multicam: refactor to heavily optimize multicam monitor retrieval

app/panel/viewer/viewerbase.h

@@ -33,6 +33,11 @@ class ViewerPanelBase : public TimeBasedPanel
 public:
   ViewerPanelBase(const QString& object_name, QWidget* parent = nullptr);
 
+  ViewerWidget *GetViewerWidget() const
+  {
+    return static_cast<ViewerWidget*>(GetTimeBasedWidget());
+  }
+
   virtual void PlayPause() override;
 
   virtual void PlayInToOut() override;
@@ -54,12 +59,22 @@ public:
 
   ColorManager *GetColorManager()
   {
-    return static_cast<ViewerWidget*>(GetTimeBasedWidget())->color_manager();
+    return GetViewerWidget()->color_manager();
   }
 
   void UpdateTextureFromNode()
   {
-    static_cast<ViewerWidget*>(GetTimeBasedWidget())->UpdateTextureFromNode();
+    GetViewerWidget()->UpdateTextureFromNode();
+  }
+
+  void AddPlaybackDevice(ViewerDisplayWidget *vw)
+  {
+    GetViewerWidget()->AddPlaybackDevice(vw);
+  }
+
+  void SetMulticamNode(MultiCamNode *n)
+  {
+    GetViewerWidget()->SetMulticamNode(n);
   }
 
 public slots:
@@ -71,7 +86,7 @@ public slots:
 
   void RequestStartEditingText()
   {
-    static_cast<ViewerWidget*>(GetTimeBasedWidget())->RequestStartEditingText();
+    GetViewerWidget()->RequestStartEditingText();
   }
 
 signals: