void TabScrollBar::Paint(Draw &w)
...
	if(total > sz.cx) {
		p = Point(ffloor(pos), 1);
		rsz = Size(fceil(size), barwidth);
	}
	else {
		p = Point(0, 1);
		rsz = Size(sz.cx, barwidth);
	}
...

	void SetBarWidth(int w) { barwidth = w; LayoutRefresh(); }