gstream-set_wrap man page
void set_wrap(bool w);
If set to true, the outputter will launch a newline if the text is too wide to fit the line. The text will be wrapped at the spaces between the words.
If a single word is too wide, it'll simply be outputted with a newline before and after it, which means that it will get a line of its own and probably be truncated by Allegro's clipping mechanism.
The inputter doesn't wrap the lines, only the outputter. The default value is false.