Source/WebCore/dom/ActiveDOMObject.h

/*
 * Copyright (C) 2008 Apple Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 
 *
 */

#ifndef ActiveDOMObject_h
#define ActiveDOMObject_h

#include <wtf/Assertions.h>

namespace WebCore {

    class ScriptExecutionContext;

    class ActiveDOMObject {
    public:
        ActiveDOMObject(ScriptExecutionContext*, void* upcastPointer);

        ScriptExecutionContext* scriptExecutionContext() const { return m_scriptExecutionContext; }
        virtual bool hasPendingActivity() const;

        virtual void contextDestroyed();

        // canSuspend() is used by the caller if there is a choice between suspending and stopping.
        // For example, a page won't be suspended and placed in the back/forward cache if it has
        // the objects that can not be suspended.
        // However, 'suspend' can be called even if canSuspend() would return 'false'. That
        // happens in step-by-step JS debugging for example - in this case it would be incorrect
        // to stop the object. Exact semantics of suspend is up to the object then.
        enum ReasonForSuspension {
            JavaScriptDebuggerPaused,
            WillShowDialog,
            DocumentWillBecomeInactive
        };
        virtual bool canSuspend() const;
        virtual void suspend(ReasonForSuspension);
        virtual void resume();
        virtual void stop();

        template<class T> void setPendingActivity(T* thisObject)
        {
            ASSERT(thisObject == this);
            thisObject->ref();
            m_pendingActivityCount++;
        }

        template<class T> void unsetPendingActivity(T* thisObject)
        {
            ASSERT(m_pendingActivityCount > 0);
            --m_pendingActivityCount;
            thisObject->deref();
        }

    protected:
        virtual ~ActiveDOMObject();

    private:
        ScriptExecutionContext* m_scriptExecutionContext;
        unsigned m_pendingActivityCount;
    };

} // namespace WebCore

#endif // ActiveDOMObject_h