GUI platforms

Almost no GUI application is programmed to directly manipulate display devices. Different APIs are used to accelerate GUI development and improve hardware independence. Such APIs are called GUI platforms. In this work, we study three of the most popular GUI platforms on handheld computers, $i.e.$, Qt, Microsoft Windows (or Windows), and X Window system. Since the nomenclatures used by these GUI platforms are quite different, Table I summarizes the different terms.

Table I: GUI nomenclatures

This work	Qt	Windows	X/GTK
Event	Signal/ Event	Message	Signal/ Event
Window	Widget	Control/ Window	Widget
Event processing routine	Slot	Callback	Callback