Given a position @p with a UTF-8 encoded string @str, find the start
of the previous UTF-8 character starting before @p. Returns %NULL if no
UTF-8 characters are present in @str before @p.
@p does not have to be at the beginning of a UTF-8 character. No check
is made to see if the character found is actually valid other than
it starts with an appropriate byte.
Given a position @p with a UTF-8 encoded string @str, find the start of the previous UTF-8 character starting before @p. Returns %NULL if no UTF-8 characters are present in @str before @p.
@p does not have to be at the beginning of a UTF-8 character. No check is made to see if the character found is actually valid other than it starts with an appropriate byte.