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/*
* Copyright (C) 2008 Apple Inc. All Rights Reserved.
* Copyright (C) 2013 Google Inc. All Rights Reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
* EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL APPLE COMPUTER, INC. OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/
#ifndef THIRD_PARTY_BLINK_RENDERER_PLATFORM_LIFECYCLE_NOTIFIER_H_
#define THIRD_PARTY_BLINK_RENDERER_PLATFORM_LIFECYCLE_NOTIFIER_H_
#include "base/auto_reset.h"
#include "third_party/blink/renderer/platform/heap/handle.h"
#include "third_party/blink/renderer/platform/wtf/hash_set.h"
namespace blink {
class LifecycleObserverBase;
template <typename T, typename Observer>
class LifecycleNotifier : public GarbageCollectedMixin {
public:
virtual ~LifecycleNotifier();
void AddObserver(LifecycleObserverBase*);
void RemoveObserver(LifecycleObserverBase*);
// NotifyContextDestroyed() should be explicitly dispatched from an
// observed context to detach its observers and, if the observer kind
// requires it, notify each observer by invoking ContextDestroyed().
//
// When ContextDestroyed() is called, it is supplied the context as
// an argument, but the observer's LifecycleContext() is still valid
// and safe to use while handling the notification.
virtual void NotifyContextDestroyed();
void Trace(blink::Visitor* visitor) override { visitor->Trace(observers_); }
bool IsIteratingOverObservers() const {
return iteration_state_ != kNotIterating;
}
protected:
LifecycleNotifier() : iteration_state_(kNotIterating) {}
T* Context() { return static_cast<T*>(this); }
// Safely iterate over the registered lifecycle observers.
//
// Adding or removing observers is not allowed during iteration. The callable
// will only be called synchronously inside ForEachObserver().
//
// Sample usage:
// ForEachObserver([](ObserverType* observer) {
// observer->SomeMethod();
// });
template <typename ForEachCallable>
void ForEachObserver(const ForEachCallable& callable) const {
base::AutoReset<IterationState> scope(&iteration_state_, kAllowingNone);
for (LifecycleObserverBase* observer_base : observers_) {
Observer* observer = static_cast<Observer*>(observer_base);
callable(observer);
}
}
// ForEachObserver() variant that does not protect against memory corruption.
//
// Only used by SynchronousMutationNotifier::NotifyUpdateCharacterData. See
// implementation comment for why it is necessary.
//
// TODO(crbug.com/862900): Fix SynchronousMutationNotifier and remove this.
template <typename ForEachCallable>
void ForEachObserverWithoutChecks(const ForEachCallable& callable) const {
for (LifecycleObserverBase* observer_base : observers_) {
Observer* observer = static_cast<Observer*>(observer_base);
callable(observer);
}
}
private:
using ObserverSet = HeapHashSet<WeakMember<LifecycleObserverBase>>;
enum IterationState {
kAllowingNone = 0,
kAllowingAddition = 1,
kAllowingRemoval = 2,
kNotIterating = kAllowingAddition | kAllowingRemoval,
};
// Iteration state is recorded while iterating the observer set,
// optionally barring add or remove mutations.
mutable IterationState iteration_state_;
ObserverSet observers_;
};
template <typename T, typename Observer>
inline LifecycleNotifier<T, Observer>::~LifecycleNotifier() {
// FIXME: Enable the following ASSERT. Also see a FIXME in
// Document::detachLayoutTree().
// DCHECK(!m_observers.size());
}
// Determine if |contextDestroyed(Observer*) is a public method on
// class type |Observer|, or any of the class types it derives from.
template <typename Observer, typename T>
class HasContextDestroyed {
using YesType = char;
using NoType = int;
template <typename V>
static YesType CheckHasContextDestroyedMethod(
V* observer,
T* context = nullptr,
typename std::enable_if<
std::is_same<decltype(observer->ContextDestroyed(context)),
void>::value>::type* g = nullptr);
template <typename V>
static NoType CheckHasContextDestroyedMethod(...);
public:
static_assert(sizeof(Observer), "Observer's class declaration not in scope");
static const bool value =
sizeof(YesType) ==
sizeof(CheckHasContextDestroyedMethod<Observer>(nullptr));
};
// If |Observer::contextDestroyed()| is present, invoke it.
template <typename Observer,
typename T,
bool = HasContextDestroyed<Observer, T>::value>
class ContextDestroyedNotifier {
STATIC_ONLY(ContextDestroyedNotifier);
public:
static void Call(Observer* observer, T* context) {
observer->ContextDestroyed(context);
}
};
template <typename Observer, typename T>
class ContextDestroyedNotifier<Observer, T, false> {
STATIC_ONLY(ContextDestroyedNotifier);
public:
static void Call(Observer*, T*) {}
};
template <typename T, typename Observer>
inline void LifecycleNotifier<T, Observer>::NotifyContextDestroyed() {
// Observer unregistration is allowed, but effectively a no-op.
base::AutoReset<IterationState> scope(&iteration_state_, kAllowingRemoval);
ObserverSet observers;
observers_.swap(observers);
for (LifecycleObserverBase* observer_base : observers) {
Observer* observer = static_cast<Observer*>(observer_base);
DCHECK(observer->LifecycleContext() == Context());
ContextDestroyedNotifier<Observer, T>::Call(observer, Context());
observer->ClearContext();
}
}
template <typename T, typename Observer>
inline void LifecycleNotifier<T, Observer>::AddObserver(
LifecycleObserverBase* observer) {
CHECK(iteration_state_ & kAllowingAddition);
observers_.insert(observer);
}
template <typename T, typename Observer>
inline void LifecycleNotifier<T, Observer>::RemoveObserver(
LifecycleObserverBase* observer) {
CHECK(iteration_state_ & kAllowingRemoval);
observers_.erase(observer);
}
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_PLATFORM_LIFECYCLE_NOTIFIER_H_
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