feat(ngSwipe): Add ngSwipeRight/Left directives to ngMobile

These directives fire an event handler on a touch-and-drag or
click-and-drag to the left or right. Includes unit tests and docs
update. Manually tested on Chrome 26, IE8, Android Chrome and iOS
Safari.

3 files changed, 180 insertions, 8 deletions

diff --git a/src/ngMobile/directive/ngClick.js b/src/ngMobile/directive/ngClick.js
index a52893b1..b3e3007d 100644
--- a/src/ngMobile/directive/ngClick.js
+++ b/src/ngMobile/directive/ngClick.js
@@ -163,7 +163,7 @@ ngMobile.directive('ngClick', ['$parse', '$timeout', '$rootElement',
 
   // Actual linking function.
   return function(scope, element, attr) {
-    var expressionFn = $parse(attr.ngClick),
+    var clickHandler = $parse(attr.ngClick),
         tapping = false,
         tapElement,  // Used to blur the element after a tap.
         startTime,   // Used to check if the tap was held too long.
@@ -221,7 +221,7 @@ ngMobile.directive('ngClick', ['$parse', '$timeout', '$rootElement',
 
         scope.$apply(function() {
           // TODO(braden): This is sending the touchend, not a tap or click. Is that kosher?
-          expressionFn(scope, {$event: event});
+          clickHandler(scope, {$event: event});
         });
       }
       tapping = false;
@@ -236,7 +236,7 @@ ngMobile.directive('ngClick', ['$parse', '$timeout', '$rootElement',
     // desktop as well, to allow more portable sites.
     element.bind('click', function(event) {
       scope.$apply(function() {
-        expressionFn(scope, {$event: event});
+        clickHandler(scope, {$event: event});
       });
     });
   };
diff --git a/src/ngMobile/directive/ngSwipe.js b/src/ngMobile/directive/ngSwipe.js
new file mode 100644
index 00000000..6de7aa57
--- /dev/null
+++ b/src/ngMobile/directive/ngSwipe.js
@@ -0,0 +1,175 @@
+'use strict';
+
+/**
+ * @ngdoc directive
+ * @name ngMobile.directive:ngSwipeLeft
+ *
+ * @description
+ * Specify custom behavior when an element is swiped to the left on a touchscreen device.
+ * A leftward swipe is a quick, right-to-left slide of the finger.
+ * Though ngSwipeLeft is designed for touch-based devices, it will work with a mouse click and drag too.
+ *
+ * @element ANY
+ * @param {expression} ngSwipeLeft {@link guide/expression Expression} to evaluate
+ * upon left swipe. (Event object is available as `$event`)
+ *
+ * @example
+    <doc:example>
+      <doc:source>
+        <div ng-show="!showActions" ng-swipe-left="showActions = true">
+          Some list content, like an email in the inbox
+        </div>
+        <div ng-show="showActions" ng-swipe-right="showActions = false">
+          <button ng-click="reply()">Reply</button>
+          <button ng-click="delete()">Delete</button>
+        </div>
+      </doc:source>
+    </doc:example>
+ */
+
+/**
+ * @ngdoc directive
+ * @name ngMobile.directive:ngSwipeRight
+ *
+ * @description
+ * Specify custom behavior when an element is swiped to the right on a touchscreen device.
+ * A rightward swipe is a quick, left-to-right slide of the finger.
+ * Though ngSwipeRight is designed for touch-based devices, it will work with a mouse click and drag too.
+ *
+ * @element ANY
+ * @param {expression} ngSwipeRight {@link guide/expression Expression} to evaluate
+ * upon right swipe. (Event object is available as `$event`)
+ *
+ * @example
+    <doc:example>
+      <doc:source>
+        <div ng-show="!showActions" ng-swipe-left="showActions = true">
+          Some list content, like an email in the inbox
+        </div>
+        <div ng-show="showActions" ng-swipe-right="showActions = false">
+          <button ng-click="reply()">Reply</button>
+          <button ng-click="delete()">Delete</button>
+        </div>
+      </doc:source>
+    </doc:example>
+ */
+
+function makeSwipeDirective(directiveName, direction) {
+  ngMobile.directive(directiveName, ['$parse', function($parse) {
+    // The maximum vertical delta for a swipe should be less than 75px.
+    var MAX_VERTICAL_DISTANCE = 75;
+    // Vertical distance should not be more than a fraction of the horizontal distance.
+    var MAX_VERTICAL_RATIO = 0.3;
+    // At least a 30px lateral motion is necessary for a swipe.
+    var MIN_HORIZONTAL_DISTANCE = 30;
+    // The total distance in any direction before we make the call on swipe vs. scroll.
+    var MOVE_BUFFER_RADIUS = 10;
+
+    function getCoordinates(event) {
+      var touches = event.touches && event.touches.length ? event.touches : [event];
