This keeps all surfaces referenced by a transaction alive until the
transaction is destroyed, and makes sure transactions are applied in
the same order as they were committed with respect to all surfaces
they reference.
v2:
* Guard against NULL entry in meta_wayland_transaction_apply.
v3:
* Keep single entries hash table.
v4:
* Unref the surface in the meta_wayland_transaction_merge_into while
loop only if the "to" transaction didn't already have an entry for it,
to prevent premature finalization of the surface (likely followed by a
crash).
v5:
* Unref the surface (implicitly via g_hash_table_iter_remove) in the
meta_wayland_transaction_merge_into while loop even if the "to"
transaction already had an entry for it, or we leak a reference.
* Use g_clear_object & g_steal_pointer to not leave behind a dangling
from->state pointer in meta_wayland_transaction_entry_merge_into.
v6:
* Add curly braces around
meta_wayland_transaction_add_placement_surfaces calls. (Jonas Ådahl)
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1880>
e26df6ac14