rework tempo editing.

most changes are due to a new design where tempo discontinuities at the
beginning of a ramped section may be set.
this allows easier mapping of live performance, especially in
the common case of a ramped ritard before the beginning of a new section.

feature summary:

holding constraint modifier (shift) while dragging the BBT ruler area
drags the tempo lines by changing the start tempo (as before)

holding copy modifier (control) while dragging the BBT ruler area
drags the tempo lines by changing the end tempo (ahem. not quite there)

dragging a tempo mark while holding constraint (shift) will change the
previous end tempo to match the marker position *worth trying*.

holding constraint and copy modifier (control + shift) while dragging
the BBT ruler area attempts to'pinch' or twist the surrounding tempi
sp that later ones are not repositioned (currently suffereng from
rounding errors)

1 files changed, 443 insertions, 130 deletions

diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 4f3899078f..6c0032a673 100644
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -45,7 +45,7 @@ using Timecode::BBT_Time;
 /* _default tempo is 4/4 qtr=120 */
 
 Meter    TempoMap::_default_meter (4.0, 4.0);
-Tempo    TempoMap::_default_tempo (120.0, 4.0);
+Tempo    TempoMap::_default_tempo (120.0, 4.0, 120.0);
 
 framepos_t
 MetricSection::frame_at_minute (const double& time) const
@@ -71,7 +71,7 @@ Meter::frames_per_grid (const Tempo& tempo, framecnt_t sr) const
 	   The return value IS NOT interpretable in terms of "beats".
 	*/
 
-	return (60.0 * sr) / (tempo.note_types_per_minute() * (_note_type/tempo.note_type()));
+	return (60.0 * sr) / (tempo.note_types_per_minute() * (_note_type / tempo.note_type()));
 }
 
 double
@@ -90,6 +90,7 @@ TempoSection::TempoSection (const XMLNode& node, framecnt_t sample_rate)
 	, _c (0.0)
 	, _active (true)
 	, _locked_to_meter (false)
+	, _legacy_end (false)
 {
 	XMLProperty const * prop;
 	LocaleGuard lg;
@@ -143,7 +144,17 @@ TempoSection::TempoSection (const XMLNode& node, framecnt_t sample_rate)
 		if (sscanf (prop->value().c_str(), "%lf", &_note_type) != 1 || _note_type < 1.0) {
 			error << _("TempoSection XML node has an illegal \"note-type\" value") << endmsg;
 			throw failed_constructor();
+		}
 	}
+
+	/* XX replace old end-beats-per-minute name with note-types-per-minute */
+	if ((prop = node.property ("end-beats-per-minute")) != 0) {
+		if (sscanf (prop->value().c_str(), "%lf", &_end_note_types_per_minute) != 1 || _end_note_types_per_minute < 0.0) {
+			info << _("TempoSection XML node has an illegal \"in-beats-per-minute\" value") << endmsg;
+			//throw failed_constructor();
+			_end_note_types_per_minute = _note_types_per_minute;
+			_legacy_end = true;
+		}
 	}
 
 	if ((prop = node.property ("movable")) == 0) {
@@ -207,6 +218,8 @@ TempoSection::get_state() const
 	root->add_property ("beats-per-minute", buf);
 	snprintf (buf, sizeof (buf), "%lf", _note_type);
 	root->add_property ("note-type", buf);
+	snprintf (buf, sizeof (buf), "%lf", _end_note_types_per_minute);
+	root->add_property ("end-beats-per-minute", buf);
 	snprintf (buf, sizeof (buf), "%s", !initial()?"yes":"no");
 	root->add_property ("movable", buf);
 	snprintf (buf, sizeof (buf), "%s", active()?"yes":"no");
@@ -234,7 +247,7 @@ TempoSection::tempo_at_minute (const double& m) const
 		return Tempo (note_types_per_minute(), note_type());
 	}
 
-	return Tempo (_tempo_at_time (m - minute()), _note_type);
+	return Tempo (_tempo_at_time (m - minute()), _note_type, _end_note_types_per_minute);
 }
 
 /** returns the session relative minute where the supplied tempo in note types per minute occurs.
@@ -274,7 +287,7 @@ TempoSection::tempo_at_pulse (const double& p) const
 		return Tempo (note_types_per_minute(), note_type());
 	}
 
-	return Tempo (_tempo_at_pulse (p - pulse()), _note_type);
+	return Tempo (_tempo_at_pulse (p - pulse()), _note_type, _end_note_types_per_minute);
 }
 
 /** returns the whole-note pulse where a tempo in note types per minute occurs.
@@ -748,7 +761,7 @@ TempoMap::TempoMap (framecnt_t fr)
 	_frame_rate = fr;
 	BBT_Time start (1, 1, 0);
 
