Track scroll event handlers in nested documents

Source/core/dom/EventHandlerRegistry.h

-// 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.
-
-#ifndef EventHandlerRegistry_h
-#define EventHandlerRegistry_h
-
-#include "core/dom/DocumentSupplementable.h"
-#include "core/events/Event.h"
-#include "wtf/HashCountedSet.h"
-
-namespace WebCore {
-
-typedef HashCountedSet<EventTarget*> EventTargetSet;
-
-// Registry for keeping track of event handlers. Handlers can either be
-// associated with an EventTarget or be "external" handlers which live outside
-// the DOM (e.g., WebViewImpl).
-class EventHandlerRegistry FINAL : public DocumentSupplement {
-public:
-    virtual ~EventHandlerRegistry();
-
-    // Supported event handler classes. Note that each one may correspond to
-    // multiple event types.
-    enum EventHandlerClass {
-        ScrollEvent,
-        EventHandlerClassCount, // Must be the last entry.
-    };
-
-    static const char* supplementName();
-    static EventHandlerRegistry* from(Document&);
-
-    // Returns true if the host Document or any child documents have any
-    // registered event handlers of the class.
-    bool hasEventHandlers(EventHandlerClass) const;
-
-    // Returns a set of EventTargets which have registered handlers of the
-    // given class. Only contains targets directly in this document; all
-    // handlers in a child Document are collapsed to a single respective
-    // Document instance in the set.
-    const EventTargetSet* eventHandlerTargets(EventHandlerClass) const;
-
-    // Registration and management of event handlers attached to EventTargets.
-    void didAddEventHandler(EventTarget&, const AtomicString& eventType);
-    void didAddEventHandler(EventTarget&, EventHandlerClass);
-    void didRemoveEventHandler(EventTarget&, const AtomicString& eventType);
-    void didRemoveEventHandler(EventTarget&, EventHandlerClass);
-    void didMoveFromOtherDocument(EventTarget&, Document& oldDocument);
-    void didRemoveAllEventHandlers(EventTarget&);
-
-    virtual void trace(Visitor*) OVERRIDE { }
-    void clearWeakMembers(Visitor*);
-
-private:
-    explicit EventHandlerRegistry(Document&);
-
-    enum ChangeOperation {
-        Add, // Add a new event handler.
-        Remove, // Remove an existing event handler.
-        RemoveAll // Remove any and all existing event handlers for a given target.
-    };
-
-    // Returns true if |eventType| belongs to a class this registry tracks.
-    static bool eventTypeToClass(const AtomicString& eventType, EventHandlerClass* result);
-
-    // Returns true if the operation actually added a new target or completely
-    // removed an existing one.
-    bool updateEventHandlerTargets(ChangeOperation, EventHandlerClass, EventTarget*);
-
-    // Called on the EventHandlerRegistry of the root Document to notify
-    // clients when we have added the first handler or removed the last one for
-    // a given event class. |hasActiveHandlers| can be used to distinguish
-    // between the two cases.
-    void notifyHasHandlersChanged(EventHandlerClass, bool hasActiveHandlers);
-
-    // Record a change operation to a given event handler class and notify any
-    // parent registry and other clients accordingly.
-    void updateEventHandlerOfType(ChangeOperation, const AtomicString& eventType, EventTarget*);
-
-    void updateEventHandlerInternal(ChangeOperation, EventHandlerClass, EventTarget*);
-
-    struct HandlerState {
-        HandlerState();
-        ~HandlerState();
-
-        OwnPtr<EventTargetSet> targets;
-    };
-
-    Document& m_document;
-    HandlerState m_eventHandlers[EventHandlerClassCount];
-};
-
-} // namespace WebCore
-
-#endif // EventHandlerRegistry_h