This is a revision of the initial API 8ba7df9105, to
address issues with dynamica ports (fa791ae9cc).
* Group meter + scope/monitor per port (atomic access)
* Use shared pointer to allow access while ports change
* Use RCU to update port map
* Add/remove ports without clearing the map
* Add signal to notify GUI about Input Port changes
This follows a special case in PortGroupList::gather().
The Virtual Keyboard is an Ardour owned async terminal port,
that is in a session bundle (not a UserBundle).
See also 728d2a3771 and 559ffcff63
* Show Treeview again if it was hidden
* Hide heading(s) and table when no ports are available
* Fix memory leak, unmanaged OptionEditorHeading
* remove unused members
This allow to restore original engine port-names as set
by the backend. ALSA MIDI, CoreAudio, CoreMIDI and PortAudio
drivers can provide human readable physical port names for
some devices.
* Expose API via Public Editor
* Skip hidden tracks in calculation
* Use a single call to query playlist extents.
This way the playlist read-lock is needed at most once per track
which speeds up calculation.
Various playlist operations can change region-properties
which results in Region::send_change being emitted while
the Playlist::RegionWriteLock is held.
This can result in recursive lock and/or deadlocks or crashes. e.g.
Insert time -> Playlist::shift -> Region::RegionPropertyChanged
-> EditorSummary::set_background_dirty -> Editor::session_gui_extents
-> Playlist::get_extent -> read-lock is taken after write-lock.
This is in preparation to subscribe to playhead cursor position
changes in the recorder-UI.
This change also clean up the API, replacing a public variable
with a const access method and follows #12 of
https://ardour.org/styleguide.html
FoldbackStrip::update_send_box() GUI relies on ->fed_by() to
determine if a FB bus has a send from a route.
Under the hood this uses direct_feeds_according_to_reality()
and InternalSend::feeds(). When `allow_feedback` is set a send is
assumed to not directly feed a target (to allow loopbacks).
This mode must not be used for foldback sends.
