window: do proper Cairo device flushing

The Cairo documentation tells us to always call cairo_device_flush()
before using other rendering APIs on the cairo surface, especially where
the Cairo device shares state with us (that is, EGL and GL state in this
case).

Add a call to cairo_device_flush() into display_acquire_window_surface(),
which the toytoolkit offers for switching to native (GL) rendering.

Signed-off-by: Pekka Paalanen <ppaalanen@gmail.com>
1 file changed