glXChooseFBConfigSGIX returns an array of GLX frame buffer
configurations that match the specified attributes. If an error occurs,
no frame buffer configurations exist on the specified screen, or if no
frame buffer configurations match the specified attributes, then NULL is
returned. Use XFree to free the memory returned by
glXChooseFBConfigSGIX.
All attributes in attrib_list, including boolean attributes, are
immediately followed by the corresponding desired value. The list is
terminated with None. If an attribute is not specified in attrib_list
then the default value (see below) is used (and the attribute is said to
be specified implicitly). For example, if GLX_STEREO is not specified
then it is assumed to be False. For some attributes, the default is
"don't care" meaning that any value is OK for this attribute, so the
attribute will not be checked.
Attributes are matched in an attribute-specific manner. Some of the
attributes, such as GLX_LEVEL, must match the specified value exactly;
others, such as, GLX_RED_SIZE must meet or exceed the specified minimum
values. If more than one GLX frame buffer configuration is found, then a
list of configurations, sorted according to the "best" match criteria, is
returned. The match criteria for each attribute and the exact sorting
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order is defined below.
The interpretations of the various GLX visual attributes are as follows:
GLX_BUFFER_SIZE Must be followed by a nonnegative integer that
indicates the desired color index buffer size.
The smallest index buffer of at least the
specified size is preferred. Ignored if
GLX_COLOR_INDEX_BIT_SGIX is not set in
GLX_RENDER_TYPE_SGIX. The default value is 0.
GLX_LEVEL Must be followed by an integer buffer-level
specification. This specification is honored
exactly. Buffer level zero corresponds to the
default frame buffer of the display. Buffer
level one is the first overlay frame buffer,
level two the second overlay frame buffer, and
so on. Negative buffer levels correspond to
underlay frame buffers. The default value is 0.
GLX_DOUBLEBUFFER Must be followed by True or False. If True is
specified then only double-buffered frame buffer
configurations are considered; if False is
specified then only single-buffered frame buffer
configurations are considered. The default
value is "don't care".
GLX_STEREO Must be followed by True or False. If True is
specified then only stereo frame buffer
configurations are considered; if False is
specified then only monoscopic frame buffer
configurations are considered. The default
value is False.
GLX_AUX_BUFFERS Must be followed by a nonnegative integer that
indicates the desired number of auxiliary
buffers. Configurations with the smallest
number of auxiliary buffers that meet or exceed
the specified number are preferred. The default
value is 0.
GLX_RED_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the
smallest available red buffer is preferred.
Otherwise, the largest available red buffer of
at least the minimum size is preferred. The
default value is 0.
GLX_GREEN_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the
smallest available green buffer is preferred.
Otherwise, the largest available green buffer of
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at least the minimum size is preferred. The
default value is 0.
GLX_BLUE_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the
smallest available blue buffer is preferred.
Otherwise, the largest available blue buffer of
at least the minimum size is preferred. The
default value is 0.
GLX_ALPHA_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, the
smallest available alpha buffer is preferred.
Otherwise, the largest available alpha buffer of
at least the minimum size is preferred. The
default value is 0.
GLX_DEPTH_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, frame
buffer configurations with no depth buffer are
preferred. Otherwise, the largest available
depth buffer of at least the minimum size is
preferred. The default value is 0.
GLX_STENCIL_SIZE Must be followed by a nonnegative integer that
indicates the desired number of stencil
bitplanes. The smallest stencil buffer of at
least the specified size is preferred. If the
desired value is zero, frame buffer
configurations with no stencil buffer are
preferred. The default value is 0.
GLX_ACCUM_RED_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, frame
buffer configurations with no red accumulation
buffer are preferred. Otherwise, the largest
possible red accumulation buffer of at least the
minimum size is preferred. The default value is
0.
GLX_ACCUM_GREEN_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, frame
buffer configurations with no green accumulation
buffer are preferred. Otherwise, the largest
possible green accumulation buffer of at least
the minimum size is preferred. The default
value is 0.
