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().