Using evsieve to use Wiimote as a mouse: Is it possible?

[vanfanel]

Hello,

I'm investigating how to use a Wiimote as a mouse on GNU/Linux on Wayland.
On X11, there's xserver-xorg-input-xwiimote (https://github.com/xwiimote/xf86-input-xwiimote) but there's nothing like that on Wayland.

Wayland's libinput backend doesn't support Wiimote, either, and won't support it:
https://gitlab.freedesktop.org/libinput/libinput/-/issues/510

So, all there's left on the horizon seems to be evsieve.

I can see the Wiimote detected in evtest as three different event nodes:

/dev/input/event15:     Nintendo Wii Remote Accelerometer
/dev/input/event16:     Nintendo Wii Remote IR
/dev/input/event17:     Nintendo Wii Remote

Starting with the IR (/dev/input/event16), evsieve reports the movement like this:

manuel@lubuntu:~$ evsieve --input /dev/input/event16 --print
Event:  type:code = abs:hat0x      value = 981         domain = /dev/input/event16
Event:  type:code = abs:hat0y      value = 317         domain = /dev/input/event16
Event:  type:code = abs:hat1x      value = 905         domain = /dev/input/event16
Event:  type:code = abs:hat1y      value = 327         domain = /dev/input/event16
Event:  type:code = abs:hat2x      value = 1023        domain = /dev/input/event16
Event:  type:code = abs:hat2y      value = 1023        domain = /dev/input/event16
Event:  type:code = abs:hat3x      value = 1023        domain = /dev/input/event16
Event:  type:code = abs:hat3y      value = 1023        domain = /dev/input/event16
Event:  type:code = abs:hat0y      value = 316         domain = /dev/input/event16
Event:  type:code = abs:hat0x      value = 982         domain = /dev/input/event16
Event:  type:code = abs:hat1x      value = 906         domain = /dev/input/event16
Event:  type:code = abs:hat1x      value = 907         domain = /dev/input/event16
Event:  type:code = abs:hat0x      value = 983         domain = /dev/input/event16
Event:  type:code = abs:hat0y      value = 317         domain = /dev/input/event16
Event:  type:code = abs:hat0y      value = 318         domain = /dev/input/event16
Event:  type:code = abs:hat1x      value = 908         domain = /dev/input/event16
Event:  type:code = abs:hat1y      value = 328         domain = /dev/input/event16
Event:  type:code = abs:hat0y      value = 319         domain = /dev/input/event16
Event:  type:code = abs:hat0x      value = 984         domain = /dev/input/event16

Looking at the docs and examples, I don't get how to translate that to mouse movement.
Mouse is detected by evtest like this:

/dev/input/event5:      ELAN0791:00 04F3:30FD Mouse

Would I have to create a "virtual" mouse? Would I have to pass motion events to /dev/input/event5 somehow using evsieve?

[KarsMulder]

It is possible to use d as the value in an event map. The variable d represents the difference between the current value of the event, and the value that the event had the last time it was emitted by its input device. This is handy for turning absolute events into relative events:

evsieve --input /dev/input/by-id/your-wiimote grab \
        --map abs:hat0x rel:x:d \
        --map abs:hat0y rel:y:d \
        --output

So, if for example an abs:hat0x:300 were to be followed up by a abs:hat0x:310 event, the latter event will be mapped to rel:x:10, which will be interpreted as moving your mouse ten arbitrary units to the right.

You can also add a factor like rel:x:0.5d to map events to half of the difference between the current value of the event and its previous value. (Though you might run into rounding issues since event values always need to be an integer value, see issue #42.)

Maybe you can use this to turn your Wiimote into a somewhat functional mouse?