Create a tablet pointer confinement protocol
pointer_constraints_unstable_v1 exists for confining the mouse cursor, but there is no analog for tablet confinement.
XGrabPointer confines both the mouse and tablet pointers. At least one open-source Linux app (the game osu!) relies on pointer confinement to be reasonably usable. It's backed by SDL (Wayland, X11 implementations).
The lack of tablet pointer confining also makes it so that running an application that uses
XGrabPointer behaves differently on X11 versus XWayland.
By default, on at least sway and GNOME with a 2-monitor setup, my Huion 420 tablet is mapped to both displays -- which is nice, since I can use it to navigate more UIs without having to put down my pen. As a workaround for my particular use-case, I can currently map it to a single output, and then fullscreen the application I'm using, but this is less than ideal.
I'm not a tablet power-user, so I'm not too familiar with what graphic designers would expect. From discussions in IRC, it's been mentioned that some drawing apps have the ability to map tablet input 1:1 to the canvas. I would imagine that for tablet confinement to be generally useful, it should remap the tablet input area to the confined region. (I am not sure how these apps work on X11, if at all, given
XGrabPointer's behaviour, but I'm not too familiar with that area.)