Comment 14 for bug 237761

So I looked further into this:

* Any clutter app running on first-switch is affected.
* Clutter 0.8 is also affected (using tests/test-actors)
* Clutter-gtk 0.6 is also affected (i.e. hooking more closely into GTK+'s event structure didn't magically fix this)
* OpenGL in general does not seem affected (glchess worked OK)
* The 'internal clutter symptom' that leads to this behavior is in _clutter_do_pick(), where the code asks glReadPixels the same question it does pre-switch, but gets a different answer post-switch: It paints the stage white, and each actor paints its own sillouette. Pre-switch, things are reported as the right color. But post-switch, the top ~400 pixels report black and below that line, they report what should have been painted at the top.
* I'm not sure where the confusion that causes glReadPixels to screw up is. Are we painting sillouettes bad? Is the GL draw buffer corrupted?