create_and_send_dnd_offer() sets the compositor of the offer to the one
from the MetaWaylandDataSource. This then later gets used in
display_from_offer() when trying to get the context from the compositor.
meta_wayland_data_source_xwayland_new() however was not setting the
compositor, so this was causing crashes when dragging things from X11
windows on Wayland.
Fixes: 2731f0cda ("wayland: Setup and use ownership chains")
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/2723
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2956>
As elsewhere, make sure objects that need to have a ownership up to the
context, and use this ownership chain to find relevant components, such
as the backend or the Wayland compositor object instance.
wayland/data-device: Hook up data devices to seats
They are tied to a seat - make that connection in struct fields too, so
that related objects can get to the context via it.
wayland: Don't get Wayland compositor via singleton getter
This means via the ownership chain or equivalent.
xwayland: Hook up manager to Wayland compositor
Same applies to the drag-n-drop struct.
xwayland: Make X11 event handling compositor instance aware
This avoids finding it via singletons in the callee.
xwayland: Don't get Wayland compositor from singleton
xwayland: Pass manager when handling dnd event
window/xwayland: Don't get Wayland compositor from singleton
xwayland/grab-keyboard: Don't get backend from singleton
xwayland: Don't get backend from singleton
wayland: Always get the backend from the context
This means traveling up the ownership chain or equivalent when
necessary.
wayland: Hook up data devices, offers and sources to the compositor
This allows tying them to a context without going through any
singletons.
wayland: Don't get display from singleton
xwayland: Don't get display from singleton
tablet: Don't get display from singleton
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2718>
The split wasn't 100% clean, and some extra private API had to be
added for it (but well, looking at the API, it's already evident
there's a cleanup/streamlining task due). This is meant to be a
refactor with no functional changes, so just go with it.
https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1193
