Clutter nowadays omits reallocations when only the stage position
changed, that is when the allocation relative to the parent changed.
As a result (apart from better performance of course), workspaces
in the overview may now end up with an outdated "actual geometry"
in case the overview moved to a new primary monitor (of equal size
as the previous one).
Work around that by emitting a signal from the overview on allocation
changes, and use that to update the cached geometry.
We can revert that change once workspaces become part of the regular
overview hierarchy.
https://gitlab.gnome.org/GNOME/gnome-shell/-/issues/3211
da36506ea5