XXX - Not complete.

Name

    SGIX_wait_group

Name Strings

    GLX_SGIX_wait_group

Version

    $Date: 1997/04/17 04:46:55 $ $Revision: 1.1 $

Number

    XXX

Dependencies

    none

Overview

    This extension provides the capability to synchronize drawing from two
    separate GLX Contexts.  A wait group is created, and GLX Contexts are 
    added as members to the wait group.  It will then be possible to 
    specify that no member will be able to continue to render until all the
    outstanding OpenGL commands from each of the members have been completed.

    This extension sets conditions that must be met before a set of OpenGL
    contexts can continue drawing.  This extension is primarily useful for
    coordinating operations in an environment where more than one OpenGL
    context may render simultaneously.

Dependencies

    none

Issues

    * Do we need a query to ask whether a context is in a group?
    * Do we need to support having contexts in multiple wait groups?

New Procedures and Functions

    void JoinWaitGroupSGIX(Display *dpy, 
			   GLXContext context, 
			   GLXContext member);

    void WaitGroupSGIX(Display *dpy, 
			   GLXContext context);

New Tokens

    none

Additions to the GLX Specification

    Add to the end of section 3.2.5, Synchronization Primitives:

    JoinWaitGroupSGIX adds <context> to the wait group containing <member> as 
    a member.  If <context> is already a member of a different group, it is 
    implicitly removed from that group first.  If <member> is None, <context> 
    is removed from the wait group that it belongs to, if any.

    A wait group is referenced by naming any context in the group; there is no
    other way to refer to a group.

    When a context is destroyed, it is removed from any wait group of
    which it is a member.

    WaitGroupSGIX causes <context> to wait until all the other member 
    contexts of the wait group have also called WaitGroupSGIX. 

    The following must be satisfied before a WaitGroupSGIX command 
    can complete:

	1. All contexts in the wait group must have issued a 
	   WaitGroupSGIX command

    OpenGL rendering commands issued by all of the member contexts
    in the wait group will complete before any of the member contexts
    can further affect the framebuffer.

    A wait group exists until the last remaining context leaves the group.

    JoinWaitGroupSGIX and WaitGroupSGIX are part of the X stream.

Errors

    JoinWaitGroupSGIX generates GLXBadContext if <context> is an invalid 
    GLX context, or if <member> is an invalid GLX context.

    WaitGroupSGIX generates GLXBadContext if <context> is an invalid
    GLX context.

New State

    Get Value				Get Command	Type	Value	Attrib
    ---------				-----------	----	-------	------
    <whether context is in a wait group>	??		B	False

New Implementation Dependent State

    None