Tempo ramps - tempo drags respect the snap modifier. add some documentation.

3 files changed, 66 insertions, 38 deletions

diff --git a/gtk2_ardour/editor_drag.cc b/gtk2_ardour/editor_drag.cc
index b6083281ab..e04a73fcf1 100644
--- a/gtk2_ardour/editor_drag.cc
+++ b/gtk2_ardour/editor_drag.cc
@@ -3318,29 +3318,6 @@ TempoMarkerDrag::motion (GdkEvent* event, bool first_move)
 
 	framepos_t pf;
 	double beat = 0.0;
-
-	if (!_editor->snap_musical()) {
-		pf = adjusted_current_frame (event);
-	} else {
-		pf = adjusted_current_frame (event, false);
-		Timecode::BBT_Time when;
-		_editor->session()->tempo_map().bbt_time (pf, when);
-		if (_real_section->position_lock_style() == MusicTime) {
-			if (_editor->snap_type() == SnapToBar) {
-				_editor->session()->tempo_map().round_bbt (when, -1);
-			} else {
-				_editor->session()->tempo_map().round_bbt (when, _editor->get_grid_beat_divisions (0));
-			}
-			beat = _editor->session()->tempo_map().bbt_to_beats (when);
-		} else {
-			if (_editor->snap_type() == SnapToBar) {
-				_editor->session()->tempo_map().round_bbt (when, -1);
-			} else {
-				_editor->session()->tempo_map().round_bbt (when, _editor->get_grid_beat_divisions (0));
-			}
-			pf = _editor->session()->tempo_map().predict_tempo_frame (_real_section, Tempo (_real_section->beats_per_minute(), _real_section->note_type()), when);
-		}
-	}
 	Tempo const tp = _marker->tempo();
 
 	if (Keyboard::modifier_state_equals (event->button.state, ArdourKeyboard::constraint_modifier ())) {
@@ -3350,12 +3327,47 @@ TempoMarkerDrag::motion (GdkEvent* event, bool first_move)
 		strs << new_bpm;
 		show_verbose_cursor_text (strs.str());
 	} else if (_movable) {
-
-		if (_real_section->position_lock_style() == MusicTime) {
-			_editor->session()->tempo_map().gui_move_tempo_beat (_real_section, tp, beat);
+		if (!_editor->snap_musical()) {
+			pf = adjusted_current_frame (event);
 		} else {
-			_editor->session()->tempo_map().gui_move_tempo_frame (_real_section, tp, pf);
+			pf = adjusted_current_frame (event, false);
+			bool use_snap;
+
+			if (Keyboard::modifier_state_equals (event->button.state, ArdourKeyboard::snap_modifier ())) {
+				if (_editor->snap_mode() == Editing::SnapOff) {
+					use_snap = true;
+				} else {
+					use_snap = false;
+				}
+			} else {
+				if (_editor->snap_mode() == Editing::SnapOff) {
+					use_snap = false;
+				} else {
+					use_snap = true;
+				}
+			}
+
+			Timecode::BBT_Time when;
+			_editor->session()->tempo_map().bbt_time (pf, when);
+			if (_real_section->position_lock_style() == MusicTime) {
+				if (use_snap && _editor->snap_type() == SnapToBar) {
+					_editor->session()->tempo_map().round_bbt (when, -1);
+				} else if (use_snap) {
+					_editor->session()->tempo_map().round_bbt (when, _editor->get_grid_beat_divisions (0));
+				}
+				beat = _editor->session()->tempo_map().bbt_to_beats (when);
+				_editor->session()->tempo_map().gui_move_tempo_beat (_real_section, tp, beat);
+			} else {
+				if (use_snap && _editor->snap_type() == SnapToBar) {
+					_editor->session()->tempo_map().round_bbt (when, -1);
+				} else if (use_snap) {
+					_editor->session()->tempo_map().round_bbt (when, _editor->get_grid_beat_divisions (0));
+				}
+				pf = _editor->session()->tempo_map().predict_tempo_frame (_real_section, Tempo (_real_section->beats_per_minute(), _real_section->note_type()), when);
+				_editor->session()->tempo_map().gui_move_tempo_frame (_real_section, tp, pf);
+			}
 		}
+
 		show_verbose_cursor_time (pf);
 	}
 	_marker->set_position (pf);
diff --git a/libs/ardour/ardour/tempo.h b/libs/ardour/ardour/tempo.h
index 2a28a65f5b..7a26a609e3 100644
--- a/libs/ardour/ardour/tempo.h
+++ b/libs/ardour/ardour/tempo.h
@@ -55,6 +55,9 @@ class LIBARDOUR_API Tempo {
 	Tempo (double bpm, double type=4.0) // defaulting to quarter note
 		: _beats_per_minute (bpm), _note_type(type) {}
 
