Enhanced snapping in song editor (#4973)

* New default behavior: Preserves offsets when moving clips, resizes in fixed increments.

* Adds shift + drag: Snaps move start position (like current behavior) or end position (new),
based on which is closest to the real position. When moving a selection,
the grabbed clip snaps into position and the rest move relative to it.

* Adds alt + drag: Allows fine adjustment of a clip's position or size,
as an alternative to ctrl + drag.

* Adds a Q dropdown in the song editor to allow finer or coarser snapping (8 bars to 1/16th bar)

* Adds a proportional snap toggle. When enabled, snapping size/Q adjusts based on zoom,
and a label appears showing the current snap size. This is disabled by default.

include/MidiTime.h

@@ -63,7 +63,7 @@ class LMMS_EXPORT MidiTime
 	MidiTime( const tact_t tact, const tick_t ticks );
 	MidiTime( const tick_t ticks = 0 );
 
-	MidiTime toNearestTact() const;
+	MidiTime quantize(float) const;
 	MidiTime toAbsoluteTact() const;
 
 	MidiTime& operator+=( const MidiTime& time );
@@ -110,4 +110,3 @@ class LMMS_EXPORT MidiTime
 
 
 #endif
-

include/SongEditor.h

@@ -73,13 +73,17 @@ class SongEditor : public TrackContainerView
 	void loadSettings( const QDomElement& element );
 
 	ComboBoxModel *zoomingModel() const;
+	ComboBoxModel *snappingModel() const;
+	float getSnapSize() const;
+	QString getSnapSizeString() const;
 
 public slots:
 	void scrolled( int new_pos );
 
 	void setEditMode( EditMode mode );
 	void setEditModeDraw();
 	void setEditModeSelect();
+	void toggleProportionalSnap();
 
 	void updatePosition( const MidiTime & t );
 	void updatePositionLine();
@@ -130,6 +134,8 @@ private slots:
 	positionLine * m_positionLine;
 
 	ComboBoxModel* m_zoomingModel;
+	ComboBoxModel* m_snappingModel;
+	bool m_proportionalSnap;
 
 	static const QVector<double> m_zoomLevels;
 
@@ -141,7 +147,6 @@ private slots:
 	EditMode m_ctrlMode; // mode they were in before they hit ctrl
 
 	friend class SongEditorWindow;
-
 } ;
 
 
@@ -170,6 +175,8 @@ protected slots:
 	void lostFocus();
 	void adjustUiAfterProjectLoad();
 
+	void updateSnapLabel();
+
 signals:
 	void playTriggered();
 	void resized();
@@ -181,13 +188,16 @@ protected slots:
 	QAction* m_addBBTrackAction;
 	QAction* m_addSampleTrackAction;
 	QAction* m_addAutomationTrackAction;
+	QAction* m_setProportionalSnapAction;
 
 	ActionGroup * m_editModeGroup;
 	QAction* m_drawModeAction;
 	QAction* m_selectModeAction;
 	QAction* m_crtlAction;
 
 	ComboBox * m_zoomingComboBox;
+	ComboBox * m_snappingComboBox;
+	QLabel* m_snapSizeLabel;
 };
 
 #endif

include/Track.h

@@ -236,7 +236,7 @@ class TrackContentObjectView : public selectableObject, public ModelView
 	// access needsUpdate member variable
 	bool needsUpdate();
 	void setNeedsUpdate( bool b );
-	
+
 public slots:
 	virtual bool close();
 	void cut();
@@ -297,6 +297,9 @@ protected slots:
 	Actions m_action;
 	QPoint m_initialMousePos;
 	QPoint m_initialMouseGlobalPos;
+	MidiTime m_initialTCOPos;
+	MidiTime m_initialTCOEnd;
+	QVector<MidiTime> m_initialOffsets;
 
 	TextFloat * m_hint;
 
@@ -311,14 +314,17 @@ protected slots:
 	bool m_gradient;
 
  	bool m_needsUpdate;
-	inline void setInitialMousePos( QPoint pos )
+	inline void setInitialPos( QPoint pos )
 	{
 		m_initialMousePos = pos;
 		m_initialMouseGlobalPos = mapToGlobal( pos );
+		m_initialTCOPos = m_tco->startPosition();
+		m_initialTCOEnd = m_initialTCOPos + m_tco->length();
 	}
+	void setInitialOffsets();
 
 	bool mouseMovedDistance( QMouseEvent * me, int distance );
-
+	MidiTime draggedTCOPos( QMouseEvent * me );
 } ;
 
 
@@ -564,13 +570,13 @@ class LMMS_EXPORT Track : public Model, public JournallingObject
 
 	using Model::dataChanged;
 
-	inline int getHeight() 
+	inline int getHeight()
 	{
 		return m_height >= MINIMAL_TRACK_HEIGHT
-			? m_height 
+			? m_height
 			: DEFAULT_TRACK_HEIGHT;
 	}
-	inline void setHeight( int height ) 
+	inline void setHeight( int height )
 	{
 		m_height = height;
 	}