refactor: opacity helper

navigatorview.h

@@ -3,6 +3,7 @@
 
 #include <QGraphicsView>
 
+class OpacityHelper;
 class GraphicsView;
 class NavigatorView : public QGraphicsView
 {
@@ -11,6 +12,7 @@ public:
     NavigatorView(QWidget *parent = nullptr);
 
     void setMainView(GraphicsView *mainView);
+    void setOpacity(qreal opacity, bool animated = true);
 
 public slots:
     void updateMainViewportRegion();
@@ -26,6 +28,7 @@ private:
     bool m_mouseDown = false;
     QPolygon m_viewportRegion;
     QGraphicsView *m_mainView = nullptr;
+    OpacityHelper *m_opacityHelper = nullptr;
 };
 
 #endif // NAVIGATORVIEW_H