Back then I didn’t experience any flickering with my demo program. I think the GTK version was 4.18.3 if I recall correctly. But now with GTK version 4.18.6 I’m experiencing heavy flickering. It seems to be related to the GtkOverlay used with a GtkMenuButton and with a GtkPopoverMenu. Because I don’t have any flickering if I don’t add the GtkMenuButton to the GtkOverlay.
I know that my MultiGLView custom widget is very complex and might not be a priority at all to this community but any help will be greatly appreciated to figure out what change was made between version 4.18.3 and version 4.18.6 that introduced the flickering.
In the mean time I will try to reproduce on a lower scale the same issue with a simplified setup.
You can bisect GTK, since you have a known good and a known bad revision.
Use git bisect to build your own version of GTK, and run your application against it. Once you find the commit that broke your application, open an issue against GTK.
Thanks Emmanuele, in the mean time I have followed an advice to switch from the “nouveau” open source graphic driver to the NVIDIA driver and the flickering just disappeared. The problem was probably not related to GTK but to the graphic driver. The last time I have try to revert back to the nouveau driver from the NVIDIA one I have ended up with an un-bootable system, a new setup of the OS was necessary. I will keep your suggestion in mind if the problem re-emerge.