script_wrappable_task_state.h | Explore in Territory

// Copyright 2023 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef THIRD_PARTY_BLINK_RENDERER_CORE_SCHEDULER_SCRIPT_WRAPPABLE_TASK_STATE_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_SCHEDULER_SCRIPT_WRAPPABLE_TASK_STATE_H_

#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"
#include "third_party/blink/renderer/platform/heap/garbage_collected.h"
#include "third_party/blink/renderer/platform/heap/member.h"

namespace v8 {
class Isolate;
}  // namespace v8

namespace blink::scheduler {
class TaskAttributionInfo;
}  // namespace blink::scheduler

namespace blink {
class AbortSignal;
class DOMTaskSignal;
class ScriptState;

// Interface for objects stored as `ScriptWrappableTaskState`.
//
// Instances of this class will either be WebSchedulingTaskState, if propagating
// abort and priority sources (web scheduling APIs), or TaskAttributionInfoImpl,
// which is exposed as TaskAttributionInfo via TaskAttributionTracker public
// APIs.
class WrappableTaskState : public GarbageCollectedMixin { … };

// `ScriptWrappableTaskState` objects are stored in V8 as continuation preserved
// embedder data (CPED). They aren't exposed directly to JS, but are
// `ScriptWrappable` so they can be stored in CPED.
//
// V8 propagates these objects to continuations by binding the current CPED and
// restoring it in microtasks:
//   1. For promises, the current CPED is bound to the promise reaction at
//      creation time (e.g. when .then() is called or a promise is awaited)
//
//   2. For promises resolved with a custom thennable, there's an extra hop
//      through a microtask to run the custom .then() function. For the promise
//      being resolved, (1) above applies. For the custom .then() function, the
//      resolve-time CPED is bound to the microtask, i.e. the CPED inside the
//      custom .then() function is the same as when the resolve happens, keeping
//      it consistent across the async hop.
//
//   3. For non-promise microtasks, which are used throughout Blink, the current
//      CPED is bound when EnqueueMicrotask() is called.
//
// Similarly, in Blink the objects these wrap are propagated to descendant tasks
// by capturing the current CPED during various API calls and restoring it prior
// to running a callback. For example, the current CPED is captured when
// setTimeout is called and restored before running the associated callback.
//
// Note: `ScriptWrappableTaskState` objects aren't directly propagated in Blink
// to avoid leaking detached windows in long timeouts. See crbug.com/353997473.
class CORE_EXPORT ScriptWrappableTaskState final : public ScriptWrappable { … };

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_SCHEDULER_SCRIPT_WRAPPABLE_TASK_STATE_H_
chromium/third_party/blink/renderer/core/scheduler/script_wrappable_task_state.h
