In-progress browser for a directory of text files
y_of_schema1 = function(editor, loc)
	local result = 0
	loc = {line=loc.line, pos=Text.pos_at_start_of_screen_line(editor, loc)}
	if loc.line == 1 and loc.pos == 1 then
		return result
	end
	for i=1,loc.line-1 do
		Text.populate_screen_line_starting_pos(editor, i)
		result = result + line_height(editor, i)
	end
	Text.populate_screen_line_starting_pos(editor, loc.line)
	for i,screen_line_starting_pos in ipairs(editor.line_cache[loc.line].screen_line_starting_pos) do
		if screen_line_starting_pos >= loc.pos then
			break
		end
		result = result + editor.line_height
	end
	return result
end