[Kde-games-devel] QGV repaint and update performance

[Mauricio Piacentini]

Martin Heni wrote:
> 2. scenario without update 
>   Xorg eats not much processor but kwin goes to 70-80%
>   Qt properly repaints only the changed/moved sprites

Notice that this does not occur all the time. I seem to remember (with 
KGoldRunner) that we have established that this occurred only when a 
certain set of conditions were met, like a certain number of update 
rects spaced apart at the same cycle, which caused a different code path 
to be hit inside QGV optimizations.  In KWin4 this does not happen 
during normal gameplay, but the intro animation triggers it.

With KGoldRunner this condition did not happen in 90% of the levels, but 
it was triggered everytime by two or three levels where we had a number 
of simultaneous update rects (over 20) and the runners were placed far 
apart.

> I assume the jumpy behaviour comes when kwin4 reaches occasionally 100% 
> processor load.

Indeed.

> However, why this is is totally unclear to me. This must be some QGV problems.
> Maybe just hope for a new Qt release. Does anybody know whether Trolltech is 
> aware of these issues? 

Yes, they are. See my reply to Tomas, we discussed and tried to address 
this before last aKademy, and Andreas (from TT) even looked at 
KGoldRunner specifically in Dublin.
QGV is in constant flux with improvements and tuning, and apparently it 
is a good fit for some games, like KPat. If you read qt4-preview there 
is some discussion regarding performance issues and improved item 
discovery in 4.3, so maybe these special cases of bad performance are 
already addressed. Maybe you could try with a 4.3 snapshot, although I 
am not sure which version will be used by KDE4.

Regards,
Mauricio Piacentini