On Thu, Mar 08, 2007 at 01:17:47PM -0800, ext Daniel Amelang wrote: > On 3/8/07, Eero Tamminen <[EMAIL PROTECTED]> wrote: > >[1] There's a bug in Cairo bugzilla about slowness on 16-bit display > > when using Render though... > > Although the compositing code could still be better optimized for > 16-bit displays, the real "bug" there was that they were recompositing > large surfaces at each scroll step, which will probably never be fast > unless compositing is hardware accelerated.
Two bugs, really:
a) the X server doesn't have sensible acceleration for 16-bit dest
pictures. I have a preliminary patch for this which I need to get
back on.
b) Cairo is dumb. It could degrade to a 16-bit surface if the target
is only 16, thus saving a great deal of memory and calculations.
Also, last I saw, it insisted on pushing every surface as ARGB32,
rather collapsing the alpha channel down to 1 bit, or removing it,
if possible. a8r8g8b8 IN a8r8g8b8 OVER r5g6b5 is an incredibly
expensive op ...
(Note that I haven't checked this for a while.)
Cheers,
Daniel
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