Setting the opaque region correctly is common source of error for
clients that simply want to express that a whole surface is opaque.
This is especially true once buffer_scale and buffer_transform come
into play, as unlike for damage, where buffer_damage is the
encouraged and user friendly way today, opaque regions are always
in logical coordinates.
As faulty opaque regions don't have a visual impact in these cases
but only increase resource consumption, these errors often remain
for long times. See
https://gitlab.freedesktop.org/gstreamer/gstreamer/-/commit/1e2bc681712d62081f49e8e74723a596d1578a34
for one of many examples.
Give an easy example how to set the opaque region in a conformant
and reliable way.
Signed-off-by: Robert Mader <robert.mader@collabora.com>
Robert Mader
4090f0eb6f