Typically, Applications do not call the DoHint method. It is called automatically when the user pauses the mouse over one of the action's client controls or menu items. 

DoHint checks for an OnHint event handler and passes HintStr to it, if the handler exists. DoHint returns true if no event handler is assigned or if the OnHint event handler indicates that the hint should be displayed using the default popup window. 

OnHint