add on last window closed handling

src/include/PMusrCanvas.h

@@ -137,6 +137,7 @@ class PMusrCanvas : public TObject, public TQObject
 
     virtual void Done(Int_t status=0); // *SIGNAL*
     virtual void HandleCmdKey(Int_t event, Int_t x, Int_t y, TObject *selected); // SLOT
+    virtual void LastCanvasClosed(); // SLOT
 
   private:
     Bool_t fValid;