compute_layout = function(node, x,y, nodes_to_render)
	-- append to nodes_to_render flattened instructions to render a hierarchy of nodes
	-- return x,y rendered until (surface coordinates)
	if node.type == 'text' then
		-- leaf node containing raw text
		node.x = x
		node.y = y
		if node.width then
			node.w = node.width
		else
			local scaled_fontsize = scale(node.fontsize or 20)
			node.w = 0
			for _,s in ipairs(node.data) do
				local text = love.graphics.newText(font(node, scaled_fontsize), node.data)
				local width = text:getWidth()
				if node.w < width then node.w = width end
			end
		end
		initialize_editor(node)
	    node.h = box_height(node)
		table.insert(nodes_to_render, node)
	elseif node.type == 'rows' then
		node.x = x
		node.y = y
		-- lay out children top to bottom
		local node_to_render
		if node.bg then
			node_to_render = {type='rectangle', r=node.bg.r, g=node.bg.g, b=node.bg.b, x=node.x, y=node.y}
			table.insert(nodes_to_render, node_to_render)
		end
		local subx,suby = x,y
		local w,h = 0,0
		local subnodes
		for _,child in ipairs(node.data) do
			if child.margin then
				suby = suby+child.margin
				h = h+child.margin
			end
			subx,suby = compute_layout(child, x,suby, nodes_to_render)
			if w < child.w then
				w = child.w
			end
			h = h+child.h
		end
		node.w = w
		node.h = h
		if node_to_render then
			node_to_render.w = w
			node_to_render.h = h
		end
	elseif node.type == 'cols' then
		node.x = x
		node.y = y
		-- lay out children left to right
		local subx,suby = x,y
		local w,h = 0,0
		for _,child in ipairs(node.data) do
			if child.margin then
				subx = subx+child.margin
				w = w+child.margin
			end
			subx,suby = compute_layout(child, subx,y, nodes_to_render)
			w = w + child.w
			if h < child.h then
				h = child.h
			end
		end
		node.w = w
		node.h = h
		if node.bg then
			table.insert(nodes_to_render, {type='rectangle', r=node.bg.r, g=node.bg.g, b=node.bg.b, x=node.x, y=node.y, w=node.w, h=node.h})
		end
	end
	return x+node.w,y+node.h
end