-	TempoSection *t = new TempoSection (0.0, 0.0, _default_tempo.note_types_per_minute(), _default_tempo.note_type(), TempoSection::Ramp, AudioTime, fr);
+	TempoSection *t = new TempoSection (0.0, 0.0, _default_tempo, TempoSection::Ramp, AudioTime, fr);
 	MeterSection *m = new MeterSection (0.0, 0.0, 0.0, start, _default_meter.divisions_per_bar(), _default_meter.note_divisor(), AudioTime, fr);
 
 	t->set_initial (true);
@@ -1075,11 +1088,29 @@ TempoMap::add_tempo (const Tempo& tempo, const double& pulse, const framepos_t&
 	}
 
 	TempoSection* ts = 0;
+	TempoSection* prev_tempo = 0;
 	{
 		Glib::Threads::RWLock::WriterLock lm (lock);
 		ts = add_tempo_locked (tempo, pulse, minute_at_frame (frame), type, pls, true);
-	}
+		for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
 
+			if ((*i)->is_tempo()) {
+				TempoSection* const this_t = static_cast<TempoSection*> (*i);
+
+				bool const ipm = ts->position_lock_style() == MusicTime;
+				bool const lm = ts->locked_to_meter();
+				if ((ipm && this_t->pulse() == ts->pulse()) || (!ipm && this_t->frame() == ts->frame())
+				    || (lm && this_t->pulse() == ts->pulse())) {
+					if (prev_tempo && prev_tempo->type() == TempoSection::Ramp) {
+						prev_tempo->set_end_note_types_per_minute (ts->note_types_per_minute());
+					}
+					break;
+				}
+				prev_tempo = this_t;
+			}
+		}
+		recompute_map (_metrics);
+	}
 
 	PropertyChanged (PropertyChange ());
 
@@ -1095,6 +1126,7 @@ TempoMap::replace_tempo (TempoSection& ts, const Tempo& tempo, const double& pul
 	}
 
 	const bool locked_to_meter = ts.locked_to_meter();
+	TempoSection* new_ts = 0;
 
 	{
 		Glib::Threads::RWLock::WriterLock lm (lock);
@@ -1109,8 +1141,31 @@ TempoMap::replace_tempo (TempoSection& ts, const Tempo& tempo, const double& pul
 				}
 			} else {
 				remove_tempo_locked (ts);
-				add_tempo_locked (tempo, pulse, minute_at_frame (frame), type, pls, true, locked_to_meter);
+				new_ts = add_tempo_locked (tempo, pulse, minute_at_frame (frame), type, pls, true, locked_to_meter);
+
+				if (new_ts && new_ts->type() == TempoSection::Constant) {
+					new_ts->set_end_note_types_per_minute (new_ts->note_types_per_minute());
+				} else {
+					for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+
+						if ((*i)->is_tempo()) {
+							TempoSection* const this_t = static_cast<TempoSection*> (*i);
+
+							bool const ipm = new_ts->position_lock_style() == MusicTime;
+							bool const lm = new_ts->locked_to_meter();
+							if ((ipm && this_t->pulse() > new_ts->pulse()) || (!ipm && this_t->frame() > new_ts->frame())
+							    || (lm && this_t->pulse() > new_ts->pulse())) {
+								//if (prev_tempo && prev_tempo->type() == TempoSection::Ramp) {
+								new_ts->set_end_note_types_per_minute (this_t->note_types_per_minute());
+									//}
+								break;
+							}
+							//prev_tempo = this_t;
+						}
+					}
+				}
 			}
+
 		} else {
 			first.set_type (type);
 			first.set_pulse (0.0);
@@ -1120,9 +1175,9 @@ TempoMap::replace_tempo (TempoSection& ts, const Tempo& tempo, const double& pul
 			{
 				/* cannot move the first tempo section */
 				*static_cast<Tempo*>(&first) = tempo;
-				recompute_map (_metrics);
 			}
 		}
+		recompute_map (_metrics);
 	}
 
 	PropertyChanged (PropertyChange ());
@@ -1132,25 +1187,20 @@ TempoSection*
 TempoMap::add_tempo_locked (const Tempo& tempo, double pulse, double minute
 			    , TempoSection::Type type, PositionLockStyle pls, bool recompute, bool locked_to_meter)
 {
-	TempoSection* t = new TempoSection (pulse, minute, tempo.note_types_per_minute(), tempo.note_type(), type, pls, _frame_rate);
+	TempoSection* t = new TempoSection (pulse, minute, tempo, type, pls, _frame_rate);
 	t->set_locked_to_meter (locked_to_meter);
-	bool solved = false;
 
 	do_insert (t);
 
 	if (recompute) {
 		if (pls == AudioTime) {
-			solved = solve_map_minute (_metrics, t, t->minute());
+			solve_map_minute (_metrics, t, t->minute());
 		} else {
-			solved = solve_map_pulse (_metrics, t, t->pulse());
+			solve_map_pulse (_metrics, t, t->pulse());
 		}
 		recompute_meters (_metrics);
 	}
 
