search string
bitmask of flags affecting the search
return location for start of match, or NULL. [out caller-allocates][allow-none]
return location for end of match, or NULL. [out caller-allocates][allow-none]
location of last possible match_start, or NULL for start of buffer. [allow-none]
whether a match was found
Same as gtk_text_iter_forward_search(), but moves backward. match_end will never be set to a GtkTextIter located after iter, even if there is a possible match_start before or at iter.