Updates to GLX_EXT_texture_from_pixmap

Deron Johnson Deron.Johnson at Sun.COM
Fri Mar 31 10:43:48 PST 2006

James Jones wrote On 03/30/06 12:30,:
> I still would
> like to make this [drawable locking] part of a separate extension though.  As I've 
> mentioned before, people may need it in cases where 
> texture_from_pixmap isn't applicable.  It also seems like something 
> better implemented mostly in core X, with some support from 
> drivers, rather than entirely in drivers as part of 
> texture_from_pixmap.

I am concerned that LockDrawables will introduce unnecessary overhead in
the tfp bind process. Since the composite manager should not access the
contents of the drawable until it is known to be locked, and
LockDrawables is an X request, it is necessary that LockDrawables be a
synchronous request, that is to say, it requires a round trip to the
server. My understanding of tfp bind, on the other hand, is that it is a
direct-access opengl routine which bypasses the X protocol and requires
less overhead.

Having a separate LockDrawables extension for other uses is okay, but I
don't think we should rely on it for tfp bind. I recommend that tfp
bind/unbind include their own locking semantics with no need to make
separate locking calls.

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