Bug 513213 - coalesce events when new event is appended to the queue, r=marcoz, ginn, davidb

accessible/src/base/nsAccessibleEventData.cpp

@@ -311,7 +311,8 @@ void
 nsAccEvent::ApplyEventRules(nsCOMArray<nsIAccessibleEvent> &aEventsToFire)
 {
   PRUint32 numQueuedEvents = aEventsToFire.Count();
-  for (PRInt32 tail = numQueuedEvents - 1; tail >= 0; tail --) {
+  PRInt32 tail = numQueuedEvents - 1;
+
   nsRefPtr<nsAccEvent> tailEvent = GetAccEventPtr(aEventsToFire[tail]);
   switch(tailEvent->mEventRule) {
     case nsAccEvent::eCoalesceFromSameSubtree:
@@ -393,7 +394,6 @@ nsAccEvent::ApplyEventRules(nsCOMArray<nsIAccessibleEvent> &aEventsToFire)
     default:
       break; // case eAllowDupes, eDoNotEmit
   } // switch
-  } // for (tail)
 }
 
 /* static */

accessible/src/base/nsDocAccessible.cpp

@@ -1185,7 +1185,7 @@ nsDocAccessible::AttributeChangedImpl(nsIContent* aContent, PRInt32 aNameSpaceID
       aAttribute == nsAccessibilityAtoms::title ||
       aAttribute == nsAccessibilityAtoms::aria_label ||
       aAttribute == nsAccessibilityAtoms::aria_labelledby) {
-    FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE,
+    FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_NAME_CHANGE,
                                targetNode);
     return;
   }
@@ -1208,7 +1208,7 @@ nsDocAccessible::AttributeChangedImpl(nsIContent* aContent, PRInt32 aNameSpaceID
       nsCOMPtr<nsIDOMNode> multiSelectDOMNode;
       multiSelectAccessNode->GetDOMNode(getter_AddRefs(multiSelectDOMNode));
       NS_ASSERTION(multiSelectDOMNode, "A new accessible without a DOM node!");
-      FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_SELECTION_WITHIN,
+      FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_SELECTION_WITHIN,
                                  multiSelectDOMNode,
                                  nsAccEvent::eAllowDupes);
 
@@ -1216,12 +1216,12 @@ nsDocAccessible::AttributeChangedImpl(nsIContent* aContent, PRInt32 aNameSpaceID
         {&nsAccessibilityAtoms::_empty, &nsAccessibilityAtoms::_false, nsnull};
       if (aContent->FindAttrValueIn(kNameSpaceID_None, aAttribute,
                                     strings, eCaseMatters) >= 0) {
-        FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_SELECTION_REMOVE,
+        FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_SELECTION_REMOVE,
                                    targetNode);
         return;
       }
 
-      FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_SELECTION_ADD,
+      FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_SELECTION_ADD,
                                  targetNode);
     }
   }
@@ -1340,7 +1340,8 @@ nsDocAccessible::ARIAAttributeChanged(nsIContent* aContent, nsIAtom* aAttribute)
         aContent->AttrValueIs(kNameSpaceID_None,
             nsAccessibilityAtoms::aria_valuetext, nsAccessibilityAtoms::_empty,
             eCaseMatters)))) {
-    FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE, targetNode);
+    FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE,
+                               targetNode);
     return;
   }
 
@@ -1357,7 +1358,7 @@ nsDocAccessible::ARIAAttributeChanged(nsIContent* aContent, nsIAtom* aAttribute)
   // at least until native API comes up with a more meaningful event.
   if (aAttribute == nsAccessibilityAtoms::aria_grabbed ||
       aAttribute == nsAccessibilityAtoms::aria_dropeffect) {
-    FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_OBJECT_ATTRIBUTE_CHANGED,
+    FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_OBJECT_ATTRIBUTE_CHANGED,
                                targetNode);
   }
 }
@@ -1592,13 +1593,14 @@ nsDocAccessible::CreateTextChangeEventForNode(nsIAccessible *aContainerAccessibl
   return event;
 }
   
