This mapping of stylus evdev input event codes into GDK button numbers
makes gdk/wayland inconsistent with gdk/x11, so depending on the backend
the same button middle-click pastes or right-click pops up menus.
Make the wayland backend consistent with X11, so that a GNOME wayland
session gets these buttons consistently mapped across all kinds of
clients.
Closes: https://gitlab.gnome.org/GNOME/gtk/-/issues/5935
We were creating the pad device on wp_tablet_pad.done, but
at that time we do not know what tablet it is associated with,
thus we cannot get appropriate vid/pid/name properties for it.
To get that, we need to wait for the pad to enter a surface,
at that time we do know what tablet it is associated with, so
we can get better information about the device.
There are pads that may plausibly "change" tablet between
one .enter event and the next (e.g. Wacom Express Key Remote),
but this situation is highly unlikely. The pad devices created
are thus persistent until that situation happens.
This is a bit spaghetti right now, since seats and devices were
heavily entangled there are a number of crossed private API calls that
should ideally not be there.
Let this be a first step, so more bits may move from the seat
implementation to devices.
This file, event though a clump of input-y objects, has more of
seats than anything else. Rename it so that we can start splitting
these objects out of it.
