glXChooseFBConfig — return a list of GLX frame buffer configurations that match the specified attributes
GLXFBConfig * glXChooseFBConfig( | Display * | dpy, |
| int | screen, | |
| const int * | attrib_list, | |
| int * | nelements); |
dpySpecifies the connection to the X server.
screenSpecifies the screen number.
attrib_list
Specifies a list of attribute/value pairs.
The last attribute must be None.
nelements
Returns the number of elements in the list returned by glXChooseFBConfig.
glXChooseFBConfig returns GLX frame buffer configurations that match the attributes
specified in attrib_list, or NULL if no matches are found.
If attrib_list is NULL, then glXChooseFBConfig returns an array of GLX
frame buffer configurations that are available on the specified screen.
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
glXChooseFBConfig.
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
GLX_DONT_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 order is
defined below.
The interpretations of the various GLX visual attributes are as follows:
GLX_FBCONFIG_ID
Must be followed by a valid XID that indicates the desired GLX frame
buffer configuration. When a GLX_FBCONFIG_ID is specified, all
attributes are ignored. The default value is GLX_DONT_CARE.
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.
This attribute is ignored if GLX_COLOR_INDEX_BIT is not set in
GLX_RENDER_TYPE. The default value is 0.
GLX_LEVEL
Must be followed by an integer buffer-level specification. This specification is honored exactly. Buffer level 0 corresponds to the default frame buffer of the display. Buffer level 1 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 GLX_DONT_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, GLX_GREEN_SIZE, GLX_BLUE_SIZE, GLX_ALPHA_SIZE
Each attribute, if present, must be followed by a nonnegative minimum size
specification or GLX_DONT_CARE.
The largest available total RGBA color buffer size (sum of GLX_RED_SIZE,
GLX_GREEN_SIZE, GLX_BLUE_SIZE, and GLX_ALPHA_SIZE)
of at least the minimum size specified for each color component is preferred.
If the requested number of bits for a color component is 0 or
GLX_DONT_CARE, it is not considered. The default value for each color
component 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 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_RENDER_TYPE
Must be followed by a mask indicating which OpenGL rendering modes
the frame buffer configuration must support.
Valid bits are GLX_RGBA_BIT and
GLX_COLOR_INDEX_BIT. If the mask is
set to GLX_RGBA_BIT | GLX_COLOR_INDEX_BIT,
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.
GLX_DRAWABLE_TYPE
Must be followed by a mask indicating which GLX drawable types
the frame buffer configuration must support. Valid bits are
GLX_WINDOW_BIT,
GLX_PIXMAP_BIT, and GLX_PBUFFER_BIT.
For example, if mask is set to
GLX_WINDOW_BIT | GLX_PIXMAP_BIT,
only frame buffer configurations that support both windows and GLX pixmaps
will be considered.
The default value is GLX_WINDOW_BIT.
GLX_X_RENDERABLE
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 GLX_DONT_CARE.
GLX_X_VISUAL_TYPE
Must be followed by one of
GLX_TRUE_COLOR,
GLX_DIRECT_COLOR,
GLX_PSEUDO_COLOR,
GLX_STATIC_COLOR,
GLX_GRAY_SCALE, or
GLX_STATIC_GRAY, indicating the desired X visual type.
Not all frame buffer configurations have an associated X visual. If
GLX_DRAWABLE_TYPE is specified in attrib_list and the
mask that follows does not have GLX_WINDOW_BIT set,
then this value is ignored. It is also ignored if
GLX_X_RENDERABLE is specified as False.
RGBA rendering may be supported for visuals of type
GLX_TRUE_COLOR,
GLX_DIRECT_COLOR,
GLX_PSEUDO_COLOR,
or GLX_STATIC_COLOR,
but color index rendering is only supported for visuals of type
GLX_PSEUDO_COLOR or GLX_STATIC_COLOR
(i.e., single-channel visuals).
The tokens GLX_GRAY_SCALE and GLX_STATIC_GRAY will
not match current OpenGL enabled visuals, but are included for future use.
The default value for GLX_X_VISUAL_TYPE is GLX_DONT_CARE.
GLX_CONFIG_CAVEAT
Must be followed by one of
GLX_NONE,
GLX_SLOW_CONFIG,
GLX_NON_CONFORMANT_CONFIG.
If GLX_NONE is specified, then only frame buffer configurations with
no caveats will be considered; if GLX_SLOW_CONFIG
is specified, then only slow frame buffer configurations will be considered; if
GLX_NON_CONFORMANT_CONFIG is specified, then only
nonconformant frame buffer configurations will be considered.
The default value is GLX_DONT_CARE.
GLX_TRANSPARENT_TYPE
Must be followed by one of
GLX_NONE,
GLX_TRANSPARENT_RGB,
GLX_TRANSPARENT_INDEX.
