[Xcb] double buffering
jamey at minilop.net
Wed Aug 23 10:38:39 PDT 2006
On Wed, Aug 23, 2006 at 12:20:20PM +0200, Thomas Hunger wrote:
> Does that mean that there is no "preferred" way for double
> buffering? So far I see two ways if dbe is deprecated:
Bart's concern is that these are all extensions, so you can't count on
any X server having them available. As a result, it would be useful to
have a client-side library that maps general double-buffering operations
onto whatever extension is available, or falls back to pixmaps and
That said, I don't know which approach is "preferred", or if all the
current mechanisms are considered lame. I'd add GLXSwapBuffers to the
list of mechanisms to evaluate though.
> 1) Rely on the composite extension and a composite client to
> redirect my drawing to off screen storage. Then send
> damage reports after redrawing.
There isn't yet a protocol to ask the composite manager to defer updates
until you're done redrawing, though that's been discussed, so the
composite extension doesn't actually buy you double-buffering right now.
One of the double-buffer extensions may continue to have use in a fully
composited world to help the server manage this.
> 2) Create background pixmap. Problem: When should I free
> the pixmap? Is there a way to create "soft-allocated"
> pixmaps which the server can claim when it needs space?
> I cannot find anything in the protocoll.
I don't believe you can create "weak-referenced pixmaps" in X, no. I'm
not sure why that's useful though: as long as you continue wanting
double-buffering, you need that pixmap sitting around, right?
> p.s. is this the wrong mailing list for this discussion? I
> found some related threads which did not really answer the
> question of double buffering:
Yes, the xorg list is the right place to ask these general X technology
questions; though you came to the right place for questions about XCB's
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