Feature: PianoRoll Knife (#5845)

* Initial PianoRoll razor feature

* Restore PianoRoll edit mode after focusOut and in razor mode.

* Show changes directly after cut.

* Fix hanging note after adjusting vol/pan with razor action.

* Extract the split action to a separate method

	This PR addresses some suggestions from a review, the most
important ones being:
	- Extracting the note split action to a separate method, called
Pattern::splitNotes
	- Removing getMouseTickPos method
	- Adding a variable that holds the current razor position and a
method to update it (quantizing if CTRL is not pressed)
	- Using [this] to capture "this" on the lambda function instead
of [=], since the latter doesn't work as intended from C++20 forward
	- Fixing some code style and adding comments

* Removes an extra call to noteUnderMouse

	By removing "&& noteUnderMouse()" from the mousePressEvent
conditional, we avoid an extra call to noteUnderMouse. The only
difference in the behavior of the tool is that now clicking on a place
that doesn't have a note will exit Razor mode.

* Style change suggested by @russiankumar

* Cancel razor action on SHIFT release.

* Make razor cut-line (color) themable.

* Add razor cut-line color to classic theme style.css

* Rename razor to knife.

* Change pixmap from razor to knife (from https://github.com/LMMS/lmms/pull/5524)

* Remove SHIFT behavior.

* Change knife shortcut to SHIFT+K

Co-authored-by: CYBERDEViL <cyberdevil@notabug.org>
Co-authored-by: Ian Caio <iancaio_dev@hotmail.com>

include/Pattern.h

@@ -76,6 +76,9 @@ public:
 	Note * addStepNote( int step );
 	void setStep( int step, bool enabled );
 
+	// Split the list of notes on the given position
+	void splitNotes(NoteVector notes, TimePos pos);
+
 	// pattern-type stuff
 	inline PatternTypes type() const
 	{

include/PianoRoll.h

@@ -70,6 +70,7 @@ class PianoRoll : public QWidget
 	Q_PROPERTY(QColor textColorLight MEMBER m_textColorLight)
 	Q_PROPERTY(QColor textShadow MEMBER m_textShadow)
 	Q_PROPERTY(QColor markedSemitoneColor MEMBER m_markedSemitoneColor)
+	Q_PROPERTY(QColor knifeCutLine MEMBER m_knifeCutLineColor)
 	Q_PROPERTY(int noteOpacity MEMBER m_noteOpacity)
 	Q_PROPERTY(bool noteBorders MEMBER m_noteBorders)
 	Q_PROPERTY(int ghostNoteOpacity MEMBER m_ghostNoteOpacity)
@@ -95,6 +96,7 @@ public:
 		ModeErase,
 		ModeSelect,
 		ModeEditDetuning,
+		ModeEditKnife
 	};
 
 	/*! \brief Resets settings to default when e.g. creating a new project */
@@ -226,7 +228,8 @@ private:
 		ActionResizeNote,
 		ActionSelectNotes,
 		ActionChangeNoteProperty,
-		ActionResizeNoteEditArea
+		ActionResizeNoteEditArea,
+		ActionKnife
 	};
 
 	enum NoteEditMode
@@ -282,6 +285,9 @@ private:
 	void playChordNotes(int key, int velocity=-1);
 	void pauseChordNotes(int key);
 
+	void setKnifeAction();
+	void cancelKnifeAction();
+
 	void updateScrollbars();
 	void updatePositionLineHeight();
 
@@ -304,6 +310,7 @@ private:
 	static QPixmap * s_toolSelect;
 	static QPixmap * s_toolMove;
 	static QPixmap * s_toolOpen;
+	static QPixmap* s_toolKnife;
 
 	static PianoRollKeyTypes prKeyOrder[];
 
@@ -389,6 +396,7 @@ private:
 
 	EditModes m_editMode;
 	EditModes m_ctrlMode; // mode they were in before they hit ctrl
+	EditModes m_knifeMode; // mode they where in before entering knife mode
 
 	bool m_mouseDownRight; //true if right click is being held down
 
@@ -408,6 +416,10 @@ private:
 	// did we start a mouseclick with shift pressed
 	bool m_startedWithShift;
 
+	// Variable that holds the position in ticks for the knife action
+	int m_knifeTickPos;
+	void updateKnifePos(QMouseEvent* me);
+
 	friend class PianoRollWindow;
 
 	StepRecorderWidget m_stepRecorderWidget;
@@ -428,6 +440,7 @@ private:
 	QColor m_textColorLight;
 	QColor m_textShadow;
 	QColor m_markedSemitoneColor;
+	QColor m_knifeCutLineColor;
 	int m_noteOpacity;
 	int m_ghostNoteOpacity;
 	bool m_noteBorders;