Returns TRUE if tag is toggled on at exactly this point. If tag
is NULL, returns TRUE if any tag is toggled on at this point. Note
that the gtk_text_iter_begins_tag() returns TRUE if iter is the
start of the tagged range;
gtk_text_iter_has_tag() tells you whether an iterator is
within a tagged range.
Returns TRUE if tag is toggled on at exactly this point. If tag is NULL, returns TRUE if any tag is toggled on at this point. Note that the gtk_text_iter_begins_tag() returns TRUE if iter is the start of the tagged range; gtk_text_iter_has_tag() tells you whether an iterator is within a tagged range.