WIP: Ash IME support

win8/metro_driver/ime/ime_popup_monitor.cc

Index: win8/metro_driver/ime/ime_popup_monitor.cc
diff --git a/win8/metro_driver/ime/ime_popup_monitor.cc b/win8/metro_driver/ime/ime_popup_monitor.cc
new file mode 100644
index 0000000000000000000000000000000000000000..19a35336fef6b4f2e01d0a4852523319d3dd9549
--- /dev/null
+++ b/win8/metro_driver/ime/ime_popup_monitor.cc
@@ -0,0 +1,75 @@
+// 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 "win8/metro_driver/ime/ime_popup_monitor.h"
+
+#include <msctf.h>
+
+#include "base/logging.h"
+#include "base/message_loop/message_loop.h"
+#include "win8/metro_driver/ime/ime_popup_observer.h"
+
+namespace metro_driver {
+namespace {
+
+ImePopupObserver* g_observer_ = NULL;
+HWINEVENTHOOK g_hook_handle_ = NULL;
+
+void CALLBACK ImeEventCallback(HWINEVENTHOOK win_event_hook_handle,
+                               DWORD event,
+                               HWND window_handle,
+                               LONG object_id,
+                               LONG child_id,
+                               DWORD event_thread,
+                               DWORD event_time) {
+  DCHECK_EQ(base::MessageLoop::TYPE_UI, base::MessageLoop::current()->type());
+  if (!g_observer_)
+    return;
+  switch (event) {
+    case EVENT_OBJECT_IME_SHOW:
+      g_observer_->OnCandidatePopupChanged(true);
+      return;
+    case EVENT_OBJECT_IME_HIDE:
+      g_observer_->OnCandidatePopupChanged(false);
+      return;
+    // Note: we never see EVENT_OBJECT_IME_CHANGE here because it is filtered
+    // out when SetWinEventHook API is called.
+  }
+}
+
+}  // namespace
+
+void AddImePopupObserver(ImePopupObserver* observer) {
+  CHECK(g_observer_ == NULL) <<
+      "Currently only one observer is supported at the same time.";
+  g_observer_ = observer;
+
+  // Unfortunately MS-IME in immersive mode does not fully support
+  // ITfUIElementSink. EVENT_OBJECT_IME_SHOW/EVENT_OBJECT_IME_HIDE is more
+  // reliable in practice.
+  // Caveats: EVENT_OBJECT_IME_SHOW/EVENT_OBJECT_IME_HIDE are supported on
+  // Windows 8 and later.
+
+  g_hook_handle_ = SetWinEventHook(
+      EVENT_OBJECT_IME_SHOW,
+      EVENT_OBJECT_IME_HIDE,
+      NULL,
+      ImeEventCallback,
+      ::GetCurrentProcessId(),
+      0,   // Hook all threads because MS-IME emits WinEvent in worker thread
+      WINEVENT_OUTOFCONTEXT);  // allows us to receive message in the UI thread
+}
+
+void RemoveImePopupObserver(ImePopupObserver* observer) {
+  if (g_observer_ != observer)
+    return;
+  g_observer_ = NULL;
+  if (!g_hook_handle_)
+    return;
+  UnhookWinEvent(g_hook_handle_);
+  g_hook_handle_ = NULL;
+}
+
+}  // namespace metro_driver
+