Some x86 clamshell design devices use portrait tablet LCD panels while
they should use a landscape panel, resoluting in a 90 degree rotated
picture.
Newer kernels detect this and rotate the fb console in software to
compensate. These kernels also export their knowledge of the LCD panel
orientation vs the casing in a "panel orientation" drm_connector property.
This commit adds support to mutter for reading the "panel orientation"
and transparently (from a mutter consumer's pov) fixing this by applying
a (hidden) rotation transform to compensate for the panel orientation.
Related: https://bugs.freedesktop.org/show_bug.cgi?id=94894https://bugzilla.gnome.org/show_bug.cgi?id=782294
7917b083cb