[Bug 17129] Slow to move translucent windows above a certain size with EXA (r300)

[bugzilla-daemon at freedesktop.org]

http://bugs.freedesktop.org/show_bug.cgi?id=17129





--- Comment #13 from Roland Scheidegger <sroland at tungstengraphics.com>  2008-08-29 06:18:03 PST ---
(In reply to comment #9)
> (In reply to comment #8)
> > (In reply to comment #7)
> > > I found an interesting phenonemon today.  If I alt-drag the translucent window
> > > if it's underneath another window, say, Konsole, then the slowness disappears
> > > (and almost no CPU time is used).  Bring it back above Konsole and the movement
> > > is slow and laggy again.  But moving it around near the side of the screen,
> > > where maybe 2/3 to 3/4's of the translucent window is off the edge of the
> > > screen (or less) causes the lagginess to subside.
> > 
> > Sounds like the translucent window is composited by the CPU instead of the GPU.
> > It would be interesting to track down why that is happening, e.g. by rebuilding
> > the driver with RADEON_TRACE_FALL defined to 1 in src/radeon_exa.c, or if that
> > doesn't show anything interesting by rebuilding xserver with DEBUG_TRACE_FALL
> > defined to 1 in exa/exa_priv.h.
> > 
> 
> Yep, that's where the issue is.  The log file shows a bunch of these:
> 
> R300CheckComposite: Component alpha not supported with source alpha and source
> value blending.
> 
> And a bunch of these:
> 
> R300CheckCompositeTexture: Unsupported picture format 0x1011000
> 
> They come in chunks of 10-20 lines.  It seems when I tried to move the window
> faster, I would get more of the former message.  Hopefully, this will all be of
> use to you.

The unsupported picture format is 1 bit alpha (PICT_a1) here, though I've no
idea if this fallback is what causes the slowdowns. As a side note, I think
this fallback could be avoided on r5xx cards since those should support such a
format - not that it would help in your case...


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