support laptop screen privacy
Some modern laptops have a built-in feature to reduce the viewing angle of their screen, for privacy. This is supported in recent kernels:
From the kernel documentation (Documentation/admin-guide/laptops/thinkpad-acpi.rst)
LCD Shadow control
------------------
procfs: /proc/acpi/ibm/lcdshadow
Some newer T480s and T490s ThinkPads provide a feature called
PrivacyGuard. By turning this feature on, the usable vertical and
horizontal viewing angles of the LCD can be limited (as if some privacy
screen was applied manually in front of the display).
procfs notes
^^^^^^^^^^^^
The available commands are::
echo '0' >/proc/acpi/ibm/lcdshadow
echo '1' >/proc/acpi/ibm/lcdshadow
The first command ensures the best viewing angle and the latter one turns
on the feature, restricting the viewing angles.
It would be nice to expose this in the settings, either in the privacy or display panel (or both ?)