Jon Leech wrote: > > On Thu, Sep 09, 1999 at 01:59:49PM -0600, Thomas Roell wrote: > > > > > Also note that the returned pointer is only valid when the current > > > context is the same as the context to which the GL was connected when > > > the pointer was obtained. > > > > What is the rationale for this constraint ? > > > > Would this imply what for every context that is created a seperate > > pointer had to be queried ? > > Mostly the rationale is support for heterogeneous multihead. > Extensions not in libGL will give back function pointers into the client > driver. It's unlikely that an implementation of an extension in one > card's driver would work for a different card. If there's an easy way > for the app to determine that two contexts both referred to the same > head, we could relax the constraint to that extent. I would propose that the driver function pointer not be directly handed back to the application. The libGL dispatcher which implements GetProcAddress could hand back either a pointer to a dynamic dispatch table entry (i.e. the application would dereference the pointer before calling the function), or a pointer to an assembly stub that jumps to the correct code depending on the current context. I'll admit that neither of these options seems very elegant, but I really dislike the idea of making the returned function pointer context-specific. I'll do a little more homework, and come up with a better, more concrete proposal. Cheers!
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