Comment 34 for bug 1210077

I digged a bit deeper into this issue and here's what I found out:

* UnityScreen::UnityScreen() connects to the correct event (coming from Upower):

    UScreen::GetDefault()->resuming.connect([this] {
      /* Force paint local::FRAMES_TO_REDRAW_ON_RESUME frames on resume */
      force_draw_countdown_ += local::FRAMES_TO_REDRAW_ON_RESUME;
    });

* UnityScreen::damageCutoff() is the place where Unity checks force_draw_countdown_ and triggers the redraw.

However it's not clear to me what's supposed to call UnityScreen->damageCutoff(). I grepped through the whole source of Unity and nothings seems to call it. Maybe this is the problem?