Allows instruments to keep the midi channel information when forwarding

include/MidiPort.h

@@ -96,7 +96,10 @@ class MidiPort : public Model, public SerializingObject
 
 	int realOutputChannel() const
 	{
-		return outputChannel() - 1;
+		// There's a possibility of outputChannel being 0 ("--"), which is used to keep all
+		// midi channels when forwarding. In that case, realOutputChannel will return the
+		// default channel 1 (whose value is 0).
+		return outputChannel() ? outputChannel() - 1 : 0;
 	}
 
 	void processInEvent( const MidiEvent& event, const MidiTime& time = MidiTime() );

src/core/midi/MidiPort.cpp

@@ -47,7 +47,7 @@ MidiPort::MidiPort( const QString& name,
 	m_midiEventProcessor( eventProcessor ),
 	m_mode( mode ),
 	m_inputChannelModel( 0, 0, MidiChannelCount, this, tr( "Input channel" ) ),
-	m_outputChannelModel( 1, 1, MidiChannelCount, this, tr( "Output channel" ) ),
+	m_outputChannelModel( 1, 0, MidiChannelCount, this, tr( "Output channel" ) ),
 	m_inputControllerModel( 0, 0, MidiControllerCount, this, tr( "Input controller" ) ),
 	m_outputControllerModel( 0, 0, MidiControllerCount, this, tr( "Output controller" ) ),
 	m_fixedInputVelocityModel( -1, -1, MidiMaxVelocity, this, tr( "Fixed input velocity" ) ),
@@ -151,18 +151,36 @@ void MidiPort::processInEvent( const MidiEvent& event, const MidiTime& time )
 
 void MidiPort::processOutEvent( const MidiEvent& event, const MidiTime& time )
 {
-	// mask event
-	if( isOutputEnabled() && realOutputChannel() == event.channel() )
+	// If we selected a channel from 1-16, we will only route the selected channel.
+	// But if we selected channel 0 ("--") we will route all channels out.
+	if( isOutputEnabled() )
 	{
-		MidiEvent outEvent = event;
-
-		if( fixedOutputVelocity() >= 0 && event.velocity() > 0 &&
-			( event.type() == MidiNoteOn || event.type() == MidiKeyPressure ) )
+		// Selected channel 0 ("--"). Route all channels
+		if( outputChannel() == 0 )
 		{
-			outEvent.setVelocity( fixedOutputVelocity() );
+			MidiEvent outEvent = event;
+
+			if( fixedOutputVelocity() >= 0 && event.velocity() > 0 &&
+				( event.type() == MidiNoteOn || event.type() == MidiKeyPressure ) )
+			{
+				outEvent.setVelocity( fixedOutputVelocity() );
+			}
+
+			m_midiClient->processOutEvent( outEvent, time, this );
 		}
+		// Selected channel between 1-16. Mask event.
+		else if( realOutputChannel() == event.channel() )
+		{
+			MidiEvent outEvent = event;
+
+			if( fixedOutputVelocity() >= 0 && event.velocity() > 0 &&
+				( event.type() == MidiNoteOn || event.type() == MidiKeyPressure ) )
+			{
+				outEvent.setVelocity( fixedOutputVelocity() );
+			}
 
-		m_midiClient->processOutEvent( outEvent, time, this );
+			m_midiClient->processOutEvent( outEvent, time, this );
+		}
 	}
 }
 

src/gui/widgets/InstrumentMidiIOView.cpp

@@ -84,8 +84,9 @@ InstrumentMidiIOView::InstrumentMidiIOView( QWidget* parent ) :
 	midiOutputLayout->setSpacing( 6 );
 
 	m_outputChannelSpinBox = new LcdSpinBox( 2, m_midiOutputGroupBox );
+	m_outputChannelSpinBox->addTextForValue( 0, "--" );
 	m_outputChannelSpinBox->setLabel( tr( "CHANNEL" ) );
-	m_outputChannelSpinBox->setEnabled( false );
+	m_outputChannelSpinBox->setEnabled( true );
 	midiOutputLayout->addWidget( m_outputChannelSpinBox );
 
 	m_fixedOutputVelocitySpinBox = new LcdSpinBox( 3, m_midiOutputGroupBox );
@@ -108,8 +109,6 @@ InstrumentMidiIOView::InstrumentMidiIOView( QWidget* parent ) :
 	midiOutputLayout->addWidget( m_fixedOutputNoteSpinBox );
 	midiOutputLayout->addStretch();
 
-	connect( m_midiOutputGroupBox->ledButton(), SIGNAL( toggled( bool ) ),
-			m_outputChannelSpinBox, SLOT( setEnabled( bool ) ) );
 	connect( m_midiOutputGroupBox->ledButton(), SIGNAL( toggled( bool ) ),
 		m_fixedOutputVelocitySpinBox, SLOT( setEnabled( bool ) ) );
 	connect( m_midiOutputGroupBox->ledButton(), SIGNAL( toggled( bool ) ),

src/tracks/InstrumentTrack.cpp

@@ -393,6 +393,14 @@ void InstrumentTrack::processOutEvent( const MidiEvent& event, const MidiTime& t
 	const MidiEvent transposedEvent = applyMasterKey( event );
 	const int key = transposedEvent.key();
 
+	// If we have a selected output midi channel between 1-16, we will use that channel to handle the midi event.
+	// But if our selected midi output channel is 0 ("--"), we will use the event channel instead.
+	auto handleEventOutputChannel = midiPort()->realOutputChannel();
+	if( midiPort()->outputChannel() == 0 )
+	{
+		handleEventOutputChannel = event.channel();
+	}
+
 	switch( event.type() )
 	{
 		case MidiNoteOn:
@@ -403,10 +411,10 @@ void InstrumentTrack::processOutEvent( const MidiEvent& event, const MidiTime& t
 			{
 				if( m_runningMidiNotes[key] > 0 )
 				{
-					m_instrument->handleMidiEvent( MidiEvent( MidiNoteOff, midiPort()->realOutputChannel(), key, 0 ), time, offset );
+					m_instrument->handleMidiEvent( MidiEvent( MidiNoteOff, handleEventOutputChannel, key, 0 ), time, offset );
 				}
 				++m_runningMidiNotes[key];
-				m_instrument->handleMidiEvent( MidiEvent( MidiNoteOn, midiPort()->realOutputChannel(), key, event.velocity() ), time, offset );
+				m_instrument->handleMidiEvent( MidiEvent( MidiNoteOn, handleEventOutputChannel, key, event.velocity() ), time, offset );
 
 			}
 			m_midiNotesMutex.unlock();
@@ -419,7 +427,7 @@ void InstrumentTrack::processOutEvent( const MidiEvent& event, const MidiTime& t
 
 			if( key >= 0 && key < NumKeys && --m_runningMidiNotes[key] <= 0 )
 			{
-				m_instrument->handleMidiEvent( MidiEvent( MidiNoteOff, midiPort()->realOutputChannel(), key, 0 ), time, offset );
+				m_instrument->handleMidiEvent( MidiEvent( MidiNoteOff, handleEventOutputChannel, key, 0 ), time, offset );
 			}
 			m_midiNotesMutex.unlock();
 			emit endNote();