Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2410 insertions, 0 deletions

diff --git a/widget/windows/IMMHandler.cpp b/widget/windows/IMMHandler.cpp
new file mode 100644
index 0000000000..0fd33bdba2
--- /dev/null
+++ b/widget/windows/IMMHandler.cpp
@@ -0,0 +1,2410 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sts=2 sw=2 et cin: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Logging.h"
+
+#include "IMMHandler.h"
+#include "nsWindow.h"
+#include "nsWindowDefs.h"
+#include "WinIMEHandler.h"
+#include "WinUtils.h"
+#include "KeyboardLayout.h"
+#include <algorithm>
+
+#include "mozilla/CheckedInt.h"
+#include "mozilla/MiscEvents.h"
+#include "mozilla/TextEvents.h"
+#include "mozilla/ToString.h"
+#include "mozilla/WindowsVersion.h"
+
+#ifndef IME_PROP_ACCEPT_WIDE_VKEY
+#  define IME_PROP_ACCEPT_WIDE_VKEY 0x20
+#endif
+
+//-------------------------------------------------------------------------
+//
+// from
+// http://download.microsoft.com/download/6/0/9/60908e9e-d2c1-47db-98f6-216af76a235f/msime.h
+// The document for this has been removed from MSDN...
+//
+//-------------------------------------------------------------------------
+
+#define RWM_MOUSE TEXT("MSIMEMouseOperation")
+
+#define IMEMOUSE_NONE 0x00  // no mouse button was pushed
+#define IMEMOUSE_LDOWN 0x01
+#define IMEMOUSE_RDOWN 0x02
+#define IMEMOUSE_MDOWN 0x04
+#define IMEMOUSE_WUP 0x10    // wheel up
+#define IMEMOUSE_WDOWN 0x20  // wheel down
+
+// For collecting other people's log, tell `MOZ_LOG=IMEHandler:4,sync`
+// rather than `MOZ_LOG=IMEHandler:5,sync` since using `5` may create too
+// big file.
+// Therefore you shouldn't use `LogLevel::Verbose` for logging usual behavior.
+extern mozilla::LazyLogModule gIMELog;
+
+static const char* GetBoolName(bool aBool) { return aBool ? "true" : "false"; }
+
+static void HandleSeparator(nsACString& aDesc) {
+  if (!aDesc.IsEmpty()) {
+    aDesc.AppendLiteral(" | ");
+  }
+}
+
+class GetIMEGeneralPropertyName : public nsAutoCString {
+ public:
+  explicit GetIMEGeneralPropertyName(DWORD aFlags) {
+    if (!aFlags) {
+      AppendLiteral("no flags");
+      return;
+    }
+    if (aFlags & IME_PROP_AT_CARET) {
+      AppendLiteral("IME_PROP_AT_CARET");
+    }
+    if (aFlags & IME_PROP_SPECIAL_UI) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_SPECIAL_UI");
+    }
+    if (aFlags & IME_PROP_CANDLIST_START_FROM_1) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_CANDLIST_START_FROM_1");
+    }
+    if (aFlags & IME_PROP_UNICODE) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_UNICODE");
+    }
+    if (aFlags & IME_PROP_COMPLETE_ON_UNSELECT) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_COMPLETE_ON_UNSELECT");
+    }
+    if (aFlags & IME_PROP_ACCEPT_WIDE_VKEY) {
+      HandleSeparator(*this);
+      AppendLiteral("IME_PROP_ACCEPT_WIDE_VKEY");
+    }
+  }
+  virtual ~GetIMEGeneralPropertyName() {}
+};
+
+class GetIMEUIPropertyName : public nsAutoCString {
+ public:
+  explicit GetIMEUIPropertyName(DWORD aFlags) {
+    if (!aFlags) {
+      AppendLiteral("no flags");
+      return;
+    }
+    if (aFlags & UI_CAP_2700) {
+      AppendLiteral("UI_CAP_2700");
+    }
+    if (aFlags & UI_CAP_ROT90) {
+      HandleSeparator(*this);
+      AppendLiteral("UI_CAP_ROT90");
+    }
+    if (aFlags & UI_CAP_ROTANY) {
+      HandleSeparator(*this);
+      AppendLiteral("UI_CAP_ROTANY");
+    }
+  }
+  virtual ~GetIMEUIPropertyName() {}
+};
+
+class GetReconvertStringLog : public nsAutoCString {
+ public:
+  explicit GetReconvertStringLog(RECONVERTSTRING* aReconv) {
+    AssignLiteral("{ dwSize=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwSize));
+    AppendLiteral(", dwVersion=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwVersion));
+    AppendLiteral(", dwStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwStrLen));
