+ /*
+ The use of pure_position_less and pure_get_rounded_position below
+ are due to the fact that this callback is called before line breaking
+ occurs. Because dots' actual Y posiitons may be linked to that of
+ beams (dots are attached to rests, which are shifted to avoid beams),
+ we instead must use their pure Y positions.
+ */
+ vector_sort (dots, pure_position_less);