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       XeviQueryExtension,  XeviQueryVersion,  XeviGetVisualInfo  - X Extended
       Visual Information functions


       #include <X11/extensions/XEVI.h>

       Bool XeviQueryExtension (Display *dpy);

       Bool XeviQueryVersion (Display *dpy,
           int *major_version_return,
           int *minor_version_return);

       int XeviGetVisualInfo (Display *dpy, VisualID *visual,
           int n_visual, ExtendedVisualInfo ** evi_return,
           int * n_info_return);


       The X11 Extended Visual Information extension (EVI) allows a client  to
       determine  information  about  core  X  visuals  beyond  what  the core
       protocol provides.

       The  EVI  application  programming  library  contains  the   interfaces
       described  below.   With the exception of XeviQueryExtension, if any of
       these routines are called with a display  that  does  not  support  the
       extension,   the   ExtensionErrorHandler   (which   can   be  set  with
       XSetExtensionErrorHandler   and   functions    the    same    way    as
       XSetErrorHandler) will be called and the function will then return.

       XeviQueryExtension  returns  True  if  the  Extended Visual Information
       extension is available on  the  given  display.   A  client  must  call
       XeviQueryExtension  before  calling  any other EVI function in order to
       negotiate a compatible protocol version; otherwise the client will  get
       undefined behavior (EVI may or may not work).

       XeviQueryVersion  returns  True if the request succeeded; the values of
       the major and minor  protocol  version  supported  by  the  server  are
       returned in major_version_return and minor_version_return.

       XeviGetVisualInfo  returns a list of ExtendedVisualInfo structures that
       describe visual information beyond that supported by the core protocol.
       This   includes  layer  information  relevant  for  systems  supporting
       overlays  and/or  underlay  planes,   and   information   that   allows
       applications  better  to  determine  the  level of hardware support for
       multiple colormaps. XeviGetVisualInfo returns Success if successful, or
       an X error otherwise.  If the argument visual is NULL, then information
       for all visuals of all screens is returned. Otherwise, it's  a  pointer
       to  a list of visuals for which extended visual information is desired.
       n_visual is the number of elements in  the  array  visual.   evi_return
       returns  a  pointer  to  a  list  of ExtendedVisualInfo. When done, the
       client should free the list using  XFree.   n_info_return  returns  the
       number of elements in the array evi_return.

       The ExtendedVisualInfo structure has the following fields:
            VisualID        core_visual_id
            int             screen
            int             level
            unsigned int    transparency_type
            unsigned int    transparency_value
            unsigned int    min_hw_colormaps
            unsigned int    max_hw_colormaps
            unsigned int    num_colormap_conflicts
            VisualID *      colormap_conflicts

       The  combination  of  core_visual_id and screen number uniquely specify
       the visual being described.

       level returns the level number for the visual, 0 for normal planes, > 0
       for overlays, < 0 for underlays.

       transparency_type  returns  the  type  of transparency supported by the
       visual. XEVI_TRANSPARENCY_NONE if  there  are  no  transparent  pixels,
       XEVI_TRANSPARENCY_PIXEL  if  the  visual  supports a transparent pixel,
       XEVI_TRANSPARENCY_MASK if the visual supports transparent plane(s).

       transparency_value  returns  the   pixel/plane   value   to   set   for
       transparency if transparency_type isn't XEVI_TRANSPARENCY_NONE.

       min_hw_colormaps  and  max_hw_colormaps  return the minimum and maximum
       number of hardware colormaps backing up the visual.

       num_colormap_conflicts   returns   the   number    of    elements    in
       colormap_conflicts.   This  array  returns  a  list of visuals that may
       cause conflicts in the use of the hardware colormap. For example, if  a
       12-bit  hardware colormap is overloaded to support 8-bit colormaps, the
       corresponding 8-bit visuals would conflict with the 12-bit visuals.


       XeviGetVisualInfo will return BadValue if passed an illegal visual  ID,
       BadAccess  if  the  X  server  does not respond, BadAlloc if there is a
       memory allocation failure.

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