+    AppendLiteral(", dwStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwStrOffset));
+    AppendLiteral(", dwCompStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwCompStrLen));
+    AppendLiteral(", dwCompStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwCompStrOffset));
+    AppendLiteral(", dwTargetStrLen=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwTargetStrLen));
+    AppendLiteral(", dwTargetStrOffset=");
+    AppendInt(static_cast<uint32_t>(aReconv->dwTargetStrOffset));
+    AppendLiteral(", result str=\"");
+    if (aReconv->dwStrLen) {
+      char16_t* strStart = reinterpret_cast<char16_t*>(
+          reinterpret_cast<char*>(aReconv) + aReconv->dwStrOffset);
+      nsDependentString str(strStart, aReconv->dwStrLen);
+      Append(NS_ConvertUTF16toUTF8(str));
+    }
+    AppendLiteral("\" }");
+  }
+  virtual ~GetReconvertStringLog() {}
+};
+
+namespace mozilla {
+namespace widget {
+
+static IMMHandler* gIMMHandler = nullptr;
+
+/******************************************************************************
+ * IMEContext
+ ******************************************************************************/
+
+IMEContext::IMEContext(HWND aWnd) : mWnd(aWnd), mIMC(::ImmGetContext(aWnd)) {}
+
+IMEContext::IMEContext(nsWindow* aWindowBase)
+    : mWnd(aWindowBase->GetWindowHandle()),
+      mIMC(::ImmGetContext(aWindowBase->GetWindowHandle())) {}
+
+void IMEContext::Init(HWND aWnd) {
+  Clear();
+  mWnd = aWnd;
+  mIMC = ::ImmGetContext(mWnd);
+}
+
+void IMEContext::Init(nsWindow* aWindowBase) {
+  Init(aWindowBase->GetWindowHandle());
+}
+
+void IMEContext::Clear() {
+  if (mWnd && mIMC) {
+    ::ImmReleaseContext(mWnd, mIMC);
+  }
+  mWnd = nullptr;
+  mIMC = nullptr;
+}
+
+/******************************************************************************
+ * IMMHandler
+ ******************************************************************************/
+
+static UINT sWM_MSIME_MOUSE = 0;  // mouse message for MSIME 98/2000
+
+WritingMode IMMHandler::sWritingModeOfCompositionFont;
+nsString IMMHandler::sIMEName;
+UINT IMMHandler::sCodePage = 0;
+DWORD IMMHandler::sIMEProperty = 0;
+DWORD IMMHandler::sIMEUIProperty = 0;
+bool IMMHandler::sAssumeVerticalWritingModeNotSupported = false;
+bool IMMHandler::sHasFocus = false;
+
+#define IMPL_IS_IME_ACTIVE(aReadableName, aActualName) \
+  bool IMMHandler::Is##aReadableName##Active() {       \
+    return sIMEName.Equals(aActualName);               \
+  }
+
+IMPL_IS_IME_ACTIVE(ATOK2006, u"ATOK 2006")
+IMPL_IS_IME_ACTIVE(ATOK2007, u"ATOK 2007")
+IMPL_IS_IME_ACTIVE(ATOK2008, u"ATOK 2008")
+IMPL_IS_IME_ACTIVE(ATOK2009, u"ATOK 2009")
+IMPL_IS_IME_ACTIVE(ATOK2010, u"ATOK 2010")
+// NOTE: Even on Windows for en-US, the name of Google Japanese Input is
+//       written in Japanese.
+IMPL_IS_IME_ACTIVE(GoogleJapaneseInput,
+                   u"Google \x65E5\x672C\x8A9E\x5165\x529B "
+                   u"IMM32 \x30E2\x30B8\x30E5\x30FC\x30EB")
+IMPL_IS_IME_ACTIVE(Japanist2003, u"Japanist 2003")
+
+#undef IMPL_IS_IME_ACTIVE
+
+// static
+bool IMMHandler::IsActiveIMEInBlockList() {
+  if (sIMEName.IsEmpty()) {
+    return false;
+  }
+#ifdef _WIN64
+  // ATOK started to be TIP of TSF since 2011.  Older than it, i.e., ATOK 2010
+  // and earlier have a lot of problems even for daily use.  Perhaps, the
+  // reason is Win 8 has a lot of changes around IMM-IME support and TSF,
+  // and ATOK 2010 is released earlier than Win 8.
+  // ATOK 2006 crashes while converting a word with candidate window.
+  // ATOK 2007 doesn't paint and resize suggest window and candidate window
+  // correctly (showing white window or too big window).
+  // ATOK 2008 and ATOK 2009 crash when user just opens their open state.
+  // ATOK 2010 isn't installable newly on Win 7 or later, but we have a lot of
+  // crash reports.