-	if (!solved && recompute) {
-		recompute_map (_metrics);
-	}
-
 	return t;
 }
 
@@ -1261,9 +1311,9 @@ TempoMap::add_meter_locked (const Meter& meter, double beat, const BBT_Time& whe
 }
 
 void
-TempoMap::change_initial_tempo (double note_types_per_minute, double note_type)
+TempoMap::change_initial_tempo (double note_types_per_minute, double note_type, double end_note_types_per_minute)
 {
-	Tempo newtempo (note_types_per_minute, note_type);
+	Tempo newtempo (note_types_per_minute, note_type, end_note_types_per_minute);
 	TempoSection* t;
 
 	for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
@@ -1283,9 +1333,9 @@ TempoMap::change_initial_tempo (double note_types_per_minute, double note_type)
 }
 
 void
-TempoMap::change_existing_tempo_at (framepos_t where, double note_types_per_minute, double note_type)
+TempoMap::change_existing_tempo_at (framepos_t where, double note_types_per_minute, double note_type, double end_ntpm)
 {
-	Tempo newtempo (note_types_per_minute, note_type);
+	Tempo newtempo (note_types_per_minute, note_type, end_ntpm);
 
 	TempoSection* prev;
 	TempoSection* first;
@@ -1433,14 +1483,14 @@ TempoMap::recompute_tempi (Metrics& metrics)
 			}
 			if (prev_t) {
 				if (t->position_lock_style() == AudioTime) {
-					prev_t->set_c (prev_t->compute_c_minute (t->note_types_per_minute(), t->minute()));
+					prev_t->set_c (prev_t->compute_c_minute (prev_t->end_note_types_per_minute(), t->minute()));
 					if (!t->locked_to_meter()) {
-						t->set_pulse (prev_t->pulse_at_ntpm (t->note_types_per_minute(), t->minute()));
+						t->set_pulse (prev_t->pulse_at_ntpm (prev_t->end_note_types_per_minute(), t->minute()));
 					}
 
 				} else {
-					prev_t->set_c (prev_t->compute_c_pulse (t->note_types_per_minute(), t->pulse()));
-					t->set_minute (prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()));
+					prev_t->set_c (prev_t->compute_c_pulse (prev_t->end_note_types_per_minute(), t->pulse()));
+					t->set_minute (prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()));
 
 				}
 			}
@@ -1745,7 +1795,7 @@ TempoMap::tempo_at_minute_locked (const Metrics& metrics, const double& minute)
 		}
 	}
 
-	return Tempo (prev_t->note_types_per_minute(), prev_t->note_type());
+	return Tempo (prev_t->note_types_per_minute(), prev_t->note_type(), prev_t->end_note_types_per_minute());
 }
 
 /** returns the frame at which the supplied tempo occurs, or
@@ -1819,7 +1869,7 @@ TempoMap::tempo_at_pulse_locked (const Metrics& metrics, const double& pulse) co
 		}
 	}
 
-	return Tempo (prev_t->note_types_per_minute(), prev_t->note_type());
+	return Tempo (prev_t->note_types_per_minute(), prev_t->note_type(), prev_t->end_note_types_per_minute());
 }
 
 double
@@ -2570,7 +2620,7 @@ TempoMap::check_solved (const Metrics& metrics) const
 				}
 
 				/* precision check ensures tempo and frames align.*/
-				if (t->frame() != frame_at_minute (prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()))) {
+				if (t->frame() != frame_at_minute (prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()))) {
 					if (!t->locked_to_meter()) {
 						return false;
 					}
@@ -2681,20 +2731,20 @@ TempoMap::solve_map_minute (Metrics& imaginary, TempoSection* section, const dou
 				if (prev_t && !section_prev && ((sml && tlm && t->pulse() > section->pulse()) || (!tlm && t->minute() > minute))) {
 					section_prev = prev_t;
 
-					section_prev->set_c (section_prev->compute_c_minute (section->note_types_per_minute(), minute));
+					section_prev->set_c (section_prev->compute_c_minute (section_prev->end_note_types_per_minute(), minute));
 					if (!section->locked_to_meter()) {
-						section->set_pulse (section_prev->pulse_at_ntpm (section->note_types_per_minute(), minute));
+						section->set_pulse (section_prev->pulse_at_ntpm (section_prev->end_note_types_per_minute(), minute));
 					}
 					prev_t = section;
 				}
 
 				if (t->position_lock_style() == MusicTime) {
-					prev_t->set_c (prev_t->compute_c_pulse (t->note_types_per_minute(), t->pulse()));
-					t->set_minute (prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()));
+					prev_t->set_c (prev_t->compute_c_pulse (prev_t->end_note_types_per_minute(), t->pulse()));
+					t->set_minute (prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()));
 				} else {
-					prev_t->set_c (prev_t->compute_c_minute (t->note_types_per_minute(), t->minute()));
+					prev_t->set_c (prev_t->compute_c_minute (prev_t->end_note_types_per_minute(), t->minute()));
 					if (!t->locked_to_meter()) {
-						t->set_pulse (prev_t->pulse_at_ntpm (t->note_types_per_minute(), t->minute()));
+						t->set_pulse (prev_t->pulse_at_ntpm (prev_t->end_note_types_per_minute(), t->minute()));
 					}
 				}
 			}
@@ -2751,12 +2801,12 @@ TempoMap::solve_map_pulse (Metrics& imaginary, TempoSection* section, const doub
 				}
 
