render improvements

Keith Packard keithp at
Tue Apr 19 06:25:30 PDT 2005

On Tue, 2005-04-19 at 07:15 -0400, Owen Taylor wrote:

> Possibly the most efficient thing to do is to simple, whenever you need
> to read data back from a pixmap in the framebuffer for a composite
> operation, is to simply kick the pixmap *out* of the framebuffer 
> permanently.

That's really bad for my most common environment where text cannot be
accelerated to windows which are about to be composited to the screen
which can (and really should) be accelerated.

We obviously just want things to go as fast as possible, and I don't
think this is actually that hard to compute -- each compositing
operation can be reasonably modeled by computing the number of pixels
read/written to each object and assigning static scores to
in-memory/on-card for each object, now we just figure out how a sequence
of operations can be most efficiently executed for a range of objects
and move each to the right side of the bus.


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