Allow extents to restrict tile ranges requested from the server

The addition of full extent tile ranges also allows us to simplify wrapX
handling for tile layers. By limiting wrapX to true and false as possible
values, we can remove a lot of guessing logic.

test/spec/ol/tilecoord.test.js

@@ -46,7 +46,79 @@ describe('ol.TileCoord', function() {
           ol.tilecoord.hash(tileCoord2));
     });
   });
+
+  describe('restrictByExtentAndZ', function() {
+
+    it('restricts by z', function() {
+      var tileGrid = new ol.tilegrid.TileGrid({
+        extent: [10, 20, 30, 40],
+        tileSize: 10,
+        resolutions: [2, 1],
+        minZoom: 1
+      });
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, 0], tileGrid))
+          .to.equal(null);
+      expect(ol.tilecoord.restrictByExtentAndZ([1, 0, 0], tileGrid))
+          .to.eql([1, 0, 0]);
+      expect(ol.tilecoord.restrictByExtentAndZ([2, 0, 0], tileGrid))
+          .to.equal(null);
+    });
+
+    it('restricts by extent when extent defines tile ranges', function() {
+      var tileGrid = new ol.tilegrid.TileGrid({
+        extent: [10, 20, 30, 40],
+        sizes: [[3, 3]],
+        tileSize: 10,
+        resolutions: [1]
+      });
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 1, 1], tileGrid))
+          .to.eql([0, 1, 1]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 2, 0], tileGrid))
+          .to.equal(null);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, 2], tileGrid))
+          .to.equal(null);
+    });
+
+    it('restricts by extent when sizes define tile ranges', function() {
+      var tileGrid = new ol.tilegrid.TileGrid({
+        origin: [10, 20],
+        sizes: [[3, 3]],
+        tileSize: 10,
+        resolutions: [1]
+      });
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, 0], tileGrid))
+          .to.eql([0, 0, 0]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, -1, 0], tileGrid))
+          .to.equal(null);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, -1], tileGrid))
+          .to.equal(null);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 2, 2], tileGrid))
+          .to.eql([0, 2, 2]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 3, 0], tileGrid))
+          .to.equal(null);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, 3], tileGrid))
+          .to.equal(null);
+    });
+
+    it('does not restrict by extent with no extent or sizes', function() {
+      var tileGrid = new ol.tilegrid.TileGrid({
+        origin: [10, 20],
+        tileSize: 10,
+        resolutions: [1]
+      });
+      expect(ol.tilecoord.restrictByExtentAndZ([0, Infinity, 0], tileGrid))
+          .to.eql([0, Infinity, 0]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, Infinity], tileGrid))
+          .to.eql([0, 0, Infinity]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, -Infinity, 0], tileGrid))
+          .to.eql([0, -Infinity, 0]);
+      expect(ol.tilecoord.restrictByExtentAndZ([0, 0, Infinity], tileGrid))
+          .to.eql([0, 0, Infinity]);
+    });
+  });
+
 });
 
 goog.require('ol.TileCoord');
 goog.require('ol.tilecoord');
+goog.require('ol.tilegrid.TileGrid');