X Consortium Standard X Version 11, Release 6.4 BobScheifler X Consortium
Standard 19931994 X Consortium Version 2.0 X Consortium X Version 11, Release 7
Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the ?Software?), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
of the Software, and to permit persons to whom the Software is furnished to do
so, subject to the following conditions: The above copyright notice and this
permission notice shall be included in all copies or substantial portions of
the Software. THE SOFTWARE IS PROVIDED ?AS IS?, WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO
EVENT SHALL THE X CONSORTIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE. Except as contained in this notice, the name of the X Consortium
shall not be used in advertising or otherwise to promote the sale, use or other
dealings in this Software without prior written authorization from the X
Consortium. X Window System is a trademark of The Open Group. This extension
enables the use of protocol requests that exceed 262140 bytes in length. The
core protocol restricts the maximum length of a protocol request to 262140
bytes, in that it uses a 16-bit length field specifying the number of 4-byte
units in the request. This is a problem in the core protocol when joining large
numbers of lines (PolyLine) or arcs (PolyArc), since these requests cannot be
broken up into smaller requests without disturbing the rendering of the join
points. It is also much more of a problem for protocol extensions, such as the
PEX extension for 3D graphics and the XIE extension for imaging, that need to
send long data lists in output commands. This extension defines a mechanism for
extending the length field beyond 16 bits. If the normal 16-bit length field of
the protocol request is zero, then an additional 32-bit field containing the
actual length (in 4-byte units) is inserted into the request, immediately
following the 16-bit length field. For example, a normal PolyLine encoding is: 
PolyLine 1 65 opcode 1 coordinate-mode 0 Origin 1 Previous 2 3+n 4 DRAWABLE
drawable 4 GCONTEXT gc 4n LISTofPOINT points An extended-length PolyLine
encoding is: PolyLine 1 65 opcode 1 coordinate-mode 0 Origin 1 Previous 2 0
extended length flag 4 4+n request length 4 DRAWABLE drawable 4 GCONTEXT gc 4n
LISTofPOINT points Extended-length protocol encodings, once enabled, can be
used on all protocol requests, including all extensions. BigReqEnable =>
maximum-request-length: CARD32 This request enables extended-length protocol
requests for the requesting client. It also returns the maximum length of a
request, in 4-byte units, that can be used in extended-length protocol
requests. This value will always be greater than the maximum-request-length
returned in the connection setup information. No new events or errors are
defined by this extension. Please refer to the X11 Protocol Encoding document
as this document uses conventions established there. The name of this extension
is ?BIG-REQUESTS?. BigReqEnable 1 Card8 opcode 1 0 bigreq opcode 2 1 request
length => 1 1 Reply 1 unused 2 CARD16 sequence number 4 0 length 4 CARD32
maximum-request-length 2 0 unused It is desirable for core Xlib, and other
extensions, to use this extension internally when necessary. It is also
desirable to make the use of this extension as transparent as possible to the X
client. For example, if enabling of the extension were delayed until the first
time it was needed, an application that used XNextRequest to determine the
sequence number of a request would no longer get the correct sequence number.
As such, XOpenDisplay will determine if the extension is supported by the
server and, if it is, enable extended-length encodings. The core Xlib functions
XDrawLines, XDrawArcs, XFillPolygon, XChangeProperty, XSetClipRectangles, and
XSetRegion are required to use extended-length encodings when necessary, if
supported by the server. Use of extended-length encodings in other core Xlib
functions (XDrawPoints, XDrawRectangles, XDrawSegments. XFillArcs,
XFillRectangles, XPutImage is permitted but not required; an Xlib
implementation may choose to split the data across multiple smaller requests
instead. To permit clients to know what the maximum-request-length for
extended-length encodings is, the following function is added to Xlib: long
XExtendedMaxRequestSize Display *display Returns zero (0) if the specified
display does not support this extension, otherwise returns the
maximum-request-length (in 4-byte units) supported by the server through the
extended-length encoding. Clive Feather (IXI) originated the extended-length
encoding used in this extension proposal.
