EGL_MESA_screen_surface version 4

Jon Smirl jonsmirl at
Wed Mar 23 19:29:15 PST 2005

On Wed, 23 Mar 2005 19:24:59 -0700, Brian Paul
<brian.paul at> wrote:
> I think that assumption is a bit optimistic.  Top-level windows might
> very well be stored as textures (perhaps stored in a format that can't
> be directly scanned out), or pbuffers, or FB objects.  I wonder if
> Dave Reveman has a preference?

The be more specific XGL needs this, I think it is addressed by
framebuffer objects.

1) apps think they are rendering to a normal window/screen like the do
in GL currently. The window is in offscreen memory and can be direct
rendered to.

2) Now the X server runs. It wants to take all of the buffers the apps
have been drawing into and treat them like textures. These textures
are then composed into the final screen.

So you need two things:
1) the app thinks it is rendering to a window/screen, but the buffer
is in off-screen memory. The buffer needs to support accelerated

2) The X sever needs to create/manage these buffers and pass them out
to the apps. It also needs to use them as textures. I'm not sure if
the current GL spec has a scheme for passing these buffers between
apps. You don't really want to have a completely shared context in
this case.

Jon Smirl
jonsmirl at

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