Define drawing function of CellularPanel, which visits nodes

src/CellularPanel.h

@@ -17,6 +17,7 @@ class ViewInfo;
 class AudacityProject;
 
 class TrackPanelCell;
+struct TrackPanelDrawingContext;
 class TrackPanelGroup;
 class TrackPanelNode;
 struct TrackPanelMouseEvent;
@@ -107,6 +108,12 @@ public:
    wxCoord MostRecentXCoord() const;
    
    void HandleCursorForPresentMouseState(bool doHit = true);
+
+   // Visit the Draw functions of all cells that intersect the panel area,
+   // and of handles associated with such cells,
+   // and of all groups of cells,
+   // repeatedly with a pass count from 0 to nPasses - 1
+   void Draw( TrackPanelDrawingContext &context, unsigned nPasses );
    
 protected:
    bool HasEscape();