+  if (IsWin8OrLater() &&
+      (IsATOK2006Active() || IsATOK2007Active() || IsATOK2008Active() ||
+       IsATOK2009Active() || IsATOK2010Active())) {
+    return true;
+  }
+#endif  // #ifdef _WIN64
+  return false;
+}
+
+// static
+void IMMHandler::EnsureHandlerInstance() {
+  if (!gIMMHandler) {
+    gIMMHandler = new IMMHandler();
+  }
+}
+
+// static
+void IMMHandler::Initialize() {
+  if (!sWM_MSIME_MOUSE) {
+    sWM_MSIME_MOUSE = ::RegisterWindowMessage(RWM_MOUSE);
+  }
+  sAssumeVerticalWritingModeNotSupported = Preferences::GetBool(
+      "intl.imm.vertical_writing.always_assume_not_supported", false);
+  InitKeyboardLayout(nullptr, ::GetKeyboardLayout(0));
+}
+
+// static
+void IMMHandler::Terminate() {
+  if (!gIMMHandler) return;
+  delete gIMMHandler;
+  gIMMHandler = nullptr;
+}
+
+// static
+bool IMMHandler::IsComposingOnOurEditor() {
+  return gIMMHandler && gIMMHandler->mIsComposing;
+}
+
+// static
+bool IMMHandler::IsComposingWindow(nsWindow* aWindow) {
+  return gIMMHandler && gIMMHandler->mComposingWindow == aWindow;
+}
+
+// static
+bool IMMHandler::IsTopLevelWindowOfComposition(nsWindow* aWindow) {
+  if (!gIMMHandler || !gIMMHandler->mComposingWindow) {
+    return false;
+  }
+  HWND wnd = gIMMHandler->mComposingWindow->GetWindowHandle();
+  return WinUtils::GetTopLevelHWND(wnd, true) == aWindow->GetWindowHandle();
+}
+
+// static
+bool IMMHandler::ShouldDrawCompositionStringOurselves() {
+  // If current IME has special UI or its composition window should not
+  // positioned to caret position, we should now draw composition string
+  // ourselves.
+  return !(sIMEProperty & IME_PROP_SPECIAL_UI) &&
+         (sIMEProperty & IME_PROP_AT_CARET);
+}
+
+// static
+bool IMMHandler::IsVerticalWritingSupported() {
+  // Even if IME claims that they support vertical writing mode but it may not
+  // support vertical writing mode for its candidate window.
+  if (sAssumeVerticalWritingModeNotSupported) {
+    return false;
+  }
+  // Google Japanese Input doesn't support vertical writing mode.  We should
+  // return false if it's active IME.
+  if (IsGoogleJapaneseInputActive()) {
+    return false;
+  }
+  return !!(sIMEUIProperty & (UI_CAP_2700 | UI_CAP_ROT90 | UI_CAP_ROTANY));
+}
+
+// static
+void IMMHandler::InitKeyboardLayout(nsWindow* aWindow, HKL aKeyboardLayout) {
+  UINT IMENameLength = ::ImmGetDescriptionW(aKeyboardLayout, nullptr, 0);
+  if (IMENameLength) {
+    // Add room for the terminating null character
+    sIMEName.SetLength(++IMENameLength);
+    IMENameLength =
+        ::ImmGetDescriptionW(aKeyboardLayout, sIMEName.get(), IMENameLength);
+    // Adjust the length to ignore the terminating null character
+    sIMEName.SetLength(IMENameLength);
+  } else {
+    sIMEName.Truncate();
+  }
+
+  WORD langID = LOWORD(aKeyboardLayout);
+  ::GetLocaleInfoW(MAKELCID(langID, SORT_DEFAULT),
+                   LOCALE_IDEFAULTANSICODEPAGE | LOCALE_RETURN_NUMBER,
+                   (PWSTR)&sCodePage, sizeof(sCodePage) / sizeof(WCHAR));
+  sIMEProperty = ::ImmGetProperty(aKeyboardLayout, IGP_PROPERTY);
+  sIMEUIProperty = ::ImmGetProperty(aKeyboardLayout, IGP_UI);
+
+  // If active IME is a TIP of TSF, we cannot retrieve the name with IMM32 API.
+  // For hacking some bugs of some TIP, we should set an IME name from the
+  // pref.
+  if (sCodePage == 932 && sIMEName.IsEmpty()) {
+    Preferences::GetString("intl.imm.japanese.assume_active_tip_name_as",
+                           sIMEName);
+  }
+
+  // Whether the IME supports vertical writing mode might be changed or
+  // some IMEs may need specific font for their UI.  Therefore, we should
+  // update composition font forcibly here.
