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NAME
glXChooseFBConfigSGIX - return a visual that matches speci-
fied attributes
C SPECIFICATION
GLXFBConfigSGIX* glXChooseFBConfigSGIX( Display *dpy,
int screen,
int *attribList,
int *nelements )
PARAMETERS
dpy Specifies the connection to the X server.
screen Specifies the screen number.
attribList Specifies a list of boolean attributes and
integer attribute/value pairs. The last attri-
bute must be None.
nelements Specifies the number of configs returned.
DESCRIPTION
A GLXFBConfigSGIX describes the format, type and size of the
color buffers and ancillary buffers for a GLXDrawable. When
the GLXDrawable is a window then the GLXFBConfigSGIX that
describes it has an associated X Visual; for GLXPixmaps and
GLXPbuffers there may or may not be an X Visual associated
with the GLXFBConfigSGIX.
Use glXChooseFBConfigSGIX to get GLXFBConfigSGIXs that match
a list of attributes or to get the list of GLXFBConfigSGIXs
that are available on the specified screen.
If attribList is NULL then glXChooseFBConfigSGIX returns an
array of GLXFBConfigSGIXs that are available on the speci-
fied screen; otherwise this call returns an array of
GLXFBConfigSGIXs that match the specified attributes. See
glXGetFBConfigAttribSGIX for a list of attributes. The
number of elements in the array is returned in nelements.
The attributes are matched in an attribute-specific manner,
as shown in Table 1 below. 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. To retrieve the GLXFBConfigSGIX, given an
i.d., use the GLX_FBCONFIG_ID_SGIX attribute. When
GLX_FBCONFIG_ID_SGIX is specified, all other attributes are
ignored, and only the GLXFBConfigSGIX with the given XID is
returned (NULL is returned if it does not exist).
If no conforming GLXFBConfigSGIX exists, or if an error
occurs then NULL is returned. If attribList is not NULL and
more than one GLXFBConfigSGIX is found, then a list of
GLXFBConfigSGIXs, sorted according to the "best" match cri-
teria, is returned. The exact sorting precedence order is
described later. Use XFree to free the memory returned by
glXChooseFBConfigSGIX.
If GLX_RENDER_TYPE_SGIX is in attribList then the value that
follows is a mask indicating which type of GLXContexts draw-
ables created with the corresponding GLXFBConfigSGIXs be
bound to. For example, if GLX_RGBA_BIT_SGIX |
GLX_COLOR_INDEX_BIT_SGIX is specified as the mask then
glXChooseFBConfigSGIX will search for GLXFBConfigSGIXs that
can be used to create drawables that can be bound to both
RGBA and color index rendering contexts. The default value
for GLX_RENDER_TYPE_SGIX is GLX_RGBA_BIT_SGIX.
The attribute GLX_DRAWABLE_TYPE_SGIX has as its value a mask
indicating the drawable types that can be created with the
corresponding GLXFBConfigSGIX (the config is said to ``sup-
port'' these drawable types). For example, a GLXFBConfigS-
GIX for which the value of GLX_DRAWABLE_TYPE_SGIX attribute
is GLX_WINDOW_BIT_SGIX | GLX_PIXMAP_BIT_SGIX can be used to
create both Windows and GLX pixmaps, while a config for
which this attribute value is GLX_WINDOW_BIT_SGIX can not be
used for creating GLX pixmaps. The default value for
GLX_DRAWABLE_TYPE_SGIX is GLX_WINDOW_BIT_SGIX.
If a GLXFBConfigSGIX supports Windows then it has an associ-
ated X Visual. The value of the GLX_X_VISUAL_TYPE_EXT attri-
bute specifies the type of X Visual. The possible values
are:
______________________________________
| GLX Token Name X Visual Type|
|_____________________________________|
| GLX_TRUE_COLOR_EXT TrueColor |
| GLX_DIRECT_COLOR_EXT DirectColor |
| GLX_PSEUDO_COLOR_EXT PseudoColor |
| GLX_STATIC_COLOR_EXT StaticColor |
| GLX_GRAY_SCALE_EXT GrayScale |
| GLX_STATIC_GRAY_EXT StaticGray |
|_____________________________________|
Note that RGBA rendering may be supported for any of the six
Visual types but color index rendering is only supported for
PseudoColor, StaticColor, GrayScale, and StaticGray visuals
(i.e., single-channel visuals). The GLX_X_VISUAL_TYPE_EXT
attribute is ignored if GLX_DRAWABLE_TYPE_SGIX is specified
in attribList and the mask that follows does not have
GLX_WINDOW_BIT_SGIX set.
