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

diff --git a/libs/ardour/tempo.cc b/libs/ardour/tempo.cc
index 8b59b06de6791314fbb3447c366eaea567fb6345..23310db4ff4b7dedbb87b7fc933606a2ef5534ed 100644 (file)
--- 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;