Keep the virtual monitor around if it's being resized. This reduces the
number of unnecessary object rebuilding that happen during monitor
rebuilding.
This changes finalize() vfunc into a dispose() vfunc in the abstract
stream source object implementation, as it needs the abstract stream
source object to close the stream early, so that various signal
listeners get disconnected early.
Closes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1904
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2270>
The new RecordVirtual API creates a virtual monitor, i.e. a region of
the stage that isn't backed by real monitor hardware. It's intended to
be used by e.g. network screens on active sessions, virtual remote
desktop screens when running headless, and scenarios like that.
A major difference between the current Record* API's is that
RecordVirtual relies on PipeWire itself to negotiate the refresh rate
and size, as it can't rely on any existing monitor, for those details.
This also means that the virtual monitor is not created until the stream
negotiation has finished and a virtual monitor resolution has been
determined.
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1698>
