chrome/browser/chrome_process_singleton.h

// Copyright 2013 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CHROME_BROWSER_CHROME_PROCESS_SINGLETON_H_
#define CHROME_BROWSER_CHROME_PROCESS_SINGLETON_H_

#include "base/files/file_path.h"
#include "base/functional/callback.h"
#include "chrome/browser/process_singleton.h"
#include "chrome/browser/process_singleton_modal_dialog_lock.h"
#include "chrome/browser/process_singleton_startup_lock.h"

// Composes a basic ProcessSingleton with ProcessSingletonStartupLock and
// ProcessSingletonModalDialogLock.
//
// Notifications from ProcessSingleton will first close a modal dialog if
// active. Otherwise, until |Unlock()| is called, they will be queued up. Once
// unlocked, notifications will be passed to the client-supplied
// NotificationCallback; which is passed as an argument by |Unlock()|.
//
// The client must ensure that SetModalDialogNotificationHandler is called
// appropriately when dialogs are displayed or dismissed during startup. If a
// dialog is active, it is closed (via the provided handler) and then the
// notification is processed as normal.
class ChromeProcessSingleton {
 public:
  explicit ChromeProcessSingleton(const base::FilePath& user_data_dir);

  ChromeProcessSingleton(const ChromeProcessSingleton&) = delete;
  ChromeProcessSingleton& operator=(const ChromeProcessSingleton&) = delete;

  ~ChromeProcessSingleton();

  // Notify another process, if available. Otherwise sets ourselves as the
  // singleton instance. Returns PROCESS_NONE if we became the singleton
  // instance. Callers are guaranteed to either have notified an existing
  // process or have grabbed the singleton (unless the profile is locked by an
  // unreachable process).
  ProcessSingleton::NotifyResult NotifyOtherProcessOrCreate();

  // Start watching for notifications from other processes. After this call,
  // the notifications sent by other process can be processed. This call
  // requires the browser threads (UI / IO) to be created. Requests that occur
  // before calling StartWatching(...) will be blocked and may timeout.
  void StartWatching();

  // Clear any lock state during shutdown.
  void Cleanup();

  // Receives a callback to be run to close the active modal dialog, or an empty
  // closure if the active dialog is dismissed.
  void SetModalDialogNotificationHandler(
      base::RepeatingClosure notification_handler);

  // Executes previously queued command-line invocations and allows future
  // invocations to be executed immediately.
  // This only has an effect the first time it is called.
  void Unlock(
      const ProcessSingleton::NotificationCallback& notification_callback);

  bool IsSingletonInstanceForTesting() const { return is_singleton_instance_; }

  // Create the chrome process singleton instance for the current process.
  static void CreateInstance(const base::FilePath& user_data_dir);
  // Delete the chrome process singleton instance.
  static void DeleteInstance();
  // Retrieve the chrome process singleton instance for the current process.
  static ChromeProcessSingleton* GetInstance();

  // Returns true if this process is the singleton instance (i.e., a
  // ProcessSingleton has been created and NotifyOtherProcessOrCreate() has
  // returned PROCESS_NONE).
  static bool IsSingletonInstance();

  // Setup the experiment for the early process singleton. Remove this code
  // when the experiment is over (http://www.crbug.com/1340599).
  static void SetupEarlySingletonFeature(const base::CommandLine& command_line);
  static void RegisterEarlySingletonFeature();
  static bool IsEarlySingletonFeatureEnabled();
  static bool ShouldMergeMetrics();

 private:
  bool NotificationCallback(const base::CommandLine& command_line,
                            const base::FilePath& current_directory);

  // Whether or not this instance is the running single instance.
  bool is_singleton_instance_ = false;

  // We compose these two locks with the client-supplied notification callback.
  // First |modal_dialog_lock_| will discard any notifications that arrive while
  // a modal dialog is active. Otherwise, it will pass the notification to
  // |startup_lock_|, which will queue notifications until |Unlock()| is called.
  // Notifications passing through both locks are finally delivered to our
  // client.
  ProcessSingletonStartupLock startup_lock_;
  ProcessSingletonModalDialogLock modal_dialog_lock_;

  // The basic ProcessSingleton
  ProcessSingleton process_singleton_;
  ProcessSingleton::NotificationCallback notification_callback_;
};

#endif  // CHROME_BROWSER_CHROME_PROCESS_SINGLETON_H_