https://verbovisualevirtuale.org/pyramid/ext/Polyline.Intersect.js

1L.Polyline.include({
2	// Check to see if this polyline has any linesegments that intersect.
3	// NOTE: does not support detecting intersection for degenerate cases.
4	intersects: function () {
5		var points = this._originalPoints,
6			len = points ? points.length : 0,
7			i, p, p1;
8
9		if (this._tooFewPointsForIntersection()) {
10			return false;
11		}
12
13		for (i = len - 1; i >= 3; i--) {
14			p = points[i - 1];
15			p1 = points[i];
16
17
18			if (this._lineSegmentsIntersectsRange(p, p1, i - 2)) {
19				return true;
20			}
21		}
22
23		return false;
24	},
25
26	// Check for intersection if new latlng was added to this polyline.
27	// NOTE: does not support detecting intersection for degenerate cases.
28	newLatLngIntersects: function (latlng, skipFirst) {
29		// Cannot check a polyline for intersecting lats/lngs when not added to the map
30		if (!this._map) {
31			return false;
32		}
33
34		return this.newPointIntersects(this._map.latLngToLayerPoint(latlng), skipFirst);
35	},
36
37	// Check for intersection if new point was added to this polyline.
38	// newPoint must be a layer point.
39	// NOTE: does not support detecting intersection for degenerate cases.
40	newPointIntersects: function (newPoint, skipFirst) {
41		var points = this._originalPoints,
42			len = points ? points.length : 0,
43			lastPoint = points ? points[len - 1] : null,
44			// The previous previous line segment. Previous line segment doesn't need testing.
45			maxIndex = len - 2;
46
47		if (this._tooFewPointsForIntersection(1)) {
48			return false;
49		}
50
51		return this._lineSegmentsIntersectsRange(lastPoint, newPoint, maxIndex, skipFirst ? 1 : 0);
52	},
53
54	// Polylines with 2 sides can only intersect in cases where points are collinear (we don't support detecting these).
55	// Cannot have intersection when < 3 line segments (< 4 points)
56	_tooFewPointsForIntersection: function (extraPoints) {
57		var points = this._originalPoints,
58			len = points ? points.length : 0;
59		// Increment length by extraPoints if present
60		len += extraPoints || 0;
61
62		return !this._originalPoints || len <= 3;
63	},
64
65	// Checks a line segment intersections with any line segments before its predecessor.
66	// Don't need to check the predecessor as will never intersect.
67	_lineSegmentsIntersectsRange: function (p, p1, maxIndex, minIndex) {
68		var points = this._originalPoints,
69			p2, p3;
70
71		minIndex = minIndex || 0;
72
73		// Check all previous line segments (beside the immediately previous) for intersections
74		for (var j = maxIndex; j > minIndex; j--) {
75			p2 = points[j - 1];
76			p3 = points[j];
77
78			if (L.LineUtil.segmentsIntersect(p, p1, p2, p3)) {
79				return true;
80			}
81		}
82
83		return false;
84	}
85});