composite and smooth moving (double buffering?)

[Felix Kühling]

I have theory to offer, as to why some windows move faster than others.
AFAIK the KDE window manager includes a composite manager which does
client-side compositing. Compositing without transparency is much faster
than with transparency with conventional XAA acceleration. Maybe the QT
applications use an RGBA visual, so they can potentially be transparent.
This means that the slow software path must be used for compositing.
Other applications use RGB visuals, so they can be composited very fast.

Just a theory ...

Regards,
  Felix

Am Mittwoch, den 05.10.2005, 08:44 +0200 schrieb Anders Storsveen:
> Thomas Lübking wrote:
> 
> >Am Mittwoch, 5. Oktober 2005 03:26 schrieb Anders Storsveen:
> >  
> >
> >>When I enable composite and try to drag the konqueror window around
> >>fast, the window will move very smooth, although very slow to, but
> >>that's another issue (probably nvidia's rendr acceleration that is slow
> >>right?).
> >>    
> >>
> >rather xaa composite implementation (i.e cache limitation?, try to reduce 
> >resolution and/or bpp) or because you didn't activate the
> >Option     "RenderAccel" "true"
> >(btw, randr but rend_e_r)
> >also it might be that the "nvidia" driver (nVidias CSS stuff) is faster than 
> >the "nv" driver that comes with X
> >
> >  
> >
> >>However, this smooth moving, which only happens to qt apps, why is this?
> >>    
> >>
> >hää? toolkit doesn't matter here (i.e. xterm is as smooth as konsole or 
> >gnome-terminal) - what exactly do you mean by run "not smooth"?
> >however, i guess it's rather a matter of the window size
> >also gtk1 apps run ARGB, i.e. they eat more cache space for the alpha channel 
> >- try to run it exporting XLIB_SKIP_ARGB_VISUALS="1"
> >  
> >
> by noy smooth I mean, my konqueror window runs with out like any
> tearing/misrendering when moving fast, however my eterm window, and
> thunderbird window runs much faster, but not as smooth (and
> "error"-free, since I see rendering glitches or "tearing". so it seems
> that the konqueror window is running just as fast as the compositer can
> run it and also render each frame complelty, however eterm and
> thunderbird seem to run unhindered, but with tearing, i did mean RENDER
> and I have RenderAccel "1".
> 
> >  
> >
> >>Could someone please explain this to me, also how it works :)
> >>    
> >>
> >basically the window content is rendered into an offscreen buffer, redirected 
> >into an application (the compmgr, probably kompmgr for kde) and there used to 
> >draw a fullsize picture onto the root window.
> >the compmgr then can do funny things on this (like adding translucency or 
> >shadows etc.)
> >
> >Thomas
> >  
> >
> 
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| Felix Kühling <fxkuehl at gmx.de>                     http://fxk.de.vu |
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