Fix incorrect positioning of tempo line subdivisions if first meter is non-zero

Commit cebefe6 assumed that frame 0 was the music origin.
Silly me.

4 files changed, 8 insertions, 7 deletions

diff --git a/gtk2_ardour/editor.cc b/gtk2_ardour/editor.cc
index 0350de1d12..6ff757c1b7 100644
--- a/gtk2_ardour/editor.cc
+++ b/gtk2_ardour/editor.cc
@@ -4518,7 +4518,7 @@ Editor::set_samples_per_pixel (framecnt_t spp)
 	samples_per_pixel = spp;
 
 	if (tempo_lines) {
-		tempo_lines->tempo_map_changed();
+		tempo_lines->tempo_map_changed(_session->tempo_map().music_origin());
 	}
 
 	bool const showing_time_selection = selection->time.length() > 0;
diff --git a/gtk2_ardour/editor_tempodisplay.cc b/gtk2_ardour/editor_tempodisplay.cc
index b11bee44d3..34a80dfc93 100644
--- a/gtk2_ardour/editor_tempodisplay.cc
+++ b/gtk2_ardour/editor_tempodisplay.cc
@@ -181,7 +181,7 @@ Editor::tempo_map_changed (const PropertyChange& /*ignored*/)
 	ENSURE_GUI_THREAD (*this, &Editor::tempo_map_changed, ignored);
 
 	if (tempo_lines) {
-		tempo_lines->tempo_map_changed();
+		tempo_lines->tempo_map_changed(_session->tempo_map().music_origin());
 	}
 
 	compute_bbt_ruler_scale (leftmost_frame, leftmost_frame + current_page_samples());
@@ -204,7 +204,7 @@ Editor::tempometric_position_changed (const PropertyChange& /*ignored*/)
 	ENSURE_GUI_THREAD (*this, &Editor::tempo_map_changed);
 
 	if (tempo_lines) {
-		tempo_lines->tempo_map_changed();
+		tempo_lines->tempo_map_changed(_session->tempo_map().music_origin());
 	}
 
 	TempoSection* prev_ts = 0;
@@ -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, new BeatsFramesConverter (_session->tempo_map(), 0));
+		tempo_lines = new TempoLines (time_line_group, ArdourCanvas::LineSet::Vertical, new BeatsFramesConverter (_session->tempo_map(), _session->tempo_map().music_origin()));
 	}
 
 	const unsigned divisions = get_grid_beat_divisions(leftmost_frame);
diff --git a/gtk2_ardour/tempo_lines.cc b/gtk2_ardour/tempo_lines.cc
index cdbde54961..8d1d183d3a 100644
--- a/gtk2_ardour/tempo_lines.cc
+++ b/gtk2_ardour/tempo_lines.cc
@@ -43,9 +43,10 @@ TempoLines::~TempoLines ()
 }
 
 void
-TempoLines::tempo_map_changed()
+TempoLines::tempo_map_changed (framepos_t new_origin)
 {
 	lines.clear ();
+	_bfc->set_origin_b (new_origin);
 }
 
 void
@@ -79,7 +80,7 @@ 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);
-		const framepos_t f = _bfc->to (Evoral::Beats (grid.begin()->qn + (l / (double) divisions)));
+		const framepos_t f = _bfc->to (Evoral::Beats (grid.begin()->qn + (l / (double) divisions))) + _bfc->origin_b();
 
 		if (f > leftmost_frame) {
 			lines.add (PublicEditor::instance().sample_to_pixel_unrounded (f), 1.0, c);
diff --git a/gtk2_ardour/tempo_lines.h b/gtk2_ardour/tempo_lines.h
index be5e1315c9..158ef7b1f9 100644
--- a/gtk2_ardour/tempo_lines.h
+++ b/gtk2_ardour/tempo_lines.h
@@ -29,7 +29,7 @@ public:
 	TempoLines (ArdourCanvas::Container* group, double screen_height, ARDOUR::BeatsFramesConverter* bfc);
 	~TempoLines ();
 
-	void tempo_map_changed();
+	void tempo_map_changed(framepos_t new_origin);
 
 	void draw (std::vector<ARDOUR::TempoMap::BBTPoint>& grid,
 		   unsigned                                              divisions,