+  if (aWindow) {
+    MaybeAdjustCompositionFont(aWindow, sWritingModeOfCompositionFont, true);
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::InitKeyboardLayout, aKeyboardLayout=%p (\"%s\"), "
+           "sCodePage=%u, sIMEProperty=%s, sIMEUIProperty=%s",
+           aKeyboardLayout, NS_ConvertUTF16toUTF8(sIMEName).get(), sCodePage,
+           GetIMEGeneralPropertyName(sIMEProperty).get(),
+           GetIMEUIPropertyName(sIMEUIProperty).get()));
+}
+
+// static
+UINT IMMHandler::GetKeyboardCodePage() { return sCodePage; }
+
+// static
+IMENotificationRequests IMMHandler::GetIMENotificationRequests() {
+  return IMENotificationRequests(
+      IMENotificationRequests::NOTIFY_POSITION_CHANGE |
+      IMENotificationRequests::NOTIFY_MOUSE_BUTTON_EVENT_ON_CHAR);
+}
+
+// used for checking the lParam of WM_IME_COMPOSITION
+#define IS_COMPOSING_LPARAM(lParam) \
+  ((lParam) & (GCS_COMPSTR | GCS_COMPATTR | GCS_COMPCLAUSE | GCS_CURSORPOS))
+#define IS_COMMITTING_LPARAM(lParam) ((lParam)&GCS_RESULTSTR)
+// Some IMEs (e.g., the standard IME for Korean) don't have caret position,
+// then, we should not set caret position to compositionchange event.
+#define NO_IME_CARET -1
+
+IMMHandler::IMMHandler()
+    : mComposingWindow(nullptr),
+      mCursorPosition(NO_IME_CARET),
+      mCompositionStart(0),
+      mIsComposing(false) {
+  MOZ_LOG(gIMELog, LogLevel::Debug, ("IMMHandler::IMMHandler is created"));
+}
+
+IMMHandler::~IMMHandler() {
+  if (mIsComposing) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  IMMHandler::~IMMHandler, ERROR, the instance is still composing"));
+  }
+  MOZ_LOG(gIMELog, LogLevel::Debug, ("IMMHandler::IMMHandler is destroyed"));
+}
+
+nsresult IMMHandler::EnsureClauseArray(int32_t aCount) {
+  NS_ENSURE_ARG_MIN(aCount, 0);
+  mClauseArray.SetCapacity(aCount + 32);
+  return NS_OK;
+}
+
+nsresult IMMHandler::EnsureAttributeArray(int32_t aCount) {
+  NS_ENSURE_ARG_MIN(aCount, 0);
+  mAttributeArray.SetCapacity(aCount + 64);
+  return NS_OK;
+}
+
+// static
+void IMMHandler::CommitComposition(nsWindow* aWindow, bool aForce) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CommitComposition, aForce=%s, aWindow=%p, hWnd=%p, "
+           "mComposingWindow=%p%s",
+           GetBoolName(aForce), aWindow, aWindow->GetWindowHandle(),
+           gIMMHandler ? gIMMHandler->mComposingWindow : nullptr,
+           gIMMHandler && gIMMHandler->mComposingWindow
+               ? IsComposingOnOurEditor() ? " (composing on editor)"
+                                          : " (composing on plug-in)"
+               : ""));
+  if (!aForce && !IsComposingWindow(aWindow)) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  bool associated = context.AssociateDefaultContext();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::CommitComposition, associated=%s",
+           GetBoolName(associated)));
+
+  if (context.IsValid()) {
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_COMPLETE, 0);
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+  }
+
+  if (associated) {
+    context.Disassociate();
+  }
+}
+
+// static
+void IMMHandler::CancelComposition(nsWindow* aWindow, bool aForce) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CancelComposition, aForce=%s, aWindow=%p, hWnd=%p, "
+           "mComposingWindow=%p%s",
+           GetBoolName(aForce), aWindow, aWindow->GetWindowHandle(),
+           gIMMHandler ? gIMMHandler->mComposingWindow : nullptr,
+           gIMMHandler && gIMMHandler->mComposingWindow
+               ? IsComposingOnOurEditor() ? " (composing on editor)"
+                                          : " (composing on plug-in)"
+               : ""));
+  if (!aForce && !IsComposingWindow(aWindow)) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  bool associated = context.AssociateDefaultContext();
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::CancelComposition, associated=%s",
+           GetBoolName(associated)));
+
+  if (context.IsValid()) {
+    ::ImmNotifyIME(context.get(), NI_COMPOSITIONSTR, CPS_CANCEL, 0);
+  }
+
+  if (associated) {
+    context.Disassociate();
+  }
+}
+
+// static
+void IMMHandler::OnFocusChange(bool aFocus, nsWindow* aWindow) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnFocusChange(aFocus=%s, aWindow=%p), sHasFocus=%s, "
+           "IsComposingWindow(aWindow)=%s, aWindow->Destroyed()=%s",
+           GetBoolName(aFocus), aWindow, GetBoolName(sHasFocus),
+           GetBoolName(IsComposingWindow(aWindow)),
+           GetBoolName(aWindow->Destroyed())));
+
+  if (!aFocus) {
+    IMEHandler::MaybeDestroyNativeCaret();
+    if (IsComposingWindow(aWindow) && aWindow->Destroyed()) {
+      CancelComposition(aWindow);
+    }
+  }
+  if (gIMMHandler) {
+    gIMMHandler->mContentSelection.reset();
+  }
+  sHasFocus = aFocus;
+}
+
+// static
+void IMMHandler::OnUpdateComposition(nsWindow* aWindow) {
+  if (!gIMMHandler) {
+    return;
+  }
+
+  IMEContext context(aWindow);
+  gIMMHandler->SetIMERelatedWindowsPos(aWindow, context);
+}
+
+// static
+void IMMHandler::OnSelectionChange(nsWindow* aWindow,
+                                   const IMENotification& aIMENotification,
+                                   bool aIsIMMActive) {
+  if (!aIMENotification.mSelectionChangeData.mCausedByComposition &&
+      aIsIMMActive) {
+    MaybeAdjustCompositionFont(
+        aWindow, aIMENotification.mSelectionChangeData.GetWritingMode());
+  }
+  // MaybeAdjustCompositionFont() may create gIMMHandler.  So, check it
+  // after a call of MaybeAdjustCompositionFont().
