Draw beat sudivisions according to snap setting.

1 files changed, 13 insertions, 31 deletions

diff --git a/gtk2_ardour/tempo_lines.cc b/gtk2_ardour/tempo_lines.cc
index cb3eebbaa8..354814604c 100644
--- a/gtk2_ardour/tempo_lines.cc
+++ b/gtk2_ardour/tempo_lines.cc
@@ -53,39 +53,14 @@ TempoLines::hide ()
 	lines.hide ();
 }
 
-static uint8_t
-tick_alpha(uint8_t base_alpha, unsigned divisions)
-{
-	if (divisions == 32) {
-		return std::max(0, base_alpha / 5);
-	} else if (divisions == 16) {
-		return std::max(0, base_alpha / 4);
-	} else if (divisions == 8) {
-		return std::max(0, base_alpha / 3);
-	} else if (divisions == 4) {
-		return std::max(0, base_alpha / 2);
-	}
-	return 0;
-}
-
 void
 TempoLines::draw_ticks (const ARDOUR::TempoMap::BBTPointList::const_iterator& b,
-                        double                                                beat_density,
+                        unsigned                                              divisions,
                         framecnt_t                                            leftmost_frame,
                         framecnt_t                                            frame_rate)
 {
-	const double   fpb       = b->tempo->frames_per_beat(frame_rate);
-	const uint32_t base      = ARDOUR_UI::config()->color_mod("measure line beat", "measure line beat");
-	unsigned       divisions = 4;
-	if (beat_density < 0.01) {
-		divisions = 32;
-	} else if (beat_density < 0.025) {
-		divisions = 16;
-	} else if (beat_density < 0.05) {
-		divisions = 8;
-	} else if (beat_density < 0.1) {
-		divisions = 4;
-	}
+	const double   fpb  = b->tempo->frames_per_beat(frame_rate);
+	const uint32_t base = ARDOUR_UI::config()->color_mod("measure line beat", "measure line beat");
 
 	for (unsigned l = 1; l < divisions; ++l) {
 		/* find the coarsest division level this tick falls on */
@@ -97,7 +72,8 @@ TempoLines::draw_ticks (const ARDOUR::TempoMap::BBTPointList::const_iterator& b,
 		}
 
 		/* draw line with alpha corresponding to coarsest level */
-		const uint32_t   c = UINT_RGBA_CHANGE_A(base, tick_alpha(UINT_RGBA_A(base), level));
+		const uint8_t    a = max(0, (int)rint(UINT_RGBA_A(base) / log2(level)));
+		const uint32_t   c = UINT_RGBA_CHANGE_A(base, a);
 		const framepos_t f = b->frame + (l * (fpb / (double)divisions));
 		if (f > leftmost_frame) {
 			lines.add (PublicEditor::instance().sample_to_pixel_unrounded (f), 1.0, c);
@@ -108,6 +84,7 @@ TempoLines::draw_ticks (const ARDOUR::TempoMap::BBTPointList::const_iterator& b,
 void
 TempoLines::draw (const ARDOUR::TempoMap::BBTPointList::const_iterator& begin,
                   const ARDOUR::TempoMap::BBTPointList::const_iterator& end,
+                  unsigned                                              divisions,
                   framecnt_t                                            leftmost_frame,
                   framecnt_t                                            frame_rate)
 {
@@ -133,13 +110,18 @@ TempoLines::draw (const ARDOUR::TempoMap::BBTPointList::const_iterator& begin,
 		return;
 	}
 
+	/* constrain divisions to a log2 factor to cap line density */
+	while (divisions > 3 && beat_density * divisions > 0.4) {
+		divisions /= 2;
+	}
+
 	lines.clear ();
 
 	if (beat_density < 0.1 && begin != end && begin->frame > 0) {
 		/* draw subdivisions of the beat before the first visible beat line */
 		ARDOUR::TempoMap::BBTPointList::const_iterator prev = begin;
 		--prev;
-		draw_ticks(prev, beat_density, leftmost_frame, frame_rate);
+		draw_ticks(prev, divisions, leftmost_frame, frame_rate);
 	}
 
 	for (i = begin; i != end; ++i) {
@@ -159,7 +141,7 @@ TempoLines::draw (const ARDOUR::TempoMap::BBTPointList::const_iterator& begin,
 
 		if (beat_density < 0.1) {
 			/* draw subdivisions of this beat */
-			draw_ticks(i, beat_density, leftmost_frame, frame_rate);
+			draw_ticks(i, divisions, leftmost_frame, frame_rate);
 		}
 	}
 }