ContentClassifierPrefMirror.h

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/* This Source Code Form is subject to the terms of the Mozilla Public

 * License, v. 2.0. If a copy of the MPL was not distributed with this

 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#ifndef mozilla_ContentClassifierPrefMirror_h

#define mozilla_ContentClassifierPrefMirror_h

#include "mozilla/StaticPtr.h"

namespace mozilla {

// Transitional shim that derives the ContentClassifier engine prefs

// (privacy.trackingprotection.content.*) from the classic Enhanced Tracking

// Protection prefs (privacy.trackingprotection.*). This lets the existing

// about:preferences ETP UI drive the content classifier without being

// rewired.

//

// Gated by privacy.trackingprotection.content.mirror.enabled (off by

// default). While enabled the mirror owns the content engine/enabled prefs

// and recomputes them on every relevant ETP pref change; while disabled it

// leaves the content prefs untouched (the last derived values, if any,

// remain in place).

//

// The whole class is meant to be deleted once the migration to the content

// classifier is complete.

class ContentClassifierPrefMirror final {

 public:

  // Idempotently register the master pref callback that drives the singleton's

  // lifecycle.

  // Parent process, main thread only. Called from

  // ContentClassifierService::Init.

  static void Init();

 private:

  ContentClassifierPrefMirror();

  ~ContentClassifierPrefMirror();

  friend class StaticAutoPtr<ContentClassifierPrefMirror>;

  // Registered once on the master pref and never unregistered, so the mirror

  // keeps listening for the master pref even while the singleton is gone.

  static void OnMirrorPrefChange(const char* aPref, void* aData);

  static void Shutdown();

  // Registered on every watched ETP source pref while the mirror is up.

  static void OnPrefChange(const char* aPref, void* aData);

  // Request a Sync() on the next turn of the event loop, coalescing bursts of

  // ETP pref changes (e.g. switching the ETP category) into a single recompute

  // so the content engine prefs - and the engine rebuilds they trigger in

  // ContentClassifierService - are touched at most once per turn.

  void ScheduleSync();

  // Recompute the content engine prefs from the current ETP pref state and

  // write them. No-op while the mirror is disabled.

  void Sync();

  static StaticAutoPtr<ContentClassifierPrefMirror> sInstance;

  // Whether a coalesced Sync() runnable is already pending. Main thread only.

  bool mSyncScheduled = false;

};

}  // namespace mozilla

#endif  // mozilla_ContentClassifierPrefMirror_h