GLX_ACCUM_BLUE_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, frame
buffer configurations with no blue accumulation
buffer are preferred. Otherwise, the largest
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possible blue accumulation buffer of at least
the minimum size is preferred. The default
value is 0.
GLX_ACCUM_ALPHA_SIZE Must be followed by a nonnegative minimum size
specification. If this value is zero, frame
buffer configurations with no alpha accumulation
buffer are preferred. Otherwise, the largest
possible alpha accumulation buffer of at least
the minimum size is preferred. The default
value is 0.
GLX_SAMPLE_BUFFERS_SGIS Must be followed by the minimum acceptable
number of multisample buffers. Configurations
with the smallest number of multisample buffers
that meet or exceed this minimum number are
preferred. Currently operation with more than
one multisample buffer is undefined, so only
values of zero or one will produce a match. The
default value is 0.
GLX_SAMPLES_SGIS Must be followed by the minimum number of
samples required in multisample buffers.
Configurations with the smallest number of
samples that meet or exceed the specified
minimum number are preferred. Note that it is
possible for color samples in the multisample
buffer to have fewer bits than colors in the
main color buffers. However, multisampled
colors maintain at least as much color
resolution in aggregate as the main color
buffers.
The default value is 0.
GLX_TRANSPARENT_TYPE_EXT Must be followed by one of GLX_NONE_EXT,
GLX_TRANSPARENT_RGB_EXT,
GLX_TRANSPARENT_INDEX_EXT. If GLX_NONE_EXT is
specified, then only opaque frame buffer
configurations will be considered; if
GLX_TRANSPARENT_RGB_EXT is specified, then only
transparent frame buffer configurations that
support RGBA rendering will be considered; if
GLX_TRANSPARENT_INDEX_EXT is specified, then
only transparent frame buffer configurations
that support color index rendering will be
considered. The default value is GLX_NONE_EXT.
GLX_TRANSPARENT_INDEX_VALUE_EXT
Must be followed by an integer value indicating
the transparent index value; the value must be
between 0 and the maximum framebuffer value for
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indices. Only frame buffer configurations that
use the specified transparent index value will
be considered. The default value is "don't
care".
This attribute is ignored unless
GLX_TRANSPARENT_TYPE_EXT is included in
attrib_list and specified as
GLX_TRANSPARENT_INDEX_EXT.
GLX_TRANSPARENT_RED_VALUE_EXT
Must be followed by an integer value indicating
the transparent red value; the value must be
between 0 and the maximum framebuffer value for
red. Only frame buffer configurations that use
the specified transparent red value will be
considered. The default value is "don't care".
This attribute is ignored unless
GLX_TRANSPARENT_TYPE_EXT is included in
attrib_list and specified as
GLX_TRANSPARENT_RGB_EXT.
GLX_TRANSPARENT_GREEN_VALUE_EXT
Must be followed by an integer value indicating
the transparent green value; the value must be
between 0 and the maximum framebuffer value for
green. Only frame buffer configurations that
use the specified transparent green value will
be considered. The default value is "don't
care".
This attribute is ignored unless
GLX_TRANSPARENT_TYPE_EXT is included in
attrib_list and specified as
GLX_TRANSPARENT_RGB_EXT.
GLX_TRANSPARENT_BLUE_VALUE_EXT
Must be followed by an integer value indicating
the transparent blue value; the value must be
between 0 and the maximum framebuffer value for
blue. Only frame buffer configurations that use
the specified transparent blue value will be
considered. The default value is "don't care".
This attribute is ignored unless
GLX_TRANSPARENT_TYPE_EXT is included in
attrib_list and specified as
GLX_TRANSPARENT_RGB_EXT.
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GLX_TRANSPARENT_ALPHA_VALUE_EXT
Must be followed by an integer value. This
attribute is always ignored; it is for future
use only.
