[FYI] All-in-one OnCandidateWindow{Show,Update,Hide}

ui/base/ime/input_method_base.h

 // Copyright (c) 2012 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_BASE_IME_INPUT_METHOD_BASE_H_
 #define UI_BASE_IME_INPUT_METHOD_BASE_H_
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
+#include "base/memory/weak_ptr.h"
 #include "base/observer_list.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ui_export.h"
 
 namespace gfx {
 class Rect;
 }  // namespace gfx
 
 namespace ui {
 
 class InputMethodObserver;
 class KeyEvent;
 class TextInputClient;
 
 // A helper class providing functionalities shared among ui::InputMethod
 // implementations.
-class UI_EXPORT InputMethodBase : NON_EXPORTED_BASE(public InputMethod) {
+class UI_EXPORT InputMethodBase
+   : NON_EXPORTED_BASE(public InputMethod),
+     public base::SupportsWeakPtr<InputMethodBase> {
  public:
   InputMethodBase();
   virtual ~InputMethodBase();
 
   // Overriden from InputMethod.
   virtual void SetDelegate(internal::InputMethodDelegate* delegate) OVERRIDE;
   virtual void Init(bool focused) OVERRIDE;
   // If a derived class overrides OnFocus()/OnBlur(), it should call parent's
   // implementation first, to make sure |system_toplevel_window_focused_| flag
   // can be updated correctly.
@@ skipping 33 matching lines @@
   // input type is not TEXT_INPUT_TYPE_NONE.
   void OnInputMethodChanged() const;
 
   // Convenience method to call delegate_->DispatchKeyEventPostIME().
   // Returns true if the event was processed
   bool DispatchKeyEventPostIME(const ui::KeyEvent& event) const;
 
   // Convenience method to notify all observers of TextInputClient changes.
   void NotifyTextInputStateChanged(const TextInputClient* client);
 
+  // Interface for for signalling candidate window events.
+  // See also *Callback functions below. To avoid reentrancy issue that
+  // TextInputClient manipulates IME state during even handling, these methods
+  // defer sending actual signals to renderer.
+  void OnCandidateWindowShown();
+  void OnCandidateWindowUpdated();
+  void OnCandidateWindowHidden();
+
   bool system_toplevel_window_focused() const {
     return system_toplevel_window_focused_;
   }
 
  private:
   void SetFocusedTextInputClientInternal(TextInputClient* client);
 
+  // Deferred callbacks for signalling TextInputClient about candidate window
+  // appearance changes.
+  void CandidateWindowShownCallback();
+  void CandidateWindowUpdatedCallback();
+  void CandidateWindowHiddenCallback();
+
   internal::InputMethodDelegate* delegate_;
   TextInputClient* text_input_client_;
 
   ObserverList<InputMethodObserver> observer_list_;
 
   bool system_toplevel_window_focused_;
 
   DISALLOW_COPY_AND_ASSIGN(InputMethodBase);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_IME_INPUT_METHOD_BASE_H_