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 LifecycleObserver_h
28#define LifecycleObserver_h
29
30#include "wtf/Assertions.h"
31
32namespace blink {
33
34template<typename T>
35class LifecycleObserver {
36public:
37    typedef T Context;
38
39    enum Type {
40        ActiveDOMObjectType,
41        DocumentLifecycleObserverType,
42        GenericType,
43        PageLifecycleObserverType,
44        DOMWindowLifecycleObserverType
45    };
46
47    explicit LifecycleObserver(Context* context, Type type = GenericType)
48        : m_lifecycleContext(0)
49        , m_observerType(type)
50    {
51        observeContext(context);
52    }
53
54    virtual ~LifecycleObserver()
55    {
56        observeContext(0);
57    }
58
59    virtual void contextDestroyed() { m_lifecycleContext = 0; }
60
61
62    Context* lifecycleContext() const { return m_lifecycleContext; }
63    Type observerType() const { return m_observerType; }
64
65protected:
66    void observeContext(Context*);
67
68    Context* m_lifecycleContext;
69    Type m_observerType;
70};
71
72//
73// These functions should be specialized for each LifecycleObserver instances.
74//
75template<typename T> void observerContext(T*, LifecycleObserver<T>*) { ASSERT_NOT_REACHED(); }
76template<typename T> void unobserverContext(T*, LifecycleObserver<T>*) { ASSERT_NOT_REACHED(); }
77
78
79template<typename T>
80inline void LifecycleObserver<T>::observeContext(typename LifecycleObserver<T>::Context* context)
81{
82    if (m_lifecycleContext)
83        unobserverContext(m_lifecycleContext, this);
84
85    m_lifecycleContext = context;
86
87    if (m_lifecycleContext)
88        observerContext(m_lifecycleContext, this);
89}
90
91} // namespace blink
92
93#endif // LifecycleObserver_h
94