+ // when the number of lines changes, we try to estimate the total height
+ // of all lines which is a rather expensive operation in terms of lines
+ // access, so if the user code may estimate the average height
+ // better/faster than we do, it should override this function to implement
+ // its own logic
+ //
+ // this function should return the best guess for the total height it may
+ // make
+ virtual wxCoord EstimateTotalHeight() const;
+