Fix track handles dissapearing

- let Qt handle resizing of Song Editor's scroll area
- don't redraw all clips when moving tracks or resizing the window

include/SongEditor.h

@@ -178,7 +178,6 @@ class SongEditorWindow : public Editor
 
 protected:
 	void resizeEvent( QResizeEvent * event ) override;
-	void changeEvent( QEvent * ) override;
 
 protected slots:
 	void play() override;

include/TrackContainerView.h

@@ -147,8 +147,6 @@ public slots:
 protected:
 	static const int DEFAULT_PIXELS_PER_BAR = 16;
 
-	void resizeEvent( QResizeEvent * ) override;
-
 	TimePos m_currentPosition;
 
 

src/gui/TrackContainerView.cpp

@@ -61,18 +61,23 @@ TrackContainerView::TrackContainerView( TrackContainer * _tc ) :
 	m_tc->setHook( this );
 	//keeps the direction of the widget, undepended on the locale
 	setLayoutDirection( Qt::LeftToRight );
+
+	// The main layout - by default it only contains the scroll area,
+	// but SongEditor uses the layout to add a TimeLineWidget on top
 	QVBoxLayout * layout = new QVBoxLayout( this );
 	layout->setMargin( 0 );
 	layout->setSpacing( 0 );
 	layout->addWidget( m_scrollArea );
 
+	// The widget that will contain all TrackViews
 	QWidget * scrollContent = new QWidget;
 	m_scrollLayout = new QVBoxLayout( scrollContent );
 	m_scrollLayout->setMargin( 0 );
 	m_scrollLayout->setSpacing( 0 );
 	m_scrollLayout->setSizeConstraint( QLayout::SetMinAndMaxSize );
 
 	m_scrollArea->setWidget( scrollContent );
+	m_scrollArea->setWidgetResizable(true);
 
 	m_scrollArea->show();
 	m_rubberBand->hide();
@@ -126,7 +131,6 @@ TrackView * TrackContainerView::addTrackView( TrackView * _tv )
 	connect( this, SIGNAL( positionChanged( const TimePos & ) ),
 				_tv->getTrackContentWidget(),
 				SLOT( changePosition( const TimePos & ) ) );
-	realignTracks();
 	return( _tv );
 }
 
@@ -143,7 +147,6 @@ void TrackContainerView::removeTrackView( TrackView * _tv )
 		disconnect( _tv );
 		m_scrollLayout->removeWidget( _tv );
 
-		realignTracks();
 		if( Engine::getSong() )
 		{
 			Engine::getSong()->setModified();
@@ -174,8 +177,6 @@ void TrackContainerView::moveTrackView( TrackView * trackView, int indexTo )
 	m_tc->m_tracks.remove( indexFrom );
 	m_tc->m_tracks.insert( indexTo, track );
 	m_trackViews.move( indexFrom, indexTo );
-
-	realignTracks();
 }
 
 
@@ -224,17 +225,15 @@ void TrackContainerView::scrollToTrackView( TrackView * _tv )
 
 
 
+/*! \brief Update all TrackViews
+ *
+ *  Called when all clips on all tracks have to be redrawn (zoom change etc)
+ */
 void TrackContainerView::realignTracks()
 {
-	m_scrollArea->widget()->setFixedWidth(width());
-	m_scrollArea->widget()->setFixedHeight(
-				m_scrollArea->widget()->minimumSizeHint().height());
-
-	for( trackViewList::iterator it = m_trackViews.begin();
-						it != m_trackViews.end(); ++it )
+	for (TrackView* trackView: m_trackViews)
 	{
-		( *it )->show();
-		( *it )->update();
+		trackView->update();
 	}
 }
 
@@ -431,15 +430,6 @@ void TrackContainerView::dropEvent( QDropEvent * _de )
 
 
 
-void TrackContainerView::resizeEvent( QResizeEvent * _re )
-{
-	realignTracks();
-	QWidget::resizeEvent( _re );
-}
-
-
-
-
 RubberBand *TrackContainerView::rubberBand() const
 {
 	return m_rubberBand;

src/gui/TrackView.cpp

@@ -369,7 +369,6 @@ void TrackView::mouseMoveEvent( QMouseEvent * me )
 	else if( m_action == ResizeTrack )
 	{
 		setFixedHeight( qMax<int>( me->y(), MINIMAL_TRACK_HEIGHT ) );
-		m_trackContainerView->realignTracks();
 		m_track->setHeight( height() );
 	}
 

src/gui/editors/SongEditor.cpp

@@ -560,8 +560,6 @@ void SongEditor::wheelEvent( QWheelEvent * we )
 		// update timeline
 		m_song->m_playPos[Song::Mode_PlaySong].m_timeLine->
 					setPixelsPerBar( pixelsPerBar() );
-		// and make sure, all Clip's are resized and relocated
-		realignTracks();
 	}
 
 	// FIXME: Reconsider if determining orientation is necessary in Qt6.
@@ -1061,14 +1059,6 @@ void SongEditorWindow::resizeEvent(QResizeEvent *event)
 }
 
 
-void SongEditorWindow::changeEvent(QEvent *event)
-{
-	QWidget::changeEvent(event);
-	if (event->type() == QEvent::WindowStateChange)
-	{
-		m_editor->realignTracks();
-	}
-}
 
 
 void SongEditorWindow::play()