+  if (gIMMHandler) {
+    gIMMHandler->mContentSelection =
+        Some(ContentSelection(aIMENotification.mSelectionChangeData));
+  }
+}
+
+// static
+void IMMHandler::MaybeAdjustCompositionFont(nsWindow* aWindow,
+                                            const WritingMode& aWritingMode,
+                                            bool aForceUpdate) {
+  switch (sCodePage) {
+    case 932:  // Japanese Shift-JIS
+    case 936:  // Simlified Chinese GBK
+    case 949:  // Korean
+    case 950:  // Traditional Chinese Big5
+      EnsureHandlerInstance();
+      break;
+    default:
+      // If there is no instance of nsIMM32Hander, we shouldn't waste footprint.
+      if (!gIMMHandler) {
+        return;
+      }
+  }
+
+  // Like Navi-Bar of ATOK, some IMEs may require proper composition font even
+  // before sending WM_IME_STARTCOMPOSITION.
+  IMEContext context(aWindow);
+  gIMMHandler->AdjustCompositionFont(aWindow, context, aWritingMode,
+                                     aForceUpdate);
+}
+
+// static
+bool IMMHandler::ProcessInputLangChangeMessage(nsWindow* aWindow, WPARAM wParam,
+                                               LPARAM lParam,
+                                               MSGResult& aResult) {
+  aResult.mResult = 0;
+  aResult.mConsumed = false;
+  // We don't need to create the instance of the handler here.
+  if (gIMMHandler) {
+    gIMMHandler->OnInputLangChange(aWindow, wParam, lParam, aResult);
+  }
+  InitKeyboardLayout(aWindow, reinterpret_cast<HKL>(lParam));
+  // We can release the instance here, because the instance may be never
+  // used. E.g., the new keyboard layout may not use IME, or it may use TSF.
+  Terminate();
+  // Don't return as "processed", the messages should be processed on nsWindow
+  // too.
+  return false;
+}
+
+// static
+bool IMMHandler::ProcessMessage(nsWindow* aWindow, UINT msg, WPARAM& wParam,
+                                LPARAM& lParam, MSGResult& aResult) {
+  // XXX We store the composing window in mComposingWindow.  If IME messages are
+  // sent to different window, we should commit the old transaction.  And also
+  // if the new window handle is not focused, probably, we should not start
+  // the composition, however, such case should not be, it's just bad scenario.