GLX_VISUAL_CAVEAT_EXT Must be followed by one of GLX_NONE_EXT,
GLX_SLOW_VISUAL_EXT, GLX_NON_CONFORMANT_EXT. If
GLX_NONE_EXT is specified, then only frame
buffer configurations with no caveats will be
considered; if GLX_SLOW_VISUAL_EXT, is specified
then only slow frame buffer configurations will
be considered; if GLX_NON_CONFORMANT_EXT is
specified then only non-conformant frame buffer
configurations will be considered. The default
value is "don't care".
GLX_DRAWABLE_TYPE_SGIX Must be followed by a mask indicating which GLX
drawable types the frame buffer configuration
must support. Valid bits are
GLX_WINDOW_BIT_SGIX, GLX_PIXMAP_BIT_SGIX and
GLX_PBUFFER_BIT_SGIX. For example, if mask is
set to GLX_WINDOW_BIT_SGIX |
GLX_PIXMAP_BIT_SGIX, only frame buffer
configurations that support both windows and GLX
pixmaps will be considered. The default value
is GLX_WINDOW_BIT_SGIX.
GLX_RENDER_TYPE_SGIX Must be followed by a mask indicating which
OpenGL rendering modes the frame buffer
configuration must support. Valid bits are
GLX_RGBA_BIT_SGIX and GLX_COLOR_INDEX_BIT_SGIX.
If the mask is set to GLX_RGBA_BIT_SGIX |
GLX_COLOR_INDEX_BIT_SGIX then only frame buffer
configurations that can be bound to both RGBA
contexts and color index contexts will be
considered. The default value is
GLX_RGBA_BIT_SGIX.
GLX_X_VISUAL_TYPE_EXT Must be followed by one of GLX_TRUE_COLOR_EXT,
GLX_DIRECT_COLOR_EXT, GLX_PSEUDO_COLOR_EXT,
GLX_STATIC_COLOR_EXT, GLX_GRAY_SCALE_EXT,
GLX_STATIC_GRAY_EXT, indicating the desired X
visual type. Not all frame buffer
configurations have an associated X visual. If
GLX_DRAWABLE_TYPE_SGIX is specified in
attrib_list and the mask that follows does not
have GLX_WINDOW_BIT_SGIX set, then this value is
ignored. It is also ignored if
GLX_X_RENDERABLE_SGIX is specified as False.
RGBA rendering may be supported for visuals of
type GLX_TRUE_COLOR_EXT, GLX_DIRECT_COLOR_EXT,
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GLX_PSEUDO_COLOR_EXT, or GLX_STATIC_COLOR_EXT,
but color index rendering is only supported for
visuals of type GLX_PSEUDO_COLOR_EXT or
GLX_STATIC_COLOR_EXT (i.e., single-channel
visuals).
The tokens GLX_GRAY_SCALE_EXT and
GLX_STATIC_GRAY_EXT will not match current
OpenGL enabled visuals, but are included for
future use.
The default value for GLX_X_VISUAL_TYPE_EXT is
"don't care".
GLX_X_RENDERABLE_SGIX Must be followed by True or False. If True is
specified, then only frame buffer configurations
that have associated X visuals (and can be used
to render to Windows and/or GLX pixmaps) will be
considered. The default value is "don't care".
GLX_FBCONFIG_ID_SGIX Must be followed by an XID for a GLXFBConfig.
When GLX_FBCONFIG_ID_SGIX is specified in
attrib_list, all other attributes are ignored,
and only the frame buffer configuration with the
given XID is returned. NULL is returned if the
frame buffer configuration does not exist. The
default value for GLX_FBCONFIG_ID_SGIX is "don't
care".
When more than one GLX frame buffer configuration matches the specified
attributes, a list of matching configurations is returned. The list is
sorted according to the following precedence rules that are applied in
ascending order (i.e., configurations that are considered equal by lower
numbered rule are sorted by the higher numbered rule):
1. by GLX_VISUAL_RATING_EXT where the precedence is GLX_NONE_EXT,
GLX_NON_CONFORMANT, GLX_SLOW_VISUAL.
