+LY_DEFINE (ly_paper_system_minimum_distance, "ly:paper-system-minimum-distance",
+ 2, 0, 0, (SCM sys1, SCM sys2),
+ "Measure the minimum distance between these two paper-systems,"
+ " using their stored skylines if possible and falling back to"
+ " their extents otherwise.")
+{
+ Real ret = 0;
+ Prob *p1 = unsmob_prob (sys1);
+ Prob *p2 = unsmob_prob (sys2);
+ Skyline_pair *sky1 = Skyline_pair::unsmob (p1->get_property ("vertical-skylines"));
+ Skyline_pair *sky2 = Skyline_pair::unsmob (p2->get_property ("vertical-skylines"));
+
+ if (sky1 && sky2)
+ ret = (*sky1)[DOWN].distance ((*sky2)[UP]);