arc: Use exo::WMHelper to abserve window focus.

components/arc/ime/arc_ime_service.cc

 // 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.
 
 #include "components/arc/ime/arc_ime_service.h"
 
 #include <utility>
 
 #include "base/logging.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/arc/ime/arc_ime_bridge_impl.h"
 #include "components/exo/shell_surface.h"
 #include "components/exo/surface.h"
-#include "ui/aura/client/focus_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/events/base_event_utils.h"
 #include "ui/events/event.h"
 #include "ui/events/keycodes/keyboard_codes.h"
 
 namespace arc {
 
@@ skipping 10 matching lines @@
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // ArcImeService main implementation:
 
 ArcImeService::ArcImeService(ArcBridgeService* bridge_service)
     : ArcService(bridge_service),
       ime_bridge_(new ArcImeBridgeImpl(this, bridge_service)),
       ime_type_(ui::TEXT_INPUT_TYPE_NONE),
       has_composition_text_(false),
-      focus_client_(nullptr),
       keyboard_controller_(nullptr),
-      test_input_method_(nullptr) {
+      test_input_method_(nullptr),
+      is_focus_observer_installed_(false) {
   aura::Env* env = aura::Env::GetInstanceDontCreate();
   if (env)
     env->AddObserver(this);
 }
 
 ArcImeService::~ArcImeService() {
   ui::InputMethod* const input_method = GetInputMethod();
   if (input_method)
     input_method->DetachTextInputClient(this);
 
-  for (aura::Window* window : arc_windows_.windows())
-    window->RemoveObserver(this);
-  if (focus_client_)
-    focus_client_->RemoveObserver(this);
+  if (is_focus_observer_installed_ && exo::WMHelper::GetInstance())

[Yusuke Sato, 2016/08/20 01:25:38]

Is the is_focus_observer_installed_ check really necessary? base::ObserverList
just ignores unknown pointers.

[Peng, 2016/08/20 13:09:23]

As I explained at line 94. It is difficult to remove
is_focus_observer_installed_, so checking it here shouldn't hurt anything. 

+    exo::WMHelper::GetInstance()->RemoveFocusObserver(this);
   aura::Env* env = aura::Env::GetInstanceDontCreate();
   if (env)
     env->RemoveObserver(this);
   // Removing |this| from KeyboardController.
   keyboard::KeyboardController* keyboard_controller =
       keyboard::KeyboardController::GetInstance();
   if (keyboard_controller && keyboard_controller_ == keyboard_controller) {
     keyboard_controller_->RemoveObserver(this);
   }
 }
@@ skipping 14 matching lines @@
   if (focused_arc_window_.windows().empty())
     return nullptr;
   return focused_arc_window_.windows().front()->GetHost()->GetInputMethod();
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // Overridden from aura::EnvObserver:
 
 void ArcImeService::OnWindowInitialized(aura::Window* new_window) {
   if (IsArcWindow(new_window)) {
-    arc_windows_.Add(new_window);
-    new_window->AddObserver(this);
+    if (!is_focus_observer_installed_) {
+      exo::WMHelper::GetInstance()->AddFocusObserver(this);

[Yusuke Sato, 2016/08/20 01:25:38]

Can't we move this to somewhere else (e.g. the constructor) which is executed
only once so we can remove is_focus_observer_installed_ member variable?

[Peng, 2016/08/20 13:09:23]

The constructor doesn't work, because this class is created before exo
initialization. That why we have to delay the observer installation to here.

+      is_focus_observer_installed_ = true;
+    }
   }
   keyboard::KeyboardController* keyboard_controller =
       keyboard::KeyboardController::GetInstance();
   if (keyboard_controller && keyboard_controller_ != keyboard_controller) {
     // Registering |this| as an observer only once per KeyboardController.
     keyboard_controller_ = keyboard_controller;
     keyboard_controller_->AddObserver(this);
   }
 }
 
-void ArcImeService::OnWindowAddedToRootWindow(aura::Window* window) {
-  aura::Window* root = window->GetRootWindow();
-  aura::client::FocusClient* focus_client = aura::client::GetFocusClient(root);
-  if (!focus_client)
-    return;
-
-  if (focus_client_) {
-    // Root windows share the same FocusClient in Ash.
-    DCHECK_EQ(focus_client_, focus_client);
-  } else {
-    focus_client_ = focus_client;
-    focus_client_->AddObserver(this);
-  }
-}
-
 ////////////////////////////////////////////////////////////////////////////////
-// Overridden from aura::client::FocusChangeObserver:
+// Overridden from exo::WMHelper::FocusChangeObserver:
 
 void ArcImeService::OnWindowFocused(aura::Window* gained_focus,
                                    aura::Window* lost_focus) {
   // The Aura focus may or may not be on sub-window of the toplevel ARC++ frame.
   // To handle all cases, judge the state by always climbing up to the toplevel.
   gained_focus = gained_focus ? gained_focus->GetToplevelWindow() : nullptr;
   lost_focus = lost_focus ? lost_focus->GetToplevelWindow() : nullptr;
   if (lost_focus == gained_focus)
     return;
 
@@ skipping 213 matching lines @@
     base::i18n::TextDirection direction) {
   return false;
 }
 
 bool ArcImeService::IsTextEditCommandEnabled(
     ui::TextEditCommand command) const {
   return false;
 }
 
 }  // namespace arc