[Development] OpenGL sluggishness on Qt5 vs Qt4

Dov Grobgeld dov.grobgeld at gmail.com
Thu Nov 20 09:13:26 CET 2014

Hello. This is my first post to this list, so if there is another forum
more suited, please let me know.

I'm writing a QT application that includes a viewer for 3D-models. I got
the same code (with an ifdef for includes) running under both qt4 and qt5
in Linux. The program loads a model of about ~70k triangles and lets the
user interact with it with the mouse. In Qt4 there is the feeling that the
model immediately follows the mouse. But in Qt5 the feeling is that the
mouse events are put into a queue and they continue being played back until
the queue is empty, which can happen a few seconds after the user has
stopped moving the mouse.

I obviously much prefer the Qt4 behaviour, and I wonder if there is any way
to coarse Qt5 to behave more like it? I have tried to block additional
mouse events until paintGL is finished, but it didn't help.

Is there an open bug about this?

Will it help if I create a minimum program reproducing the problem?

Here are my system info:

System: Fedora 19, 32-bit


OpenGL vendor string: Intel Open Source Technology Center
OpenGL renderer string: Mesa DRI Intel(R) 965G
OpenGL version string: 2.1 Mesa 10.1.5
OpenGL shading language version string: 1.20

Qt4: 4.8.6 (fedora provided package)
Qt5: 5.3.2 (fedora provided package)

Thank you very much in advance!

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