BUG
	intermittent (really rarely) segmentation fault when resizing the widget
	sometimes scroll doesn't pause
	multiple show widgets are not properly displayed
		(can't find out why... :()

CAUTION
	adding text and pixmaps MUST be done after the widget is mapped
		: after the widget and its parents are shown
	large sized widget is extremely slow, be careful
	running the program in networked condition is not recommended
	gtk_show_draw_function should be careful about scroll interval,
		that is, pause may not be made in exact center of the widget,
		so make some empty area in periphery of the returning pixmap.

TODO
	Add support for '\n' in text
	Add background pixmap and background color
	Change text and pixmap functions to enable adding before widget is shown
