Fix stuck notes on notestacking

Fixes #865. Added a check so we don't add subnotes to a note that is already released (can happen with very short midinotes, eg. sliding the mouse accross the gui piano).
I also added a mutex to incoming midievent handling in instrumenttrack. Not sure if strictly necessary, but seems like this would prevent problems in the long run.
Also fixed a glitch in noteplayhandle where silent master notes got stuck playing indefinitely ( isMasternote() returns true even if the nph just hadChildren, so it never gets ended if it did - instead we check if we still have subnotes).

include/InstrumentTrack.h

@@ -230,6 +230,7 @@ private:
 	NotePlayHandle* m_notes[NumKeys];
 	int m_runningMidiNotes[NumKeys];
 	bool m_sustainPedalPressed;
+	QMutex m_notesMutex;
 
 	bool m_silentBuffersProcessed;
 

src/core/InstrumentFunctions.cpp

@@ -235,7 +235,7 @@ void InstrumentFunctionNoteStacking::processNote( NotePlayHandle * _n )
 	// time an audio-buffer is rendered...
 	if( ( _n->origin() == NotePlayHandle::OriginArpeggio || ( _n->hasParent() == false && _n->instrumentTrack()->isArpeggioEnabled() == false ) ) &&
 			_n->totalFramesPlayed() == 0 &&
-			m_chordsEnabledModel.value() == true )
+			m_chordsEnabledModel.value() == true && ! _n->isReleased() )
 	{
 		// then insert sub-notes for chord
 		const int selected_chord = m_chordsModel.value();

src/core/NotePlayHandle.cpp

@@ -101,7 +101,7 @@ NotePlayHandle::NotePlayHandle( InstrumentTrack* instrumentTrack,
 		m_instrumentTrack->midiNoteOn( *this );
 	}
 
-	if( hasParent() || !instrumentTrack->isArpeggioEnabled() )
+	if( hasParent() || ! m_instrumentTrack->isArpeggioEnabled() )
 	{
 		const int baseVelocity = m_instrumentTrack->midiPort()->baseVelocity();
 
@@ -229,7 +229,7 @@ void NotePlayHandle::play( sampleFrame * _working_buffer )
 		// because we do not allow NotePlayHandle::isFinished() to be true
 		// until all sub-notes are completely played and no new ones
 		// are inserted by arpAndChordsTabWidget::processNote()
-		if( isMasterNote() )
+		if( ! m_subNotes.isEmpty() )
 		{
 			m_releaseFramesToDo = m_releaseFramesDone + 2 * engine::mixer()->framesPerPeriod();
 		}
@@ -349,7 +349,7 @@ void NotePlayHandle::noteOff( const f_cnt_t _s )
 	m_framesBeforeRelease = _s;
 	m_releaseFramesToDo = qMax<f_cnt_t>( 0, actualReleaseFramesToDo() );
 
-	if( hasParent() || !instrumentTrack()->isArpeggioEnabled() )
+	if( hasParent() || ! m_instrumentTrack->isArpeggioEnabled() )
 	{
 		// send MidiNoteOff event
 		f_cnt_t realOffset = offset() + _s; // get actual frameoffset of release, in global time

src/tracks/InstrumentTrack.cpp

@@ -240,7 +240,7 @@ MidiEvent InstrumentTrack::applyMasterKey( const MidiEvent& event )
 void InstrumentTrack::processInEvent( const MidiEvent& event, const MidiTime& time, f_cnt_t offset )
 {
 	engine::mixer()->lock();
-
+	QMutexLocker locker( &m_notesMutex );
 	bool eventHandled = false;
 
 	switch( event.type() )