Started implementing a test of Area.RepaintAll()/Repaint().
Finished the Area.Repaint() test and fixed found bugs. There's some weird issue left in GTK+ Areas...
Quick update to Area GTK+ drawing in an attempt fo figure out what's going on: we store the Area's width/height already; no need to get it back out from GTK+ itself.
Fixed Area.Repaint() bugs on GTK+.