+	/* ..or more aptly 'pulse divisions per minute'.
+	   Nothing to do with actual beats, which are defined by the meter and tempo.
+	*/
 	double beats_per_minute () const { return _beats_per_minute; }
 	void set_beats_per_minute (double bpm) { _beats_per_minute = bpm; }
 	double note_type () const { return _note_type; }
diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index fec74ccfe0..13b98c613b 100644
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -604,7 +604,28 @@ MeterSection::get_state() const
 }
 
 /***********************************************************************/
-
+/*
+  Tempo Map Overview
+
+  We have tempos, which are nice to think of in whole pulses per minute,
+  and meters which divide tempo pulses into bars (via divisions_per_bar)
+  and beats (via note_divisor).
+  Tempos and meters may be locked to audio or music.
+  Because the notion of a beat cannot be determined without both tempo and meter, the first tempo
+  and first meter are special. they must move together, and must be locked to audio.
+  Audio locked tempos which lie before the first meter are made inactive.
+  They will be re-activated if the first meter is again placed before them.
+
+  Both tempos and meters have a pulse position and a frame position.
+  Recomputing the tempo map is the process where the 'missing' position
+  (pulse in the case of AudioTime and frame for MusicTime) is calculated
+  based on the lock preference (position_lock_style).
+
+  It is important to keep the _metrics in an order that makes sense.
+  Because ramped MusicTime and AudioTime tempos can interact with each other
+  and cause reordering, care must be taken to keep _metrics in a solved state.
+  Solved means ordered by frame or pulse with frame-accurate precision (see check_solved()).
+*/
 struct MetricSectionSorter {
     bool operator() (const MetricSection* a, const MetricSection* b) {
 	    return a->pulse() < b->pulse();
@@ -2004,18 +2025,10 @@ TempoMap::check_solved (Metrics& metrics, bool by_frame)
 				if ((by_frame && t->frame() < prev_ts->frame()) || (!by_frame && t->pulse() < prev_ts->pulse())) {
 					return false;
 				}
-				if (by_frame && t->frame() != prev_ts->frame_at_pulse (t->pulse(), _frame_rate)) {
+				/* precision check ensures pulses and frames align independent of lock style.*/
+				if (t->frame() != prev_ts->frame_at_pulse (t->pulse(), _frame_rate)) {
 					return false;
 				}
-				/*
-				if (!by_frame && fabs (t->pulse() - prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate)) > 0.00001) {
-					std::cerr << "beat precision too low for bpm: " << t->beats_per_minute() << std::endl <<
-						" |error          :" << t->pulse() - prev_ts->pulse_at_tempo (t->pulses_per_minute(), t->frame(), _frame_rate) << std::endl <<
-						"|frame at beat   :" << prev_ts->frame_at_pulse (t->pulse(), _frame_rate) << std::endl <<
-						" |frame at tempo : " << prev_ts->frame_at_tempo (t->pulses_per_minute(), t->pulse(), _frame_rate) << std::endl;
-					return false;
-				}
-				*/
 			}
 			prev_ts = t;
 		}