Added click tolerance also for non-touch devices (#4396)

* Added option for click tolerance. This option is used as a threshold to determine if the user event should be considered a click or a drag.

* Updated docs for clickTolerance to state the correct default value.

* Added tests for click threshold

spec/suites/map/handler/Map.DragSpec.js

@@ -73,6 +73,46 @@ describe("Map.Drag", function () {
 			mouse.wait(100).moveTo(200, 200, 0)
 				.down().moveBy(5, 0, 20).moveBy(256, 32, 200).up();
 		});
+
+		it("does not change the center of the map when mouse is moved less than the drag threshold", function (done) {
+			var container = document.createElement('div');
+			container.style.width = container.style.height = '600px';
+			container.style.top = container.style.left = 0;
+			container.style.position = 'absolute';
+
+			document.body.appendChild(container);
+
+			var map = new L.Map(container, {
+				dragging: true,
+				inertia: false
+			});
+
+			var originalCenter = L.latLng(0, 0);
+			map.setView(originalCenter, 1);
+
+			var spy = sinon.spy();
+			map.on('drag', spy);
+
+			var hand = new Hand({
+				timing: 'fastframe',
+				onStop: function () {
+					var center = map.getCenter();
+					var zoom = map.getZoom();
+					document.body.removeChild(container);
+					expect(center).to.be(originalCenter); // Expect center point to be the same as before the click
+					expect(spy.callCount).to.eql(0); // No drag event should have been fired.
+					expect(zoom).to.be(1);
+
+					done();
+				}
+			});
+			var mouse = hand.growFinger('mouse');
+
+			// We move 2 pixels to stay below the default 3-pixel threshold of
+			// L.Draggable. This should result in a click and not a drag.
+			mouse.wait(100).moveTo(200, 200, 0)
+				.down().moveBy(1, 0, 20).moveBy(1, 0, 200).up();
+		});
 	});
 
 	describe("touch events", function () {
@@ -111,6 +151,47 @@ describe("Map.Drag", function () {
 			toucher.wait(100).moveTo(200, 200, 0)
 				.down().moveBy(5, 0, 20).moveBy(256, 32, 200).up();
 		});
+
+		it("does not change the center of the map when finger is moved less than the drag threshold", function (done) {
+			var container = document.createElement('div');
+			container.style.width = container.style.height = '600px';
+			container.style.top = container.style.left = 0;
+			container.style.position = 'absolute';
+
+			document.body.appendChild(container);
+
+			var map = new L.Map(container, {
+				dragging: true,
+				inertia: false
+			});
+
+			var originalCenter = L.latLng(0, 0);
+			map.setView(originalCenter, 1);
+
+			var spy = sinon.spy();
+			map.on('drag', spy);
+
+			var hand = new Hand({
+				timing: 'fastframe',
+				onStop: function () {
+					var center = map.getCenter();
+					var zoom = map.getZoom();
+					document.body.removeChild(container);
+					expect(center).to.be(originalCenter); // Expect center point to be the same as before the click
+					expect(spy.callCount).to.eql(0); // No drag event should have been fired.
+					expect(zoom).to.be(1);
+
+					done();
+				}
+			});
+
+			var toucher = hand.growFinger('touch');
+
+			// We move 2 pixels to stay below the default 3-pixel threshold of
+			// L.Draggable. This should result in a click and not a drag.
+			toucher.wait(100).moveTo(200, 200, 0)
+				.down().moveBy(1, 0, 20).moveBy(1, 0, 200).up();
+		});
 	});
 
 });

src/dom/Draggable.js

@@ -16,6 +16,13 @@
 
 L.Draggable = L.Evented.extend({
 
+	options: {
+		// @option clickTolerance: Number = 3
+		// The max number of pixels a user can shift the mouse pointer during a click
+		// for it to be considered a valid click (as opposed to a mouse drag).
+		clickTolerance: 3
+	},
+
 	statics: {
 		START: L.Browser.touch ? ['touchstart', 'mousedown'] : ['mousedown'],
 		END: {
@@ -103,7 +110,7 @@ L.Draggable = L.Evented.extend({
 		    offset = newPoint.subtract(this._startPoint);
 
 		if (!offset.x && !offset.y) { return; }
-		if (L.Browser.touch && Math.abs(offset.x) + Math.abs(offset.y) < 3) { return; }
+		if (Math.abs(offset.x) + Math.abs(offset.y) < this.options.clickTolerance) { return; }
 
 		L.DomEvent.preventDefault(e);