 				if (t->position_lock_style() == MusicTime) {
-					prev_t->set_c (prev_t->compute_c_pulse (t->note_types_per_minute(), t->pulse()));
-					t->set_minute (prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()));
+					prev_t->set_c (prev_t->compute_c_pulse (prev_t->end_note_types_per_minute(), t->pulse()));
+					t->set_minute (prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()));
 				} else {
-					prev_t->set_c (prev_t->compute_c_minute (t->note_types_per_minute(), t->minute()));
+					prev_t->set_c (prev_t->compute_c_minute (prev_t->end_note_types_per_minute(), t->minute()));
 					if (!t->locked_to_meter()) {
-						t->set_pulse (prev_t->pulse_at_ntpm (t->note_types_per_minute(), t->minute()));
+						t->set_pulse (prev_t->pulse_at_ntpm (prev_t->end_note_types_per_minute(), t->minute()));
 					}
 				}
 			}
@@ -2765,8 +2815,8 @@ TempoMap::solve_map_pulse (Metrics& imaginary, TempoSection* section, const doub
 	}
 
 	if (section_prev) {
-		section_prev->set_c (section_prev->compute_c_pulse (section->note_types_per_minute(), pulse));
-		section->set_minute (section_prev->minute_at_ntpm (section->note_types_per_minute(), pulse));
+		section_prev->set_c (section_prev->compute_c_pulse (section_prev->end_note_types_per_minute(), pulse));
+		section->set_minute (section_prev->minute_at_ntpm (section_prev->end_note_types_per_minute(), pulse));
 	}
 
 #if (0)
@@ -3338,18 +3388,35 @@ TempoMap::gui_set_meter_position (MeterSection* ms, const framepos_t& frame)
 }
 
 bool
-TempoMap::gui_change_tempo (TempoSection* ts, const Tempo& bpm)
+TempoMap::gui_change_tempo (TempoSection* ts, const Tempo& bpm, bool change_end)
 {
 	Metrics future_map;
 	bool can_solve = false;
 	{
 		Glib::Threads::RWLock::WriterLock lm (lock);
 		TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, ts);
-		tempo_copy->set_note_types_per_minute (bpm.note_types_per_minute());
+
+		if (change_end && tempo_copy->type() == TempoSection::Constant) {
+			tempo_copy->set_end_note_types_per_minute (bpm.note_types_per_minute());
+			tempo_copy->set_note_types_per_minute (bpm.note_types_per_minute());
+		} else if (change_end) {
+			tempo_copy->set_end_note_types_per_minute (bpm.note_types_per_minute());
+		} else {
+			tempo_copy->set_note_types_per_minute (bpm.note_types_per_minute());
+		}
+
 		recompute_tempi (future_map);
 
 		if (check_solved (future_map)) {
-			ts->set_note_types_per_minute (bpm.note_types_per_minute());
+			if (change_end && ts->type() == TempoSection::Constant) {
+				ts->set_end_note_types_per_minute (bpm.note_types_per_minute());
+				ts->set_note_types_per_minute (bpm.note_types_per_minute());
+			} else if (change_end) {
+				ts->set_end_note_types_per_minute (bpm.note_types_per_minute());
+			} else {
+				ts->set_note_types_per_minute (bpm.note_types_per_minute());
+			}
+
 			recompute_map (_metrics);
 			can_solve = true;
 		}
@@ -3363,11 +3430,12 @@ TempoMap::gui_change_tempo (TempoSection* ts, const Tempo& bpm)
 	if (can_solve) {
 		MetricPositionChanged (PropertyChange ()); // Emit Signal
 	}
+
 	return can_solve;
 }
 
 void
-TempoMap::gui_stretch_tempo (TempoSection* ts, const framepos_t& frame, const framepos_t& end_frame)
+TempoMap::gui_stretch_tempo (TempoSection* ts, const framepos_t frame, const framepos_t end_frame)
 {
 	/*
 	  Ts (future prev_t)   Tnext
@@ -3387,105 +3455,237 @@ TempoMap::gui_stretch_tempo (TempoSection* ts, const framepos_t& frame, const fr
 		}
 
 		TempoSection* prev_t = copy_metrics_and_point (_metrics, future_map, ts);
-		TempoSection* prev_to_prev_t = 0;
-		const frameoffset_t fr_off = end_frame - frame;
-
-		assert (prev_t);
 
-		if (prev_t->pulse() > 0.0) {
-			prev_to_prev_t = const_cast<TempoSection*>(&tempo_section_at_minute_locked (future_map, minute_at_frame (prev_t->frame() - 1)));
+		if (!prev_t) {
+			return;
 		}
 
