XdbeGetVisualInfo

XdbeGetVisualInfo(3X11)		 X FUNCTIONS	      XdbeGetVisualInfo(3X11)



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  corre-
       sponds  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  perfor-
       mance  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(), XdbeDeallocate-
       BackBufferName(), XdbeEndIdiom(),  XdbeFreeVisualInfo(),	 XdbeGetBack-
       BufferAttributes(), XdbeQueryExtension(), XdbeSwapBuffers().




						      XdbeGetVisualInfo(3X11)