+
+  aResult.mResult = 0;
+  switch (msg) {
+    case WM_INPUTLANGCHANGE:
+      return ProcessInputLangChangeMessage(aWindow, wParam, lParam, aResult);
+    case WM_IME_STARTCOMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEStartComposition(aWindow, aResult);
+    case WM_IME_COMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEComposition(aWindow, wParam, lParam, aResult);
+    case WM_IME_ENDCOMPOSITION:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMEEndComposition(aWindow, aResult);
+    case WM_IME_CHAR:
+      return OnIMEChar(aWindow, wParam, lParam, aResult);
+    case WM_IME_NOTIFY:
+      return OnIMENotify(aWindow, wParam, lParam, aResult);
+    case WM_IME_REQUEST:
+      EnsureHandlerInstance();
+      return gIMMHandler->OnIMERequest(aWindow, wParam, lParam, aResult);
+    case WM_IME_SELECT:
+      return OnIMESelect(aWindow, wParam, lParam, aResult);
+    case WM_IME_SETCONTEXT:
+      return OnIMESetContext(aWindow, wParam, lParam, aResult);
+    case WM_KEYDOWN:
+      return OnKeyDownEvent(aWindow, wParam, lParam, aResult);
+    case WM_CHAR:
+      if (!gIMMHandler) {
+        return false;
+      }
+      return gIMMHandler->OnChar(aWindow, wParam, lParam, aResult);
+    default:
+      return false;
+  };
+}
+
+/****************************************************************************
+ * message handlers
+ ****************************************************************************/
+
+void IMMHandler::OnInputLangChange(nsWindow* aWindow, WPARAM wParam,
+                                   LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnInputLangChange, hWnd=%p, wParam=%08zx, "
+           "lParam=%08" PRIxLPTR,
+           aWindow->GetWindowHandle(), wParam, lParam));
+
+  aWindow->NotifyIME(REQUEST_TO_COMMIT_COMPOSITION);
+  NS_ASSERTION(!mIsComposing, "ResetInputState failed");
+
+  if (mIsComposing) {
+    HandleEndComposition(aWindow);
+  }
+
+  aResult.mConsumed = false;
+}
+
+bool IMMHandler::OnIMEStartComposition(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEStartComposition, hWnd=%p, mIsComposing=%s",
+           aWindow->GetWindowHandle(), GetBoolName(mIsComposing)));
+  aResult.mConsumed = ShouldDrawCompositionStringOurselves();
+  if (mIsComposing) {
+    NS_WARNING("Composition has been already started");
+    return true;
+  }
+
+  IMEContext context(aWindow);
+  HandleStartComposition(aWindow, context);
+  return true;
+}
+
+bool IMMHandler::OnIMEComposition(nsWindow* aWindow, WPARAM wParam,
+                                  LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnIMEComposition, hWnd=%p, lParam=%08" PRIxLPTR
+       ", mIsComposing=%s, "
+       "GCS_RESULTSTR=%s, GCS_COMPSTR=%s, GCS_COMPATTR=%s, GCS_COMPCLAUSE=%s, "
+       "GCS_CURSORPOS=%s,",
+       aWindow->GetWindowHandle(), lParam, GetBoolName(mIsComposing),
+       GetBoolName(lParam & GCS_RESULTSTR), GetBoolName(lParam & GCS_COMPSTR),
+       GetBoolName(lParam & GCS_COMPATTR), GetBoolName(lParam & GCS_COMPCLAUSE),
+       GetBoolName(lParam & GCS_CURSORPOS)));
+
+  IMEContext context(aWindow);
+  aResult.mConsumed = HandleComposition(aWindow, context, lParam);
+  return true;
+}
+
+bool IMMHandler::OnIMEEndComposition(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEEndComposition, hWnd=%p, mIsComposing=%s",
+           aWindow->GetWindowHandle(), GetBoolName(mIsComposing)));
+
+  aResult.mConsumed = ShouldDrawCompositionStringOurselves();
+  if (!mIsComposing) {
+    return true;
+  }
+
+  // Korean IME posts WM_IME_ENDCOMPOSITION first when we hit space during
+  // composition. Then, we should ignore the message and commit the composition
+  // string at following WM_IME_COMPOSITION.
+  MSG compositionMsg;
+  if (WinUtils::PeekMessage(&compositionMsg, aWindow->GetWindowHandle(),
+                            WM_IME_STARTCOMPOSITION, WM_IME_COMPOSITION,
+                            PM_NOREMOVE) &&
+      compositionMsg.message == WM_IME_COMPOSITION &&
+      IS_COMMITTING_LPARAM(compositionMsg.lParam)) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMEEndComposition, WM_IME_ENDCOMPOSITION is "
+             "followed by WM_IME_COMPOSITION, ignoring the message..."));
+    return true;
+  }
+
+  // Otherwise, e.g., ChangJie doesn't post WM_IME_COMPOSITION before
+  // WM_IME_ENDCOMPOSITION when composition string becomes empty.
+  // Then, we should dispatch a compositionupdate event, a compositionchange
+  // event and a compositionend event.
+  // XXX Shouldn't we dispatch the compositionchange event with actual or
+  //     latest composition string?
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::OnIMEEndComposition, mCompositionString=\"%s\"%s",
+           NS_ConvertUTF16toUTF8(mCompositionString).get(),
+           mCompositionString.IsEmpty() ? "" : ", but canceling it..."));
+
+  HandleEndComposition(aWindow, &EmptyString());
+
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMEChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                           MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMEChar, hWnd=%p, char=%08zx",
+           aWindow->GetWindowHandle(), wParam));
+
+  // We don't need to fire any compositionchange events from here. This method
+  // will be called when the composition string of the current IME is not drawn
+  // by us and some characters are committed. In that case, the committed
+  // string was processed in nsWindow::OnIMEComposition already.
