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tempo map: fix incorrect computation of ::bbt_at() (#9049)

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This caused problems with TempoMap::get_grid() ("gone backwards").
This commit is contained in:
Paul Davis 2022-10-30 19:34:52 -06:00
parent bdacfb8724
commit 9c2c08973d
1 changed files with 18 additions and 3 deletions
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21
libs/temporal/tempo.cc
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@ -627,7 +627,21 @@ TempoMetric::bbt_at (timepos_t const & pos) const
superclock_t sc = pos.superclocks();
const Beats dq = _tempo->quarters_at_superclock (sc) - _meter->beats();
/* Use the later of the tempo or meter as the reference point to
* compute the BBT distance. All map points are fully defined by all 3
* time types, but we need the latest one to avoid incorrect
* computations of quarter duration.
*/
const Point* reference_point;
if (_tempo->beats() < _meter->beats()) {
reference_point = _meter;
} else {
reference_point = _tempo;
}
const Beats dq = _tempo->quarters_at_superclock (sc) - reference_point->beats();
DEBUG_TRACE (DEBUG::TemporalMap, string_compose ("qn @ %1 = %2, meter @ %3 , delta %4\n", sc, _tempo->quarters_at_superclock (sc), _meter->beats(), dq));
@ -641,8 +655,9 @@ TempoMetric::bbt_at (timepos_t const & pos) const
const BBT_Offset bbt_offset (0, note_value_count, dq.get_ticks());
DEBUG_TRACE (DEBUG::TemporalMap, string_compose ("BBT offset from meter @ %1: %2\n", _meter->bbt(), bbt_offset));
return _meter->bbt_add (_meter->bbt(), bbt_offset);
DEBUG_TRACE (DEBUG::TemporalMap, string_compose ("BBT offset from %3 @ %1: %2\n", (_tempo->beats() < _meter->beats() ? _meter->bbt() : _tempo->bbt()), bbt_offset,
(_tempo->beats() < _meter->beats() ? "meter" : "tempo")));
return _meter->bbt_add (reference_point->bbt(), bbt_offset);
}
superclock_t