Tempo lines display subdivisions correctly over a tempo change

TempoMap::get_grid() supplies a list of beat positions, leaving the lines
to work out any subdivision positions.
This is fine, unless a tempo section falls in between beats.
Use a BeatsFramesConverter along with a quarter note position
(in the BBTPointsList) to make this easier.

gtk2_ardour/editor_tempodisplay.cc

@@ -394,7 +394,7 @@ Editor::draw_measures (std::vector<ARDOUR::TempoMap::BBTPoint>& grid)
 	}
 
 	if (tempo_lines == 0) {
-		tempo_lines = new TempoLines (time_line_group, ArdourCanvas::LineSet::Vertical);
+		tempo_lines = new TempoLines (time_line_group, ArdourCanvas::LineSet::Vertical, new BeatsFramesConverter (_session->tempo_map(), 0));
 	}
 
 	const unsigned divisions = get_grid_beat_divisions(leftmost_frame);

gtk2_ardour/tempo_lines.cc

@@ -29,8 +29,9 @@
 
 using namespace std;
 
-TempoLines::TempoLines (ArdourCanvas::Container* group, double)
+TempoLines::TempoLines (ArdourCanvas::Container* group, double, ARDOUR::BeatsFramesConverter* bfc)
 	: lines (group, ArdourCanvas::LineSet::Vertical)
+	, _bfc (bfc)
 {
 	lines.set_extent (ArdourCanvas::COORD_MAX);
 }
@@ -72,20 +73,8 @@ TempoLines::draw_ticks (std::vector<ARDOUR::TempoMap::BBTPoint>& grid,
 		/* draw line with alpha corresponding to coarsest level */
 		const uint8_t    a = max(8, (int)rint(UINT_RGBA_A(base) / (0.8 * log2(level))));
 		const uint32_t   c = UINT_RGBA_CHANGE_A(base, a);
-		framepos_t f = 0;
+		const framepos_t f = _bfc->to (Evoral::Beats (grid.begin()->qn + (l / (double) divisions)));
 
-		if (grid.begin()->c != 0.0) {
-			const double beat_divisions = (l / ((double) divisions)) * (grid.begin()->tempo.note_type() / grid.begin()->meter.note_divisor());
-			const double time_at_division = log (((grid.begin()->c * (beat_divisions)) /
-							   grid.begin()->tempo.note_types_per_minute()) + 1) / grid.begin()->c;
-
-			f = grid.begin()->frame + (framecnt_t) floor ((time_at_division * 60.0 * frame_rate) + 0.5);
-		} else {
-			const double fpb  = grid.begin()->tempo.frames_per_note_type (frame_rate)
-				* (grid.begin()->tempo.note_type() / grid.begin()->meter.note_divisor());
-
-			f = grid.begin()->frame + (l * (fpb / (double) divisions));
-		}
 		if (f > leftmost_frame) {
 			lines.add (PublicEditor::instance().sample_to_pixel_unrounded (f), 1.0, c);
 		}

gtk2_ardour/tempo_lines.h

@@ -19,13 +19,14 @@
 #ifndef __ardour_tempo_lines_h__
 #define __ardour_tempo_lines_h__
 
+#include "ardour/beats_frames_converter.h"
 #include "ardour/tempo.h"
 
 #include "canvas/line_set.h"
 
 class TempoLines {
 public:
-	TempoLines (ArdourCanvas::Container* group, double screen_height);
+	TempoLines (ArdourCanvas::Container* group, double screen_height, ARDOUR::BeatsFramesConverter* bfc);
 
 	void tempo_map_changed();
 
@@ -44,6 +45,7 @@ private:
 	                 ARDOUR::framecnt_t                                    frame_rate);
 
 	ArdourCanvas::LineSet lines;
+	ARDOUR::BeatsFramesConverter* _bfc;
 };
 
 #endif /* __ardour_tempo_lines_h__ */

libs/ardour/ardour/tempo.h

@@ -343,16 +343,16 @@ class LIBARDOUR_API TempoMap : public PBD::StatefulDestructible
 	};
 
 	struct BBTPoint {
-		framepos_t          frame;
 		Meter               meter;
 		Tempo               tempo;
-		double              c;
+		framepos_t          frame;
 		uint32_t            bar;
 		uint32_t            beat;
+		double              qn;
 
 		BBTPoint (const MeterSection& m, const Tempo& t, framepos_t f,
-		          uint32_t b, uint32_t e, double func_c)
-		: frame (f), meter (m.divisions_per_bar(), m.note_divisor()), tempo (t.note_types_per_minute(), t.note_type(), t.end_note_types_per_minute()), c (func_c), bar (b), beat (e) {}
+		          uint32_t b, uint32_t e, double qnote)
+		: meter (m), tempo (t), frame (f), bar (b), beat (e), qn (qnote) {}
 
 		Timecode::BBT_Time bbt() const { return Timecode::BBT_Time (bar, beat, 0); }
 		operator Timecode::BBT_Time() const { return bbt(); }

libs/ardour/tempo.cc

@@ -4162,11 +4162,11 @@ TempoMap::get_grid (vector<TempoMap::BBTPoint>& points,
 	if (bar_mod == 0) {
 		while (pos >= 0 && pos < upper) {
 			pos = frame_at_minute (minute_at_beat_locked (_metrics, cnt));
-			const TempoSection tempo = tempo_section_at_minute_locked (_metrics, minute_at_frame (pos));
 			const MeterSection meter = meter_section_at_minute_locked (_metrics, minute_at_frame (pos));
 			const BBT_Time bbt = bbt_at_beat_locked (_metrics, cnt);
+			const double qn = pulse_at_beat_locked (_metrics, cnt) * 4.0;
 
-			points.push_back (BBTPoint (meter, tempo_at_minute_locked (_metrics, minute_at_frame (pos)), pos, bbt.bars, bbt.beats, tempo.c()));
+			points.push_back (BBTPoint (meter, tempo_at_minute_locked (_metrics, minute_at_frame (pos)), pos, bbt.bars, bbt.beats, qn));
 			++cnt;
 		}
 	} else {
@@ -4181,9 +4181,10 @@ TempoMap::get_grid (vector<TempoMap::BBTPoint>& points,
 
 		while (pos >= 0 && pos < upper) {
 			pos = frame_at_minute (minute_at_bbt_locked (_metrics, bbt));
-			const TempoSection tempo = tempo_section_at_minute_locked (_metrics, minute_at_frame (pos));
 			const MeterSection meter = meter_section_at_minute_locked (_metrics, minute_at_frame (pos));
-			points.push_back (BBTPoint (meter, tempo_at_minute_locked (_metrics, minute_at_frame (pos)), pos, bbt.bars, bbt.beats, tempo.c()));
+			const double qn = pulse_at_bbt_locked (_metrics, bbt) * 4.0;
+
+			points.push_back (BBTPoint (meter, tempo_at_minute_locked (_metrics, minute_at_frame (pos)), pos, bbt.bars, bbt.beats, qn));
 			bbt.bars += bar_mod;
 		}
 	}