In rare cases DiskWriter::run() may call finish_capture()
concurrently with the butler thread from transport_stopped_wallclock,
this can lead to memory corruption (CaptureInfo).
Using a Mutex here is not great, but it is not usually contended
and better than crashing at rec-stop.
We should probably change DiskWrWiter::_was_recording into an
atomic bool, and use CAS to prevent concurrent calls.
The GUI was able to free memory (MidiTracer::disconnect),
while the tracer is concurrently still in use in rt-context.
This lead to memory corruption in MIDI::Parser::scanner.
port-meta-data depends on the audioengine backend/device
settings. Those are only available after the engine is started,
not from within the backend's _start() method.
This is is only relevant for callback based backends.
Backends with a blocking process thread explicitly emit
port-manager callbacks there before entering the main loop.
Record, move recorded region(s), delete the recorded source, undo.
Undo would undo the region-move, of a region that no longer
exists and has no source.
This fixes the following issue:
1. Import a file to a new track
2. Delete the track
3. Editor Source list: select imported file,
-> Remove the selected source
-> Yes, remove the Regions and Sources
The Track and Region no longer exist in the Editor,
only the playlist still exists!
The sources to be deleted are found when iterating over whole-file
regions in `EditorSources::remove_selected_sources`. Also
RegionFactory::get_regions_using_source correctly returns
regions, _editor->remove_regions does nothing since there
is no RegionView for the given region(s). This then cashes in
```
libs/ardour/playlist.cc:2400: virtual XMLNode& ARDOUR::Playlist::state(bool) const: Assertion `r->sources ().size () > 0 && r->master_sources ().size () > 0' failed.
```
The eventual goal is to keep the set of used regions
in sync, and allow to remove explicit calls to
`sync_all_regions_with_regions`.
This prevents `all_regions` to retain a reference to
a region that has been destroyed.
* Do not emit signal with source-lock mutex held
* explicitly drop references when called directly; notably from
EditorSources::remove_selected_sources
