2GVF47BINWURV2RS7QY6BOOV4X7NX2WWAF2CG42DSCCKI7MVSJ4QC
-- fragments: snippets of the line guaranteed to not straddle screen lines
-- screen_line_starting_pos: optional array of grapheme indices if it wraps over more than one screen line
-- screen_line_starting_pos: optional array of codepoint indices if it wraps over more than one screen line