gboolean gtk_text_iter_forward_visible_lines ( GtkTextIter* iter, int count )
count visible lines forward, if possible.
count would move past the start or end of the buffer, moves to
the start or end of the buffer.
The return value indicates whether the iterator moved
onto a dereferenceable position; if the iterator didn’t move, or
moved onto the end iterator, then
FALSE is returned. If
count is 0,
the function does nothing and returns
count is negative,
moves backward by 0 -