GLX_X_RENDERABLE_SGIX is a boolean indicating whether X can
be used to render into a drawable created with the GLXFBCon-
figSGIX. This attribute is True if the GLXFBConfigSGIX sup-
ports Windows and/or GLX pixmaps.
All attributes in attribList, including boolean attributes,
are immediately followed by the corresponding desired value.
The list is terminated with None. If an attribute is not
specified in attribList then the default value (listed in
Table 1) is used (it 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 attri-
bute, so the attribute will not be checked.
_________________________________________________________________
| Attribute default sorting criteria|
|________________________________________________________________|_
| GLX_BUFFER_SIZE 0 smaller |
| GLX_LEVEL 0 exact |
| GLX_DOUBLEBUFFER don't care smaller |
| GLX_STEREO False exact |
| GLX_AUX_BUFFERS 0 smaller |
| GLX_RED_SIZE 0 larger |
| GLX_GREEN_SIZE 0 larger |
| GLX_BLUE_SIZE 0 larger |
| GLX_ALPHA_SIZE 0 larger |
| GLX_DEPTH_SIZE 0 larger |
| GLX_STENCIL_SIZE 0 larger |
| GLX_ACCUM_RED_SIZE 0 larger |
| GLX_ACCUM_GREEN_SIZE 0 larger |
| GLX_ACCUM_BLUE_SIZE 0 larger |
| GLX_ACCUM_ALPHA_SIZE 0 larger |
| GLX_SAMPLE_BUFFERS_SGIS 0 smaller |
| GLX_SAMPLES_SGIS 0 smaller |
| GLX_X_VISUAL_TYPE_EXT don't care exact |
| GLX_TRANSPARENT_TYPE_EXT don't care exact |
| GLX_NONE_EXT don't care exact |
| GLX_TRANSPARENT_INDEX_VALUE_EXT don't care exact |
| GLX_TRANSPARENT_RED_VALUE_EXT don't care exact |
| GLX_TRANSPARENT_GREEN_VALUE_EXT don't care exact |
| GLX_TRANSPARENT_BLUE_VALUE_EXT don't care exact |
| GLX_TRANSPARENT_ALPHA_VALUE_EXT don't care exact |
| GLX_VISUAL_CAVEAT_EXT don't care exact |
| GLX_DRAWABLE_TYPE_SGIX don't care exact |
| GLX_WINDOW_BIT_SGIX don't care mask |
| GLX_RENDER_TYPE_SGIX don't care mask |
| GLX_RGBA_BIT_SGIX don't care mask |
| GLX_X_RENDERABLE_SGIX don't care exact |
| GLX_FBCONFIG_ID_SGIX don't care exact |
| GLX_MAX_PBUFFER_WIDTH_SGIX 0 minimum |
| GLX_MAX_PBUFFER_HEIGHT_SGIX 0 minimum |
| GLX_MAX_PBUFFER_PIXELS_SGIX 0 minimum |
| GLX_OPTIMAL_PBUFFER_WIDTH_SGIX ignored ignored |
| GLX_OPTIMAL_PBUFFER_HEIGHT_SGIX ignored ignored |
|________________________________________________________________|
When more than one GLXFBConfigSGIX matches the specifica-
tion, 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_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 com-
ponents (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, GLX_STATIC_COLOR_EXT,
GLX_GRAY_SCALE_EXT, GLX_STATIC_GRAY_EXT
The definition of the sorting criteria is as follow:
smaller configs with attribute value that meets or exceeds
the specified value are returned, with precedence
given to smaller values (when a value is not expli-
citly requested, the default is implied);
larger when the value is requested explicitly, only con-
figs with a corresponding attribute value that meet
or exceed the specified value are returned, with
precedence given to larger values. When the value
is not requested explicitly behaves exactly like
the ``smaller'' criterion.
exact only configs whose corresponding attribute value
exactly matches the requested value are considered.
mask - only configs for which the set bits of
corresponding attribute include all the bits that
are set in the requested value are considered
(Additional bits might be set in the attribute).
NOTES
GLX_SGIX_fbconfig extension should be supported for this
function to be valid.
ERRORS
NULL is returned if an undefined GLX attribute is encoun-
tered in attribList. or dpy does not support GLX extension
or screen is invalid.
SEE ALSO
glXCreateContextWithConfigSGIX, glXCreateGLXPixmapWithCon-
figSGIX, glXGetVisualFromFBConfigSGIX, glXGetFBConfigFrom-
VisualSGIX, glXGetFBConfigAttribSGIX
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