Comment 3 for bug 1211076

wl_display_flush doesn't process incoming events (mouse, ...).

In theory it would be better (for CPU consumption and performance) to use wl_display_flush, and sometimes (for example 60 per second) use wl_display_roundtrip. I doubt however the performance impact is worth it (anyway egl would have to do a roundtrip if it doesn't get enough release events from the compositor, so every 2-3 frames, egl would do a roundtrip limited to egl events).

Replacing wl_display_dispatch by wl_display_roundtrip is the easiest solution and solves the issues.