Testing segment intersection with extent

If needed, this function can be modified to take two additional coorinates that will be set to the intersection points.

src/ol/extent.js

@@ -643,6 +643,59 @@ ol.extent.scaleFromCenter = function(extent, value) {
 };
 
 
+/**
+ * Determine if the segment between two coordinates intersects (crosses,
+ * touches, or is contained by) the provided extent.
+ * @param {ol.Extent} extent The extent.
+ * @param {ol.Coordinate} start Segment start coordinate.
+ * @param {ol.Coordinate} end Segment end coordinate.
+ * @return {boolean} The segment intersects the extent.
+ */
+ol.extent.segmentIntersects = function(extent, start, end) {
+  var intersects = false;
+  var startRel = ol.extent.coordinateRelationship(extent, start);
+  var endRel = ol.extent.coordinateRelationship(extent, end);
+  if (startRel === ol.extent.Relationship.INTERSECTING ||
+      endRel === ol.extent.Relationship.INTERSECTING) {
+    intersects = true;
+  } else {
+    var minX = extent[0];
+    var minY = extent[1];
+    var maxX = extent[2];
+    var maxY = extent[3];
+    var startX = start[0];
+    var startY = start[1];
+    var endX = end[0];
+    var endY = end[1];
+    var slope = (endY - startY) / (endX - startX);
+    var x, y;
+    if (!!(endRel & ol.extent.Relationship.ABOVE) &&
+        !(startRel & ol.extent.Relationship.ABOVE)) {
+      // potentially intersects top
+      x = endX - ((endY - maxY) / slope);
+      intersects = x >= minX && x <= maxX;
+    } else if (!!(endRel & ol.extent.Relationship.RIGHT) &&
+        !(startRel & ol.extent.Relationship.RIGHT)) {
+      // potentially intersects right
+      y = endY - ((endX - maxX) * slope);
+      intersects = y >= minY && y <= maxY;
+    } else if (!!(endRel & ol.extent.Relationship.BELOW) &&
+        !(startRel & ol.extent.Relationship.BELOW)) {
+      // potentially intersects bottom
+      x = endX - ((endY - minY) / slope);
+      intersects = x >= minX && x <= maxX;
+    } else if (!!(endRel & ol.extent.Relationship.LEFT) &&
+        !(startRel & ol.extent.Relationship.LEFT)) {
+      // potentially intersects left
+      y = endY - ((endX - minX) * slope);
+      intersects = y >= minY && y <= maxY;
+    }
+
+  }
+  return intersects;
+};
+
+
 /**
  * @param {ol.Extent} extent1 Extent 1.
  * @param {ol.Extent} extent2 Extent 2.

test/spec/ol/extent.test.js

@@ -300,6 +300,131 @@ describe('ol.extent', function() {
     });
   });
 
+  describe('segmentIntersects()', function() {
+
+    var extent = [-180, -90, 180, 90];
+    var north = [0, 100];
+    var northeast = [190, 100];
+    var east = [190, 0];
+    var southeast = [190, -100];
+    var south = [0, -100];
+    var southwest = [-190, -100];
+    var west = [-190, 0];
+    var northwest = [-190, 100];
+    var center = [0, 0];
+    var top = [0, 90];
+    var right = [180, 0];
+    var bottom = [-90, 0];
+    var left = [-180, 0];
+    var inside = [10, 10];
+
+    it('returns true if contained', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, inside);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses top', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, north);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses right', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, east);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses bottom', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, south);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses left', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, west);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns false if above', function() {
+      var intersects = ol.extent.segmentIntersects(extent, northwest, north);
+      expect(intersects).to.be(false);
+    });
+
+    it('returns false if right', function() {
+      var intersects = ol.extent.segmentIntersects(extent, northeast, east);
+      expect(intersects).to.be(false);
+    });
+
+    it('returns false if below', function() {
+      var intersects = ol.extent.segmentIntersects(extent, south, southwest);
+      expect(intersects).to.be(false);
+    });
+
+    it('returns false if left', function() {
+      var intersects = ol.extent.segmentIntersects(extent, west, southwest);
+      expect(intersects).to.be(false);
+    });
+
+    it('returns true if crosses top to bottom', function() {
+      var intersects = ol.extent.segmentIntersects(extent, north, south);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses bottom to top', function() {
+      var intersects = ol.extent.segmentIntersects(extent, south, north);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses left to right', function() {
+      var intersects = ol.extent.segmentIntersects(extent, west, east);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses right to left', function() {
+      var intersects = ol.extent.segmentIntersects(extent, east, west);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses northwest to east', function() {
+      var intersects = ol.extent.segmentIntersects(extent, northwest, east);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if crosses south to west', function() {
+      var intersects = ol.extent.segmentIntersects(extent, south, west);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if touches top', function() {
+      var intersects = ol.extent.segmentIntersects(extent, northwest, top);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if touches right', function() {
+      var intersects = ol.extent.segmentIntersects(extent, southeast, right);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if touches bottom', function() {
+      var intersects = ol.extent.segmentIntersects(extent, bottom, south);
+      expect(intersects).to.be(true);
+    });
+
+    it('returns true if touches left', function() {
+      var intersects = ol.extent.segmentIntersects(extent, left, west);
+      expect(intersects).to.be(true);
+    });
+
+    it('works for zero length inside', function() {
+      var intersects = ol.extent.segmentIntersects(extent, center, center);
+      expect(intersects).to.be(true);
+    });
+
+    it('works for zero length outside', function() {
+      var intersects = ol.extent.segmentIntersects(extent, north, north);
+      expect(intersects).to.be(false);
+    });
+
+  });
+
   describe('transform', function() {
 
     it('does transform', function() {