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

ui/base/ime/input_method_imm32.cc

 // Copyright (c) 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.
 
 #include "ui/base/ime/input_method_imm32.h"
 
 #include "base/basictypes.h"
 #include "ui/base/ime/composition_text.h"
 #include "ui/base/ime/text_input_client.h"
 #include "ui/base/ime/win/tsf_input_scope.h"
@@ skipping 220 matching lines @@
 LRESULT InputMethodIMM32::OnImeNotify(UINT message,
                                       WPARAM wparam,
                                       LPARAM lparam,
                                       BOOL* handled) {
   *handled = FALSE;
 
   // Update |is_candidate_popup_open_|, whether a candidate window is open.
   switch (wparam) {
   case IMN_OPENCANDIDATE:
     is_candidate_popup_open_ = true;
+    NotifyCandidateWindowStateChanged();

[yukawa, 2013/11/25 05:07:42]

I'm not sure if we can safely call back external code from here.  Using PostTask
to avoid nested message handler might be safer.  Please note that objects that
implement TextInputClient can do anything (e.g., calling
InputMehotd::CancelComposition) at this line.

     break;
   case IMN_CLOSECANDIDATE:
     is_candidate_popup_open_ = false;
+    NotifyCandidateWindowStateChanged();
+    break;
+  case IMN_CHANGECANDIDATE:
+    // TODO(kochi): The IME API expects this event to notify window size change,
+    // while this may fire more often without window resize. There is no generic

[yukawa, 2013/11/25 05:07:42]

"There is no generic way to get bounds of candidate window."
I haven't investigated yet but we might be able to use IMC_GETCANDIDATEPOS
request. If this is true, we might want to
say "Not all IMEs support IMC_GETCANDIDATEPOS request."

+    // way to get bounds of candidate window.
+    NotifyCandidateWindowStateChanged();
     break;
   }
 
   return 0;
 }
 
 void InputMethodIMM32::ConfirmCompositionText() {
   if (composing_window_handle_)
     imm32_manager_.CleanupComposition(composing_window_handle_);
 
@@ skipping 23 matching lines @@
       enabled_ = true;
       break;
   }
 
   imm32_manager_.SetTextInputMode(window_handle, text_input_mode);
   tsf_inputscope::SetInputScopeForTsfUnawareWindow(
       window_handle, text_input_type, text_input_mode);
 }
 
 }  // namespace ui