Extended Visual Information Extension
X Project Team Standard
Peter Daifuku
Silicon Graphics, Inc.
X Version 11, Release 7.7
Version 1.0
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Table of Contents
1. Introduction
2. Goals
3. Requests
4. Events and Errors
5. Changes to existing protocol.
6. Encoding
7. C Language Binding
Chapter 1. Introduction
EVI (Extended Visual Information extension) allows a client to determine
information about core X visuals beyond what the core protocol provides.
Chapter 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 additional 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.
Chapter 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_version indicate what
version of the protocol the client wants the server to implement. The server
version numbers returned indicate the protocol this extension actually
supports. 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 revisions 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-compatible 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).
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 transparent pixel, 2 for transparent
mask.
• transparency_value: value to get transparent pixel if transparency
supported.
• min_hw_colormaps: minimum number of hardware colormaps backing up the
visual.
• max_hw_colormaps: maximum number of hardware colormaps backing up the
visual.
(architectures with static colormap allocation/reallocation would have min
= max)
• num_colormap_conflicts: number of elements in colormap_conflicts.
• colormap_conflicts: list of visuals that may conflict with this one. For
example, if a 12-bit colormap is overloaded to support 8-bit visuals, the
8-bit visuals would conflict with the 12-bit visuals.
Chapter 4. Events and Errors
No new events or errors are defined by this extension.
Chapter 5. Changes to existing protocol.
None.
Chapter 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 LISTofVISUALINFO items
VISUALINFO
4 VisualID core_visual_id
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
Chapter 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 protocol 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/extensions/XEVI.h>.
Bool XeviQueryVersion(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_version_return to the
major and minor EVI protocol version supported 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.
int XeviGetVisualInfo(Display *display, VisualID *visual, int n_visual,
ExtendedVisualInfo **evi_return, int *n_info_return);
display Specifies the connection to the X server.
If NULL, then information for all visuals of all screens is
visual returned. Otherwise, a pointer to a list of visuals for which
extended visual information is desired.
n_visual If 0, then information for all visuals of all screens is
returned. Otherwise, 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 list of ExtendedVisualInfo.
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.
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