XeviQueryExtension(3X11)

     NAME
          XeviQueryExtension, XeviQueryVersion, XeviGetVisualInfo - X
          Extended Visual Information functions

     SYNOPSIS
          #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);

     DESCRIPTION
          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.


     ERRORS
          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.