Improve bbt ruler drawing performance for large time ranges.

	- when the timeline displays many bars, zoom/autoscroll
	  speed is improved by calculating the bbt ruler scale first
	  then requesting a suitably scaled grid.

1 files changed, 8 insertions, 15 deletions

diff --git a/gtk2_ardour/editor_rulers.cc b/gtk2_ardour/editor_rulers.cc
index 6c9e45abc8..2f12604872 100644
--- a/gtk2_ardour/editor_rulers.cc
+++ b/gtk2_ardour/editor_rulers.cc
@@ -710,14 +710,12 @@ Editor::update_fixed_rulers ()
 }
 
 void
-Editor::update_tempo_based_rulers (std::vector<TempoMap::BBTPoint>& grid)
+Editor::update_tempo_based_rulers ()
 {
 	if (_session == 0) {
 		return;
 	}
 
-	compute_bbt_ruler_scale (grid, leftmost_frame, leftmost_frame+current_page_samples());
-
 	_bbt_metric->units_per_pixel = samples_per_pixel;
 
 	if (ruler_bbt_action->get_active()) {
@@ -1009,7 +1007,7 @@ Editor::metric_get_timecode (std::vector<ArdourCanvas::Ruler::Mark>& marks, gdou
 }
 
 void
-Editor::compute_bbt_ruler_scale (std::vector<ARDOUR::TempoMap::BBTPoint>& grid, framepos_t lower, framepos_t upper)
+Editor::compute_bbt_ruler_scale (framepos_t lower, framepos_t upper)
 {
 	if (_session == 0) {
 		return;
@@ -1107,22 +1105,17 @@ Editor::compute_bbt_ruler_scale (std::vector<ARDOUR::TempoMap::BBTPoint>& grid,
                 bbt_beat_subdivision = 4;
 		break;
 	}
-	if (distance (grid.begin(), grid.end()) == 0) {
+
+	const double ceil_upper_beat = floor (max (0.0, _session->tempo_map().beat_at_frame (upper))) + 1.0;
+	if (ceil_upper_beat == floor_lower_beat) {
 		return;
 	}
 
-	i = grid.end();
-	i--;
+	bbt_bars = _session->tempo_map().bbt_at_beat (ceil_upper_beat).bars - _session->tempo_map().bbt_at_beat (floor_lower_beat).bars;
 
-	/* XX ?? */
-	if ((*i).beat >= (*grid.begin()).beat) {
-		bbt_bars = (*i).bar - (*grid.begin()).bar;
-	} else {
-		bbt_bars = (*i).bar - (*grid.begin()).bar;
-	}
+	beats = (ceil_upper_beat - floor_lower_beat) - bbt_bars;
+	double beat_density = ((beats + 1) * ((double) (upper - lower) / (double) (1 + beat_after_upper_pos - beat_before_lower_pos))) / 5.0;
 
-	beats = distance (grid.begin(), grid.end()) - bbt_bars;
-	double beat_density = ((distance (grid.begin(), grid.end()) + 1) * ((double) (upper - lower) / (double) (1 + grid.back().frame - grid.front().frame))) / 5.0;
 	/* Only show the bar helper if there aren't many bars on the screen */
 	if ((bbt_bars < 2) || (beats < 5)) {
 	        bbt_bar_helper_on = true;