A1 = function(id, preserve_screen_top_of_cursor_node)
	-- like A, but translate a single node in Nodes to Surface
	-- this only works because Nodes is a flat array; we don't support row/col types here yet
	print('A1', id)
	-- delete previously added shapes for this node:
	for i=#Surface,1,-1 do
		local x = Surface[i]
		if x.id == id then
			table.remove(Surface, i)
		end
	end
	-- translate Nodes to Surface
	local node = Nodes[id]
	compute_layout(node, node.x,node.y, Surface, preserve_screen_top_of_cursor_node)
	-- continue the pipeline
	B(preserve_screen_top_of_cursor_node)
end