Fix spurious error playing initial grace notes (issue 1412)

This happens because the MIDI output starts at tick 0, regardless of
when the first event is. Initial grace notes start start at negative
ticks, so midi_walker::output_event thinks they're out of order. Fixed
by starting at the first event.

diff --git a/lily/midi-walker.cc b/lily/midi-walker.cc
index b97630b0d147ed8ebc05d63c111b8928c3667cad..0ae5265bd370dd92aa93fb25b381fab1ad87f9cf 100644 (file)
--- a/lily/midi-walker.cc
+++ b/lily/midi-walker.cc
@@ -58,7 +58,9 @@ Midi_walker::Midi_walker (Audio_staff *audio_staff, Midi_track *track)
   index_ = 0;
   items_ = audio_staff->audio_items_;
   vector_sort (items_, audio_item_less);
-  last_tick_ = 0;
+  //Pieces that begin with grace notes start at negative times. This
+  //is OK - MIDI output doesn't use absolute ticks, only differences.
+  last_tick_ = items_.empty () ? 0 : items_[0]->audio_column_->ticks ();
   percussion_ = audio_staff->percussion_;
   merge_unisons_ = audio_staff->merge_unisons_;
 }