Gtk+/Gnome Application Development
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What a Widget Does

A minimal widget implements the following (though GtkWidget's default implementation may be sufficient in many cases):

• Creation and destruction; this means the usual GtkObject boilerplate (instance and class initializers, shutdown, destroy and finalize methods). See the chapter called The GTK+ Object and Type System, especially the section called Object and Class Structures in the chapter called The GTK+ Object and Type System and the section called Object Finalization in the chapter called The GTK+ Object and Type System. Also see the section called Widget Life Cycle in the chapter called GTK+ Basics.

• The realize/map/unmap/unrealize cycle discussed in the section called Realizing, Mapping, and Showing in the chapter called GTK+ Basics. Widgets must be able to create and uncreate their associated X resources any number of times, and they must be able to show and hide themselves any number of times.

• Geometry negotiation, discussed in the section called Size Allocation in the chapter called GTK+ Basics. Your widget must respond to size requests, and honor size allocations.

• Drawing; widgets must be able to draw themselves on the screen. For container widgets, the widget itself may be invisible but it must ensure child widgets are drawn.

• The widget's unique functionality. Typically this means implementing handlers for some of the widget's event signals.