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/*
* Copyright (C) 2008 Apple 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_CORE_EXECUTION_CONTEXT_EXECUTION_CONTEXT_LIFECYCLE_OBSERVER_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_EXECUTION_CONTEXT_EXECUTION_CONTEXT_LIFECYCLE_OBSERVER_H_
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/context_lifecycle_observer.h"
namespace blink {
class ExecutionContext;
class LocalDOMWindow;
class LocalFrame;
// ExecutionContextClient and ExecutionContextLifecycleObserver are helpers to
// associate an object with an ExecutionContext. It is unsafe to access an
// associated GC object, *including via GetExecutionContext()*, in the
// destructor of a GC object.
//
// To discourage incorrect usage, these objects both start returning null
// once the execution context shuts down. For a window, this occurs when
// the frame navigates to another window or is detached. For a worker global
// scope, this occurs when it shuts down.
//
// * If an object only needs to refer to a valid ExecutionContext but does not
// need to stop or suspend any activity, it should be a
// ExecutionContextClient.
// * If an object associated with an ExecutionContext has shutdown logic to
// perform, such as halting activity or disconnecting from longer-lived
// objects, it should be a PausableObject.
// * If an object additionally must suspend its activity during pause (see
// execution_context_lifecycle_state_observer.h), it should be a
// ExecutionContextLifecycleStateObserver (and thus, transitively, also a
// ExecutionContextLifecycleObserver).
//
// If your object has activity which requires that it be kept alive, even if no
// other object has a reference to it, consider whether your object should also
// derive from ActiveScriptWrappable.
// ExecutionContextClient provides access to the associated execution context
// until it is shut down (e.g. for a window, at navigation or frame detach).
class CORE_EXPORT ExecutionContextClient : public GarbageCollectedMixin {
public:
// Returns the execution context until it is detached.
// From then on, returns null instead.
ExecutionContext* GetExecutionContext() const;
// If the execution context is a window, returns it. Returns nullptr if the
// execution context is not a window or if it has been detached.
LocalDOMWindow* DomWindow() const;
// If associated with a live window, returns the associated frame.
// Returns null otherwise.
LocalFrame* GetFrame() const;
void Trace(Visitor*) override;
protected:
explicit ExecutionContextClient(ExecutionContext*);
explicit ExecutionContextClient(LocalFrame*);
private:
WeakMember<ExecutionContext> execution_context_;
};
// ExecutionContextLifecycleObserver provides an additional ContextDestroyed()
// hook to execute cleanup code when a context is shut down (e.g. for a
// document, at navigation or frame detach -- not when its destructor runs).
//
// Execution context associated objects which have ongoing activity,
// registration with objects which outlive the context, or resources which
// should be promptly released, should consider deriving from
// PausableObject. As a rule of thumb: if the destructor contains
// non-trivial logic, that logic may belong in ContextDestroyed() instead.
//
// If there is ongoing activity associated with the object, consider whether it
// needs to be paused when execution is suspended (see
// ExecutionContextLifecycleStateObserver).
//
// If none of the above applies, prefer the simpler ExecutionContextClient.
class CORE_EXPORT ExecutionContextLifecycleObserver
: public ContextLifecycleObserver {
public:
// Returns the execution context until it is detached.
// From then on, returns null instead.
ExecutionContext* GetExecutionContext() const;
virtual void SetExecutionContext(ExecutionContext*);
// If associated with a live document, returns the associated frame.
// Returns null otherwise.
LocalFrame* GetFrame() const;
enum Type {
kGenericType,
kStateObjectType,
};
Type ObserverType() const { return observer_type_; }
bool IsExecutionContextLifecycleObserver() const override { return true; }
void Trace(Visitor*) override;
protected:
explicit ExecutionContextLifecycleObserver(
ExecutionContext* execution_context,
Type type = kGenericType);
private:
Type observer_type_;
};
} // namespace blink
#endif // THIRD_PARTY_BLINK_RENDERER_CORE_EXECUTION_CONTEXT_EXECUTION_CONTEXT_LIFECYCLE_OBSERVER_H_
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