Touchpad: Add manual button remapping

[mvlassis]

Description

A useful enhancement might be to add the option to configure the button remapping on the touchpad. This allows us to change what action is executed for each button. For reference, on X11 uses the ButtonMapping option.

As an example, on X11 I have this configuration option to assign the left and middle parts of the touchpad to left click, while leaving the right part to right click:

Option "ButtonMapping" "1 1 3 4 5 6 7"

Note that this is different from simply disabling middle click using the already present configuration option middle_button_emulation in Hyprland, since that assigns the whole right half of the touchpad for right clicks instead, which I find unwieldy.

Thanks everyone who works on Hyprland!

[fufexan]

The only similar thing I could find in libinput's docs is tap_button_map, which we already implement. Though it can only have two possible values, lmr and lrm. You can also control whether to use clickfinger (1, 2, or 3 taps) or button areas (non-configurable, from what I gather).

[mvlassis]

So this seems to be limitation of Wayland's libinput, that is unfortunate. Well, in case this is at some point provided by libinput, maybe it could be taken into consideration to add it to Hyprland

Thanks!

[fufexan]

xinput also uses libinput, so in theory this should be achievable. But I haven't found anything related to it.
Libinput doesn't have xorg/wayland-specific implementations.

[vaxerski]

we can still do it in hyprland