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\s+2\fBVEXlib\fP\s-2
\s+1\fBVideo Extension to X Client Library\fP\s-1
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\s-1Scott Hennes
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Tektronix, Inc.
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X Window System is a trademark of M.I.T.
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Copyright \(co 1990
Tektronix, Inc.
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Permission to use, copy, modify, and distribute this document
for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and
that both that copyright notice and this permission
notice are retained, and that the name of Tektronix not be used
in advertising or publicity pertaining to this document without
specific, written prior permission.
Tektronix makes no representations about the suitability of this
document or the protocol defined in this document for any purpose.
It is provided ``as is'' without express or implied warranty.
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\s+1\fBSection 1\fP\s-1

\s+1\fBIntroduction\fP\s-1
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Section 1: Introduction
.XE
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This document describes
.PN VEXlib ,
the client library for the Video Extension to X.
It assumes the reader is familiar with Xlib and with the VEX Protocol.
This initial draft does not attempt to duplicate much of the VEX Protocol
document and the reader must rely on that document to understand the
semantics of many VEXlib routines and data structures.
.LP
.PN VEXlib 
does not have an explicit initialization routine.  Each routine will attempt
to initialize the library if it is not already initialized.  A client
can determine whether or not the VEX extension is available in a server
by using the core routine,
.PN XQueryExtension.
This routine must also be used to obtain the VEX event and error base numbers.
The name of the extension is "VEX".
.LP
Library initialization does an implicit call to
.PN XVEXQueryVideo .
Client access to information sent in the server reply is through these
routines:
.PN XVEXOverlapsOfScreen ,
.PN XVEXTimestamps ,
.PN XVEXGetVisualInfo ,
.PN XVEXGetVins ,
.PN XVEXGetVouts ,
.PN XVEXGetVdevs ,
and
.PN XVEXGetConnectState
All information returned by these routines remains valid for the life of
the connection except for
.PN XVEXTimestamps ,
.PN XVEXGetConnectState ,
and
.PN XVEXGetVdevs.
Timestamp values change when the library receives VEXConnectivity events
and
.PN XVEXQueryVideo
replies.
Device connection information should be considered out of date when
the client receives a VEXConnectivity event.  Valid data may be obtained by
calling
.PN XVEXGetConnectState 
after the client receives a VEXConnectivity event whose count field is zero.
Video Device information should be considered out of date when
the client receives a VEXChange event.  Valid data may be obtained by
calling
.PN XVEXQueryVideo
and then
.PN XVEXGetVdevs.
.bp
