Preserve FX channel when replacing track (#5957)

* Preserve FX channel when replacing track

* Add comment

include/InstrumentTrack.h

@@ -232,6 +232,8 @@ class LMMS_EXPORT InstrumentTrack : public Track, public MidiEventProcessor
 	{
 		return m_previewMode;
 	}
+
+	void replaceInstrument(DataFile dataFile);
 
 	void autoAssignMidiDevice( bool );
 

src/gui/FileBrowser.cpp

@@ -776,15 +776,11 @@ void FileBrowserTreeWidget::handleFile(FileItem * f, InstrumentTrack * it)
 			break;
 		}
 
-		case FileItem::LoadAsPreset:
-		{
-			DataFile dataFile( f->fullName() );
-			InstrumentTrack::removeMidiPortNode( dataFile );
-			it->setSimpleSerializing();
-			it->loadSettings( dataFile.content().toElement() );
+		case FileItem::LoadAsPreset: {
+			DataFile dataFile(f->fullName());
+			it->replaceInstrument(dataFile);
 			break;
 		}
-
 		case FileItem::ImportAsProject:
 			ImportFilter::import( f->fullName(),
 							Engine::getSong() );

src/tracks/InstrumentTrack.cpp

@@ -954,6 +954,22 @@ void InstrumentTrack::setPreviewMode( const bool value )
 
 
 
+void InstrumentTrack::replaceInstrument(DataFile dataFile)
+{
+	// loadSettings clears the FX channel, so we save it here and set it back later
+	int effectChannel = effectChannelModel()->value();
+
+	InstrumentTrack::removeMidiPortNode(dataFile);
+	setSimpleSerializing();
+	loadSettings(dataFile.content().toElement());
+
+	m_effectChannelModel.setValue(effectChannel);
+	Engine::getSong()->setModified();
+}
+
+
+
+
 QString InstrumentTrack::getSavedInstrumentName(const QDomElement &thisElement) const
 {
 	QDomElement elem = thisElement.firstChildElement("instrument");
@@ -1835,13 +1851,8 @@ void InstrumentTrackWindow::dropEvent( QDropEvent* event )
 	}
 	else if( type == "presetfile" )
 	{
-		DataFile dataFile( value );
-		InstrumentTrack::removeMidiPortNode( dataFile );
-		m_track->setSimpleSerializing();
-		m_track->loadSettings( dataFile.content().toElement() );
-
-		Engine::getSong()->setModified();
-
+		DataFile dataFile(value);
+		m_track->replaceInstrument(dataFile);
 		event->accept();
 		setFocus();
 	}