-		TempoSection* next_t = 0;
-		for (Metrics::iterator i = future_map.begin(); i != future_map.end(); ++i) {
-			TempoSection* t = 0;
-			if ((*i)->is_tempo()) {
-				t = static_cast<TempoSection*> (*i);
-				if (t->frame() > ts->frame()) {
-					next_t = t;
-					break;
-				}
-			}
-		}
 		/* minimum allowed measurement distance in frames */
-		const framepos_t min_dframe = 2;
+		framepos_t const min_dframe = 2;
+
+		double new_bpm;
+
+		if (frame > prev_t->frame() + min_dframe && end_frame > prev_t->frame() + min_dframe) {
+
+			new_bpm = prev_t->note_types_per_minute() * ((frame - prev_t->frame())
+										   / (double) (end_frame - prev_t->frame()));
+		} else {
+			new_bpm = prev_t->note_types_per_minute();
+		}
+
+		std::cout << "new bpm : " << new_bpm << std::endl;
+		new_bpm = min (new_bpm, (double) 1000.0);
 
-		/* the change in frames is the result of changing the slope of at most 2 previous tempo sections.
-		   constant to constant is straightforward, as the tempo prev to prev_t has constant slope.
+		/* don't clamp and proceed here.
+		   testing has revealed that this can go negative,
+		   which is an entirely different thing to just being too low.
 		*/
-		double contribution = 0.0;
 
-		if (next_t && prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
-			contribution = (prev_t->frame() - prev_to_prev_t->frame()) / (double) (next_t->frame() - prev_to_prev_t->frame());
+		if (new_bpm < 0.5) {
+			goto out;
 		}
 
-		const frameoffset_t prev_t_frame_contribution = fr_off - (contribution * (double) fr_off);
+		if (prev_t && prev_t->type() == TempoSection::Ramp) {
+			prev_t->set_note_types_per_minute (new_bpm);
+		} else {
+			prev_t->set_end_note_types_per_minute (new_bpm);
+			prev_t->set_note_types_per_minute (new_bpm);
+		}
 
-		const double start_pulse = prev_t->pulse_at_minute (minute_at_frame (frame));
-		const double end_pulse = prev_t->pulse_at_minute (minute_at_frame (end_frame));
+		recompute_tempi (future_map);
+		recompute_meters (future_map);
 
-		double new_bpm;
+		if (check_solved (future_map)) {
+			if (prev_t && prev_t->type() == TempoSection::Ramp) {
+				ts->set_note_types_per_minute (new_bpm);
+			} else {
+				ts->set_end_note_types_per_minute (new_bpm);
+				ts->set_note_types_per_minute (new_bpm);
+			}
+			recompute_tempi (_metrics);
+			recompute_meters (_metrics);
+		}
+	}
 
-		if (prev_t->type() == TempoSection::Constant || prev_t->c() == 0.0) {
+	MetricPositionChanged (PropertyChange ()); // Emit Signal
 
-			if (prev_t->position_lock_style() == MusicTime) {
-				if (prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
-					if (frame > prev_to_prev_t->frame() + min_dframe && (frame + prev_t_frame_contribution) > prev_to_prev_t->frame() + min_dframe) {
+out:
+	Metrics::const_iterator d = future_map.begin();
+	while (d != future_map.end()) {
+		delete (*d);
+		++d;
+	}
 
-						new_bpm = prev_t->note_types_per_minute() * ((frame - prev_to_prev_t->frame())
-											/ (double) ((frame + prev_t_frame_contribution) - prev_to_prev_t->frame()));
-					} else {
-						new_bpm = prev_t->note_types_per_minute();
-					}
-				} else {
-					/* prev to prev is irrelevant */
+}
+void
+TempoMap::gui_stretch_tempo_end (TempoSection* ts, const framepos_t frame, const framepos_t end_frame)
+{
+	/*
+	  Ts (future prev_t)   Tnext
+	  |                    |
+	  |     [drag^]        |
+	  |----------|----------
+	        e_f  qn_beats(frame)
+	*/
 
-					if (start_pulse > prev_t->pulse() && end_pulse > prev_t->pulse()) {
-						new_bpm = prev_t->note_types_per_minute() * ((start_pulse - prev_t->pulse()) / (end_pulse - prev_t->pulse()));
-					} else {
-						new_bpm = prev_t->note_types_per_minute();
-					}
-				}
-			} else {
-				/* AudioTime */
-				if (prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
-					if (frame > prev_to_prev_t->frame() + min_dframe && end_frame > prev_to_prev_t->frame() + min_dframe) {
+	Metrics future_map;
 
-						new_bpm = prev_t->note_types_per_minute() * ((frame - prev_to_prev_t->frame())
-											/ (double) ((end_frame) - prev_to_prev_t->frame()));
-					} else {
-						new_bpm = prev_t->note_types_per_minute();
-					}
-				} else {
-					/* prev_to_prev_t is irrelevant */
+	{
+		Glib::Threads::RWLock::WriterLock lm (lock);
 
