resize event comes in
	new window size taken
	windows: dialog base units re-measured
	call main widget sizing function
main widget sizing function
	get preferred size of all subwidgets
		windows: uses dialog base units
	produce map of which controls are next to which controls
	properly space controls
		windows: uses dialog base units
	return list of size allocations back to window sizer
window sizer
	mac: converts coordinate space
	asks each widget to adjust the allocation based on neighboring control
each widget adjustment
	mac: neighboring control baselines are aligned for labels
	gtk: vertical alignment of text changed to top if neighboring control is multi-line
		TODO - should it be center-aligned or not
	windows: none