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      1 /*
      2  * Copyright (C) 2008 Apple Inc. All Rights Reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1. Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2. Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     15  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     16  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
     17  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
     18  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
     19  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
     20  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
     21  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     23  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     24  *
     25  */
     26 
     27 #ifndef ActiveDOMObject_h
     28 #define ActiveDOMObject_h
     29 
     30 #include <wtf/Assertions.h>
     31 
     32 namespace WebCore {
     33 
     34     class ScriptExecutionContext;
     35 
     36     class ActiveDOMObject {
     37     public:
     38         ActiveDOMObject(ScriptExecutionContext*, void* upcastPointer);
     39 
     40         ScriptExecutionContext* scriptExecutionContext() const { return m_scriptExecutionContext; }
     41         virtual bool hasPendingActivity() const;
     42 
     43         virtual void contextDestroyed();
     44 
     45         // canSuspend() is used by the caller if there is a choice between suspending and stopping.
     46         // For example, a page won't be suspended and placed in the back/forward cache if it has
     47         // the objects that can not be suspended.
     48         // However, 'suspend' can be called even if canSuspend() would return 'false'. That
     49         // happens in step-by-step JS debugging for example - in this case it would be incorrect
     50         // to stop the object. Exact semantics of suspend is up to the object then.
     51         enum ReasonForSuspension {
     52             JavaScriptDebuggerPaused,
     53             WillShowDialog,
     54             DocumentWillBecomeInactive
     55         };
     56         virtual bool canSuspend() const;
     57         virtual void suspend(ReasonForSuspension);
     58         virtual void resume();
     59         virtual void stop();
     60 
     61         template<class T> void setPendingActivity(T* thisObject)
     62         {
     63             ASSERT(thisObject == this);
     64             thisObject->ref();
     65             m_pendingActivityCount++;
     66         }
     67 
     68         template<class T> void unsetPendingActivity(T* thisObject)
     69         {
     70             ASSERT(m_pendingActivityCount > 0);
     71             --m_pendingActivityCount;
     72             thisObject->deref();
     73         }
     74 
     75     protected:
     76         virtual ~ActiveDOMObject();
     77 
     78     private:
     79         ScriptExecutionContext* m_scriptExecutionContext;
     80         unsigned m_pendingActivityCount;
     81     };
     82 
     83 } // namespace WebCore
     84 
     85 #endif // ActiveDOMObject_h
     86