Many tablets have a native portrait mode panel, yet come with a keyboard dock,
where the device gets docked in landscape mode. To avoid the display being
on its side when mutter starts while the tablet is docked, we need to take
the accelerometer reported orientation into account even if there is a
tablet-mode-switch which indicates that the device is NOT in tablet-mode
(because it is docked).
Add special handling for the first time the "orientation-changed"
signal gets signalled by the orientation-manager, which happens after it
has successfully claimed the accelerometer with iio-sensor-proxy.
The added special handling of the initial "orientation-changed" signal
does a number of checks:
1. panel_orientation_managed is false because of the tablet-mode-switch and not
because of other reasons.
2. The device has a native portrait mode panel (and thus likely needs rotation
to display the image the right way up when docked).
If all these checks succeed then it continues with creating a new
monitors-config based on the orientation ignoring the panel_orientation_managed
value (for the initial/first "orientation-changed" signal only).
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1506
ec18a559c6