-nsresult nsDocAccessible::FireDelayedToolkitEvent(PRUint32 aEvent,
+nsresult
+nsDocAccessible::FireDelayedAccessibleEvent(PRUint32 aEventType,
                                             nsIDOMNode *aDOMNode,
                                             nsAccEvent::EEventRule aAllowDupes,
                                             PRBool aIsAsynch)
 {
   nsCOMPtr<nsIAccessibleEvent> event =
-    new nsAccEvent(aEvent, aDOMNode, aIsAsynch, aAllowDupes);
+    new nsAccEvent(aEventType, aDOMNode, aIsAsynch, aAllowDupes);
   NS_ENSURE_TRUE(event, NS_ERROR_OUT_OF_MEMORY);
 
   return FireDelayedAccessibleEvent(event);
@@ -1616,6 +1618,10 @@ nsDocAccessible::FireDelayedAccessibleEvent(nsIAccessibleEvent *aEvent)
   }
 
   mEventsToFire.AppendObject(aEvent);
+
+  // Filter events.
+  nsAccEvent::ApplyEventRules(mEventsToFire);
+
   if (mEventsToFire.Count() == 1) {
     // This is be the first delayed event in queue, start timer
     // so that event gets fired via FlushEventsCallback
@@ -1643,9 +1649,6 @@ nsDocAccessible::FlushPendingEvents()
     // visibility. We don't flush the display because we don't care about
     // painting. If no flush is necessary the method will simple return.
     presShell->FlushPendingNotifications(Flush_Layout);
-
-    // filter events
-    nsAccEvent::ApplyEventRules(mEventsToFire);
   }
   
   for (PRUint32 index = 0; index < length; index ++) {
@@ -2105,7 +2108,7 @@ nsDocAccessible::InvalidateCacheSubtree(nsIContent *aChild,
     // nsIAccessibleStates::STATE_INVISIBLE for the event's accessible object.
     PRUint32 additionEvent = isAsynch ? nsIAccessibleEvent::EVENT_ASYNCH_SHOW :
                                         nsIAccessibleEvent::EVENT_DOM_CREATE;
-    FireDelayedToolkitEvent(additionEvent, childNode,
+    FireDelayedAccessibleEvent(additionEvent, childNode,
                                nsAccEvent::eCoalesceFromSameSubtree,
                                isAsynch);
 
@@ -2113,7 +2116,7 @@ nsDocAccessible::InvalidateCacheSubtree(nsIContent *aChild,
     // an EVENT_MENUPOPUP_START if it did.
     nsRoleMapEntry *roleMapEntry = nsAccUtils::GetRoleMapEntry(childNode);
     if (roleMapEntry && roleMapEntry->role == nsIAccessibleRole::ROLE_MENUPOPUP) {
-      FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_MENUPOPUP_START,
+      FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_MENUPOPUP_START,
                                  childNode, nsAccEvent::eRemoveDupes,
                                  isAsynch);
     }
@@ -2123,7 +2126,7 @@ nsDocAccessible::InvalidateCacheSubtree(nsIContent *aChild,
     while (PR_TRUE) {
       if (roleMapEntry && roleMapEntry->role == nsIAccessibleRole::ROLE_ALERT) {
         nsCOMPtr<nsIDOMNode> alertNode(do_QueryInterface(ancestor));
-        FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_ALERT, alertNode,
+        FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_ALERT, alertNode,
                                    nsAccEvent::eRemoveDupes, isAsynch);
         break;
       }

accessible/src/base/nsDocAccessible.h

@@ -121,13 +121,13 @@ public:
   /**
    * Non-virtual method to fire a delayed event after a 0 length timeout.
    *
-   * @param aEvent       [in] the nsIAccessibleEvent event type
+   * @param aEventType   [in] the nsIAccessibleEvent event type
    * @param aDOMNode     [in] DOM node the accesible event should be fired for
    * @param aAllowDupes  [in] rule to process an event (see EEventRule constants)
    * @param aIsAsynch    [in] set to PR_TRUE if this is not being called from
    *                      code synchronous with a DOM event
    */
-  nsresult FireDelayedToolkitEvent(PRUint32 aEvent, nsIDOMNode *aDOMNode,
+  nsresult FireDelayedAccessibleEvent(PRUint32 aEventType, nsIDOMNode *aDOMNode,
                                       nsAccEvent::EEventRule aAllowDupes = nsAccEvent::eRemoveDupes,
                                       PRBool aIsAsynch = PR_FALSE);
 

