load_subtree = function(id, out, depth)
	-- load a file and recursively all replies to it
--	print('load_subtree', id)
	local item = initialize_item(id, depth)
	-- every item renders to a row consisting of two
	-- columns: padding and 'item stuff'
	local row = cols(Inter_comment_spacing)
	table.insert(out, row)
	table.insert(row.data, indent(depth))
	-- item stuff consists of text and a reply button
	local item_stuff = rows()
	table.insert(row.data, item_stuff)
	table.insert(item_stuff.data, item)
	table.insert(item_stuff.data,
		reply_button(id, depth))
	for i,reply_id in ipairs(item.metadata.replies) do
		local reply = load_subtree(reply_id, out, depth+1)
	end
	return item
end