Implement "pinned" mode in ash.

ash/wm/screen_pinning_controller.h

Index: ash/wm/screen_pinning_controller.h
diff --git a/ash/wm/screen_pinning_controller.h b/ash/wm/screen_pinning_controller.h
new file mode 100644
index 0000000000000000000000000000000000000000..0e0b42d861259b816a144ad0cf54f5e076667575
--- /dev/null
+++ b/ash/wm/screen_pinning_controller.h
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+// Copyright 2016 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 ASH_WM_SCREEN_PINNING_CONTROLLER_H_
+#define ASH_WM_SCREEN_PINNING_CONTROLLER_H_
+
+#include <memory>
+#include <vector>
+
+#include "ash/display/window_tree_host_manager.h"
+#include "base/macros.h"
+
+namespace ash {
+
+class WindowTreeHostManager;
+class WmShellCommon;
+class WmWindow;
+
+// Handles pinned state.
+class ScreenPinningController : public WindowTreeHostManager::Observer {
+ public:
+  ScreenPinningController(WmShellCommon* wm_shell_common,
+                          WindowTreeHostManager* window_tree_host_manager);
+  ~ScreenPinningController() override;
+
+  // Sets a pinned window. It is not allowed to call this when there already
+  // is a pinned window.
+  void SetPinnedWindow(WmWindow* pinned_window);
+
+  // Returns true if in pinned mode, otherwise false.
+  bool IsPinned() const;
+
+  // Called when a new window is added to the container which has the pinned
+  // window.
+  void OnWindowAddedToPinnedContainer(WmWindow* new_window);
+
+  // Called when a window will be removed from the container which has the
+  // pinned window.
+  void OnWillRemoveWindowFromPinnedContainer(WmWindow* window);
+
+  // Called when a window stacking is changed in the container which has the
+  // pinned window.
+  void OnPinnedContainerWindowStackingChanged(WmWindow* window);
+
+  // Called when a new window is added to a system modal container.
+  void OnWindowAddedToSystemModalContainer(WmWindow* new_window);
+
+  // Called when a window will be removed from a system modal container.
+  void OnWillRemoveWindowFromSystemModalContainer(WmWindow* window);
+
+  // Called when a window stacking is changed in a system modal container.
+  void OnSystemModalContainerWindowStackingChanged(WmWindow* window);
+
+  // Called when a dim window in the system modal container is destroying.
+  void OnDimWindowDestroying(WmWindow* window);
+
+ private:
+  class PinnedContainerWindowObserver;
+  class PinnedContainerChildWindowObserver;
+  class SystemModalContainerWindowObserver;
+  class SystemModalContainerChildWindowObserver;
+  class DimWindowObserver;
+
+  // Keeps the pinned window on top of the siblings.
+  void KeepPinnedWindowOnTop();
+
+  // Keeps the dim window at bottom of the container.
+  void KeepDimWindowAtBottom(WmWindow* container);
+
+  // WindowTreeHostManager::Observer:
+  void OnDisplayConfigurationChanged() override;
+
+  // Pinned window should be on top in the parent window.
+  WmWindow* pinned_window_ = nullptr;
+
+  // Dim background window just behind of the pinned window.
+  // Not owned. The parent has its ownership.
+  WmWindow* background_window_ = nullptr;
+
+  // In pinned mode, all displays other than the one where pinned_window_ is.
+  // Similar to background_window_, not owned.
+  std::vector<WmWindow*> dim_windows_;
+
+  // Set true only when restacking done by this controller.
+  bool in_restacking_ = false;
+
+  // For OnPinnedStateChanged event notification.
+  // While this controller is alive, it needs to be ensured that the instances
+  // refered from the pointers should be alive.
+  WmShellCommon* wm_shell_common_;
+
+  // Keep references to remove this as a observer.
+  // While this controller is alive, it needs to be ensured that the instances
+  // refered from the pointers should be alive.
+  WindowTreeHostManager* window_tree_host_manager_;
+
+  // Window observers to translate events for the window to this controller.
+  std::unique_ptr<PinnedContainerWindowObserver>
+      pinned_container_window_observer_;
+  std::unique_ptr<PinnedContainerChildWindowObserver>
+      pinned_container_child_window_observer_;
+  std::unique_ptr<SystemModalContainerWindowObserver>
+      system_modal_container_window_observer_;
+  std::unique_ptr<SystemModalContainerChildWindowObserver>
+      system_modal_container_child_window_observer_;
+  std::unique_ptr<DimWindowObserver> dim_window_observer_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScreenPinningController);
+};
+
+}  // namespace ash
+
+#endif  // ASH_WM_SCREEN_PINNING_CONTROLLER_H_