accessible/src/base/nsRootAccessible.cpp

@@ -396,7 +396,8 @@ void nsRootAccessible::TryFireEarlyLoadEvent(nsIDOMNode *aDocNode)
   NS_ASSERTION(rootContentTreeItem, "No root content tree item");
   if (rootContentTreeItem == treeItem) {
     // No frames or iframes, so we can fire the doc load finished event early
-    FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_INTERNAL_LOAD, aDocNode);
+    FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_INTERNAL_LOAD,
+                               aDocNode);
   }
 }
 
@@ -538,7 +539,7 @@ PRBool nsRootAccessible::FireAccessibleFocusEvent(nsIAccessible *aAccessible,
     }
   }
 
-  FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_FOCUS,
+  FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_FOCUS,
                              finalFocusNode, nsAccEvent::eRemoveDupes,
                              aIsAsynch);
 
@@ -893,7 +894,8 @@ nsresult nsRootAccessible::HandleEventWithTarget(nsIDOMEvent* aEvent,
     FireCurrentFocusEvent();
   }
   else if (eventType.EqualsLiteral("ValueChange")) {
-    FireDelayedToolkitEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE, aTargetNode, nsAccEvent::eRemoveDupes);
+    FireDelayedAccessibleEvent(nsIAccessibleEvent::EVENT_VALUE_CHANGE,
+                               aTargetNode, nsAccEvent::eRemoveDupes);
   }
 #ifdef DEBUG
   else if (eventType.EqualsLiteral("mouseover")) {

accessible/tests/mochitest/Makefile.in

@@ -98,6 +98,7 @@ _TEST_FILES =\
 		test_events_draganddrop.html \
 		test_events_focus.xul \
 		test_events_mutation.html \
+		test_events_mutation_coalesce.html \
 		test_events_tree.xul \
 		test_events_valuechange.html \
 		test_groupattrs.xul \

accessible/tests/mochitest/events.js

@@ -1,8 +1,11 @@
 ////////////////////////////////////////////////////////////////////////////////
 // Constants
 
+const EVENT_ASYNCH_HIDE = nsIAccessibleEvent.EVENT_ASYNCH_HIDE;
+const EVENT_ASYNCH_SHOW = nsIAccessibleEvent.EVENT_ASYNCH_SHOW;
 const EVENT_DOCUMENT_LOAD_COMPLETE =
   nsIAccessibleEvent.EVENT_DOCUMENT_LOAD_COMPLETE;
+const EVENT_DOM_CREATE = nsIAccessibleEvent.EVENT_DOM_CREATE;
 const EVENT_DOM_DESTROY = nsIAccessibleEvent.EVENT_DOM_DESTROY;
 const EVENT_FOCUS = nsIAccessibleEvent.EVENT_FOCUS;
 const EVENT_NAME_CHANGE = nsIAccessibleEvent.EVENT_NAME_CHANGE;
@@ -123,15 +126,10 @@ function invokerChecker(aEventType, aTarget)
  *     // (used in the case when invoker expects single event).
  *     DOMNode getter: function() {},
  *
- *     // Array of items defining events expected (or not expected, see
+ *     // Array of checker objects defining expected events on invoker's action.
- *     // 'doNotExpectEvents' property) on invoker's action.
  *     //
- *     // Every array item should be either
+ *     // Checker object interface:
- *     // 1) an array consisted from two elements, the first element is DOM or
- *     // a11y event type, second element is event target (DOM node or
- *     // accessible).
  *     //
- *     // 2) object (invoker's checker object) like
  *     // var checker = {
  *     //   type getter: function() {}, // DOM or a11y event type
  *     //   target getter: function() {}, // DOM node or accessible
@@ -141,9 +139,9 @@ function invokerChecker(aEventType, aTarget)
  *     // };
  *     eventSeq getter() {},
  *
- *     // [optional, used together with 'eventSeq'] Boolean indicates if events
+ *     // Array of checker objects defining unexpected events on invoker's
- *     // specified by 'eventSeq' property shouldn't be triggerd by invoker.
+ *     // action.
- *     doNotExpectEvents getter() {},
+ *     unexpectedEventSeq getter() {},
  *
  *     // The ID of invoker.
  *     getID: function(){} // returns invoker ID
@@ -174,8 +172,7 @@ function eventQueue(aEventType)
 
