[macos] Continuously increasing memory consumption when calling QWidget::update()

There are several QWidgets in QGridLayout and those QWidgets need to be updated continuously in short time interval. Based on Activity Monitor these updates consume continuously increasing amount of memory. The curious thing is that if the application is switched to background and then back to front, the memory consumption drops close to initial consumption, but continues to grow again. The same happens while debugging when you stop in a breakpoint even if the application stays in front. It seems like the application cannot free memory until it is given a break. On Windows and on Linux the memory consumption is stable.

The attached example can be used to reproduced the problem. Just run the example, keep it visible and follow its memory consumption. Then put it background and visible again and notice the change in the memory consumption. The example's paintEvent() is empty. Thus it doesn't draw anything, but the problem still exists.