+
+  // We need to consume the message so that Windows don't send two WM_CHAR msgs
+  aResult.mConsumed = true;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMECompositionFull(nsWindow* aWindow, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMECompositionFull, hWnd=%p",
+           aWindow->GetWindowHandle()));
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMENotify(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                             MSGResult& aResult) {
+  switch (wParam) {
+    case IMN_CHANGECANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CHANGECANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_CLOSECANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CLOSECANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_CLOSESTATUSWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_CLOSESTATUSWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_GUIDELINE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_GUIDELINE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_OPENCANDIDATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_OPENCANDIDATE, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_OPENSTATUSWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_OPENSTATUSWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCANDIDATEPOS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCANDIDATEPOS, "
+               "lParam=%08" PRIxLPTR,
+               aWindow->GetWindowHandle(), lParam));
+      break;
+    case IMN_SETCOMPOSITIONFONT:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCOMPOSITIONFONT",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCOMPOSITIONWINDOW:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCOMPOSITIONWINDOW",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETCONVERSIONMODE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETCONVERSIONMODE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETOPENSTATUS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETOPENSTATUS",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETSENTENCEMODE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETSENTENCEMODE",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_SETSTATUSWINDOWPOS:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_SETSTATUSWINDOWPOS",
+               aWindow->GetWindowHandle()));
+      break;
+    case IMN_PRIVATE:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMENotify, hWnd=%p, IMN_PRIVATE",
+               aWindow->GetWindowHandle()));
+      break;
+  }
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+bool IMMHandler::OnIMERequest(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                              MSGResult& aResult) {
+  switch (wParam) {
+    case IMR_RECONVERTSTRING:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_RECONVERTSTRING",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed = HandleReconvert(aWindow, lParam, &aResult.mResult);
+      return true;
+    case IMR_QUERYCHARPOSITION:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_QUERYCHARPOSITION",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed =
+          HandleQueryCharPosition(aWindow, lParam, &aResult.mResult);
+      return true;
+    case IMR_DOCUMENTFEED:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, IMR_DOCUMENTFEED",
+               aWindow->GetWindowHandle()));
+      aResult.mConsumed = HandleDocumentFeed(aWindow, lParam, &aResult.mResult);
+      return true;
+    default:
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::OnIMERequest, hWnd=%p, wParam=%08zx",
+               aWindow->GetWindowHandle(), wParam));
+      aResult.mConsumed = false;
+      return true;
+  }
+}
+
+// static
+bool IMMHandler::OnIMESelect(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                             MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnIMESelect, hWnd=%p, wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam));
+
+  // not implement yet
+  aResult.mConsumed = false;
+  return true;
+}
+
+// static
+bool IMMHandler::OnIMESetContext(nsWindow* aWindow, WPARAM wParam,
+                                 LPARAM lParam, MSGResult& aResult) {
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnIMESetContext, hWnd=%p, %s, lParam=%08" PRIxLPTR,
+           aWindow->GetWindowHandle(), wParam ? "Active" : "Deactive", lParam));
+
+  aResult.mConsumed = false;
+
+  // NOTE: If the aWindow is top level window of the composing window because
+  // when a window on deactive window gets focus, WM_IME_SETCONTEXT (wParam is
+  // TRUE) is sent to the top level window first.  After that,
+  // WM_IME_SETCONTEXT (wParam is FALSE) is sent to the top level window.
+  // Finally, WM_IME_SETCONTEXT (wParam is TRUE) is sent to the focused window.
+  // The top level window never becomes composing window, so, we can ignore
+  // the WM_IME_SETCONTEXT on the top level window.
+  if (IsTopLevelWindowOfComposition(aWindow)) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMESetContext, hWnd=%p is top level window",
+             aWindow->GetWindowHandle()));
+    return true;
+  }
+
+  // When IME context is activating on another window,
+  // we should commit the old composition on the old window.
+  bool cancelComposition = false;
+  if (wParam && gIMMHandler) {
+    cancelComposition = gIMMHandler->CommitCompositionOnPreviousWindow(aWindow);
+  }
+
+  if (wParam && (lParam & ISC_SHOWUICOMPOSITIONWINDOW) &&
+      ShouldDrawCompositionStringOurselves()) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::OnIMESetContext, ISC_SHOWUICOMPOSITIONWINDOW is "
+             "removed"));
+    lParam &= ~ISC_SHOWUICOMPOSITIONWINDOW;
+  }
+
+  // We should sent WM_IME_SETCONTEXT to the DefWndProc here because the
+  // ancestor windows shouldn't receive this message.  If they receive the
+  // message, we cannot know whether which window is the target of the message.
+  aResult.mResult = ::DefWindowProc(aWindow->GetWindowHandle(),
+                                    WM_IME_SETCONTEXT, wParam, lParam);
+
+  // Cancel composition on the new window if we committed our composition on
+  // another window.
