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 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 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 "ContextDestructionObserver.h" 31#include <wtf/Assertions.h> 32#include <wtf/Forward.h> 33 34namespace WebCore { 35 36class ActiveDOMObject : public ContextDestructionObserver { 37public: 38 explicit ActiveDOMObject(ScriptExecutionContext*); 39 40 // The suspendIfNeeded must be called exactly once after object construction to update 41 // the suspended state to match that of the ScriptExecutionContext. 42 void suspendIfNeeded(); 43 void assertSuspendIfNeededWasCalled() const; 44 45 virtual bool hasPendingActivity() const; 46 47 // The canSuspend function is used by the caller if there is a choice between suspending 48 // and stopping. For example, a page won't be suspended and placed in the back/forward 49 // cache if it contains any objects that cannot be suspended. 50 51 // However, the suspend function will sometimes be called even if canSuspend returns false. 52 // That happens in step-by-step JS debugging for example - in this case it would be incorrect 53 // to stop the object. Exact semantics of suspend is up to the object in cases like that. 54 55 enum ReasonForSuspension { 56 JavaScriptDebuggerPaused, 57 WillDeferLoading, 58 DocumentWillBecomeInactive, 59 PageWillBeSuspended, 60 DocumentWillBePaused 61 }; 62 63 // These three functions must not have a side effect of creating or destroying 64 // any ActiveDOMObject. That means they must not result in calls to arbitrary JavaScript. 65 virtual bool canSuspend() const; 66 virtual void suspend(ReasonForSuspension); 67 virtual void resume(); 68 69 // This function must not have a side effect of creating an ActiveDOMObject. 70 // That means it must not result in calls to arbitrary JavaScript. 71 // It can, however, have a side effect of deleting an ActiveDOMObject. 72 virtual void stop(); 73 74 template<class T> void setPendingActivity(T* thisObject) 75 { 76 ASSERT(thisObject == this); 77 thisObject->ref(); 78 ++m_pendingActivityCount; 79 } 80 81 template<class T> void unsetPendingActivity(T* thisObject) 82 { 83 ASSERT(m_pendingActivityCount > 0); 84 --m_pendingActivityCount; 85 thisObject->deref(); 86 } 87 88protected: 89 virtual ~ActiveDOMObject(); 90 91private: 92 unsigned m_pendingActivityCount; 93#if !ASSERT_DISABLED 94 bool m_suspendIfNeededWasCalled; 95#endif 96}; 97 98#if ASSERT_DISABLED 99 100inline void ActiveDOMObject::assertSuspendIfNeededWasCalled() const 101{ 102} 103 104#endif 105 106} // namespace WebCore 107 108#endif // ActiveDOMObject_h 109