[ Previous | Next | Contents | Glossary | Home | Search ]
OpenGL 1.1 for AIX: Reference Manual
glXChooseVisual Subroutine
Purpose
Returns a visual matching the attributes specified.
Library
OpenGL C bindings library: libGL.a
XVisualInfo Structure
XVisualInfo* glXChooseVisual(Display *dpy,
screen,
int *AttributeList)
int
Description
The glXChooseVisual subroutine returns a pointer to an XVisualInfo structure that describes the visual best
meeting a minimum specification. The Boolean GLX attributes of the returned visual match the specified values;
the integer GLX attributes meet or exceed the specified 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
the XFree subroutine.
All Boolean GLX attributes default to False, except for GLX_USE_GL. The GLX_USE_GL attribute defaults
to True. All integer GLX attributes default to 0 (zero). Default specifications are superseded by attributes
included in AttributeList specified. Boolean attributes included in the specified AttributeList are understood to be
True. Integer attributes are followed immediately by the corresponding specified (or minimum) value.
The AttributeList must be terminated with the Noneattribute.
The GLX visual attributes are defined as follows:
Attribute
GLX_USE_GL
GLX_BUFFER_SIZE
GLX_LEVEL
GLX_RGBA
GLX_DOUBLEBUFFER
Definition
This attribute is ignored. Only visuals that can be rendered
with GLX are considered.
This attribute must be followed by a nonnegative integer
indicating the desired color index buffer size. The smallest
index buffer of at least the specified size is preferred. This
attribute is ignored if the GLX_RGBAattribute is asserted.
This attribute must be followed by an integer buffer-level
specification. This specification is honored exactly. Buffer
level 0 (zero) corresponds to the default frame buffer of the
display. Buffer level 1 (one) is the first overlay frame
buffer, level 2 the second overlay frame buffer, and so on.
Negative buffer levels correspond to underlay frame
buffers.
This attribute specifies that if present, only TrueColor and
DirectColor visuals are considered. Otherwise, only
PseudoColor and StaticColor visuals are considered.
This attribute specifies that only double-buffered visuals are
GLX_STEREO
GLX_AUX_BUFFERS
GLX_RED_SIZE
GLX_GREEN_SIZE
GLX_BLUE_SIZE
GLX_ALPHA_SIZE
GLX_DEPTH_SIZE
GLX_STENCIL_SIZE
GLX_ACCUM_RED_SIZE
GLX_ACCUM_GREEN_SIZE
GLX_ACCUM_BLUE_SIZE
GLX_ACCUM_ALPHA_SIZE
GLX_TRANSPARENT_TYPE_EXT
considered. Otherwise, only single-buffered visuals are
considered.
This attribute specifies that only stereo visuals are to be
considered. Otherwise, only monoscopic visuals are
considered.
This attribute must be followed by a nonnegative integer
indicating the desired number of auxiliary buffers
(preferably visuals with the smallest number of auxiliary
buffers that meets or exceeds the specified number).
This attribute must be followed by a nonnegative minimum
size specification. If 0, the smallest available red buffer is
preferred. Otherwise, the largest available red buffer of at
least the minimum size is preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, the smallest available green buffer is
preferred. Otherwise, the largest available green buffer of at
least the minimum size is preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, the smallest available blue buffer is
preferred. Otherwise, the largest available blue buffer of at
least the minimum size is preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, the smallest available alpha buffer is
preferred. Otherwise, the largest available alpha buffer of at
least the minimum size is preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, visuals with no depth buffer are
preferred. Otherwise, the largest available depth buffer of at
least the minimum size is preferred.
This attribute must be followed by a nonnegative integer
indicating the desired number of stencil bitplanes. The
smallest stencil buffer of at least the specified size is
preferred. If the desired value is 0, visuals with no stencil
buffer are preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, visuals with no red accumulation
buffer are preferred. Otherwise, the largest possible red
accumulation buffer of at least the minimum size is
preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, visuals with no green accumulation
buffer are preferred. Otherwise, the largest possible green
accumulation buffer of at least the minimum size is
preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, visuals with no blue accumulation
buffer are preferred. Otherwise, the largest possible blue
accumulation buffer of at least the minimum size is
preferred.
This attribute must be followed by a nonnegative minimum
size specification. If 0, visuals with no alpha accumulation
buffer are preferred. Otherwise, the largest possible alpha
accumulation buffer of at least the minimum size is
preferred.
This attribute defines the type of transparency (if any) in the
visual. It must be one of the following:
GLX_NONE_EXT
no transparency
GLX_TRANSPARENT_INDEX_EXT
PseudoColor transparency
GLX_TRANSPARENT_RGB_EXT
RGB Transparency
GLX_TRANSPARENT_RED_VALUE_EXT
This attribute must be followed by the red value of the RGB
transparent pixel.
GLX_TRANSPARENT_BLUE_VALUE_EXT This attribute must be followed by the blue value of the
RGB transparent pixel.
GLX_TRANSPARENT_GREEN_VALUE_EXT This attribute must be followed by the green value of the
RGB transparent pixel.
GLX_TRANSPARENT_ALPHA_VALUE_EXT This attribute must be followed by the alpha value of the
RGB transparent pixel.
GLX_TRANSPARENT_INDEX_VALUE_EXT This attribute must be followed by the INDEX transparent
pixel.
GLX_X_VISUAL_TYPE_EXT
This attribute must be followed by the visual type:
GLX_TRUE_COLOR_EXT
TrueColor colormap
GLX_DIRECT_COLOR_EXT
DirectColor colormap
GLX_PSEUDO_COLOR_EXT
PseudoColor colormap
GLX_STATIC_COLOR_EXT
StaticColor colormap
GLX_GRAY_SCALE_EXT
Grayscale colormap
GLX_STATIC_GRAY_EXT
StaticGray colormap
GLX_VISUAL_CAVEAT_EXT
This attribute must be followed by:
0 or GLX_NONE_EXT
no rating
GLX_SLOW_VISUAL_EXT
not an optimal visual
Parameters
dpy
Specifies the connection to the X server.
screen
Specifies the screen number.
AttributeList Specifies a list of Boolean attributes and integer attribute/value pairs. The last attribute must
be None.
Notes
XVisualInfo is defined in the Xutil.h file. 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 GLX pixmaps. GLX pixmaps are supported for
visuals whose GLX_BUFFER_SIZE is one of the pixmap depths supported by the X server.
Return Values
Null Indicates that an undefined GLX attribute is encountered in the specified AttributeList.
Examples
The following example specifies a single-buffered RGB visual in the normal frame buffer (not an overlay or
underlay). The returned visual supports at least 4 bits each of red, green, and blue and possibly no alpha bits. It
does not support color-index mode, double-buffering, or stereo display. The code shown in the example may or
may not have one or more auxiliary color buffers, a depth buffer, a stencil buffer, or an accumulation buffer.
AttributeList = {GLX_RGBA, GLX_RED_SIZE, 4, GLX_GREEN_SIZE, 4,
GLX_BLUE_SIZE, 4, None};
GLX implementers are strongly discouraged from changing the selection algorithm used by
the glXChooseVisual subroutine. Selections may change from between releases of the client-side library.
Files
/usr/include/GL/gl.h Contains C language constraints, variable type definitions, and ANSI function prototypes
for OpenGL.
Related Information
The glXCreateContext subroutine, glXGetConfig subroutine.
OpenGL in the AIXwindows (GLX) Environment.
OpenGL Overview.
[ Previous | Next | Contents | Glossary | Home | Search ]