+      var e = (event.changedTouches && event.changedTouches[0]) ||
+          (event.originalEvent && event.originalEvent.changedTouches &&
+              event.originalEvent.changedTouches[0]) ||
+          touches[0].originalEvent || touches[0];
+
+      return {
+        x: e.clientX,
+        y: e.clientY
+      };
+    }
+
+    return function(scope, element, attr) {
+      var swipeHandler = $parse(attr[directiveName]);
+      var startCoords, valid;
+      var totalX, totalY;
+      var lastX, lastY;
+
+      function validSwipe(event) {
+        // Check that it's within the coordinates.
+        // Absolute vertical distance must be within tolerances.
+        // Horizontal distance, we take the current X - the starting X.
+        // This is negative for leftward swipes and positive for rightward swipes.
+        // After multiplying by the direction (-1 for left, +1 for right), legal swipes
+        // (ie. same direction as the directive wants) will have a positive delta and
+        // illegal ones a negative delta.
+        // Therefore this delta must be positive, and larger than the minimum.
+        if (!startCoords) return false;
+        var coords = getCoordinates(event);
+        var deltaY = Math.abs(coords.y - startCoords.y);
+        var deltaX = (coords.x - startCoords.x) * direction;
+        return valid && // Short circuit for already-invalidated swipes.
+            deltaY < MAX_VERTICAL_DISTANCE &&
+            deltaX > 0 &&
+            deltaX > MIN_HORIZONTAL_DISTANCE &&
+            deltaY / deltaX < MAX_VERTICAL_RATIO;
+      }
+
+      element.bind('touchstart mousedown', function(event) {
+        startCoords = getCoordinates(event);
+        valid = true;
+        totalX = 0;
+        totalY = 0;
+        lastX = startCoords.x;
+        lastY = startCoords.y;
+      });
+
+      element.bind('touchcancel', function(event) {
+        valid = false;
+      });
+
+      element.bind('touchmove mousemove', function(event) {
+        if (!valid) return;
+
+        // Android will send a touchcancel if it thinks we're starting to scroll.
+        // So when the total distance (+ or - or both) exceeds 10px in either direction,
+        // we either:
+        // - On totalX > totalY, we send preventDefault() and treat this as a swipe.
+        // - On totalY > totalX, we let the browser handle it as a scroll.
+
+        // Invalidate a touch while it's in progress if it strays too far away vertically.
+        // We don't want a scroll down and back up while drifting sideways to be a swipe just
+        // because you happened to end up vertically close in the end.
+        if (!startCoords) return;
+        var coords = getCoordinates(event);
+
+        if (Math.abs(coords.y - startCoords.y) > MAX_VERTICAL_DISTANCE) {
+          valid = false;
+          return;
+        }
+
+        totalX += Math.abs(coords.x - lastX);
+        totalY += Math.abs(coords.y - lastY);
+
+        lastX = coords.x;
+        lastY = coords.y;
+
+        if (totalX < MOVE_BUFFER_RADIUS && totalY < MOVE_BUFFER_RADIUS) {
+          return;
+        }
+
+        // One of totalX or totalY has exceeded the buffer, so decide on swipe vs. scroll.
+        if (totalY > totalX) {
+          valid = false;
+          return;
+        } else {
+          event.preventDefault();
+        }
+      });
+
+      element.bind('touchend mouseup', function(event) {
+        if (validSwipe(event)) {
+          // Prevent this swipe from bubbling up to any other elements with ngSwipes.
+          event.stopPropagation();
+          scope.$apply(function() {
+            swipeHandler(scope, {$event:event});
+          });
+        }
+      });
+    };
+  }]);
+}
+
+// Left is negative X-coordinate, right is positive.
+makeSwipeDirective('ngSwipeLeft', -1);
+makeSwipeDirective('ngSwipeRight', 1);
+
diff --git a/src/ngMobile/mobile.js b/src/ngMobile/mobile.js
index c8fd8843..daa28f5b 100644
--- a/src/ngMobile/mobile.js
+++ b/src/ngMobile/mobile.js
@@ -4,13 +4,10 @@
  * @ngdoc overview
  * @name ngMobile
  * @description
- */
-
-/*
- * Touch events and other mobile helpers by Braden Shepherdson (braden.shepherdson@gmail.com)
+ * Touch events and other mobile helpers.
  * Based on jQuery Mobile touch event handling (jquerymobile.com)
  */
 
-// define ngSanitize module and register $sanitize service
+// define ngMobile module
 var ngMobile = angular.module('ngMobile', []);