--    mode = 'text'
--    string data
--    screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line

--    mode = 'text',
--    string data,
--    a (y) coord in pixels (updated while painting screen),
--    some cached data that's blown away and recomputed when data changes:
--      fragments: snippets of rendered love.graphics.Text, guaranteed to not wrap
--      screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line