Fix notes getting stuck under high CPU conditions (LMMS#4908)

include/NotePlayHandle.h

@@ -302,6 +302,7 @@ class EXPORT NotePlayHandle : public PlayHandle, public Note
 	NotePlayHandleList m_subNotes;			// used for chords and arpeggios
 	volatile bool m_released;				// indicates whether note is released
 	bool m_releaseStarted;
+	bool m_hasMidiNote;
 	bool m_hasParent;						// indicates whether note has parent
 	NotePlayHandle * m_parent;			// parent note
 	bool m_hadChildren;

src/core/NotePlayHandle.cpp

@@ -63,6 +63,7 @@ NotePlayHandle::NotePlayHandle( InstrumentTrack* instrumentTrack,
 	m_subNotes(),
 	m_released( false ),
 	m_releaseStarted( false ),
+	m_hasMidiNote( false ),
 	m_hasParent( parent != NULL  ),
 	m_parent( parent ),
 	m_hadChildren( false ),
@@ -106,17 +107,6 @@ NotePlayHandle::NotePlayHandle( InstrumentTrack* instrumentTrack,
 		m_instrumentTrack->midiNoteOn( *this );
 	}
 
-	if( hasParent() || ! m_instrumentTrack->isArpeggioEnabled() )
-	{
-		const int baseVelocity = m_instrumentTrack->midiPort()->baseVelocity();
-
-		// send MidiNoteOn event
-		m_instrumentTrack->processOutEvent(
-			MidiEvent( MidiNoteOn, midiChannel(), midiKey(), midiVelocity( baseVelocity ) ),
-			MidiTime::fromFrames( offset(), Engine::framesPerTick() ),
-			offset() );
-	}
-
 	if( m_instrumentTrack->instrument()->flags() & Instrument::IsSingleStreamed )
 	{
 		setUsesBuffer( false );
@@ -208,6 +198,21 @@ void NotePlayHandle::play( sampleFrame * _working_buffer )
 	}
 
 	lock();
+
+	if( m_totalFramesPlayed == 0 && !m_hasMidiNote
+		&& ( hasParent() || ! m_instrumentTrack->isArpeggioEnabled() ) )
+	{
+		m_hasMidiNote = true;
+
+		const int baseVelocity = m_instrumentTrack->midiPort()->baseVelocity();
+
+		// send MidiNoteOn event
+		m_instrumentTrack->processOutEvent(
+			MidiEvent( MidiNoteOn, midiChannel(), midiKey(), midiVelocity( baseVelocity ) ),
+			MidiTime::fromFrames( offset(), Engine::framesPerTick() ),
+			offset() );
+	}
+
 	if( m_frequencyNeedsUpdate )
 	{
 		updateFrequency();
@@ -360,8 +365,10 @@ void NotePlayHandle::noteOff( const f_cnt_t _s )
 	m_framesBeforeRelease = _s;
 	m_releaseFramesToDo = qMax<f_cnt_t>( 0, actualReleaseFramesToDo() );
 
-	if( hasParent() || ! m_instrumentTrack->isArpeggioEnabled() )
+	if( m_hasMidiNote )
 	{
+		m_hasMidiNote = false;
+
 		// send MidiNoteOff event
 		m_instrumentTrack->processOutEvent(
 				MidiEvent( MidiNoteOff, midiChannel(), midiKey(), 0 ),