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 "ContextDestructionObserver.h"
31#include <wtf/Assertions.h>
32#include <wtf/Forward.h>
33
34namespace WebCore {
35
36class ActiveDOMObject : public ContextDestructionObserver {
37public:
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        PageWillBeSuspended
60    };
61    virtual bool canSuspend() const;
62    virtual void suspend(ReasonForSuspension);
63    virtual void resume();
64    virtual void stop();
65
66    template<class T> void setPendingActivity(T* thisObject)
67    {
68        ASSERT(thisObject == this);
69        thisObject->ref();
70        m_pendingActivityCount++;
71    }
72
73    template<class T> void unsetPendingActivity(T* thisObject)
74    {
75        ASSERT(m_pendingActivityCount > 0);
76        --m_pendingActivityCount;
77        thisObject->deref();
78    }
79
80protected:
81    virtual ~ActiveDOMObject();
82
83private:
84    unsigned m_pendingActivityCount;
85#if !ASSERT_DISABLED
86    bool m_suspendIfNeededCalled;
87#endif
88};
89
90} // namespace WebCore
91
92#endif // ActiveDOMObject_h
93