     // XXX: Intermittent test_events_caretmove.html fails withouth timeout,
     // see bug 474952.
-    window.setTimeout(function(aQueue) { aQueue.processNextInvoker(); }, 500,
+    this.processNextInvokerInTimeout(true);
-                      this);
   }
 
   /**
@@ -198,15 +195,20 @@ function eventQueue(aEventType)
 
     var invoker = this.getInvoker();
     if (invoker) {
+      if ("finalCheck" in invoker)
+        invoker.finalCheck();
+
       if (invoker.wasCaught) {
         for (var idx = 0; idx < invoker.wasCaught.length; idx++) {
           var id = this.getEventID(idx);
           var type = this.getEventType(idx);
+          var unexpected = this.mEventSeq[idx].unexpected;
+
           var typeStr = (typeof type == "string") ?
             type : gAccRetrieval.getStringEventType(type);
 
           var msg = "test with ID = '" + id + "' failed. ";
-          if (invoker.doNotExpectEvents) {
+          if (unexpected) {
             var wasCaught = invoker.wasCaught[idx];
             if (!testFailed)
               testFailed = wasCaught;
@@ -256,12 +258,23 @@ function eventQueue(aEventType)
       return;
     }
 
-    if (invoker.doNotExpectEvents) {
+    if (this.areAllEventsUnexpected())
+      this.processNextInvokerInTimeout(true);
+  }
+
+  this.processNextInvokerInTimeout = function eventQueue_processNextInvokerInTimeout(aUncondProcess)
+  {
+    if (!aUncondProcess && this.areAllEventsExpected()) {
+      // We need delay to avoid events coalesce from different invokers.
+      var queue = this;
+      SimpleTest.executeSoon(function() { queue.processNextInvoker(); });
+      return;
+    }
+
     // Check in timeout invoker didn't fire registered events.
     window.setTimeout(function(aQueue) { aQueue.processNextInvoker(); }, 500,
                       this);
   }
-  }
 
   /**
    * Handle events for the current invoker.
@@ -282,16 +295,23 @@ function eventQueue(aEventType)
     if ("debugCheck" in invoker)
       invoker.debugCheck(aEvent);
 
-    if (invoker.doNotExpectEvents) {
+    // Search through unexpected events to ensure no one of them was handled.
-      // Search through event sequence to ensure it doesn't contain handled
-      // event.
     for (var idx = 0; idx < this.mEventSeq.length; idx++) {
-        if (this.compareEvents(idx, aEvent))
+      if (this.mEventSeq[idx].unexpected && this.compareEvents(idx, aEvent))
         invoker.wasCaught[idx] = true;
     }
-    } else {
+
-      // We wait for events in order specified by eventSeq variable.
+    // Wait for next expected event in an order specified by event sequence.
-      var idx = this.mEventSeqIdx + 1;
+
+    // Compute next expected event index.
+    for (var idx = this.mEventSeqIdx + 1;
+         idx < this.mEventSeq.length && this.mEventSeq[idx].unexpected; idx++);
+
+    if (idx == this.mEventSeq.length) {
+      // There is no expected events in the sequence.
+      this.processNextInvokerInTimeout();
+      return;
+    }
 
     var matched = this.compareEvents(idx, aEvent);
     this.dumpEventToDOM(aEvent, idx, matched);
@@ -300,17 +320,15 @@ function eventQueue(aEventType)
       this.checkEvent(idx, aEvent);
       invoker.wasCaught[idx] = true;
 
+      // The last event is expected and was handled, proceed next invoker.
       if (idx == this.mEventSeq.length - 1) {
-          // We need delay to avoid events coalesce from different invokers.
+        this.processNextInvokerInTimeout();
-          var queue = this;
-          SimpleTest.executeSoon(function() { queue.processNextInvoker(); });
         return;
       }
 
       this.mEventSeqIdx = idx;
     }
   }
-  }
 
   // Helpers
   this.getInvoker = function eventQueue_getInvoker()
@@ -325,12 +343,26 @@ function eventQueue(aEventType)
 
   this.setEventHandler = function eventQueue_setEventHandler(aInvoker)
   {
+    // Create unique event sequence concatenating expected and unexpected
+    // events.
     this.mEventSeq = ("eventSeq" in aInvoker) ?
       aInvoker.eventSeq :
       [ new invokerChecker(this.mDefEventType, aInvoker.DOMNode) ];
 