2. larger total number of RGBA color components (GLX_RED_BITS,
GLX_GREEN_BITS, GLX_BLUE_BITS, and GLX_ALPHA_BITS) that have higher
number of bits,
3. smaller GLX_INDEX_BITS,
4. single buffered configuration (GLX_DOUBLE_BUFFER being False)
precedes a double buffered one,
5. smaller GLX_AUX_BUFFERS,
6. smaller GLX_SAMPLE_BUFFERS_SGIS,
7. smaller GLX_SAMPLES_SGIS,
8. larger GLX_DEPTH_BITS,
9. smaller GLX_STENCIL_BITS,
10. larger total number of accumulation buffer color components
(GLX_ACCUM_RED_BITS, GLX_ACCUM_GREEN_BITS, GLX_ACCUM_BLUE_BITS, and
GLX_ACCUM_ALPHA_BITS) that have higher number of bits;
11. sort by GLX_VISUAL_TYPE_EXT where the precedence order is
GLX_TRUE_COLOR_EXT, GLX_DIRECT_COLOR_EXT, GLX_PSEUDO_COLOR_EXT,
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GLX_STATIC_COLOR_EXT, GLX_GRAY_SCALE_EXT, GLX_STATIC_GRAY_EXT,
EXAMPLES
attrib_list =
{GLX_RENDER_TYPE_SGIX, GLX_RGBA_BIT_SGIX, GLX_RED_SIZE, 4,
GLX_GREEN_SIZE, 4, GLX_BLUE_SIZE, 4, None};
Specifies a frame buffer configuration that supports RGBA rendering and
exists in the normal frame buffer, not an overlay or underlay buffer.
The returned visual supports at least four bits each of red, green, and
blue, and possibly no bits of alpha. It does not support stereo display.
It may or may not have one or more auxiliary color buffers, a back
buffer, a depth buffer, a stencil buffer, or an accumulation buffer.
NOTES
glXChooseFBConfigSGIX is part of the GLX_SGIX_fbconfig extension.
glXChooseFBConfigSGIX is implemented as a client-side utility; it does
not require a round-trip to the X server.
glXChooseFBConfigSGIX and glXGetFBConfigAttribSGIX can be used to
implement selection algorithms other than the generic one implemented by
glXChooseFBConfigSGIX. Call glXChooseFBConfigSGIX to retrieve all the
frame buffer configurations on a particular screen or, alternatively, all
the frame buffer configurations with a particular set of attributes. Next
call glXGetFBConfigAttribSGIX to retrieve additional attributes for the
frame buffer configurations and then select between them.
GLX implementers are strongly discouraged, but not proscribed, from
changing the selection algorithm used by glXChooseFBConfigSGIX.
Therefore, selections may change from release to release of the client-
side library.
GLX_SAMPLE_BUFFERS_SGIS and GLX_SAMPLES_SGIS are not valid attributes
unless the SGIS_multisample extension is supported.
GLX_X_VISUAL_TYPE_EXT, GLX_TRANSPARENT_TYPE_EXT,
GLX_TRANSPARENT_INDEX_VALUE_EXT, GLX_TRANSPARENT_RED_VALUE_EXT,
GLX_TRANSPARENT_GREEN_VALUE_EXT, GLX_TRANSPARENT_BLUE_VALUE_EXT, and
GLX_TRANSPARENT_ALPHA_VALUE_EXT are not valid attributes unless the
EXT_visual_info extension is supported.
GLX_VISUAL_CAVEAT_EXT is not a valid attribute unless the
EXT_visual_rating extension is supported.
ERRORS
NULL is returned if an undefined GLX attribute is encountered in
attrib_list, if screen is invalid or if dpy does not support the GLX
extension.
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glXChooseFBConfigSGIX(3G) OpenGL Reference - GLX glXChooseFBConfigSGIX(3G)MACHINE DEPENDENCIES
The SGIS_multisample extension is supported only on RealityEngine,
RealityEngine2, and VTX systems and InfiniteReality systems.
SEE ALSO
glXGetFBConfigAttribSGIX, glXCreateContextWithConfigSGIX,
glXCreateGLXPixmapWithConfigSGIX, glXGetVisualFromFBConfigSGIX.
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