-					if (frame > prev_t->frame() + min_dframe && end_frame > prev_t->frame() + min_dframe) {
-						new_bpm = prev_t->note_types_per_minute() * ((frame - prev_t->frame()) / (double) (end_frame - prev_t->frame()));
-					} else {
-						new_bpm = prev_t->note_types_per_minute();
-					}
-				}
+		if (!ts) {
+			return;
+		}
+
+		TempoSection* prev_t = copy_metrics_and_point (_metrics, future_map, ts);
+
+/*
+		TempoSection* next_t = 0;
+		for (Metrics::const_iterator i = future_map.begin(); i != future_map.end(); ++i) {
+			if ((*i)->is_tempo() && (*i)->minute() >  prev_t->minute()) {
+				next_t = static_cast<TempoSection*> (*i);
+				break;
 			}
+		}
+
+		if (!next_t) {
+			return;
+		}
+*/
+		if (!prev_t) {
+			return;
+		}
+
+
+		/* minimum allowed measurement distance in frames */
+		framepos_t const min_dframe = 2;
+		double new_bpm;
+
+		if (frame > prev_t->frame() + min_dframe && end_frame > prev_t->frame() + min_dframe) {
+			new_bpm = prev_t->end_note_types_per_minute() * ((frame - prev_t->frame())
+										 / (double) (end_frame - prev_t->frame()));
 		} else {
+			new_bpm = prev_t->end_note_types_per_minute();
+		}
 
-			double frame_ratio = 1.0;
-			double pulse_ratio = 1.0;
-			const double pulse_pos = frame;
+		new_bpm = min (new_bpm, (double) 1000.0);
 
-			if (prev_to_prev_t) {
-				if (pulse_pos > prev_to_prev_t->frame() + min_dframe && (pulse_pos - fr_off) > prev_to_prev_t->frame() + min_dframe) {
-					frame_ratio = (((pulse_pos - fr_off) - prev_to_prev_t->frame()) / (double) ((pulse_pos) - prev_to_prev_t->frame()));
-				}
-				if (end_pulse > prev_to_prev_t->pulse() && start_pulse > prev_to_prev_t->pulse()) {
-					pulse_ratio = ((start_pulse - prev_to_prev_t->pulse()) / (end_pulse - prev_to_prev_t->pulse()));
-				}
+		if (new_bpm < 0.5) {
+			goto out;
+		}
+
+		if (prev_t && prev_t->type() == TempoSection::Ramp) {
+			prev_t->set_end_note_types_per_minute (new_bpm);
+		} else {
+			if (prev_t) {
+				prev_t->set_note_types_per_minute (new_bpm);
+				prev_t->set_end_note_types_per_minute (prev_t->note_types_per_minute());
+			}
+		}
+
+		recompute_tempi (future_map);
+		recompute_meters (future_map);
+
+		if (check_solved (future_map)) {
+			if (prev_t && prev_t->type() == TempoSection::Ramp) {
+				ts->set_end_note_types_per_minute (new_bpm);
 			} else {
-				if (pulse_pos > prev_t->frame() + min_dframe && (pulse_pos - fr_off) > prev_t->frame() + min_dframe) {
-					frame_ratio = (((pulse_pos - fr_off) - prev_t->frame()) / (double) ((pulse_pos) - prev_t->frame()));
+				if (prev_t) {
+					ts->set_end_note_types_per_minute (prev_t->note_types_per_minute());
+					ts->set_note_types_per_minute (prev_t->note_types_per_minute());
 				}
-				pulse_ratio = (start_pulse / end_pulse);
 			}
-			new_bpm = prev_t->note_types_per_minute() * (pulse_ratio * frame_ratio);
+			recompute_tempi (_metrics);
+			recompute_meters (_metrics);
+		}
+	}
+
+	MetricPositionChanged (PropertyChange ()); // Emit Signal
+
+out:
+	Metrics::const_iterator d = future_map.begin();
+	while (d != future_map.end()) {
+		delete (*d);
+		++d;
+	}
+
+}
+bool
+TempoMap::gui_twist_tempi (TempoSection* ts, const Tempo& bpm, const framepos_t frame, const framepos_t end_frame)
+{
+	TempoSection* next_t = 0;
+	TempoSection* next_to_next_t = 0;
+	Metrics future_map;
+	bool can_solve = false;
+
+	/* minimum allowed measurement distance in frames */
+	framepos_t const min_dframe = 2;
+
+	{
+		Glib::Threads::RWLock::WriterLock lm (lock);
+		if (!ts) {
+			return false;
+		}
+
+		TempoSection* tempo_copy = copy_metrics_and_point (_metrics, future_map, ts);
+		TempoSection* prev_to_prev_t = 0;
+		const frameoffset_t fr_off = end_frame - frame;
+
+		if (!tempo_copy) {
+			return false;
+		}
+
+		if (tempo_copy->pulse() > 0.0) {
+			prev_to_prev_t = const_cast<TempoSection*>(&tempo_section_at_minute_locked (future_map, minute_at_frame (tempo_copy->frame() - 1)));
+		}
+
+		for (Metrics::const_iterator i = future_map.begin(); i != future_map.end(); ++i) {
+			if ((*i)->is_tempo() && (*i)->minute() >  tempo_copy->minute()) {
+				next_t = static_cast<TempoSection*> (*i);
+				break;
+			}
+		}
+
+		if (!next_t) {
+			return false;
+		}
+
+		for (Metrics::const_iterator i = future_map.begin(); i != future_map.end(); ++i) {
+			if ((*i)->is_tempo() && (*i)->minute() >  next_t->minute()) {
+				next_to_next_t = static_cast<TempoSection*> (*i);
+				break;
+			}
+		}
+
+		if (!next_to_next_t) {
+			std::cout << "no next to next t" << std::endl;
+			return false;
+		}
+
+		double prev_contribution = 0.0;
+
+		if (next_t && prev_to_prev_t && prev_to_prev_t->type() == TempoSection::Ramp) {
+			prev_contribution = (tempo_copy->frame() - prev_to_prev_t->frame()) / (double) (next_t->frame() - prev_to_prev_t->frame());
+		}
+
+		const frameoffset_t tempo_copy_frame_contribution = fr_off - (prev_contribution * (double) fr_off);
+
+
+		framepos_t old_tc_pos = tempo_copy->frame();
+		framepos_t old_next_pos = next_t->frame();
+		double old_next_minute = next_t->minute();
+		framepos_t old_next_to_next_pos = next_to_next_t->frame();
+		double old_next_to_next_minute = next_to_next_t->minute();
+
+		double new_bpm;
+		double new_next_bpm;
+		double new_copy_end_bpm;
+
+		if (frame > prev_to_prev_t->frame() + min_dframe && (frame + tempo_copy_frame_contribution) > prev_to_prev_t->frame() + min_dframe) {
+			new_bpm = tempo_copy->note_types_per_minute() * ((frame - tempo_copy->frame())
+										       / (double) (end_frame - tempo_copy->frame()));
+		} else {
+			new_bpm = tempo_copy->note_types_per_minute();
 		}
 
