I see, thanks. It would be nice if we could implement it on top of the WM_POINTER messages.
Fwiw we can, and have, some pointer/touchpad tests now (see https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/dinput/tests/device8....), which can be run without any actual hardware as they are implemented using a virtual HID device.
Then, although they are not exposed as an actual HID device, the X11 XI2 touch events are also routed through the same path (see https://gitlab.winehq.org/wine/wine/-/blob/master/dlls/winex11.drv/mouse.c#L...), and translated into WM_POINTER* messages, we could do the same for Wayland events.