MIDI Draw: change behavior regarding MIDI Channel of new notes

When adding a note, use these criteria to choose the channel number:
* if the user has explicitly specified a note in the pulldown, use that
* if the user has AUTO selected and we are in a region, choose the nearest note's channel (consistent with velocity behavior)
* as a fallback, query the track for its channel-filter (old behavior)

gtk2_ardour/editor.cc

@@ -3485,8 +3485,8 @@ Editor::setup_tooltips ()
 	set_tooltip (tav_shrink_button, _("Shrink Tracks"));
 	set_tooltip (visible_tracks_selector, _("Number of visible tracks"));
 	set_tooltip (draw_length_selector, _("Note Length to Draw (AUTO uses the current Grid setting)"));
-	set_tooltip (draw_velocity_selector, _("Note Velocity to Draw"));
-	set_tooltip (draw_channel_selector, _("Note Channel to Draw"));
+	set_tooltip (draw_velocity_selector, _("Note Velocity to Draw (AUTO uses the nearest note's velocity)"));
+	set_tooltip (draw_channel_selector, _("Note Channel to Draw (AUTO uses the nearest note's channel)"));
 	set_tooltip (grid_type_selector, _("Grid Mode"));
 	set_tooltip (snap_mode_button, _("Snap Mode\n\nRight-click to visit Snap preferences."));
 	set_tooltip (edit_point_selector, _("Edit Point"));

gtk2_ardour/midi_automation_line.cc

@@ -76,7 +76,7 @@ MidiAutomationLine::get_verbose_cursor_string (double fraction) const
 		return AutomationLine::get_verbose_cursor_string(fraction);
 	}
 
-	const uint8_t channel = mtv->get_channel_for_add();
+	const uint8_t channel = mtv->get_preferred_midi_channel();
 	boost::shared_ptr<const ValueNameList> value_names = mtv->route()->instrument_info().value_name_list_by_control (channel, _parameter.id());
 
 	if (!value_names) {

gtk2_ardour/midi_region_view.cc

@@ -829,6 +829,7 @@ MidiRegionView::show_list_editor ()
 	_list_editor->present ();
 }
 
+
 /** Add a note to the model, and the view, at a canvas (click) coordinate.
  * \param t time in samples relative to the position of the region
  * \param y vertical position in pixels
@@ -855,7 +856,7 @@ MidiRegionView::create_note_at (timepos_t const & t, double y, Temporal::Beats l
 	Temporal::Beats region_start = t.beats();
 
 	const double  note     = view->y_to_note(y);
-	const uint8_t chan     = mtv->get_channel_for_add();
+	const uint8_t chan     = get_channel_for_add(region_start);
 	const uint8_t velocity = get_velocity_for_add (region_start);
 
 	const boost::shared_ptr<NoteType> new_note (new NoteType (chan, region_start, length, (uint8_t)note, velocity));
@@ -2002,7 +2003,7 @@ MidiRegionView::change_patch_change (MidiModel::PatchChangePtr old_change, const
 /** Add a patch change to the region.
  *  @param t Time in samples relative to region position
  *  @param patch Patch to add; time and channel are ignored (time is converted from t, and channel comes from
- *  MidiTimeAxisView::get_channel_for_add())
+ *  MidiTimeAxisView::get_preferred_midi_channel())
  */
 void
 MidiRegionView::add_patch_change (timecnt_t const & t, Evoral::PatchChange<Temporal::Beats> const & patch)
@@ -3917,7 +3918,7 @@ MidiRegionView::update_ghost_note (double x, double y, uint32_t state)
 	_ghost_note->note()->set_time (snapped_beats);
 	_ghost_note->note()->set_length (length);
 	_ghost_note->note()->set_note (y_to_note (y));
-	_ghost_note->note()->set_channel (mtv->get_channel_for_add ());
+	_ghost_note->note()->set_channel (mtv->get_preferred_midi_channel ());
 	_ghost_note->note()->set_velocity (get_velocity_for_add (snapped_beats));
 
 	update_note (_ghost_note, false);
@@ -4249,6 +4250,32 @@ MidiRegionView::show_verbose_cursor (string const & text, double xoffset, double
 	trackview.editor().verbose_cursor()->set_offset (ArdourCanvas::Duple (xoffset, yoffset));
 }
 
