third_party/WebKit/Source/core/dom/ScopedWindowFocusAllowedIndicator.h

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef ScopedWindowFocusAllowedIndicator_h
#define ScopedWindowFocusAllowedIndicator_h

#include "core/dom/ContextLifecycleObserver.h"
#include "core/dom/ExecutionContext.h"
#include "wtf/Noncopyable.h"

namespace blink {

class ScopedWindowFocusAllowedIndicator final {
  USING_FAST_MALLOC(ScopedWindowFocusAllowedIndicator);
  WTF_MAKE_NONCOPYABLE(ScopedWindowFocusAllowedIndicator);

 public:
  explicit ScopedWindowFocusAllowedIndicator(ExecutionContext* executionContext)
      : m_observer(new Observer(executionContext)) {}
  ~ScopedWindowFocusAllowedIndicator() { m_observer->dispose(); }

 private:
  class Observer final : public GarbageCollected<Observer>,
                         public ContextLifecycleObserver {
    USING_GARBAGE_COLLECTED_MIXIN(Observer);

   public:
    explicit Observer(ExecutionContext* executionContext)
        : ContextLifecycleObserver(executionContext) {
      if (executionContext)
        executionContext->allowWindowInteraction();
    }

    void dispose() {
      if (getExecutionContext())
        getExecutionContext()->consumeWindowInteraction();
    }
  };

  // In Oilpan, destructors are not allowed to touch other on-heap objects.
  // The Observer indirection is needed to keep
  // ScopedWindowFocusAllowedIndicator off-heap and thus allows its destructor
  // to call getExecutionContext()->consumeWindowInteraction().
  Persistent<Observer> m_observer;
};

}  // namespace blink

#endif  // ScopedWindowFocusAllowedIndicator_h