third_party/blink/renderer/core/display_lock/display_lock_context.h

// Copyright 2018 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 THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_
#define THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_

#include "third_party/blink/renderer/bindings/core/v8/active_script_wrappable.h"
#include "third_party/blink/renderer/bindings/core/v8/script_promise_resolver.h"
#include "third_party/blink/renderer/core/core_export.h"
#include "third_party/blink/renderer/platform/bindings/script_wrappable.h"

namespace blink {

class DisplayLockSuspendedHandle;
class Element;
class V8DisplayLockCallback;
class DisplayLockScopedLogger;
class CORE_EXPORT DisplayLockContext final
    : public ScriptWrappable,
      public ActiveScriptWrappable<DisplayLockContext>,
      public ContextLifecycleObserver {
  DEFINE_WRAPPERTYPEINFO();
  USING_GARBAGE_COLLECTED_MIXIN(DisplayLockContext);

 public:
  // Conceptually the states are private, but made public for debugging /
  // logging.
  enum State {
    kUninitialized,
    kSuspended,
    kCallbacksPending,
    kDisconnected,
    kCommitting,
    kResolving,
    kResolved
  };

  enum LifecycleUpdateState {
    kNeedsStyle,
    kNeedsLayout,
    kNeedsPrePaint,
    kNeedsPaint,
    kDone
  };

  DisplayLockContext(Element*, ExecutionContext*);
  ~DisplayLockContext() override;

  // GC functions.
  void Trace(blink::Visitor*) override;
  void Dispose();

  // ContextLifecycleObserver overrides.
  void ContextDestroyed(ExecutionContext*) override;
  // ActiveScriptWrappable overrides. If there is an outstanding task scheduled
  // to process the callback queue, then this return true.
  // TODO(vmpstr): In the future this would also be true while we're doing
  // co-operative work.
  bool HasPendingActivity() const final;

  // Notify that the lock was requested. Note that for a new context, this has
  // to be called first. For an existing lock, this will either extend the
  // lifetime of the current lock, or start acquiring a new lock (depending on
  // whether this lock is active or passive).
  void RequestLock(V8DisplayLockCallback*, ScriptState*);

  // Returns true if the promise associated with this context was already
  // resolved (or rejected).
  bool IsResolved() const { return state_ == kResolved; }

  // Returns a ScriptPromise associated with this context.
  ScriptPromise Promise() const {
    DCHECK(resolver_);
    return resolver_->Promise();
  }

  // Called when the connected state may have changed.
  void NotifyConnectedMayHaveChanged();

  // Rejects the associated promise if one exists, and clears the current queue.
  // This effectively makes the context finalized.
  void RejectAndCleanUp();

  // JavaScript interface implementation.
  void schedule(V8DisplayLockCallback*);
  DisplayLockSuspendedHandle* suspend();
  Element* lockedElement() const;

  // Lifecycle observation / state functions.
  bool ShouldStyle() const;
  void DidStyle();
  bool ShouldLayout() const;
  void DidLayout();
  bool ShouldPrePaint() const;
  void DidPrePaint();
  bool ShouldPaint() const;
  void DidPaint();

  void DidAttachLayoutTree();

 private:
  friend class DisplayLockSuspendedHandle;

  // Schedules a new callback. If this is the first callback to be scheduled,
  // then a valid ScriptState must be provided, which will be used to create a
  // new ScriptPromiseResolver. In other cases, the ScriptState is ignored.
  void ScheduleCallback(V8DisplayLockCallback*);

  // Processes the current queue of callbacks.
  void ProcessQueue();

  // Called by the suspended handle in order to resume context operations.
  void Resume();

  // Called by the suspended handle informing us that it was disposed without
  // resuming, meaning it will never resume.
  void NotifyWillNotResume();

  // Schedule a task if one is required. Specifically, this would schedule a
  // task if one was not already scheduled and if we need to either process
  // callbacks or to resolve the associated promise.
  void ScheduleTaskIfNeeded();

  // A function that finishes resolving the promise by establishing a microtask
  // checkpoint. Note that this should be scheduled after entering the
  // kResolving state. If the state is still kResolving after the microtask
  // checkpoint finishes (ie, the lock was not re-acquired), we enter the final
  // kResolved state.
  void FinishResolution();

  // Initiate a commit.
  void StartCommit();

  // The following functions propagate dirty bits from the locked element up to
  // the ancestors in order to be reached. They return true if the element or
  // its subtree were dirty, and false otherwise.
  bool MarkAncestorsForStyleRecalcIfNeeded();
  bool MarkAncestorsForLayoutIfNeeded();

  HeapVector<Member<V8DisplayLockCallback>> callbacks_;
  Member<ScriptPromiseResolver> resolver_;
  Member<Element> element_;

  bool process_queue_task_scheduled_ = false;
  unsigned suspended_count_ = 0;
  State state_ = kUninitialized;
  LifecycleUpdateState lifecycle_update_state_ = kNeedsStyle;
};

}  // namespace blink

#endif  // THIRD_PARTY_BLINK_RENDERER_CORE_DISPLAY_LOCK_DISPLAY_LOCK_CONTEXT_H_