+    for (var idx = 0; idx < this.mEventSeq.length; idx++)
+      this.mEventSeq[idx].unexpected = false;
+
+    var unexpectedSeq = aInvoker.unexpectedEventSeq;
+    if (unexpectedSeq) {
+      for (var idx = 0; idx < unexpectedSeq.length; idx++)
+        unexpectedSeq[idx].unexpected = true;
+
+      this.mEventSeq = this.mEventSeq.concat(unexpectedSeq);
+    }
+
     this.mEventSeqIdx = -1;
 
+    // Register event listeners
     if (this.mEventSeq) {
       aInvoker.wasCaught = new Array(this.mEventSeq.length);
 
@@ -390,6 +422,16 @@ function eventQueue(aEventType)
     return true;
   }
 
+  this.getEventID = function eventQueue_getEventID(aIdx)
+  {
+    var eventItem = this.mEventSeq[aIdx];
+    if ("getID" in eventItem)
+      return eventItem.getID();
+    
+    var invoker = this.getInvoker();
+    return invoker.getID();
+  }
+
   this.compareEvents = function eventQueue_compareEvents(aIdx, aEvent)
   {
     var eventType1 = this.getEventType(aIdx);
@@ -426,14 +468,24 @@ function eventQueue(aEventType)
       invoker.check(aEvent);
   }
 
-  this.getEventID = function eventQueue_getEventID(aIdx)
+  this.areAllEventsExpected = function eventQueue_areAllEventsExpected()
   {
-    var eventItem = this.mEventSeq[aIdx];
+    for (var idx = 0; idx < this.mEventSeq.length; idx++) {
-    if ("getID" in eventItem)
+      if (this.mEventSeq[idx].unexpected)
-      return eventItem.getID();
+        return false;
+    }
 
-    var invoker = this.getInvoker();
+    return true;
-    return invoker.getID();
+  }
+
+  this.areAllEventsUnexpected = function eventQueue_areAllEventsUnxpected()
+  {
+    for (var idx = 0; idx < this.mEventSeq.length; idx++) {
+      if (!this.mEventSeq[idx].unexpected)
+        return false;
+    }
+
+    return true;
   }
 
   this.dumpEventToDOM = function eventQueue_dumpEventToDOM(aOrigEvent,

accessible/tests/mochitest/test_events_mutation.html

@@ -52,6 +52,7 @@
       this.DOMNode = getNode(aNodeOrID);
       this.doNotExpectEvents = aDoNotExpectEvents;
       this.eventSeq = [];
+      this.unexpectedEventSeq = [];
 
       /**
        * Change default target (aNodeOrID) registered for the given event type.
@@ -59,9 +60,9 @@
       this.setTarget = function mutateA11yTree_setTarget(aEventType, aTarget)
       {
         var type = this.getA11yEventType(aEventType);
-        for (var idx = 0; idx < this.eventSeq.length; idx++) {
+        for (var idx = 0; idx < this.getEventSeq().length; idx++) {
-          if (this.eventSeq[idx].type == type) {
+          if (this.getEventSeq()[idx].type == type) {
-            this.eventSeq[idx].target = aTarget;
+            this.getEventSeq()[idx].target = aTarget;
             return idx;
           }
         }
@@ -78,7 +79,7 @@
         var type = this.getA11yEventType(aEventType);
         for (var i = 1; i < aTargets.length; i++) {
           var checker = new invokerChecker(type, aTargets[i]);
-          this.eventSeq.splice(++targetIdx, 0, checker);
+          this.getEventSeq().splice(++targetIdx, 0, checker);
         }
       }
 
