Obtains an iterator pointing to char_offset within the given line. Note
characters, not bytes; UTF-8 may encode one character as multiple bytes.
Before the 3.20 version, it was not allowed to pass an invalid location.
Since the 3.20 version, if line_number is greater than the number of lines
in the buffer, the end iterator is returned. And if char_offset is off the
end of the line, the iterator at the end of the line is returned.
Obtains an iterator pointing to char_offset within the given line. Note characters, not bytes; UTF-8 may encode one character as multiple bytes.
Before the 3.20 version, it was not allowed to pass an invalid location.
Since the 3.20 version, if line_number is greater than the number of lines in the buffer, the end iterator is returned. And if char_offset is off the end of the line, the iterator at the end of the line is returned.