win8/metro_driver/ime/ime_popup_monitor.cc

   1 // Copyright 2013 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "win8/metro_driver/ime/ime_popup_monitor.h"
   6
   7 #include <windows.h>
   8
   9 #include "base/logging.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "win8/metro_driver/ime/ime_popup_observer.h"
  12
  13 namespace metro_driver {
  14 namespace {
  15
  16 ImePopupObserver* g_observer_ = NULL;
  17 HWINEVENTHOOK g_hook_handle_ = NULL;
  18
  19 void CALLBACK ImeEventCallback(HWINEVENTHOOK win_event_hook_handle,
  20                                DWORD event,
  21                                HWND window_handle,
  22                                LONG object_id,
  23                                LONG child_id,
  24                                DWORD event_thread,
  25                                DWORD event_time) {
  26   // This function is registered to SetWinEventHook to be called back on the UI
  27   // thread.
  28   DCHECK(base::MessageLoopForUI::IsCurrent());
  29
  30   if (!g_observer_)
  31     return;
  32   switch (event) {
  33     case EVENT_OBJECT_IME_SHOW:
  34       g_observer_->OnImePopupChanged(ImePopupObserver::kPopupShown);
  35       return;
  36     case EVENT_OBJECT_IME_HIDE:
  37       g_observer_->OnImePopupChanged(ImePopupObserver::kPopupHidden);
  38       return;
  39     case EVENT_OBJECT_IME_CHANGE:
  40       g_observer_->OnImePopupChanged(ImePopupObserver::kPopupUpdated);
  41       return;
  42   }
  43 }
  44
  45 }  // namespace
  46
  47 void AddImePopupObserver(ImePopupObserver* observer) {
  48   CHECK(g_observer_ == NULL)
  49       << "Currently only one observer is supported at the same time.";
  50   g_observer_ = observer;
  51
  52   // IMEs running under immersive mode are supposed to generate WinEvent
  53   // whenever their popup UI such as candidate window is shown, updated, and
  54   // hidden to support accessibility applications.
  55   // http://msdn.microsoft.com/en-us/library/windows/apps/hh967425.aspx#accessibility
  56   // Note that there is another mechanism in TSF, called ITfUIElementSink, to
  57   // subscribe when the visibility of an IME's UI element is changed. However,
  58   // MS-IME running under immersive mode does not fully support this API.
  59   // Thus, WinEvent is more reliable for this purpose.
  60   g_hook_handle_ = SetWinEventHook(
  61       EVENT_OBJECT_IME_SHOW,
  62       EVENT_OBJECT_IME_CHANGE,
  63       NULL,
  64       ImeEventCallback,
  65       GetCurrentProcessId(),  // monitor the metro_driver process only
  66       0,   // hook all threads because MS-IME emits WinEvent in a worker thread
  67       WINEVENT_OUTOFCONTEXT);  // allows us to receive message in the UI thread
  68   LOG_IF(ERROR, !g_hook_handle_) << "SetWinEventHook failed.";
  69 }
  70
  71 void RemoveImePopupObserver(ImePopupObserver* observer) {
  72   if (g_observer_ != observer)
  73     return;
  74   g_observer_ = NULL;
  75   if (!g_hook_handle_)
  76     return;
  77   const bool unhook_succeeded = !!UnhookWinEvent(g_hook_handle_);
  78   LOG_IF(ERROR, !unhook_succeeded) << "UnhookWinEvent failed.";
  79   g_hook_handle_ = NULL;
  80 }
  81
  82 }  // namespace metro_driver