fix hanging mouse in piano roll (LMMS#4822)

src/gui/TimeLineWidget.cpp

@@ -88,6 +88,7 @@ TimeLineWidget::TimeLineWidget( const int xoff, const int yoff, const float ppt,
 
 	m_xOffset -= s_posMarkerPixmap->width() / 2;
 
+	setMouseTracking(true);
 	m_pos.m_timeLine = this;
 
 	QTimer * updateTimer = new QTimer( this );
@@ -365,6 +366,7 @@ void TimeLineWidget::mousePressEvent( QMouseEvent* event )
 
 void TimeLineWidget::mouseMoveEvent( QMouseEvent* event )
 {
+	parentWidget()->update(); // essential for widgets that this timeline had taken their mouse move event from.
 	const MidiTime t = m_begin + static_cast<int>( qMax( event->x() - m_xOffset - m_moveXOff, 0 ) * MidiTime::ticksPerTact() / m_ppt );
 
 	switch( m_action )

src/gui/editors/PianoRoll.cpp

@@ -1294,6 +1294,7 @@ void PianoRoll::leaveEvent(QEvent * e )
 
 	QWidget::leaveEvent( e );
 	s_textFloat->hide();
+	this->update(); // cleaning inner mouse-related graphics
 }
 
 
@@ -3160,7 +3161,7 @@ void PianoRoll::paintEvent(QPaintEvent * pe )
 		case ModeSelect: cursor = s_toolSelect; break;
 		case ModeEditDetuning: cursor = s_toolOpen; break;
 	}
-	if( cursor != NULL )
+	if( cursor != NULL && mapFromGlobal( QCursor::pos() ).y() > PR_TOP_MARGIN )
 	{
 		p.drawPixmap( mapFromGlobal( QCursor::pos() ) + QPoint( 8, 8 ),
 								*cursor );