Flickering [5.10.0 regression]

First of all, this is a regression compared to past version (<= 5.9.1)

I have a large Qt window, with lots of widgets inside it. No native nsview inside it, pure Qt.

While this complex window is created and its widgets appear, it happens that the underlying OSX Desktop appears during a few milliseconds, causing a big flash. This is weird, because the window starts as a large window, with a custom painted background, and the OSX Desktop appears after that, on top of it (a part of it, actually).

Later, when the window is fully build, some user actions cause widgets to be hidden and replaced by others. When this happens, parts of the OSX Desktop come again, causing flickering. Some backingstore issue?

I can't create a demo application, but maybe you could give me an idea where I should look in the many 5.10.0 cocoa changes, so that I can find the origin of the problem.

Not sure this is the same problem, but I have also reported QTBUG-65152