
















	   Extended Visual Information Extension



			Version 1.0
		  X Project Team Standard
		 X Version 11, Release 6.8






		       Peter Daifuku
		   Silicon Graphics, Inc.









Copyright (C) 1986-1997   The Open Group    All Rights
Reserved

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1.  Introduction

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

2.  Goals

As the X Window System has evolved, it has become clear that
the information returned by the core X protocol regarding
Visuals is often insufficient for a client to determine
which is the most appropriate visual for its needs. This
extension allows clients to query the X server for addi-
tional visual information, specifically as regards colormaps
and framebuffer levels.

This extension is meant to address the needs of pure X
clients only. It is specifically and purposefully not
designed to address the needs of X extensions. Extensions
that have an impact on visual information should provide
their own mechanisms for delivering that information. For
example, the Double Buffering Extension (DBE) provides its
own mechanism for determining which visuals support double-
buffering.

3.  Requests

__
|    GetVersion

     client_major_version: CARD8
     client_minor_version: CARD8

  =>

     server_major_version: CARD8
     server_minor_version: CARD8
|__

If supplied, the client_major_version and client_minor_ver-
sion indicate what version of the protocol the client wants
the server to implement.  The server version numbers
returned indicate the protocol this extension actually sup-
ports. This might not equal the version sent by the client.
An implementation can (but need not) support more than one
version simultaneously. The server_major_version and the
server_minor_version are a mechanism to support future revi-
sions of the EVI protocol that may be necessary. In general,
the major version would increment for incompatible changes,
and the minor version would increment for small upward-com-
patible changes. Servers that support the protocol defined
in this document will return a server_major_version of one
(1), and a server_minor_version of zero (0).




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	  X11 Extended Visual Information extension

__
|    GetVisualInfo

     visual_list: LISTofVISUALID

  =>

     per_visual_info: LISTofVISUALINFO

where:

VISUALINFO:   [core_visual_id: VISUALID
	       screen: CARD8
	       level: INT8
	       transparency_type: CARD8
	       unused: CARD8
	       transparency_value: CARD32
	       min_hw_colormaps: CARD8
	       max_hw_colormaps: CARD8
	       num_colormap_conflicts: CARD16
	       colormap_conflicts: LISTofVISUALID]
|__



	 - level is 0 for normal planes, > 0 for overlays, <
     0 for underlays.
	 - transparency_type is 0 for none, 1 for transpar-
     ent pixel, 2 for
	   transparent mask.
	 - transparency_value: value to get transparent
     pixel if transparency
	 supported.
	 - min_hw_colormaps: minimum number of hardware col-
     ormaps backing up the visual.
	 - max_hw_colormaps: maximum number of hardware col-
     ormaps backing up the visual.
	 (architectures with static colormap alloca-
     tion/reallocation would have min = max)
	 - num_colormap_conflicts: number of elements in
     colormap_conflicts.
	 - colormap_conflicts: list of visuals that may con-
     flict with this one. For
	 example, if a 12-bit colormap is overloaded to sup-
     port 8-bit visuals, the
	 8-bit visuals would conflict with the 12-bit visu-
     als.


4.  Events and Errors

No new events or errors are defined by this extension.






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	  X11 Extended Visual Information extension


5.  Changes to existing protocol.

None.


6.  Encoding

The name of this extension is "Extended-Visual-Information".

The conventions used here are the same as those for the core
X11 Protocol Encoding.


GetVersion
  1  CARD8		 opcode
  1  0			 EVI opcode
  2  2			 request length
  2  CARD16		 client_major_version
  2  CARD16		 client_minor_version


 =>
  1  1			 reply
  1			 unused
  2  CARD16		 sequence number
  4  0			 length
  2  CARD16		 server_major_version
  2  CARD16		 server_minor_version
  20			 unused



GetVisualInfo
  1  CARD8		 opcode
  1  1			 EVI opcode
  2  2+n		 request length
  4  CARD32		 n_visual
  4n CARD32		 visual_ids


 =>
  1  1			 reply
  1			 unused
  2  CARD16		 sequence number
  4  n			 length
  4  CARD32		 n_info
  4  CARD32		 n_conflicts
  16			 unused
  16n	       LISTofVISUALINFOitems



  VISUALINFO
  4  VisualID		 core_visual_id



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	  X11 Extended Visual Information extension


  1  INT8		 screen
  1  INT8		 level
  1  CARD8		 transparency_type
  1  CARD8		 unused
  4  CARD32		 transparency_value
  1  CARD8		 min_hw_colormaps
  1  CARD8		 max_hw_colormaps
  2  CARD16		 num_colormap_conflicts



7.  C Language Binding

The C functions provide direct access to the protocol and
add no additional semantics.  For complete details on the
effects of these functions, refer to the appropriate proto-
col request, which can be derived by deleting Xevi at the
start of the function. All functions that have return type
Status will return nonzero for success and zero for failure.

The include file for this extension is: <X11/exten-
sions/XEVI.h>.

__
|
BoolXeviQueryVersion(
    Display *display,
    int *major_version_return,
    int *minor_version_return)

|__


display   Specifies the connection to the X server.

major_version_return
	  Returns the major version supported by the server.

minor_version_return
	  Returns the minor version supported by the server.

XeviQueryVersion sets major_version_return and minor_ver-
sion_return to the major and minor EVI protocol version sup-
ported by the server.  If the EVI library is compatible with
the version returned by the server, it returns nonzero.  If
dpy does not support the EVI extension, or if there was an
error during communication with the server, or if the server
and library protocol versions are incompatible, it returns
zero.  No other Xevi functions may be called before this
function. If a client violates this rule, the effects of all
subsequent Xevi calls that it makes are undefined.

To get the extended information for any subset of visuals
use XeviGetVisualInfo.



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	  X11 Extended Visual Information extension

__
|
intXeviGetVisualInfo(
    Display *display,
    VisualID *visual,
    int n_visual,
    ExtendedVisualInfo **evi_return,
    int *n_info_return)

|__


display   Specifies the connection to the X server.

visual	  If NULL, then information for all visuals of all
	  screens is returned. Otherwise, a pointer to a
	  list of visuals for which extended visual informa-
	  tion is desired.

n_visual  If 0, then information for all visuals of all
	  screens is returned. Otherwise, the number of ele-
	  ments 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 list of
	  ExtendedVisualInfo.

XeviGetVisualInfo returns a list of ExtendedVisualInfo
structures that describe visual information beyond that sup-
ported 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 col-
ormaps. XeviGetVisualInfo returns Success if successful, or
an X error otherwise.


















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