chore($$forceReflow): create service for issuing reflows in animations

angularFiles.js

@@ -21,6 +21,7 @@ var angularFiles = {
     'src/ng/controller.js',
     'src/ng/document.js',
     'src/ng/exceptionHandler.js',
+    'src/ng/forceReflow.js',
     'src/ng/http.js',
     'src/ng/httpBackend.js',
     'src/ng/interpolate.js',

src/AngularPublic.js

@@ -63,6 +63,7 @@
   $DocumentProvider,
   $ExceptionHandlerProvider,
   $FilterProvider,
+  $$ForceReflowProvider,
   $InterpolateProvider,
   $IntervalProvider,
   $$HashMapProvider,
@@ -219,6 +220,7 @@ function publishExternalAPI(angular) {
         $document: $DocumentProvider,
         $exceptionHandler: $ExceptionHandlerProvider,
         $filter: $FilterProvider,
+        $$forceReflow: $$ForceReflowProvider,
         $interpolate: $InterpolateProvider,
         $interval: $IntervalProvider,
         $http: $HttpProvider,

src/ng/forceReflow.js

@@ -0,0 +1,24 @@
+'use strict';
+
+var $$ForceReflowProvider = function() {
+  this.$get = ['$document', function($document) {
+    return function(domNode) {
+      //the line below will force the browser to perform a repaint so
+      //that all the animated elements within the animation frame will
+      //be properly updated and drawn on screen. This is required to
+      //ensure that the preparation animation is properly flushed so that
+      //the active state picks up from there. DO NOT REMOVE THIS LINE.
+      //DO NOT OPTIMIZE THIS LINE. THE MINIFIER WILL REMOVE IT OTHERWISE WHICH
+      //WILL RESULT IN AN UNPREDICTABLE BUG THAT IS VERY HARD TO TRACK DOWN AND
+      //WILL TAKE YEARS AWAY FROM YOUR LIFE.
+      if (domNode) {
+        if (!domNode.nodeType && domNode instanceof jqLite) {
+          domNode = domNode[0];
+        }
+      } else {
+        domNode = $document[0].body;
+      }
+      return domNode.offsetWidth + 1;
+    };
+  }];
+};

src/ngMock/angular-mocks.js

@@ -755,11 +755,23 @@ angular.mock.animate = angular.module('ngAnimateMock', ['ng'])
 
   .config(['$provide', function($provide) {
 
-    $provide.decorator('$animate', ['$delegate', '$timeout', '$browser', '$$rAF',
-                            function($delegate,   $timeout,   $browser,   $$rAF) {
+    $provide.factory('$$forceReflow', function() {
+      function reflowFn() {
+        reflowFn.totalReflows++;
+      }
+      reflowFn.totalReflows = 0;
+      return reflowFn;
+    });
+
+    $provide.decorator('$animate', ['$delegate', '$timeout', '$browser', '$$rAF', '$$forceReflow',
+                            function($delegate,   $timeout,   $browser,   $$rAF,   $$forceReflow) {
+
       var animate = {
         queue: [],
         cancel: $delegate.cancel,
+        get reflows() {
+          return $$forceReflow.totalReflows;
+        },
         enabled: $delegate.enabled,
         triggerCallbackEvents: function() {
           $$rAF.flush();

test/ng/forceReflowSpec.js

@@ -0,0 +1,52 @@
+'use strict';
+
+describe('$$forceReflow', function() {
+  it('should issue a reflow by touching the `document.body.client` when no param is provided', function() {
+    module(function($provide) {
+      var doc = jqLite('<div></div>');
+      doc[0].body = {};
+      doc[0].body.offsetWidth = 10;
+      $provide.value('$document', doc);
+    });
+    inject(function($$forceReflow) {
+      var value = $$forceReflow();
+      expect(value).toBe(11);
+    });
+  });
+
+  it('should issue a reflow by touching the `domNode.offsetWidth` when a domNode param is provided',
+    inject(function($$forceReflow) {
+
+    var elm = {};
+    elm.offsetWidth = 100;
+    expect($$forceReflow(elm)).toBe(101);
+  }));
+
+  it('should issue a reflow by touching the `jqLiteNode[0].offsetWidth` when a jqLite node param is provided',
+    inject(function($$forceReflow) {
+
+    var elm = {};
+    elm.offsetWidth = 200;
+    elm = jqLite(elm);
+    expect($$forceReflow(elm)).toBe(201);
+  }));
+
+  describe('$animate with ngAnimateMock', function() {
+    beforeEach(module('ngAnimateMock'));
+
+    it('should keep track of how many reflows have been issued',
+      inject(function($$forceReflow, $animate) {
+
+      var elm = {};
+      elm.offsetWidth = 10;
+
+      expect($animate.reflows).toBe(0);
+
+      $$forceReflow(elm);
+      $$forceReflow(elm);
+      $$forceReflow(elm);
+
+      expect($animate.reflows).toBe(3);
+    }));
+  });
+});