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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 "core/dom/ContextLifecycleObserver.h"
     31 #include "wtf/Assertions.h"
     32 #include "wtf/Forward.h"
     33 
     34 namespace WebCore {
     35 
     36 class ActiveDOMObject : public ContextLifecycleObserver {
     37 public:
     38     ActiveDOMObject(ScriptExecutionContext*);
     39 
     40     // suspendIfNeeded() should be called exactly once after object construction to synchronize
     41     // the suspend state with that in ScriptExecutionContext.
     42     void suspendIfNeeded();
     43 #if !ASSERT_DISABLED
     44     bool suspendIfNeededCalled() const { return m_suspendIfNeededCalled; }
     45 #endif
     46 
     47     virtual bool hasPendingActivity() const;
     48 
     49     // canSuspend() is used by the caller if there is a choice between suspending and stopping.
     50     // For example, a page won't be suspended and placed in the back/forward cache if it has
     51     // the objects that can not be suspended.
     52     // However, 'suspend' can be called even if canSuspend() would return 'false'. That
     53     // happens in step-by-step JS debugging for example - in this case it would be incorrect
     54     // to stop the object. Exact semantics of suspend is up to the object then.
     55     enum ReasonForSuspension {
     56         JavaScriptDebuggerPaused,
     57         WillDeferLoading,
     58         DocumentWillBecomeInactive
     59     };
     60     virtual bool canSuspend() const;
     61     virtual void suspend(ReasonForSuspension);
     62     virtual void resume();
     63     virtual void stop();
     64 
     65     template<class T> void setPendingActivity(T* thisObject)
     66     {
     67         ASSERT(thisObject == this);
     68         thisObject->ref();
     69         m_pendingActivityCount++;
     70     }
     71 
     72     template<class T> void unsetPendingActivity(T* thisObject)
     73     {
     74         ASSERT(m_pendingActivityCount > 0);
     75         --m_pendingActivityCount;
     76         thisObject->deref();
     77     }
     78 
     79 protected:
     80     virtual ~ActiveDOMObject();
     81 
     82 private:
     83     unsigned m_pendingActivityCount;
     84 #if !ASSERT_DISABLED
     85     bool m_suspendIfNeededCalled;
     86 #endif
     87 };
     88 
     89 } // namespace WebCore
     90 
     91 #endif // ActiveDOMObject_h
     92