Hi
On Wed, Apr 3, 2013 at 3:50 PM, Clemens Brunner <clemens.brun...@tugraz.at>wrote: > On 04/03/2013 03:24 PM, Andreas Pakulat wrote: > That being said, here with Qt4.8 even a full-screen window will not >> cause a significant slowdown, except during the resize phase. Once the >> resize is done the timer fires every 25 ms again. So I guess the >> calculation inside the paint function simply take some time and once the >> widget doesn't resize anymore the paint function is not called anymore. >> > > OK, but (1) I was not referring to the resize phase, and (2) this only > works well on Windows. On Mac OS X and Linux, the timer depends on the size > of the window being updated -- for a full screen window, the timer fires > every 100ms (not during the resize) because QGraphicsView cannot handle the > computations within a time frame less than 100ms anymore. As I said, with Qt4.8 I don't see this here on Linux at all, once the window is at a certain size the timer fires every 25 ms again. This is on a somewhat new system with Debians standard Qt/PyQt packages. So its not necessarily a general problem with Linux/PyQt, but might be limited to the systems you've used so far to reproduce this or a configuration thing etc. > If you need high precision timers then you'll need to write >> platform-specific code. QTimer is not meant for that. >> >> Why this works better on Windows with Py(Qt/Side) can have many reasons, >> the whole graphicsstack is different there, the QTimer might be >> implemented differently there. Maybe windows delays the painting during >> resize somewhat more so that there are less repaint-events given to Qt >> or maybe the functions used in your paint() are more optimized on Windows. >> > > Well, the fact that it does work equally well on all three platforms when > I use Qt directly from a C++ program indicates that this is an issue with > the Python wrapper It could also be the fact that the various helpers inside your paint are slower in Python on *nix for whatever reason. Did you try further simplifying the paint function, for example simply painting 1 line across the whole rect in multiple steps? Or try out a single step? That way you'd be able to get rid of all the math which could affect the result too. > , and not a different implementation within the Qt framework. Furthermore, > since PyQt and PySide produce a Python wrapper that does work just like its > C++ counterpart under Windows makes me think that it must be an > implementation detail of PyQt/PySide that could probably be fixed. I doubt there's much difference in the PyQt/PySide code between Windows and *nix, after all the C API of CPython is the same on both platforms. One difference though is the compiler being used for both - at least usually it is a different one - and of course the platform itself. Does a fixed-length sleep instead of the paint() function produce a different result on Linux? Meaning, does it matter what exactly happens in paint or that its just not a noop? Andreas
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