This question already has an answer here:
I can switch the screen illumination manually off by pressing Fn+F6 on my laptop keyboard. This is the same as automatically switching it off on idle as it can be set in the power management.
The screen illumination will turn on again if I press any key. I want to keep on typing with a dark screen, i.e. I want to be able to switch it on again only by pressing one specific key combination. (In fact, external illumination e.g. from the sun behind my back can be sufficient to make the screen readable. This is also more eye friendly to me.)
How can I find which software mechanism turns the illumination on again on any key pressed so that I can restrict this mechanism to a particular combination?
This question seems not to be related to screen brighness as it is treated in this question. I can already adjust the brightness to be quite dark with another keyboard combination, but in the darkest setting
/sys/class/backlight/acpi_video0/actual_brightness contains already
0 whereas the screen illumination is still brighter than off. So the switch I think about might be adressed by the Fn+F6 mechanism somewhere else than in the
/sys/class/backlight/acpi_video0 tree. The files therein do not change when the screen illumination is turned off completely, only when the brightness is changed but still on.
I'm using MATE/Gnome on an old acer laptop, but hints for other system configurations might be helpful as well.