swap 1st layer and support

js/geo-polygon.js

@@ -1050,6 +1050,14 @@ var gs_base_polygon = exports;
         return out;
     };
 
+    PRO.shortestSegmentLength() {
+        var len = Infinity;
+        this.forEachSegment(function(p1, p2) {
+            len = Math.min(len, p1.distTo2D(p2));
+        });
+        return len;
+    };
+
     /**
      * @param {Polygon} poly clipping mask
      * @returns {?Polygon[]}