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List:       kde-games-devel
Subject:    [Kde-games-devel] Re: QCanvas and delayed key events
From:       thomas.friedrichsmeier () ruhr-uni-bochum ! de
Date:       2001-11-25 18:15:17
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Hi!

Some time ago, you posted a problem with delayed key-input-handling on 
kde-games-devel. At that time I didn't have this problem with my game, but 
now I'm sometimes experiencing it, and I'd be very interested to know, 
whether you solved the problem somehow.
I might add a couple of observations I have made about the problem, which 
kind of make it seem to me, that this is a sort of bug in QCanvas, but 
possibly, somebody else has a better understanding of QCanvas' workings 
and can figure out the real causes.

- First of all, the slowdown is not limited to key-handling. Rather, the entire 
GUI is becoming unresponsive for me, some other timer-events (within the 
actual game) obviously don't get called as often as they should.
- The problem is not 100% reproducible. On my fast machine, I've been 
seeing it occasionally, without any clear patterns, on my slow machine (also 
with less mem) it's a little more predictable + often.
- The problem seems to come in very suddenly. On my fast machine, I'm 
typically seeing some 0.9 - 4% CPU-usage for my game, so you would think 
there is a lot of resources left, still, there are those sudden slowdowns.
- When slowdown occurs, it always follows the addition / creation of new 
sprites, but it seems like a single sprite can make the difference from 
smooth 100 fps at hardly any CPU-usage to sluggish jerkiness.
- On my slow machine (where it is easier to see any patterns), the number of 
sprites does not seem to influence the slowdown too much. Rather size of 
sprites and complexity of animations (number of frames, not frame-rate) 
seem to be related to the problem.

So far my observations. All this really doesn't make much sense to me. I've 
checked my code about a hundred times for strange things that might be 
going on inside, but other than a couple of memory leaks (fixing those did 
not affect the problem) I didnt' find anything. Hopefully somebody can make 
some sense of this.

Thomas
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