NAME
XdbeGetVisualInfo - Get dbe Visual Informations
SYNOPSIS
#include <X11/extensions/Xdbe.h>
XdbeScreenVisualInfo *XdbeGetVisualInfo(
Display *dpy,
Drawable *screen_specifiers,
int *num_screens)
DESCRIPTION
This function returns information about which visuals support double buffering.
The argument
num_screens specifies how many elements there are in the
screen_specifiers list. Each drawable in
screen_specifiers
designates a screen for which the supported visuals are being requested. If
num_screens is zero, information for all screens is requested. In this
case, upon return from this function,
num_screens will be set to the
number of screens that were found. If an error occurs, this function returns
NULL, else it returns a pointer to a list of
XdbeScreenVisualInfo
structures of length
num_screens. The nth element in the returned list
corresponds to the nth drawable in the
screen_specifiers list, unless
num_screens was passed in with the value zero, in which case the nth
element in the returned list corresponds to the nth screen of the server,
starting with screen zero. The
XdbeScreenVisualInfo structure has the
following fields:
int count
XdbeVisualInfo *visinfo
count specifies the number of items in
visinfo. visinfo
specifies a list of visuals, depths, and performance hints for this screen.
The
XdbeVisualInfo structure has the following fields:
VisualID visual
int depth
int perflevel
visual specifies one visual ID that supports double-buffering.
depth specifies the depth of the visual.
perflevel is a
performance hint.
The only operation defined on a
perflevel is comparison to a
perflevel of another visual on the same screen. The visual having the
higher
perflevel is likely to have better double-buffering graphics
performance than the visual having the lower
perflevel. Nothing can be
deduced from the following: the magnitude of the difference of two
perflevels, a
perflevel value in isolation, or comparing
perflevels from different servers.
ERRORS
- BadDrawable
- One or more values passed in screen_specifiers is
not a valid drawable.
SEE ALSO
DBE,
XdbeAllocateBackBufferName(), XdbeBeginIdiom(),
XdbeDeallocateBackBufferName(), XdbeEndIdiom(),
XdbeFreeVisualInfo(), XdbeGetBackBufferAttributes(),
XdbeQueryExtension(), XdbeSwapBuffers().