Here a really good news for BulbCalculator.
I finally solved the problem with the OpenGL library I am using (libQGLViewer) that make it unusable.
Actually the library still use the old QGLWidget instead of the the QOpenGLWidget, so once you use the libQGLViewer in a MDI subwindow, for some reason it lock all the MDI subwindows; the strange thing is that if you use the “tabbed” configuration for the MDI subwindow, everything work.
Anyway, after a bit of working, I finally succeeded in porting the libQGLWidet library to the new QOpenGLWidget, so all works again.
At this point, as soon as the upstream developer for the library answer, I will know if I need to maintain the library myself, I need to integrate in my source tree or whatever, but at least I can move forward and make a new interesting release.