Xgl/Xegl future?

Adam Jackson ajax at nwnk.net
Mon Aug 22 12:03:49 PDT 2005

On Monday 22 August 2005 12:37, Matthias Hopf wrote:
> On Aug 21, 05 20:53:34 -0400, Adam Jackson wrote:
> > If you are direct rendering, then you need some cooperation over the
> > protocol: the server needs to tell the client to render offscreen rather
> > than to the front buffer, and the client needs to inform the server of
> > the offscreen buffer's location.  The only challenge is deciding what
> > channel to do that over, SAREA or DRI protocol or maybe GLX protocol +
> > DRM interface.
> The even more crucial problem is that one process would like to render
> into this buffer (the application, direct rendering), and another
> process would like to bind this buffer to a texture (composition
> manager, when using direct rendering, or the Xserver, when using
> indirect rendering for composition or no composition at all).  Currently
> there is no OpenGL extension for sharing offscreen buffers (or anything
> else!) between processes, there is only a notion for sharing between
> contextes of the same process.

The key point here is that the mechanism by which the server tells the (dumb) 
client where to draw, is the same mechanism by which the compmgr will acquire 
these pictures for compositing.  You're just passing around handles to 
framebuffer memory.

You are right that there's no extension for that yet (well, 
MESA_render_texture in xgl is a low-grade version of this), but that just 
means we have to write the extension in addition to the code that uses it.

- ajax
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