assert(Glib.Utf8.validate s);
source_buffer#delete ~start:iter
~stop:(iter#copy#backward_chars
(MatitaGtkMisc.utf8_string_length inplaceof + len));
assert(Glib.Utf8.validate s);
source_buffer#delete ~start:iter
~stop:(iter#copy#backward_chars
(MatitaGtkMisc.utf8_string_length inplaceof + len));