@@ -103,24 +104,29 @@
         }
       }
 
+      this.getEventSeq = function mutateA11yTree_getEventSeq()
+      {
+        return this.doNotExpectEvents ? this.unexpectedEventSeq : this.eventSeq;
+      }
+
       this.mIsDOMChange = aIsDOMChange;
 
       if (aEventTypes & kHideEvent) {
         var checker = new invokerChecker(this.getA11yEventType(kHideEvent),
                                          this.DOMNode);
-        this.eventSeq.push(checker);
+        this.getEventSeq().push(checker);
       }
 
       if (aEventTypes & kShowEvent) {
         var checker = new invokerChecker(this.getA11yEventType(kShowEvent),
                                          this.DOMNode);
-        this.eventSeq.push(checker);
+        this.getEventSeq().push(checker);
       }
 
       if (aEventTypes & kReorderEvent) {
         var checker = new invokerChecker(this.getA11yEventType(kReorderEvent),
                                          this.DOMNode.parentNode);
-        this.eventSeq.push(checker);
+        this.getEventSeq().push(checker);
       }
     }
 

accessible/tests/mochitest/test_events_mutation_coalesce.html

@@ -0,0 +1,409 @@
+<html>
+
+<head>
+  <title>Accessible mutation events coalescence testing</title>
+
+  <link rel="stylesheet" type="text/css"
+        href="chrome://mochikit/content/tests/SimpleTest/test.css" />
+
+  <script type="application/javascript"
+          src="chrome://mochikit/content/MochiKit/packed.js"></script>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/SimpleTest.js"></script>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/tests/SimpleTest/EventUtils.js"></script>
+
+  <script type="application/javascript"
+          src="chrome://mochikit/content/a11y/accessible/common.js"></script>
+  <script type="application/javascript"
+          src="chrome://mochikit/content/a11y/accessible/events.js"></script>
+
+  <script type="application/javascript">
+
+    ////////////////////////////////////////////////////////////////////////////
+    // Invoker base classes
+
+    const kRemoveElm = 1;
+    const kHideElm = 2;
+    const kAddElm = 3;
+    const kShowElm = 4;
+
+    /**
+     * Base class to test of mutation events coalescence.
+     */
+    function coalescenceBase(aChildAction, aParentAction,
+                             aPerformActionOnChildInTheFirstPlace,
+                             aIsChildsToDo)
+    {
+      // Invoker interface
+
+      this.invoke = function coalescenceBase_invoke()
+      {
+        if (aPerformActionOnChildInTheFirstPlace) {
+          this.invokeAction(this.childNode, aChildAction);
+          this.invokeAction(this.parentNode, aParentAction);
+        } else {
+          this.invokeAction(this.parentNode, aParentAction);
+          this.invokeAction(this.childNode, aChildAction);
+        }
+      }
+
+      this.getID = function coalescenceBase_getID()
+      {
+        var childAction = this.getActionName(aChildAction) + " child";
+        var parentAction = this.getActionName(aParentAction) + " parent";
+
+        if (aPerformActionOnChildInTheFirstPlace)
+          return childAction + " and then " + parentAction;
+
+        return parentAction + " and then " + childAction;
+      }
+
+      this.finalCheck = function coalescenceBase_check()
+      {
+        if (!aIsChildsToDo)
+          return;
+
+        todo(false,
+             "Unexpected event " + this.getEventType(aChildAction) +
+             " for child in the test '" + this.getID() + "'");
+      }
+
+      // Implementation details
+
+      this.invokeAction = function coalescenceBase_invokeAction(aNode, aAction)
+      {
+        switch (aAction) {
+          case kRemoveElm:
+            aNode.parentNode.removeChild(aNode);
+            break;
+
+          case kHideElm:
+            aNode.style.display = "none";
+            break;
+
+          case kAddElm:
+            if (aNode == this.parentNode)
+              this.hostNode.appendChild(this.parentNode);
+            else
+              this.parentNode.appendChild(this.childNode);
+            break;
+
+          case kShowElm:
+            aNode.style.display = "block";
+
+          default:
+            return INVOKER_ACTION_FAILED;
+        }
+      }
+
+      this.getEventType = function coalescenceBase_getEventType(aAction)
+      {
+        switch (aAction) {
+          case kRemoveElm:
+            return EVENT_DOM_DESTROY;
+          case kHideElm:
+            return EVENT_ASYNCH_HIDE;
+          case kAddElm:
+            return EVENT_DOM_CREATE;
+          case kShowElm:
+            return EVENT_ASYNCH_SHOW;
