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.\" $XFree86: xc/doc/man/Xext/Xevi.man,v 1.2 2001/01/27 18:20:19 dawes Exp $
.\"
.TH XEVI __libmansuffix__ __xorgversion__ "X FUNCTIONS"
.SH NAME
XeviQueryExtension, XeviQueryVersion, XeviGetVisualInfo - X Extended Visual Information functions
.SH SYNOPSIS
\&#include <X11/extensions/XEVI.h>

Bool
XeviQueryExtension (Display *dpy);
.LP
Bool
XeviQueryVersion (Display *dpy, 
    int *major_version_return,
    int *minor_version_return);
.LP
int
XeviGetVisualInfo (Display *dpy, VisualID *visual,
    int n_visual, ExtendedVisualInfo ** evi_return,
    int * n_info_return);
.fi
.SH 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
.BR XeviQueryExtension,
if any of these routines are
called with a display that does not support the extension, the
ExtensionErrorHandler (which can be set with
.BR XSetExtensionErrorHandler
and functions the same way as
.BR XSetErrorHandler )
will be called and the function will then return.
.PP
.BR XeviQueryExtension
returns 
.BR True
if the Extended Visual Information extension is available on the given display.
A client must call
.BR 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).
.PP
.BR XeviQueryVersion
returns
.BR True
if the request succeeded; the values of the major and minor protocol
version supported by the server are returned in
.I major_version_return
and
.I minor_version_return.
.PP
.BR 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 
.BR Success 
if successful, or an X error otherwise.
If the argument
.I 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.
.I n_visual
is the number of elements in the array visual.
.I evi_return
returns a pointer to a list of ExtendedVisualInfo. When done, the client
should free the list using XFree\.
.I n_info_return
returns the number of elements in the array evi_return.
.LP
The
.BR ExtendedVisualInfo
structure has the following fields:
.in +.5i
.nf
.ta 1.6i
VisualID	\fIcore_visual_id\fR    
int 	\fIscreen\fR	    	
int 	\fIlevel\fR 	    	
unsigned int	\fItransparency_type\fR 
unsigned int	\fItransparency_value\fR 
unsigned int	\fImin_hw_colormaps\fR
unsigned int	\fImax_hw_colormaps\fR
unsigned int	\fInum_colormap_conflicts\fR
VisualID *  	\fIcolormap_conflicts\fR
.fi
.LP
The combination of 
.I core_visual_id
and
.I screen
number uniquely specify the visual being described.
.LP
.I level
returns the level number for the visual, 0 for normal planes, > 0 for
overlays, < 0 for underlays.
.LP
.I
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).
.LP
.I transparency_value
returns the pixel/plane value to set for transparency if transparency_type isn't
XEVI_TRANSPARENCY_NONE.
.LP
.I min_hw_colormaps
and
.I max_hw_colormaps
return the minimum and maximum number of hardware colormaps backing up the
visual. 
.LP
.I num_colormap_conflicts
returns the number of elements in 
.I 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.

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