feat($swipe): Refactor swipe logic from ngSwipe to $swipe service.

This new service is used by the ngSwipeLeft/Right directives, and by the
separate ngCarousel and swipe-to-delete directives which are under
development.

2 files changed, 152 insertions, 78 deletions

diff --git a/src/ngMobile/directive/ngSwipe.js b/src/ngMobile/directive/ngSwipe.js
index 6de7aa57..e68e45da 100644
--- a/src/ngMobile/directive/ngSwipe.js
+++ b/src/ngMobile/directive/ngSwipe.js
@@ -55,36 +55,20 @@
  */
 
 function makeSwipeDirective(directiveName, direction) {
-  ngMobile.directive(directiveName, ['$parse', function($parse) {
+  ngMobile.directive(directiveName, ['$parse', '$swipe', function($parse, $swipe) {
     // 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) {
+      function validSwipe(coords) {
         // Check that it's within the coordinates.
         // Absolute vertical distance must be within tolerances.
         // Horizontal distance, we take the current X - the starting X.
@@ -94,7 +78,6 @@ function makeSwipeDirective(directiveName, direction) {
         // 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.
@@ -104,65 +87,20 @@ function makeSwipeDirective(directiveName, direction) {
             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) {
+      $swipe.bind(element, {
+        'start': function(coords) {
+          startCoords = coords;
+          valid = true;
+        },
+        'cancel': function() {
           valid = false;
-          return;
-        }
-
-        totalX += Math.abs(coords.x - lastX);
-        totalY += Math.abs(coords.y - lastY);
-
-        lastX = coords.x;
-        lastY = coords.y;
-
-        if (totalX < MOVE_BUFFER_RADIUS && totalY < MOVE_BUFFER_RADIUS) {
-          return;
-        }
-
-        // One of totalX or totalY has exceeded the buffer, so decide on swipe vs. scroll.
-        if (totalY > totalX) {
-          valid = false;
-          return;
-        } else {
-          event.preventDefault();
-        }
-      });
-
-      element.bind('touchend mouseup', function(event) {
-        if (validSwipe(event)) {
-          // Prevent this swipe from bubbling up to any other elements with ngSwipes.
-          event.stopPropagation();
-          scope.$apply(function() {
-            swipeHandler(scope, {$event:event});
-          });
+        },
+        'end': function(coords) {
+          if (validSwipe(coords)) {
+            scope.$apply(function() {
+              swipeHandler(scope);
+            });
+          }
         }
       });
     };
diff --git a/src/ngMobile/swipe.js b/src/ngMobile/swipe.js
new file mode 100644
index 00000000..612d65fd
--- /dev/null
+++ b/src/ngMobile/swipe.js
@@ -0,0 +1,136 @@
+'use strict';
+
+    /**
+     * @ngdoc object
+     * @name ngMobile.$swipe
+     *
+     * @description
+     * The `$swipe` service is a service that abstracts the messier details of hold-and-drag swipe
+     * behavior, to make implementing swipe-related directives more convenient.
+     *
+     * It is used by the `ngSwipeLeft` and `ngSwipeRight` directives in `ngMobile`, and by
+     * `ngCarousel` in a separate component.
+     *
+     * # Usage
+     * The `$swipe` service is an object with a single method: `bind`. `bind` takes an element
+     * which is to be watched for swipes, and an object with four handler functions. See the
+     * documentation for `bind` below.
+     */
+
+ngMobile.factory('$swipe', [function() {
+  // 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 {
+    /**
+     * @ngdoc method
+     * @name ngMobile.$swipe#bind
+     * @methodOf ngMobile.$swipe
+     *
+     * @description
+     * The main method of `$swipe`. It takes an element to be watched for swipe motions, and an
+     * object containing event handlers.
+     *
+     * The four events are `start`, `move`, `end`, and `cancel`. `start`, `move`, and `end`
+     * receive as a parameter a coordinates object of the form `{ x: 150, y: 310 }`.
+     *
+     * `start` is called on either `mousedown` or `touchstart`. After this event, `$swipe` is
+     * watching for `touchmove` or `mousemove` events. These events are ignored until the total
+     * distance moved in either dimension exceeds a small threshold.
+     *
+     * Once this threshold is exceeded, either the horizontal or vertical delta is greater.
+     * - If the horizontal distance is greater, this is a swipe and `move` and `end` events follow.
+     * - If the vertical distance is greater, this is a scroll, and we let the browser take over.
+     *   A `cancel` event is sent.
+     *
+     * `move` is called on `mousemove` and `touchmove` after the above logic has determined that
+     * a swipe is in progress.
+     *
+     * `end` is called when a swipe is successfully completed with a `touchend` or `mouseup`.
+     *
+     * `cancel` is called either on a `touchcancel` from the browser, or when we begin scrolling
+     * as described above.
+     *
+     */
+    bind: function(element, eventHandlers) {
+      // Absolute total movement, used to control swipe vs. scroll.
+      var totalX, totalY;
+      // Coordinates of the start position.
+      var startCoords;
+      // Last event's position.
+      var lastPos;
+      // Whether a swipe is active.
+      var active = false;
+
+      element.bind('touchstart mousedown', function(event) {
+        startCoords = getCoordinates(event);
+        active = true;
+        totalX = 0;
+        totalY = 0;
+        lastPos = startCoords;
+        eventHandlers['start'] && eventHandlers['start'](startCoords);
+      });
+
+      element.bind('touchcancel', function(event) {
+        active = false;
+        eventHandlers['cancel'] && eventHandlers['cancel']();
+      });
+
+      element.bind('touchmove mousemove', function(event) {
+        if (!active) 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.
+
+        if (!startCoords) return;
+        var coords = getCoordinates(event);
+
+        totalX += Math.abs(coords.x - lastPos.x);
+        totalY += Math.abs(coords.y - lastPos.y);
+
+        lastPos = coords;
+
+        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) {
+          // Allow native scrolling to take over.
+          active = false;
+          eventHandlers['cancel'] && eventHandlers['cancel']();
+          return;
+        } else {
+          // Prevent the browser from scrolling.
+          event.preventDefault();
+
+          eventHandlers['move'] && eventHandlers['move'](coords);
+        }
+      });
+
+      element.bind('touchend mouseup', function(event) {
+        if (!active) return;
+        active = false;
+        eventHandlers['end'] && eventHandlers['end'](getCoordinates(event));
+      });
+    }
+  };
+}]);
+
+