Refactor backdrop

ash/wm/workspace/backdrop_controller.h

 // Copyright 2014 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_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_
-#define ASH_WM_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_
+#ifndef ASH_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_
+#define ASH_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_
 
 #include <memory>
 
-#include "ash/ash_export.h"
-#include "ash/wm/workspace/workspace_layout_manager_backdrop_delegate.h"
+#include "ash/shell_observer.h"
+#include "ash/system/accessibility_observer.h"
+#include "ash/wm/wm_types.h"
 #include "base/macros.h"
 
+namespace aura {
+class Window;
+}
+
 namespace views {
 class Widget;
 }
 
+namespace ui {
+class EventHandler;
+}
+
 namespace ash {
+namespace test {
+class WorkspaceControllerTestApi;
+}
 
-class WmWindow;
+namespace wm {
+class WindowState;
+}
 
-// A background which gets created for a container |window| and which gets
+class BackdropDelegate;
+
+// A backdrop which gets created for a container |window| and which gets
 // stacked behind the topmost window (within that container) covering the
 // entire container.

[James Cook, 2017/05/15 21:57:39]

Please expand this comment to say why the backdrop exists. I had to ask Dominik,
who said:

"i believe it refers to the black background that exo inserts under maximized
arc apps that are unresizable.
in some cases, portrait apps are sized to fill the screen vertically and
positioned in the center of the workspace. the remaining space is filled with a
black backdrop.
it's also used as a target window for accessibility input events"

so maybe something like that

[oshima, 2017/05/16 08:22:09]

I updated to be more generic

[James Cook, 2017/05/16 15:12:14]

Can you copy the text you added to the CL description here. It would help me
know what the feature does. This part:

The maximized mode creates a backdrop window so that a user will not see the
content of windows behind the top window,
in case it doesn't cover the entire window. (can happen if the maximize size is
specified)

and it might be nice to say something like "it's common for ARC apps and
packaged Chrome apps not to be resizable" since I think that's the motivation
for this feature.

[oshima, 2017/05/17 07:44:33]

I added the comment, although I don't want to put too much implementation
specific information because:
a) the term "resizeable" is very subtle concept in android. b) It can and will
become stale.

-class ASH_EXPORT WorkspaceBackdropDelegate
-    : public WorkspaceLayoutManagerBackdropDelegate {
+class BackdropController : public ShellObserver, public AccessibilityObserver {
  public:
-  explicit WorkspaceBackdropDelegate(WmWindow* container);
-  ~WorkspaceBackdropDelegate() override;
+  explicit BackdropController(WmWindow* container);

[James Cook, 2017/05/15 21:57:39]

Is it possible to take aura::Window* here?

[James Cook, 2017/05/16 15:12:14]

Again, can you take aura::Window here instead of WmWindow?

[oshima, 2017/05/17 07:44:34]

Done.

+  ~BackdropController() override;
 
-  // WorkspaceLayoutManagerBackdropDelegate overrides:
-  void OnWindowAddedToLayout(WmWindow* child) override;
-  void OnWindowRemovedFromLayout(WmWindow* child) override;
-  void OnChildWindowVisibilityChanged(WmWindow* child, bool visible) override;
-  void OnWindowStackingChanged(WmWindow* window) override;
+  void OnWindowAddedToLayout(aura::Window* child);

[James Cook, 2017/05/15 21:57:39]

Thanks for switching from WmWindow to aura::Window!

+  void OnWindowRemovedFromLayout(aura::Window* child);
+  void OnChildWindowVisibilityChanged(aura::Window* child, bool visible);
+  void OnWindowStackingChanged(aura::Window* window);
   void OnPostWindowStateTypeChange(wm::WindowState* window_state,
-                                   wm::WindowStateType old_type) override;
+                                   wm::WindowStateType old_type);
+
+  void SetBackdropDelegate(std::unique_ptr<BackdropDelegate> delegate);
+
+  // Update the visibility of, and Restack the backdrop relatively to

[James Cook, 2017/05/15 21:57:39]

nit: Restack -> restack, relatively -> relative

[oshima, 2017/05/16 08:22:08]

Done.

+  // the other windows in the container.
+  void UpdateBackdrop();
+
+  // ShellObserver:
+  void OnOverviewModeStarting() override;
+  void OnOverviewModeEnded() override;
+
+  // AccessibilityObserver:
+  void OnAccessibilityModeChanged(
+      AccessibilityNotificationVisibility notify) override;
 
  private:
-  // Restack the backdrop relatively to the other windows in the container.
-  void RestackBackdrop();
+  friend class test::WorkspaceControllerTestApi;
 
-  // Returns the current visible top level window in the container.
-  WmWindow* GetCurrentTopWindow();
+  void EnsureBackdropWidget();
+
+  void UpdateAccessibilityMode();
 
   // Show the overlay.
   void Show();
 
-  // The background which covers the rest of the screen.
-  views::Widget* background_ = nullptr;
-  // WmWindow for |background_|.
-  WmWindow* background_window_ = nullptr;
+  // Hide the overlay.

[James Cook, 2017/05/15 21:57:39]

overlay -> backdrop? and above?

[oshima, 2017/05/16 08:22:09]

Done.

+  void Hide();
 
-  // The window which is being "maximized".
+  // Returns the current visible top level window in the container.
+  aura::Window* GetTopmostWindowWithBackdrop();
+
+  // The backdrop which covers the rest of the screen.
+  views::Widget* backdrop_ = nullptr;
+
+  // aura::Window for |backdrop_|.
+  aura::Window* backdrop_window_ = nullptr;
+
+  // The container of the window that should have a backdrop.
   WmWindow* container_;
 
+  std::unique_ptr<BackdropDelegate> delegate_;
+
+  // Event hanlder used to implement actions for accessibility.
+  std::unique_ptr<ui::EventHandler> backdrop_event_handler_;
+  ui::EventHandler* original_event_handler_ = nullptr;
+
   // If true, the |RestackOrHideWindow| might recurse.
   bool in_restacking_;

[James Cook, 2017/05/15 21:57:39]

nit: initialize here, like the others

[oshima, 2017/05/16 08:22:08]

Done.

 
-  DISALLOW_COPY_AND_ASSIGN(WorkspaceBackdropDelegate);
+  // True to temporarily hide the backdrop. Used in
+  // overview mode.
+  bool force_hidden_ = false;
+
+  DISALLOW_COPY_AND_ASSIGN(BackdropController);
 };
 
 }  // namespace ash
 
-#endif  // ASH_WM_MAXIMIZE_MODE_WORKSPACE_BACKDROP_DELEGATE_H_
+#endif  // ASH_WM_WORKSPACE_WORKSPACE_BACKDROP_DELEGATE_IMPL_H_