 		/* don't clamp and proceed here.
@@ -3493,17 +3693,95 @@ TempoMap::gui_stretch_tempo (TempoSection* ts, const framepos_t& frame, const fr
 		   which is an entirely different thing to just being too low.
 		*/
 		if (new_bpm < 0.5) {
-			return;
+			return false;
 		}
+
 		new_bpm = min (new_bpm, (double) 1000.0);
-		prev_t->set_note_types_per_minute (new_bpm);
+
+		tempo_copy->set_note_types_per_minute (new_bpm);
+		if (tempo_copy->type() == TempoSection::Constant) {
+			tempo_copy->set_end_note_types_per_minute (new_bpm);
+		}
 		recompute_tempi (future_map);
-		recompute_meters (future_map);
 
 		if (check_solved (future_map)) {
+
+			if (!next_t) {
+				return false;
+			}
 			ts->set_note_types_per_minute (new_bpm);
-			recompute_tempi (_metrics);
-			recompute_meters (_metrics);
+			if (ts->type() == TempoSection::Constant) {
+				ts->set_end_note_types_per_minute (new_bpm);
+			}
+			recompute_map (_metrics);
+			can_solve = true;
+		}
+
+		if (next_t->type() == TempoSection::Constant || next_t->c() == 0.0) {
+			if (frame > prev_to_prev_t->frame() + min_dframe && end_frame > prev_to_prev_t->frame() + min_dframe) {
+
+				new_next_bpm = next_t->note_types_per_minute() * ((next_to_next_t->minute() - old_next_minute)
+											/ (double) ((old_next_to_next_minute) - old_next_minute));
+
+			} else {
+				new_next_bpm = next_t->note_types_per_minute();
+			}
+
+			next_t->set_note_types_per_minute (new_next_bpm);
+			recompute_tempi (future_map);
+
+			if (check_solved (future_map)) {
+				for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+					if ((*i)->is_tempo() && (*i)->minute() >  ts->minute()) {
+						next_t = static_cast<TempoSection*> (*i);
+						break;
+					}
+				}
+
+				if (!next_t) {
+					return false;
+				}
+				next_t->set_note_types_per_minute (new_next_bpm);
+				recompute_map (_metrics);
+				can_solve = true;
+			}
+		} else {
+			double next_frame_ratio = 1.0;
+			double copy_frame_ratio = 1.0;
+
+			if (next_to_next_t) {
+				next_frame_ratio =  (next_to_next_t->frame() - old_next_pos) / (double) (old_next_to_next_pos -  old_next_pos);
+
+				copy_frame_ratio =   ((old_tc_pos - next_t->frame()) / (double) (old_tc_pos - old_next_pos));
+
+			} else {
+				//next_frame_ratio = (((next_to_next_pos - fr_off) - next_t->frame()) / (double) ((next_to_next_pos) - next_t->frame()));
+				//next_pulse_ratio = (start_pulse / end_pulse);
+			}
+
+			new_next_bpm = next_t->note_types_per_minute() * next_frame_ratio;
+			new_copy_end_bpm =  tempo_copy->end_note_types_per_minute() * copy_frame_ratio;
+
+			next_t->set_note_types_per_minute (new_next_bpm);
+			tempo_copy->set_end_note_types_per_minute (new_copy_end_bpm);
+			recompute_tempi (future_map);
+
+			if (check_solved (future_map)) {
+				for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+					if ((*i)->is_tempo() && (*i)->minute() >  ts->minute()) {
+						next_t = static_cast<TempoSection*> (*i);
+						break;
+					}
+				}
+
+				if (!next_t) {
+					return false;
+				}
+				next_t->set_note_types_per_minute (new_next_bpm);
+				ts->set_end_note_types_per_minute (new_copy_end_bpm);
+				recompute_map (_metrics);
+				can_solve = true;
+			}
 		}
 	}
 
