Feedback on GL_EXT_texture_from_pixmap

[Deron Johnson]

I've reviewed the extension spec and I feel that this is definitely
heading in the right direction. Looking Glass definitely needs something
like this and I'm eager to try it out.

A couple of questions/concerns:

My biggest concern is about the statement that clients need to rebind
in order to get the latest pixmap contents for use by texturing. This
seems to be an accomodation for devices which copy on BindTexImage.
I'm mostly interested in getting excellent performance on devices which
don't do a copy. Forcing clients to go through an expensive rebind
transaction when it is not necessary for a device seems like an
unnecessary slow-down. Perhaps one way of addressing this is to
indicate to the user in the FBconfig whether the device is going to
do a copy so that the client can rebind or not.

Also, could someone please provide an example of how to switch
between rendering with one pixmap texture and then rendering
with another pixmap texture? I'm not exactly sure whether a
release is necessary in between; an example would clarify this.

Another question that I have is whether this extension will be
supported by other versions of Xorg besides Xgl? Or is Xgl eventually
going to be mainstreamed into Xorg? If so, in what time frame?

Finally, do we need a new request to tell the Composite extension
to round up its backing pixmap dimensions to the nearest power
of two? Otherwise we can use texture_from_pixmap on devices that
don't support rectangle_texture and/or non-power-of-two extension.