"GTK+ theming as of now
The look of GTK+, just as with all modern graphic tool kits, is
defined by themes. Theming in GTK+ consist of three parts: Engines,
Styles and Configuration. All in all it can be summarised as:
"Themes provide styles, which can be configured and assigned to
widgets". But let's start at the beginning.
"GTK+ provides a set of drawing primitives: lines, boxes,
arrows, and so on. Whenever a widget is drawn, these drawing
primitives are used. The implementation provided by GTK+ is very
basic and not very sophisticated, but it can be overridden."
