First parameter is a pointer to a menu strip, here NIL, since we don't have one. Here we use a convenience function of the text class, that generates a standard text object that is centered. Third parameter tell the window groub object to put some space around the text object. A handler is a class that can convert any or a special input message to an other message and sends the resulting message to the given destination. However the baseclas just returns the input message.
Most converters are handwritten, but some special converters are given by the corresponding objects.
The event loop will get finished when the display receives a close message or its exit method gets called.