revert: remove OpacityHelper

- remove OpacityHelper
- remove all related animation
- now bottom toolbar and navigation view are always visible

app/navigatorview.h

@@ -7,7 +7,6 @@
 
 #include <QGraphicsView>
 
-class OpacityHelper;
 class GraphicsView;
 class NavigatorView : public QGraphicsView
 {
@@ -16,7 +15,6 @@ public:
     NavigatorView(QWidget *parent = nullptr);
 
     void setMainView(GraphicsView *mainView);
-    void setOpacity(qreal opacity, bool animated = true);
 
 public slots:
     void updateMainViewportRegion();
@@ -32,7 +30,6 @@ private:
     bool m_mouseDown = false;
     QPolygon m_viewportRegion;
     QGraphicsView *m_mainView = nullptr;
-    OpacityHelper *m_opacityHelper = nullptr;
 };
 
 #endif // NAVIGATORVIEW_H