layer-surface: Take transparency into account and refresh layer-surface list less often
It is sufficient if we invalidate the list of layer surfaces when the surfaces changes layers or exclusive zone (which can affect the ordering within a layer). This makes us hit the fast path in phoc_output_get_layer_surfaces_for_layer()
way more often as we don't invalidate on every commit. Needs thorough testing so I'll add that to next already.
We also fix a the "covers whole screen check" to take transparent surfaces into account (which I somehow forgot in the initial submission although I had it on my "to check" list). At least this patch needs to go into 0.45.
/cc @arun-mani-j
Signed-off-by: Guido Günther agx@sigxcpu.org