A = function(preserve_screen_top_of_cursor_node)
	print('A')
	-- translate Nodes to Surface
	while #Surface > 0 do table.remove(Surface) end
	for key,node in pairs(Nodes) do
		node.id = key
		compute_layout(node, node.x,node.y, Surface, preserve_screen_top_of_cursor_node)
	end
	-- draw edges after all nodes have been initialized
	for key,node in pairs(Nodes) do
		for _,d in ipairs(node.outgoing_edges) do
			compute_layout_for_edge(key, d)
		end
	end
	-- continue the pipeline
	B(preserve_screen_top_of_cursor_node)
	-- TODO: ugly that we're manipulating editor objects twice
end