feat(collapse): make collapse work with bootstrap3

Closes #1240

If starting out collapsed, the expand animation would jump since the `initialAnimSkip` was still `true`.

src/collapse/collapse.js

@@ -1,83 +1,81 @@
-angular.module('ui.bootstrap.collapse',['ui.bootstrap.transition'])
+angular.module('ui.bootstrap.collapse', ['ui.bootstrap.transition'])
 
-// The collapsible directive indicates a block of html that will expand and collapse
-.directive('collapse', ['$transition', function($transition) {
-  // CSS transitions don't work with height: auto, so we have to manually change the height to a
-  // specific value and then once the animation completes, we can reset the height to auto.
-  // Unfortunately if you do this while the CSS transitions are specified (i.e. in the CSS class
-  // "collapse") then you trigger a change to height 0 in between.
-  // The fix is to remove the "collapse" CSS class while changing the height back to auto - phew!
-  var fixUpHeight = function(scope, element, height) {
-    // We remove the collapse CSS class to prevent a transition when we change to height: auto
-    element.removeClass('collapse');
-    element.css({ height: height });
-    // It appears that  reading offsetWidth makes the browser realise that we have changed the
-    // height already :-/
-    var x = element[0].offsetWidth;
-    element.addClass('collapse');
-  };
+  .directive('collapse', ['$transition', function ($transition, $timeout) {
 
-  return {
-    link: function(scope, element, attrs) {
+    return {
+      link: function (scope, element, attrs) {
 
-      var isCollapsed;
-      var initialAnimSkip = true;
+        var initialAnimSkip = true;
+        var currentTransition;
 
-      scope.$watch(attrs.collapse, function(value) {
-        if (value) {
-          collapse();
-        } else {
-          expand();
+        function doTransition(change) {
+          var newTransition = $transition(element, change);
+          if (currentTransition) {
+            currentTransition.cancel();
+          }
+          currentTransition = newTransition;
+          newTransition.then(newTransitionDone, newTransitionDone);
+          return newTransition;
+
+          function newTransitionDone() {
+            // Make sure it's this transition, otherwise, leave it alone.
+            if (currentTransition === newTransition) {
+              currentTransition = undefined;
+            }
+          }
+        }
+
+        function expand() {
+          if (initialAnimSkip) {
+            initialAnimSkip = false;
+            expandDone();
+          } else {
+            var targetElHeight = element[0].scrollHeight;
+            if (targetElHeight) {
+              element.removeClass('collapse').addClass('collapsing');
+              doTransition({ height: element[0].scrollHeight + 'px' }).then(expandDone);
+            } else {
+              expandDone();
+            }
+          }
         }
-      });
-
 
-      var currentTransition;
-      var doTransition = function(change) {
-        if ( currentTransition ) {
-          currentTransition.cancel();
+        function expandDone() {
+          element.removeClass('collapsing');
+          element.addClass('collapse in');
+          element.css({height: 'auto'});
         }
-        currentTransition = $transition(element,change);
-        currentTransition.then(
-          function() { currentTransition = undefined; },
-          function() { currentTransition = undefined; }
-        );
-        return currentTransition;
-      };
 
-      var expand = function () {
-        isCollapsed = false;
-        if (initialAnimSkip) {
-          initialAnimSkip = false;
-          expandDone();
-        } else {
-          var targetElHeight = element[0].scrollHeight;
-          if (targetElHeight) {
-            doTransition({ height: targetElHeight + 'px' }).then(expandDone);
+        function collapse() {
+          if (initialAnimSkip) {
+            initialAnimSkip = false;
+            collapseDone();
+            element.css({height: 0});
           } else {
-            expandDone();
+            // CSS transitions don't work with height: auto, so we have to manually change the height to a specific value
+            element.css({ height: element[0].scrollHeight + 'px' });
+            //trigger reflow so a browser relaizes that height was updated from auto to a specific value
+            var x = element[0].offsetWidth;
+
+            element.removeClass('collapse in').addClass('collapsing');
+
+            doTransition({ height: 0 }).then(collapseDone);
           }
         }
-      };
 
-      function expandDone() {
-        if ( !isCollapsed ) {
-          fixUpHeight(scope, element, 'auto');
-          element.addClass('in');
+        function collapseDone() {
+          element.removeClass('collapsing');
+          element.addClass('collapse');
         }
+
+        scope.$watch(attrs.collapse, function (shouldCollapse) {
+          if (shouldCollapse) {
+            collapse();
+          } else {
+            expand();
+          }
+        });
+
       }
-
-      var collapse = function() {
-        isCollapsed = true;
-        element.removeClass('in');
-        if (initialAnimSkip) {
-          initialAnimSkip = false;
-          fixUpHeight(scope, element, 0);
-        } else {
-          fixUpHeight(scope, element, element[0].scrollHeight + 'px');
-          doTransition({'height':'0'});
-        }
-      };
-    }
-  };
-}]);
+    };
+  }]);