+
+uint8_t
+MidiRegionView::get_channel_for_add (MidiModel::TimeType time) const
+{
+	/* first, use the user-specified channel in the editor */
+	PublicEditor& editor  = trackview.editor();
+	if (editor.draw_channel() != Editing::DRAW_CHAN_AUTO) {
+		return editor.draw_channel();
+	}
+
+	/* second, use the nearest note in the region-view (consistent with get_velocity_for_add behavior) */
+	if (!_model->notes().empty()) {
+		MidiModel::Notes::const_iterator m = _model->note_lower_bound(time);
+		return (*m)->channel();
+	}
+
+	/* lastly: query the track's channel filter */
+	MidiTimeAxisView* const mtv  = dynamic_cast<MidiTimeAxisView*>(&trackview);
+	if (mtv) {
+		return mtv->get_preferred_midi_channel();
+	}
+
+	/* fallback: ch0 */
+	return 0;
+}
+
 uint8_t
 MidiRegionView::get_velocity_for_add (MidiModel::TimeType time) const
 {

gtk2_ardour/midi_region_view.h

@@ -441,6 +441,7 @@ public:
 	void show_verbose_cursor (boost::shared_ptr<NoteType>) const;
 
 	uint8_t get_velocity_for_add (ARDOUR::MidiModel::TimeType time) const;
+	uint8_t get_channel_for_add (ARDOUR::MidiModel::TimeType time) const;
 
 	uint8_t  _current_range_min;
 	uint8_t  _current_range_max;

gtk2_ardour/midi_time_axis.cc

@@ -1724,7 +1724,7 @@ MidiTimeAxisView::stop_step_editing ()
  *  of the channel selector.
  */
 uint8_t
-MidiTimeAxisView::get_channel_for_add () const
+MidiTimeAxisView::get_preferred_midi_channel () const
 {
 	if (_editor.draw_channel() != Editing::DRAW_CHAN_AUTO) {
 		return _editor.draw_channel();

gtk2_ardour/midi_time_axis.h

@@ -108,7 +108,7 @@ public:
 	void first_idle ();
 	void set_note_highlight (uint8_t note);
 
-	uint8_t get_channel_for_add () const;
+	uint8_t get_preferred_midi_channel () const;
 
 	void get_per_region_note_selection (std::list<std::pair<PBD::ID, std::set<boost::shared_ptr<Evoral::Note<Temporal::Beats> > > > >&);
 	void use_midnam_info ();

gtk2_ardour/piano_roll_header.cc

@@ -688,7 +688,7 @@ PianoRollHeader::send_note_on (uint8_t note)
 	//cerr << "note on: " << (int) note << endl;
 
 	if (track) {
-		_event[0] = (MIDI_CMD_NOTE_ON | mtv->get_channel_for_add ());
+		_event[0] = (MIDI_CMD_NOTE_ON | mtv->get_preferred_midi_channel ());
 		_event[1] = note;
 		_event[2] = 100;
 
@@ -703,7 +703,7 @@ PianoRollHeader::send_note_off (uint8_t note)
 	MidiTimeAxisView*                    mtv   = dynamic_cast<MidiTimeAxisView*> (&_view.trackview ());
 
 	if (track) {
-		_event[0] = (MIDI_CMD_NOTE_OFF | mtv->get_channel_for_add ());
+		_event[0] = (MIDI_CMD_NOTE_OFF | mtv->get_preferred_midi_channel ());
 		_event[1] = note;
 		_event[2] = 100;