text: // Copyright 2013 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 UI_WM_CORE_DEFAULT_ACTIVATION_CLIENT_H_
  #define UI_WM_CORE_DEFAULT_ACTIVATION_CLIENT_H_
  
  #include <vector>
  
  #include "base/memory/raw_ptr.h"
  #include "base/observer_list.h"
  #include "ui/aura/window_observer.h"
  #include "ui/wm/core/wm_core_export.h"
  #include "ui/wm/public/activation_change_observer.h"
  #include "ui/wm/public/activation_client.h"
  
  namespace wm {
  
  class ActivationChangeObserver;
  
  // Simple ActivationClient implementation for use by tests and other targets
  // that just need basic behavior (e.g. activate windows whenever requested,
  // restack windows at the top when they're activated, etc.). This object deletes
  // itself when the root window it is associated with is destroyed.
  class WM_CORE_EXPORT DefaultActivationClient : public ActivationClient,
                                                 public aura::WindowObserver {
   public:
    explicit DefaultActivationClient(aura::Window* root_window);
  
    DefaultActivationClient(const DefaultActivationClient&) = delete;
    DefaultActivationClient& operator=(const DefaultActivationClient&) = delete;
  
    // Overridden from ActivationClient:
    void AddObserver(ActivationChangeObserver* observer) override;
    void RemoveObserver(ActivationChangeObserver* observer) override;
    void ActivateWindow(aura::Window* window) override;
    void DeactivateWindow(aura::Window* window) override;
    const aura::Window* GetActiveWindow() const override;
    aura::Window* GetActivatableWindow(aura::Window* window) const override;
    const aura::Window* GetToplevelWindow(
        const aura::Window* window) const override;
    bool CanActivateWindow(const aura::Window* window) const override;
  
    // Overridden from WindowObserver:
    void OnWindowDestroyed(aura::Window* window) override;
  
   private:
    class Deleter;
  
    ~DefaultActivationClient() override;
    void RemoveActiveWindow(aura::Window* window);
  
    void ActivateWindowImpl(ActivationChangeObserver::ActivationReason reason,
                            aura::Window* window);
  
    // This class explicitly does NOT store the active window in a window property
    // to make sure that ActivationChangeObserver is not treated as part of the
    // aura API. Assumptions to that end will cause tests that use this client to
    // fail.
    std::vector<aura::Window*> active_windows_;
  
    // The window which was active before the currently active one.
    raw_ptr<aura::Window> last_active_;
  
    base::ObserverList<ActivationChangeObserver>::Unchecked observers_;
  };
  
  }  // namespace wm
  
  #endif  // UI_WM_CORE_DEFAULT_ACTIVATION_CLIENT_H_
  