Track scroll event handlers in nested documents

Source/core/dom/EventHandlerRegistry.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/EventHandlerRegistry.h"
 
 #include "core/dom/Document.h"
 #include "core/events/ThreadLocalEventNames.h"
 #include "core/events/WheelEvent.h"
 #include "core/frame/FrameHost.h"
 #include "core/frame/LocalFrame.h"
 #include "core/page/Chrome.h"
 #include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "core/page/scrolling/ScrollingCoordinator.h"
 
 namespace WebCore {
 
+EventHandlerRegistry::DocumentObserver::DocumentObserver(Document& document)
+    : ActiveDOMObject(&document)
+{
+    suspendIfNeeded();

[abarth-chromium, 2014/04/22 16:18:23]

As a general pattern, we don't call suspendIfNeeded() inside constructors
because it can call back into virtual functions on |this| that might be
overridden in subclasses.  I understand that won't happen for this class because
it's FINAL, but it's a pattern we avoid generally in the code base to simplify
our lives.  Instead, we use a static |create| function that calls
suspendIfNeeded() after we're done constructing the object.

[Sami, 2014/04/22 18:05:18]

Okay, it sounds like I can move the call to suspendIfNeeded to the registry's
constructor instead.

+}
+
+EventHandlerRegistry::DocumentObserver::~DocumentObserver()
+{
+}
+
+void EventHandlerRegistry::DocumentObserver::stop()
+{
+    Document* document = static_cast<Document*>(lifecycleContext());
+    Document* parentDocument = document->parentDocument();
+    if (!parentDocument)
+        return;
+    EventHandlerRegistry* parentRegistry = EventHandlerRegistry::from(*parentDocument);
+    parentRegistry->didRemoveAllEventHandlers(*document);
+}
+
 EventHandlerRegistry::HandlerState::HandlerState()
 {
 }
 
 EventHandlerRegistry::HandlerState::~HandlerState()
 {
 }
 
 EventHandlerRegistry::EventHandlerRegistry(Document& document)
     : m_document(document)
+    , m_documentObserver(DocumentObserver(document))
 {

[abarth-chromium, 2014/04/22 16:18:23]

What's the point of having a separate DocumentObserver class?  Instead,
EventHandlerRegistry could inherit from DocumentLifecycleObserver and listen for
documentWasDetached.

[Sami, 2014/04/22 18:05:18]

First, it better isolates the implementation from the clients of
EventHandlerRegistry; an "EventHandlerRegistry is-a DocumentLifecycleObserver"
relation does not make any sense for them. Second, in another patch I'm planning
to add a window observer as a separated nested class. I think having code for
observing documents and DOM windows in separate classes makes things clearer.

 }
 
 EventHandlerRegistry::~EventHandlerRegistry()
 {
 }
 
 const char* EventHandlerRegistry::supplementName()
 {
     return "EventHandlerRegistry";
 }
@@ skipping 27 matching lines @@
 {
     EventTargetSet* targets = m_eventHandlers[handlerClass].targets.get();
     return targets && targets->size();
 }
 
 bool EventHandlerRegistry::updateEventHandlerTargets(ChangeOperation op, EventHandlerClass handlerClass, EventTarget* target)
 {
     EventTargetSet* targets = m_eventHandlers[handlerClass].targets.get();
     if (op == Add) {
 #if ASSERT_ENABLED
-        if (Node* node = target->toNode())
-            ASSERT(&node->document() == &m_document);
+        if (Node* node = target->toNode()) {
+            // The node should either be in the document, or be the Document node of a child
+            // of the document.
+            ASSERT(&node->document() == &m_document
+                || (node->isDocumentNode() && toDocument(node)->parentDocument() == &m_document));
+        }
 #endif // ASSERT_ENABLED
 
         if (!targets) {
             m_eventHandlers[handlerClass].targets = adoptPtr(new EventTargetSet);
             targets = m_eventHandlers[handlerClass].targets.get();
         }
 
         if (!targets->add(target).isNewEntry) {
             // Just incremented refcount, no real change.
+#if ASSERT_ENABLED
+            // If this is a child document node, then the count should never go above 1.
+            if (Node* node = target->toNode())
+                ASSERT(!node->isDocumentNode() || &node->document() == &m_document);
+#endif // ASSERT_ENABLED
             return false;
         }
     } else {
         // Note that we can't assert that |target| is in this document because
         // it might be in the process of moving out of it.
         ASSERT(op == Remove || op == RemoveAll);
         ASSERT(op == RemoveAll || targets->contains(target));
         if (!targets)
             return false;
 
@@ skipping 17 matching lines @@
     if (!m_document.isActive()) {
         return;
     }
 
     bool hadHandlers = hasEventHandlers(handlerClass);
     updateEventHandlerTargets(op, handlerClass, target);
     bool hasHandlers = hasEventHandlers(handlerClass);
 
     // Notify the parent document's registry if we added the first or removed
     // the last handler.
-    if (hadHandlers != hasHandlers && !m_document.parentDocument()) {
-        // This is the root registry; notify clients accordingly.
-        notifyHasHandlersChanged(handlerClass, hasHandlers);
+    if (hadHandlers != hasHandlers) {
+        if (Document* parent = m_document.parentDocument()) {
+            // Report change to parent with our Document as the target.
+            EventHandlerRegistry::from(*parent)->updateEventHandlerInternal(op, handlerClass, &m_document);
+        } else {
+            // This is the root registry; notify clients accordingly.
+            notifyHasHandlersChanged(handlerClass, hasHandlers);
+        }

[abarth-chromium, 2014/04/22 16:18:23]

Can we implement this algorithm iteratively instead of recursively?

[Sami, 2014/04/22 18:05:18]

Sure, done. I'm having trouble deciding which way is better, but PTAL.

     }
 }
 
 void EventHandlerRegistry::updateEventHandlerOfType(ChangeOperation op, const AtomicString& eventType, EventTarget* target)
 {
     EventHandlerClass handlerClass;
     if (!eventTypeToClass(eventType, &handlerClass))
         return;
     updateEventHandlerInternal(op, handlerClass, target);
 }
@@ skipping 54 matching lines @@
         if (scrollingCoordinator)
             scrollingCoordinator->updateHaveScrollEventHandlers();
         break;
     default:
         ASSERT_NOT_REACHED();
         break;
     }
 }
 
 } // namespace WebCore