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 // The suspendIfNeeded must be called exactly once after object construction to update
39 // the suspended state to match that of the ScriptExecutionContext.
40 void suspendIfNeeded();
41 void assertSuspendIfNeededWasCalled() const;
42
43 virtual bool hasPendingActivity() const;
44
45 // The canSuspendForDocumentSuspension() function is used by the caller if there is a choice between suspending
46 // and stopping. For example, a page won't be suspended and placed in the back/forward
47 // cache if it contains any objects that cannot be suspended.
48
49 // However, the suspend function will sometimes be called even if canSuspendForDocumentSuspension() returns false.
50 // That happens in step-by-step JS debugging for example - in this case it would be incorrect
51 // to stop the object. Exact semantics of suspend is up to the object in cases like that.
52
53 enum ReasonForSuspension {
54 JavaScriptDebuggerPaused,
55 WillDeferLoading,
56 PageCache,
57 PageWillBeSuspended,
58 };
59
60 virtual const char* activeDOMObjectName() const = 0;
61
62 // These three functions must not have a side effect of creating or destroying
63 // any ActiveDOMObject. That means they must not result in calls to arbitrary JavaScript.
64 virtual bool canSuspendForDocumentSuspension() const = 0; // Returning false in canSuspendForDocumentSuspension() will prevent the page from entering the PageCache.
65 virtual void suspend(ReasonForSuspension);
66 virtual void resume();
67
68 // This function must not have a side effect of creating an ActiveDOMObject.
69 // That means it must not result in calls to arbitrary JavaScript.
70 // It can, however, have a side effect of deleting an ActiveDOMObject.
71 virtual void stop();
72
73 template<class T> void setPendingActivity(T* thisObject)
74 {
75 ASSERT(thisObject == this);
76 thisObject->ref();
77 ++m_pendingActivityCount;
78 }
79
80 template<class T> void unsetPendingActivity(T* thisObject)
81 {
82 ASSERT(m_pendingActivityCount > 0);
83 --m_pendingActivityCount;
84 thisObject->deref();
85 }
86
87protected:
88 explicit ActiveDOMObject(ScriptExecutionContext*);
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