allow continuation of tempo via right-click 'Continue' where appropriate.

- this is the opposite of 'Ramp to Next'.
	  it removes discontinuities between the
	  last end tempo and the current by altering the current one.

gtk2_ardour/editor.h

@@ -1688,6 +1688,7 @@ class Editor : public PublicEditor, public PBD::ScopedConnectionList, public ARD
 	void rename_marker (ArdourMarker *marker);
 	void toggle_marker_lock_style ();
 	void toggle_tempo_type ();
+	void continue_previous_tempo ();
 	void ramp_to_next_tempo ();
 	void toggle_marker_menu_lock ();
 	void toggle_marker_menu_glue ();

gtk2_ardour/editor_markers.cc

@@ -1000,6 +1000,11 @@ Editor::build_tempo_marker_menu (TempoMarker* loc, bool can_remove)
 		items.push_back (MenuElem (_("Ramp to Next"), sigc::mem_fun(*this, &Editor::ramp_to_next_tempo)));
 	}
 
+	TempoSection* prev_ts = _session->tempo_map().previous_tempo_section (&loc->tempo());
+	if (prev_ts && prev_ts->end_note_types_per_minute() != loc->tempo().note_types_per_minute()) {
+		items.push_back (MenuElem (_("Continue"), sigc::mem_fun(*this, &Editor::continue_previous_tempo)));
+	}
+
 	if (loc->tempo().position_lock_style() == AudioTime && can_remove) {
 		items.push_back (MenuElem (_("Lock to Music"), sigc::mem_fun(*this, &Editor::toggle_marker_lock_style)));
 	} else if (can_remove) {
@@ -1460,6 +1465,35 @@ Editor::toggle_tempo_type ()
 	}
 }
 
+void
+Editor::continue_previous_tempo ()
+{
+	TempoMarker* tm;
+	MeterMarker* mm;
+	dynamic_cast_marker_object (marker_menu_item->get_data ("marker"), &mm, &tm);
+
+	if (tm) {
+		TempoMap& tmap (_session->tempo_map());
+		TempoSection* tsp = &tm->tempo();
+		TempoSection* prev_ts = tmap.previous_tempo_section (&tm->tempo());
+		if (prev_ts) {
+			const Tempo tempo (prev_ts->end_note_types_per_minute(), tsp->note_type(), tsp->end_note_types_per_minute());
+			const double pulse = tsp->pulse();
+			const framepos_t frame = tsp->frame();
+			const PositionLockStyle pls = tsp->position_lock_style();
+
+			begin_reversible_command (_("continue previous tempo"));
+			XMLNode &before = _session->tempo_map().get_state();
+
+			tmap.replace_tempo (*tsp, tempo, pulse, frame, pls);
+
+			XMLNode &after = _session->tempo_map().get_state();
+			_session->add_command(new MementoCommand<TempoMap>(_session->tempo_map(), &before, &after));
+			commit_reversible_command ();
+		}
+	}
+}
+
 void
 Editor::ramp_to_next_tempo ()
 {

libs/ardour/ardour/tempo.h

@@ -367,6 +367,7 @@ class LIBARDOUR_API TempoMap : public PBD::StatefulDestructible
 	const MeterSection& meter_section_at_frame (framepos_t frame) const;
 	const MeterSection& meter_section_at_beat (double beat) const;
 
+	TempoSection* previous_tempo_section (TempoSection*) const;
 	TempoSection* next_tempo_section (TempoSection*) const;
 
 	/** add a tempo section locked to pls. ignored values will be set in recompute_tempi()

libs/ardour/tempo.cc

@@ -4285,6 +4285,43 @@ TempoMap::tempo_section_at_beat_locked (const Metrics& metrics, const double& be
 	return *prev_t;
 }
 
+TempoSection*
+TempoMap::previous_tempo_section (TempoSection* ts) const
+{
+	if (!ts) {
+		return 0;
+	}
+
+	Glib::Threads::RWLock::ReaderLock lm (lock);
+
+	TempoSection* prev = 0;
+
+	for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+
+		if ((*i)->is_tempo()) {
+			TempoSection* t = static_cast<TempoSection*> (*i);
+
+			if (!t->active()) {
+				continue;
+			}
+
+			if (prev && t == ts) {
+
+				return prev;
+			}
+
+			prev = t;
+		}
+	}
+
+	if (prev == 0) {
+		fatal << endmsg;
+		abort(); /*NOTREACHED*/
+	}
+
+	return 0;
+}
+
 TempoSection*
 TempoMap::next_tempo_section (TempoSection* ts) const
 {