GLXCHOOSEVISUAL() GLXCHOOSEVISUAL()
NAME
glXChooseVisual - return a visual that matches specified attributes
C SPECIFICATION
XVisualInfo* glXChooseVisual( Display *dpy,
int screen,
int *attribList )
delim $$
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 attribute must be None.
DESCRIPTION
glXChooseVisual returns a pointer to an XVisualInfo structure describing the visual that best meets a minimum specification. The boolean
GLX attributes of the visual that is returned will match the specified values, and the integer GLX attributes will meet or exceed the spec-
ified minimum values. If all other attributes are equivalent, then TrueColor and PseudoColor visuals have priority over DirectColor and
StaticColor visuals, respectively. If no conforming visual exists, NULL is returned. To free the data returned by this function, use
XFree.
All boolean GLX attributes default to False except GLX_USE_GL, which defaults to True. All integer GLX attributes default to zero.
Default specifications are superseded by attributes included in attribList. Boolean attributes included in attribList are understood to be
True. Integer attributes and enumerated type attributes are followed immediately by the corresponding desired or minimum value. The list
must be terminated with None.
The interpretations of the various GLX visual attributes are as follows:
GLX_USE_GL Ignored. Only visuals that can be rendered with GLX are considered.
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_RGBA is asserted.
GLX_LEVEL Must be followed by an integer buffer-level specification. This specification is honored exactly. Buffer level zero
corresponds to the main 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.
GLX_RGBA If present, only TrueColor and DirectColor visuals are considered. Otherwise, only PseudoColor and StaticColor visu-
als are considered.
GLX_DOUBLEBUFFER If present, only double-buffered visuals are considered. Otherwise, only single-buffered visuals are considered.
GLX_STEREO If present, only stereo visuals are considered. Otherwise, only monoscopic visuals are considered.
GLX_AUX_BUFFERS Must be followed by a nonnegative integer that indicates the desired number of auxiliary buffers. Visuals with the
smallest number of auxiliary buffers that meets or exceeds the specified number are preferred.
GLX_RED_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, the smallest available red buf-
fer is preferred. Otherwise, the largest available red buffer of at least the minimum size is preferred.
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 at least the minimum size is preferred.
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.
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.
GLX_DEPTH_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, visuals with no depth buffer
are preferred. Otherwise, the largest available depth buffer of at least the minimum size is preferred.
GLX_STENCIL_SIZE Must be followed by a nonnegative integer that indicates the desired number of stencil bitplanes. The smallest sten-
cil buffer of at least the specified size is preferred. If the desired value is zero, visuals with no stencil buffer
are preferred.
GLX_ACCUM_RED_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, visuals with no red accumula-
tion buffer are preferred. Otherwise, the largest possible red accumulation buffer of at least the minimum size is
preferred.
GLX_ACCUM_GREEN_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, visuals with no green accumula-
tion buffer are preferred. Otherwise, the largest possible green accumulation buffer of at least the minimum size is
preferred.
GLX_ACCUM_BLUE_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, visuals with no blue accumula-
tion buffer are preferred. Otherwise, the largest possible blue accumulation buffer of at least the minimum size is
preferred.
GLX_ACCUM_ALPHA_SIZE Must be followed by a nonnegative minimum size specification. If this value is zero, visuals with no alpha accumula-
tion buffer are preferred. Otherwise, the largest possible alpha accumulation buffer of at least the minimum size is
preferred.
EXAMPLES
attribList =
{GLX_RGBA, GLX_RED_SIZE, 4, GLX_GREEN_SIZE, 4, GLX_BLUE_SIZE, 4, None};
Specifies a single-buffered RGB visual 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 color index mode, double-buffering, or
stereo display. It may or may not have one or more auxiliary color buffers, a depth buffer, a stencil buffer, or an accumulation buffer.
NOTES
XVisualInfo is defined in Xutil.h. It is a structure that includes visual, visualID, screen, and depth elements.
glXChooseVisual is implemented as a client-side utility using only XGetVisualInfo and glXGetConfig. Calls to these two routines can be
used to implement selection algorithms other than the generic one implemented by glXChooseVisual.
GLX implementers are strongly discouraged, but not proscribed, from changing the selection algorithm used by glXChooseVisual. Therefore,
selections may change from release to release of the client-side library.
There is no direct filter for picking only visuals that support GLXPixmaps. GLXPixmaps are supported for visuals whose GLX_BUFFER_SIZE is
one of the pixmap depths supported by the X server.
ERRORS
NULL is returned if an undefined GLX attribute is encountered in attribList.
SEE ALSO
glXCreateContext, glXGetConfig
GLXCHOOSEVISUAL()