Touchpad and touchscreen pressure
Currently only tablets have a pressure event in Wayland, but touchscreens and touchpads can be pressure sensitive too. This information is just lost at the compositor level, pressure can be used to detect taps in libinput and that's it. Sending it to applications would allow for "3D Touch" style functionality. e.g. the https://pressurejs.com demo should work properly with touchpads and touchscreens, not just tablet pens. (It does work with pens in Firefox.)
Seems easy to do in the protocol: just a new pressure
event that could be included in a wl_touch.frame
/ wl_pointer.frame
.