If GLX_NONE is specified, then only opaque
frame buffer configurations will be considered; if GLX_TRANSPARENT_RGB
is specified, then only transparent
frame buffer configurations that support RGBA rendering will be considered;
if GLX_TRANSPARENT_INDEX is specified,
then only transparent frame buffer configurations that support color
index rendering will be considered.
The default value is GLX_NONE.
GLX_TRANSPARENT_INDEX_VALUE
Must be followed by an integer value indicating the transparent
index value; the value must be between 0 and the maximum
frame buffer value for indices.
Only frame buffer configurations that use the
specified transparent index value will be considered.
The default value is GLX_DONT_CARE.
This attribute is ignored unless GLX_TRANSPARENT_TYPE is
included in attrib_list and specified as GLX_TRANSPARENT_INDEX.
GLX_TRANSPARENT_RED_VALUE
Must be followed by an integer value indicating the transparent
red value; the value must be between 0 and the maximum
frame buffer value for red.
Only frame buffer configurations that use the
specified transparent red value will be considered.
The default value is GLX_DONT_CARE.
This attribute is
ignored unless GLX_TRANSPARENT_TYPE is included in
attrib_list and specified as GLX_TRANSPARENT_RGB.
GLX_TRANSPARENT_GREEN_VALUE
Must be followed by an integer value indicating the transparent
green value; the value must be between 0 and the maximum
frame buffer value for green.
Only frame buffer configurations that use the
specified transparent green value will be considered.
The default value is GLX_DONT_CARE.
This attribute is
ignored unless GLX_TRANSPARENT_TYPE is included in
attrib_list and specified as GLX_TRANSPARENT_RGB.
GLX_TRANSPARENT_BLUE_VALUE
Must be followed by an integer value indicating the transparent
blue value; the value must be between 0 and the maximum
frame buffer value for blue.
Only frame buffer configurations that use the
specified transparent blue value will be considered.
The default value is GLX_DONT_CARE.
This attribute is ignored unless GLX_TRANSPARENT_TYPE is included in
attrib_list and specified as GLX_TRANSPARENT_RGB.
GLX_TRANSPARENT_ALPHA_VALUE
Must be followed by an integer value indicating the transparent
alpha value; the value must be between 0 and the maximum
frame buffer value for alpha.
Only frame buffer configurations that use the
specified transparent alpha value will be considered.
The default value is GLX_DONT_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, which are applied in ascending order (i.e., configurations that are considered equal by a lower numbered rule are sorted by the higher numbered rule):
By GLX_CONFIG_CAVEAT where the precedence is GLX_NONE,
GLX_SLOW_CONFIG, and GLX_NON_CONFORMANT_CONFIG.
Larger total number of RGBA color components
(GLX_RED_SIZE, GLX_GREEN_SIZE, GLX_BLUE_SIZE,
plus GLX_ALPHA_SIZE)
that have higher number of bits. If the requested number of bits in
attrib_list is zero or GLX_DONT_CARE for a particular color
component, then the number of bits for that component is not considered.
Smaller GLX_BUFFER_SIZE.
Single buffered configuration (GLX_DOUBLEBUFFER being
False precedes a double buffered one.
Smaller GLX_AUX_BUFFERS.
Larger GLX_DEPTH_SIZE.
Smaller GLX_STENCIL_SIZE.
Larger total number of accumulation buffer color components
(GLX_ACCUM_RED_SIZE, GLX_ACCUM_GREEN_SIZE,
GLX_ACCUM_BLUE_SIZE, plus GLX_ACCUM_ALPHA_SIZE) that have
higher number of bits. If the requested number of bits in attrib_list is
zero or GLX_DONT_CARE for a particular color component, then the
number of bits for that component is not considered.
By GLX_X_VISUAL_TYPE where the precedence order is
GLX_TRUE_COLOR, GLX_DIRECT_COLOR, GLX_PSEUDO_COLOR,
GLX_STATIC_COLOR, GLX_GRAY_SCALE, GLX_STATIC_GRAY.
attrib_list =
{GLX_RENDER_TYPE, GLX_RGBA_BIT,
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.
glXChooseFBConfig is available only if the GLX version is 1.3 or greater.
If the GLX version is 1.1 or 1.0, the GL version must be 1.0. If the GLX version is 1.2, then the GL version must be 1.1. If the GLX version is 1.3, then the GL version must be 1.2.
glXGetFBConfigs and glXGetFBConfigAttrib can
be used to implement selection algorithms other than the generic
one implemented by glXChooseFBConfig. Call glXChooseFBConfig 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 glXGetFBConfigAttrib
to retrieve additional attributes for the frame buffer configurations and then
select between them.
GLX implementations are strongly discouraged,
but not proscribed,
from changing the selection algorithm used by glXChooseFBConfig.
Therefore, selections may change from release to release
of the client-side library.
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.
Copyright © 1991-2006 Silicon Graphics, Inc. This document is licensed under the SGI Free Software B License. For details, see http://oss.sgi.com/projects/FreeB/.