To obtain a float between 0 and 1 we have to devide the integer by the
highest possible value instead of the number of values.
Fixes off by one errors in the tests on some hardware/driver
combinations.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>
So we can properly handle matching DRM and WL_SHM formats in a unified
manner.
Add extensive testing between these and existing pre-multiplied alpha
formats, i.e. all formats we support on Wayland.
Note that unfortunately for some format combinations the value in the
alpha channel is not cleared as expected, likely because of fast-paths
in Cogl. If both source and destination format is opaque, it always
works, however. This thereby includes all cases where they are the same.
Co-Authored-By: Jonas Ådahl <jadahl@gmail.com>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/3065>
There are two tests; one checks that clearing with a color that cannot
be represented using 8 bits per channel doesn't loose precision when
painted, then read back using glReadPixels(). Would the texture backing
store have 8 bits per channel instead of 10, we'd get a different value
back.
The other test checks that painting from one fbo to another also doesn't
loose that precision.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2461>
