Consider fullscreen views as opaque for rendering
Despite drawing a black background behind them, Weston still paints surfaces behind fullscreen views. The opaque region of the fullscreen surface isn’t taken into account either.
This leads to a serious increase in power consumption when another surface is updating quickly behind the fullscreen one.
Here is a demo using <debug>+f to see the regions being composited, we can observe that every time the (fullscreen) terminal is displayed again it continues to get composited at the rhythm of the video beneath it:
fullscreen-not-opaque