@Christian-Ehrlicher and @SGaist - thanks very much for help, and you are both right of course. Super-useful to have your additional eyes on my code!

Bump as I re-edited the topic with new info from "scratch"

Woah sweet! will do that thanks!

@Dariusz @SGaist I though I cant create widgets in non main thread? Correct, but you can emit a signal from the thread and react on it in the main thread.

I managed to solve the problem by adding eventFilter to my subclass of QOpenGLWindow and then installing event filter for the owning container (and some of its parents).

Hello, I know they don't inherit one another, that's why I'm asking if it's possible. :) I have a form with QOpenGLWidget laid out and want to use Qt3D, which does require a QWindow subclass for its painting routines. Now I was thinking maybe creating an attached QOpenGLWindow and sharing contexts but I'm not quite sure if this is the way. Anyway, createWindowsContainer is a possible solution, but I'd need to handle the layout insertion manually, this is why I'm asking. Kind regards.

@yoavmil Thank you, that resolved the issue. I have now set it up in main to show and then immediately hide the main window. I connected the splash screen close slot to a custom signal indicating when the model has finished loading. So now the main window becomes visible upon the model loading and the splash screen persists until receiving the very same signal.