The callback would schedule a clutter_actor_destroy() on the first
argument. Unless told otherwise, this is the same actor that is
already being destroyed, so this is a no-op.
Instead, the intent is to make the clone follow up destruction of
the window actor so that it results in correct removal of this
window from the ShellWindowPreviewLayout. Use a swapped connection
to pass the clone actor as the first argument of the signal callback.
Fixes: 04c781674c ("Move WindowPreviewLayout from JS to C")
Closes: https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/6570
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/2756>
This layout manager is used quite often and the time we spend calling
it's allocate and get_preferred_width/heigth functions increases with
every open window.
We can save a lot of precious time during the layout cycle by moving
this layout manager from JS to C, thus avoiding the overhead of
trampolining between C and JS land.
In a measurement where the average time spent in vfunc_allocate() of the
Workspace actor was measured while opening an overview with 20 windows,
the average time spent went down from 3.1 ms to 2.3 ms.
Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/1743>