+        }
+      }
+
+      this.getActionName = function coalescenceBase_getActionName(aAction)
+      {
+        switch (aAction) {
+          case kRemoveElm:
+            return "remove";
+          case kHideElm:
+            return "hide";
+          case kAddElm:
+            return "add";
+          case kShowElm:
+            return "show";
+          default:
+            return "??";
+        }
+      }
+
+      this.initSequence = function coalescenceBase_initSequence()
+      {
+        // expected events
+        var eventType = this.getEventType(aParentAction);
+        this.eventSeq = [
+          new invokerChecker(eventType, this.parentNode),
+          new invokerChecker(EVENT_REORDER, this.hostNode)
+        ];
+
+        // unexpected events
+        this.unexpectedEventSeq = [
+          new invokerChecker(EVENT_REORDER, this.parentNode)
+        ];
+
+        if (!aIsChildsToDo) {
+          var eventType = this.getEventType(aChildAction);
+          var checker = new invokerChecker(eventType, this.childNode);
+          this.unexpectedEventSeq.unshift(checker);
+        }
+      }
+    }
+
+    /**
+     * Remove or hide mutation events coalescence testing.
+     */
+    function removeOrHidecoalescenceBase(aChildID, aParentID,
+                                         aChildAction, aParentAction,
+                                         aPerformActionOnChildInTheFirstPlace,
+                                         aIsChildsToDo)
+    {
+      this.__proto__ = new coalescenceBase(aChildAction, aParentAction,
+                                           aPerformActionOnChildInTheFirstPlace,
+                                           aIsChildsToDo);
+
+      this.init = function removeOrHidecoalescenceBase_init()
+      {
+        this.childNode = getNode(aChildID);
+        this.parentNode = getNode(aParentID);
+        this.hostNode = this.parentNode.parentNode;
+
+        // ensure child accessible is created
+        getAccessible(this.childNode);
+      }
+
+      // Initalization
+
+      this.init();
+      this.initSequence();
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // Invokers
+
+    /**
+     * Remove child node and then its parent node from DOM tree.
+     */
+    function removeChildNParent(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kRemoveElm, kRemoveElm,
+                                                       true, true);
+    }
+
+    /**
+     * Remove parent node and then its child node from DOM tree.
+     */
+    function removeParentNChild(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kRemoveElm, kRemoveElm,
+                                                       false);
+    }
+
+    /**
+     * Hide child node and then its parent node.
+     */
+    function hideChildNParent(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kHideElm, kHideElm,
+                                                       true);
+    }
+
+    /**
+     * Hide parent node and then its child node.
+     */
+    function hideParentNChild(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kHideElm, kHideElm,
+                                                       false);
+    }
+
+    /**
+     * Hide child node and then remove its parent node.
+     */
+    function hideChildNRemoveParent(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kHideElm, kRemoveElm,
+                                                       true);
+    }
+
+    /**
+     * Hide parent node and then remove its child node.
+     */
+    function hideParentNRemoveChild(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kRemoveElm, kHideElm,
+                                                       false, true);
+    }
+
+    /**
+     * Remove child node and then hide its parent node.
+     */
+    function removeChildNHideParent(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kRemoveElm, kHideElm,
+                                                       true, true);
+    }
+
+    /**
+     * Remove parent node and then hide its child node.
+     */
+    function removeParentNHideChild(aChildID, aParentID)
+    {
+      this.__proto__ = new removeOrHidecoalescenceBase(aChildID, aParentID,
+                                                       kHideElm, kRemoveElm,
+                                                       false);
+    }
+
+    /**
+     * Create and append parent node and create and append child node to it.
+     */
+    function addParentNChild(aHostID, aPerformActionOnChildInTheFirstPlace)
+    {
+      this.init = function addParentNChild_init()
+      {
