QOpenGLWidget loop and glFinish()

[yoavmil]

I am build a 3D viewer, sometimes rendering heavy stuff. and I want to render it over and over again. Using QOpenGLWidget.
the problem is that the previous frame isn't fully rendered, and I get just a few triangles, and the frame is re-rendered again.
in order to render again right after last rendering finished, I tried to use a QTimer, with 0 interval, calling update(), didn't help.
tried to call update() at the end of paintGL(), didn't help.
tried to connect to frameSwapped, didn't help.
and it looks line glFinish() isn't blocking.

please advise.