PianoRoll: optionally display notes from other tracks

I added a button to show/hide the notes from the other tracks in
piano roll, notes from other tracks appear in light transluscent white.
This is useful when making complex melodies in order to avoid dissonances
that are sometimes hard to detect otherwise.

Signed-off-by: Tobias Doerffel <tobias.doerffel@gmail.com>

include/piano_roll.h

@@ -113,7 +113,8 @@ protected:
 
 	int getKey( int _y ) const;
 	static inline void drawNoteRect( QPainter & _p, int _x, int _y,
-					int  _width, note * _n );
+					int  _width, note * _n,
+					bool isFromOtherTrack = false);
 	void removeSelection();
 	void selectAll();
 	void getSelectedNotes( NoteVector & _selected_notes );
@@ -136,6 +137,8 @@ protected slots:
 	void pasteNotes();
 	void deleteSelectedNotes();
 
+	void showNotesFromOtherTracks();
+
 	void updatePosition( const midiTime & _t );
 	void updatePositionAccompany( const midiTime & _t );
 
@@ -239,6 +242,8 @@ private:
 	toolButton * m_copyButton;
 	toolButton * m_pasteButton;
 
+	toolButton * m_showOtherTracksButton;
+
 	comboBox * m_zoomingComboBox;
 	comboBox * m_quantizeComboBox;
 	comboBox * m_noteLenComboBox;
@@ -257,6 +262,8 @@ private:
 	bool m_recording;
 	QList<note> m_recordingNotes;
 
+	bool m_showOtherTracks;
+
 	note * m_currentNote;
 	Actions m_action;
 	NoteEditMode m_noteEditMode;