gtk-text-buffer-iter-at-line-offset (buffer line offset)

buffer -- a gtk-text-buffer object
line -- an integer with the line number counting from 0
offset -- an integer with the char offset from the start of the line

A gtk-text-iter iterator.

Obtains an iterator pointing to offset within the given line. Note characters, not bytes, UTF-8 may encode one character as multiple bytes.

If the line argument is greater than the number of lines in the text buffer, the end iterator is returned. And if the offset argument is off the end of the line, the iterator at the end of the line is returned.