This happened initially during session load.
The GUI thread performed a direct refill (blocking wait)
`Session::post_engine_init() -> Track::seek() -> DiskReader::seek() -> DiskReader::do_refill_with_alloc()`
while concurrently the butler thread does the same:
```
Session::butler_transport_work() -> Track::non_realtime_locate() -> Route::non_realtime_locate()
-> DiskIOProcessor::non_realtime_locate() -> DiskReader::seek() -> DiskReader::do_refill_with_alloc()
-> DiskReader::refill_audio()
```
We do not want the GUI to wait, so now we just request a locate
and let refill happen in the background.
In case a user manually renames a session-folder and snapshot
it should still be impossible to delete the last snapshot
even if it is not named after the session-dir.
In theory this is impossible (one cannot delete the current snapshot)
Previously this setting was ignored. It is relevant when loading a demo
session, where initially there is no user Config instant.xml.
ARDOUR_UI::setup_windows is called directly after the engine starts, but
before the session is set.
Region actions are generally set insensitive whilst recording, so
special-case the "add-region-cue-marker" action by explicitly enabling it
when starting to roll in record. Additionally, the action becomes disabled
again after it's been executed, so re-enable it after queuing the cue when
recording.
Add a list of marker locations to the session, for the the UI to add the
current location to when "add-region-cue-marker" happens whilst recording.
On record-stop, create source markers at the locations in that list in all
newly-recorded audio regions.
This change still runs the triggerbox during latency-preroll, but as with the disk reader,
the transport speed argument is set to zero. The triggerbox notices this and behaves
appropriately (I think !)
When an archive are saved, a new folder in interchange/ is created,
named after the archive. However session-archive also retains files
in the session-folder that Ardour does not know about.
This can cause that the the original interchange folder is retained.
It will be empty with just the .DS_Store file in it. The result is
that the session may not load if there is an ambiguity.
Triggerboxen were being executed during the latency preroll phase, which is
inappropriate. ::fast_forward() will prepare them to run at precisely the
correct time. So we add an explicit clause to avoid this.
This allows new user to select the soundcard and I/O settings
when loading demo sessions at first run, or when tricking Ardour
to open an existing session (try to create an existing session,
user may choose to load it instead).
Normally a user can only create a new session after first running
Ardour, and creating new sessions always shows the dialog (to
set the samplerate).
When loading the very first session is canceled (e.g.
sample-rate mismatch -> Do not load session) or fails otherwise,
execution returns to the startupFSM.
Loading another session after that then takes the same path again:
StartupFSM::dialog_response_handler() -> StartupFSM::engine_running()
-> ARDOUR_UI::attach_to_engine()
The call needs to be idempotent, otherwise setup_windows(),
create_editor() etc are called a second time and Ardour crashes.