@@ -3512,10 +3790,12 @@ TempoMap::gui_stretch_tempo (TempoSection* ts, const framepos_t& frame, const fr
 		delete (*d);
 		++d;
 	}
+	if (can_solve) {
+		MetricPositionChanged (PropertyChange ()); // Emit Signal
+	}
 
-	MetricPositionChanged (PropertyChange ()); // Emit Signal
+	return can_solve;
 }
-
 /** Returns the exact bbt-based beat corresponding to the bar, beat or quarter note subdivision nearest to
  * the supplied frame, possibly returning a negative value.
  *
@@ -4203,6 +4483,32 @@ TempoMap::fix_legacy_session ()
 		}
 	}
 }
+void
+TempoMap::fix_legacy_end_session ()
+{
+	TempoSection* prev_t = 0;
+
+	for (Metrics::iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
+		TempoSection* t;
+
+		if ((t = dynamic_cast<TempoSection*>(*i)) != 0) {
+
+			if (!t->active()) {
+				continue;
+			}
+
+			if (prev_t) {
+				if (prev_t->type() == TempoSection::Ramp) {
+					prev_t->set_end_note_types_per_minute (t->note_types_per_minute());
+				} else {
+					prev_t->set_end_note_types_per_minute (prev_t->note_types_per_minute());
+				}
+			}
+
+			prev_t = t;
+		}
+	}
+}
 
 XMLNode&
 TempoMap::get_state ()
@@ -4279,6 +4585,12 @@ TempoMap::set_state (const XMLNode& node, int /*version*/)
 					fix_legacy_session();
 					break;
 				}
+
+				if (t->legacy_end()) {
+					fix_legacy_end_session();
+					break;
+				}
+
 				break;
 			}
 		}
@@ -4337,19 +4649,20 @@ TempoMap::dump (std::ostream& o) const
 	for (Metrics::const_iterator i = _metrics.begin(); i != _metrics.end(); ++i) {
 
 		if ((t = dynamic_cast<const TempoSection*>(*i)) != 0) {
-			o << "Tempo @ " << *i << t->note_types_per_minute() << " BPM (pulse = 1/" << t->note_type()
+			o << "Tempo @ " << *i << " start : " << t->note_types_per_minute() << " end : " << t->end_note_types_per_minute() << " BPM (pulse = 1/" << t->note_type()
 			  << " type= " << enum_2_string (t->type()) << ") "  << " at pulse= " << t->pulse()
 			  << " minute= " << t->minute() << " frame= " << t->frame() << " (initial? " << t->initial() << ')'
 			  << " pos lock: " << enum_2_string (t->position_lock_style()) << std::endl;
 			if (prev_t) {
-				o <<  "  current      : " << t->note_types_per_minute()
+				o <<  "  current start  : " << t->note_types_per_minute()
+				  <<  "  current end  : " << t->end_note_types_per_minute()
 				  << " | " << t->pulse() << " | " << t->frame() << " | " << t->minute() << std::endl;
 				o << "  previous     : " << prev_t->note_types_per_minute()
 				  << " | " << prev_t->pulse() << " | " << prev_t->frame() << " | " << prev_t->minute() << std::endl;
 				o << "  calculated   : " << prev_t->tempo_at_pulse (t->pulse())
-				  << " | " << prev_t->pulse_at_ntpm (t->note_types_per_minute(), t->minute())
-				  << " | " << frame_at_minute (prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()))
-				  << " | " << prev_t->minute_at_ntpm (t->note_types_per_minute(), t->pulse()) << std::endl;
+				  << " | " << prev_t->pulse_at_ntpm (prev_t->end_note_types_per_minute(), t->minute())
+				  << " | " << frame_at_minute (prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()))
+				  << " | " << prev_t->minute_at_ntpm (prev_t->end_note_types_per_minute(), t->pulse()) << std::endl;
 			}
 			prev_t = t;
 		} else if ((m = dynamic_cast<const MeterSection*>(*i)) != 0) {