+        this.hostNode = getNode(aHostID);
+        this.parentNode = document.createElement("select");
+        this.childNode = document.createElement("option");
+        this.childNode.textContent = "testing";
+      }
+
+      this.__proto__ = new coalescenceBase(kAddElm, kAddElm,
+                                           aPerformActionOnChildInTheFirstPlace);
+
+      this.init();
+      this.initSequence();
+    }
+
+    /**
+     * Show parent node and show child node to it.
+     */
+    function showParentNChild(aParentID, aChildID,
+                              aPerformActionOnChildInTheFirstPlace)
+    {
+      this.init = function showParentNChild_init()
+      {
+        this.parentNode = getNode(aParentID);
+        this.hostNode = this.parentNode.parentNode;
+        this.childNode = getNode(aChildID);
+      }
+
+      this.__proto__ = new coalescenceBase(kShowElm, kShowElm,
+                                           aPerformActionOnChildInTheFirstPlace);
+
+      this.init();
+      this.initSequence();
+    }
+
+    /**
+     * Create and append child node to the DOM and then show parent node.
+     */
+    function showParentNAddChild(aParentID,
+                                aPerformActionOnChildInTheFirstPlace)
+    {
+      this.init = function showParentNAddChild_init()
+      {
+        this.parentNode = getNode(aParentID);
+        this.hostNode = this.parentNode.parentNode;
+        this.childNode = document.createElement("option");
+        this.childNode.textContent = "testing";
+      }
+
+      this.__proto__ = new coalescenceBase(kAddElm, kShowElm,
+                                           aPerformActionOnChildInTheFirstPlace,
+                                           true);
+
+      this.init();
+      this.initSequence();
+    }
+
+    ////////////////////////////////////////////////////////////////////////////
+    // Do tests.
+
+    var gQueue = null;
+    // var gA11yEventDumpID = "eventdump"; // debug stuff
+
+    function doTests()
+    {
+      gQueue = new eventQueue();
+
+      gQueue.push(new removeChildNParent("option1", "select1"));
+      gQueue.push(new removeParentNChild("option2", "select2"));
+      gQueue.push(new hideChildNParent("option3", "select3"));
+      gQueue.push(new hideParentNChild("option4", "select4"));
+      gQueue.push(new hideChildNRemoveParent("option5", "select5"));
+      gQueue.push(new hideParentNRemoveChild("option6", "select6"));
+      gQueue.push(new removeChildNHideParent("option7", "select7"));
+      gQueue.push(new removeParentNHideChild("option8", "select8"));
+
+      gQueue.push(new addParentNChild("testContainer", false));
+      gQueue.push(new addParentNChild("testContainer", true));
+      gQueue.push(new showParentNChild("select9", "option9", false));
+      gQueue.push(new showParentNChild("select10", "option10", true));
+      gQueue.push(new showParentNAddChild("select11", false));
+      gQueue.push(new showParentNAddChild("select12", true));
+
+      gQueue.invoke(); // Will call SimpleTest.finish();
+    }
+
+    SimpleTest.waitForExplicitFinish();
+    addA11yLoadEvent(doTests);
+  </script>
+</head>
+
+<body>
+
+  <a target="_blank"
+     href="https://bugzilla.mozilla.org/show_bug.cgi?id=513213"
+     title="coalesce events when new event is appended to the queue">
+    Mozilla Bug 513213
+  </a>
+
+  <p id="display"></p>
+  <div id="content" style="display: none"></div>
+  <pre id="test">
+  </pre>
+  <div id="eventdump"></div>
+
+  <div id="testContainer">
+    <select id="select1">
+      <option id="option1">option</option>
+    </select>
+    <select id="select2">
+      <option id="option2">option</option>
+    </select>
+    <select id="select3">
+      <option id="option3">option</option>
+    </select>
+    <select id="select4">
+      <option id="option4">option</option>
+    </select>
+    <select id="select5">
+      <option id="option5">option</option>
+    </select>
+    <select id="select6">
+      <option id="option6">option</option>
+    </select>
+    <select id="select7">
+      <option id="option7">option</option>
+    </select>
+    <select id="select8">
+      <option id="option8">option</option>
+    </select>
+
+    <select id="select9" style="display: none">
+      <option id="option9" style="display: none">testing</option>
+    </select>
+    <select id="select10" style="display: none">
+      <option id="option10" style="display: none">testing</option>
+    </select>
+    <select id="select11" style="display: none"></select>
+    <select id="select12" style="display: none"></select>
+  </div>
+</body>
+</html>