At the construction phase, CAknStylusPopUpMenu is given a MEikMenuObserver object, which is usually a pointer to the application’s UI (CAknAppUi) or another class that implements the interface. The stylus pop up menu will grab the stylus event when one of its items is tapped on and it will then report the item’s command ID to the menu observer. It is then up to the application to handle the command in the implementation of MEikMenuObserver::HandleCommandL().
When an item is tapped, the menu calls its observer's (iMenuObserver) ProcessCommandL. Typically the observer is application's AppUi. It is then the observer's responsibility to handle the command appropriately. The observer is informed with KErrCancel if the menu is closed without making a selection.