From e2729c12a89e25cec7247ef92077f125d2909484 Mon Sep 17 00:00:00 2001
From: Paul Davis <paul@linuxaudiosystems.com>
Date: Tue, 17 Jan 2012 03:00:32 +0000
Subject: [PATCH] fix bug with tempo computation where passed in positions or
 offsets are negative

git-svn-id: svn://localhost/ardour2/branches/3.0@11252 d708f5d6-7413-0410-9779-e7cbd77b26cf
---
 libs/ardour/tempo.cc | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 8b59b06de6..23310db4ff 100644
--- a/libs/ardour/tempo.cc
+++ b/libs/ardour/tempo.cc
@@ -2006,6 +2006,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
 	const TempoSection* tempo;
 	const TempoSection* t;
 	double frames_per_beat;
+	framepos_t effective_pos = max (pos, (framepos_t) 0);
 
 	meter = &first_meter ();
 	tempo = &first_tempo ();
@@ -2017,7 +2018,7 @@ TempoMap::framepos_plus_bbt (framepos_t pos, BBT_Time op) const
 
 	for (i = metrics.begin(); i != metrics.end(); ++i) {
 
-		if ((*i)->frame() > pos) {
+		if ((*i)->frame() > effective_pos) {
 			break;
 		}
 
@@ -2138,8 +2139,9 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 {
 	Glib::RWLock::ReaderLock lm (lock);
 	Metrics::const_iterator next_tempo;
-	const TempoSection* tempo;
-	
+	const TempoSection* tempo = 0;
+	framepos_t effective_pos = max (pos, (framepos_t) 0);
+
 	/* Find the relevant initial tempo metric  */
 
 	for (next_tempo = metrics.begin(); next_tempo != metrics.end(); ++next_tempo) {
@@ -2148,7 +2150,7 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 
 		if ((t = dynamic_cast<const TempoSection*>(*next_tempo)) != 0) {
 
-			if ((*next_tempo)->frame() > pos) {
+			if ((*next_tempo)->frame() > effective_pos) {
 				break;
 			}
 
@@ -2162,6 +2164,8 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 	   next_tempo -> the next tempo after "pos", possibly metrics.end()
 	*/
 
+	assert (tempo);
+
 	Evoral::MusicalTime beats = 0;
 
 	while (distance) {
@@ -2178,6 +2182,7 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 		/* Update */
 		pos += sub;
 		distance -= sub;
+		assert (tempo);
 		beats += sub / tempo->frames_per_beat (_frame_rate);
 		
 		/* Move on if there's anything to move to */
@@ -2199,6 +2204,7 @@ TempoMap::framewalk_to_beats (framepos_t pos, framecnt_t distance) const
 				}
 			}
 		}
+		assert (tempo);
 	}
 
 	return beats;
-- 
2.30.2