don't mix framepos with quarter notes when calculating _start frames.

	- quarter note precision is greater than the frame-based
	  _position. using it as a reference may cause a rounding error
	  if the region is locked to MusicTime.

	- also fixes a _start position bug when trimming midi regions.

	- we really need a better api for this kind of thing.

	- in combination with the previous two patches, this should fix
	  various missing first note issues.

diff --git a/libs/ardour/midi_region.cc b/libs/ardour/midi_region.cc
index 7d7619680a5b1adc6af102f64f6ca5ed45d262f0..f5c9df1b6e53f483c0597d07947e85cd8271e113 100644 (file)
--- a/libs/ardour/midi_region.cc
+++ b/libs/ardour/midi_region.cc
@@ -265,7 +265,8 @@ MidiRegion::update_after_tempo_map_change (bool /* send */)
                  For now, the musical position at the region start is retained, but subsequent events
                  will maintain their beat distance according to the map.
                */
-               _start = _position - _session.tempo_map().frame_at_pulse (pulse() - (_start_beats / 4.0));
+               _start = _session.tempo_map().frame_at_quarter_note (pulse() * 4.0)
+                       - _session.tempo_map().frame_at_quarter_note ((pulse() * 4.0) - start_beats());
 
                /* _length doesn't change for audio-locked regions. update length_beats to match. */
                _length_beats = _session.tempo_map().quarter_note_at_frame (_position + _length) - _session.tempo_map().quarter_note_at_frame (_position);
@@ -312,7 +313,8 @@ MidiRegion::set_position_internal (framepos_t pos, bool allow_bbt_recompute, con
        }
 
        /* set _start to new position in tempo map */
-       _start = _position - _session.tempo_map().frame_at_pulse (pulse() - (_start_beats / 4.0));
+       _start = _session.tempo_map().frame_at_quarter_note (pulse() * 4.0)
+               - _session.tempo_map().frame_at_quarter_note ((pulse() * 4.0) - start_beats());
 
        /* in construction from src */
        if (_length_beats == 0.0) {
@@ -325,7 +327,7 @@ MidiRegion::set_position_internal (framepos_t pos, bool allow_bbt_recompute, con
                /* leave _length_beats alone, and change _length to reflect the state of things
                   at the new position (tempo map may dictate a different number of frames).
                */
-               Region::set_length_internal (_session.tempo_map().frame_at_pulse (pulse() + (_length_beats / 4.0)) - _position, sub_num);
+               Region::set_length_internal (_session.tempo_map().frame_at_quarter_note ((pulse() * 4.0) + length_beats()) - _position, sub_num);
        }
 }
 
@@ -631,7 +633,8 @@ MidiRegion::trim_to_internal (framepos_t position, framecnt_t length, const int3
                what_changed.add (Properties::position);
 
                double new_start_qn = start_beats() + (pos_qn - old_pos_qn);
-               const framepos_t new_start = _position - _session.tempo_map().frame_at_quarter_note (pos_qn - new_start_qn);
+               const framepos_t new_start = _session.tempo_map().frame_at_quarter_note (pos_qn)
+                       - _session.tempo_map().frame_at_quarter_note (pos_qn - new_start_qn);
 
                if (!verify_start_and_length (new_start, length)) {
                        return;