Thanks for the detailed answer, those security protocols in particular are quite interesting. Regarding rendering callbacks (thumbnails & etc), it's perhaps no

Thanks for the detailed answer, those security protocols in particular are quite interesting. Regarding rendering callbacks (thumbnails & etc), it's perhaps not as specific a problem as it might seem. In classic OpenGL, the potential to block the render loop (and thus the entire window event system) when placing a swap buffer (ie present) call is incredibly frustrating. Also, particularly on resource constrained devices, an event driven approach can be quite useful (both for performance and battery reasons). It's generally just a much more flexible model overall. You mentioned a custom xcompmgr implementation. I didn't think X11 used a callback model though? Was I mistaken? (Again, I've only ever done cross platform OpenGL code using wrapper libraries. That's always involved a potentially blocking call to swap the buffer at the end of the render loop in my experience.)