Bart van Deenen wrote: > On Monday 17 November 2008 10:09:51 Bart van Deenen wrote: > > > On Monday 17 November 2008 09:54:38 Gunnar Sletta wrote: > > > > > Ok. I'm starting to get somewhere. I've added instrumentation to the > > > > > code (not shown here) which uses System.currentTimeMillis() to > measure > > > > > intervals, and it turns out that the interval between two consecutive > > > > > calls to timerEvent is very erratic! My 'render' function (currently > > > > > with a much simplified QPixmap tree under it) only takes a few > ms. The > > > > > QTimer is supposed to run at 40 ms interval, but the actual intervals > > > > > are anywhere between 15 and 300 ms! > > > > > > > > A timer tries to fire as close to, but at least 40 ms after the last > > > > one, but there are no guarantees. I've never seen such behaviour, so I > > > > would have to see your code to know more > > > > > > I'm simplifying the code to narrow it down to where the problem > occurs, and > > > then I'll post it. Thanks for thinking along. > > > > > > Bart > > I've narrowed down my source code to something simple. Unfortunately, > now the erraticness is gone! It seems to have to do with the number or > size of QPixmaps I'm using to draw my main QPixmap :-( > > Here's my non-erratic code. The only difference with my problem code is > that the 'render' function here consists of one QPixmap being drawn into > my root object, and that with the trouble code there's a lot of QPixmaps > rendering into each other, and finally being combined into the root > QPixmap. The problem is not the overal time it takes to do the > rendering; with a simplified tree of objects that is consistently below > 5 ms. I don't understand where the problem is starting to occur :-(. > Next I'll add some more of my 'sprite_object's to see if it's the number > or size of them that matters.
There is also the fact that the precision of System.currentTimeMillis() is system dependent. On windows its precision is ~17ms on Linux I believe it is between 1 and 5ms, so you also have to factor that into benchmarks and run enough iterations for the precision to be of no consequence. best regards, Gunnar _______________________________________________ Qt-jambi-interest mailing list [email protected] http://lists.trolltech.com/mailman/listinfo/qt-jambi-interest
