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[wysota]

2) I resize the window WITHOUT PLAY THE FILE
in this case I have to update the wave so I can not move the updatewave inside the setCurrentTimePosition

Call updateWave() from the resizeEvent() as well. It's still worth it to write another method to have the paint event not have to execute the if statement every time your widget is redrawn.

[franco.amato]

Call updateWave() from the resizeEvent() as well. It's still worth it to write another method to have the paint event not have to execute the if statement every time your widget is redrawn.

I moved the updateWave inside the resize event but the resizing process now seems slower.

What do you think about?

[wysota]

During every resize your wave is being updated. It would be wise to update it only when the user stops resizing but then it might not be worth the effort. Maybe you should stick with generating the pixmap during paint event for now until you reach a point where it becomes a bottleneck.