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 mirrors the classic Enhanced Tracking Protection

// prefs (privacy.trackingprotection.*) onto the ContentClassifier engine

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

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

// rewired.

//

// Driven by privacy.trackingprotection.content.mirror.mode, which has three

// states:

//

//   0 (off, the default) - the mirror is down and clears the content prefs if

//     it mirrored them before.

//   1 (on) - the mirror owns the content engine/enabled prefs and recomputes

//     them on every relevant ETP pref change.

//   2 (handover) - the mirror stops mirroring but leaves the mirrored values

//     in place, handing them to whoever owns the content prefs next.

//

// Off is the state reached by doing nothing, so a lapsed rollout releases the

// prefs rather than stranding them.

//

// 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();

  // Clear the content prefs the mirror wrote, so they fall back to

  // their default-branch values.

  static void ReleaseMirroredPrefs();

  // 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, write

  // them, and take ownership of 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