+  if (cancelComposition) {
+    CancelComposition(aWindow, true);
+  }
+
+  aResult.mConsumed = true;
+  return true;
+}
+
+bool IMMHandler::OnChar(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                        MSGResult& aResult) {
+  // The return value must be same as aResult.mConsumed because only when we
+  // consume the message, the caller shouldn't do anything anymore but
+  // otherwise, the caller should handle the message.
+  aResult.mConsumed = false;
+  if (IsIMECharRecordsEmpty()) {
+    return aResult.mConsumed;
+  }
+  WPARAM recWParam;
+  LPARAM recLParam;
+  DequeueIMECharRecords(recWParam, recLParam);
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnChar, aWindow=%p, wParam=%08zx, lParam=%08" PRIxLPTR ", "
+       "recorded: wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam, recWParam, recLParam));
+  // If an unexpected char message comes, we should reset the records,
+  // of course, this shouldn't happen.
+  if (recWParam != wParam || recLParam != lParam) {
+    ResetIMECharRecords();
+    return aResult.mConsumed;
+  }
+  // Eat the char message which is caused by WM_IME_CHAR because we should
+  // have processed the IME messages, so, this message could be come from
+  // a windowless plug-in.
+  aResult.mConsumed = true;
+  return aResult.mConsumed;
+}
+
+/****************************************************************************
+ * others
+ ****************************************************************************/
+
+TextEventDispatcher* IMMHandler::GetTextEventDispatcherFor(nsWindow* aWindow) {
+  return aWindow == mComposingWindow && mDispatcher
+             ? mDispatcher.get()
+             : aWindow->GetTextEventDispatcher();
+}
+
+void IMMHandler::HandleStartComposition(nsWindow* aWindow,
+                                        const IMEContext& aContext) {
+  MOZ_ASSERT(!mIsComposing,
+             "HandleStartComposition is called but mIsComposing is TRUE");
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return;
+  }
+  if (!contentSelection->HasRange()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "there is no selection"));
+    return;
+  }
+
+  AdjustCompositionFont(aWindow, aContext, contentSelection->WritingModeRef());
+
+  mCompositionStart = contentSelection->OffsetAndDataRef().StartOffset();
+  mCursorPosition = NO_IME_CARET;
+
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->StartComposition(status, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "TextEventDispatcher::StartComposition() failure"));
+    return;
+  }
+
+  mIsComposing = true;
+  mComposingWindow = aWindow;
+  mDispatcher = dispatcher;
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleStartComposition, START composition, "
+           "mCompositionStart=%u",
+           mCompositionStart));
+}
+
+bool IMMHandler::HandleComposition(nsWindow* aWindow,
+                                   const IMEContext& aContext, LPARAM lParam) {
+  // for bug #60050
+  // MS-IME 95/97/98/2000 may send WM_IME_COMPOSITION with non-conversion
+  // mode before it send WM_IME_STARTCOMPOSITION.
+  // However, ATOK sends a WM_IME_COMPOSITION before WM_IME_STARTCOMPOSITION,
+  // and if we access ATOK via some APIs, ATOK will sometimes fail to
+  // initialize its state.  If WM_IME_STARTCOMPOSITION is already in the
+  // message queue, we should ignore the strange WM_IME_COMPOSITION message and
+  // skip to the next.  So, we should look for next composition message
+  // (WM_IME_STARTCOMPOSITION or WM_IME_ENDCOMPOSITION or WM_IME_COMPOSITION),
+  // and if it's WM_IME_STARTCOMPOSITION, and one more next composition message
+  // is WM_IME_COMPOSITION, current IME is ATOK, probably.  Otherwise, we
+  // should start composition forcibly.
+  if (!mIsComposing) {
+    MSG msg1, msg2;
+    HWND wnd = aWindow->GetWindowHandle();
+    if (WinUtils::PeekMessage(&msg1, wnd, WM_IME_STARTCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
+        msg1.message == WM_IME_STARTCOMPOSITION &&
+        WinUtils::PeekMessage(&msg2, wnd, WM_IME_ENDCOMPOSITION,
+                              WM_IME_COMPOSITION, PM_NOREMOVE) &&
+        msg2.message == WM_IME_COMPOSITION) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("IMMHandler::HandleComposition, Ignores due to find a "
+               "WM_IME_STARTCOMPOSITION"));
+      return ShouldDrawCompositionStringOurselves();
+    }
+  }
+
+  bool startCompositionMessageHasBeenSent = mIsComposing;
+
+  //
+  // This catches a fixed result
+  //
+  if (IS_COMMITTING_LPARAM(lParam)) {
+    if (!mIsComposing) {
+      HandleStartComposition(aWindow, aContext);
+    }
+
+    GetCompositionString(aContext, GCS_RESULTSTR, mCompositionString);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleComposition, GCS_RESULTSTR"));
+
+    HandleEndComposition(aWindow, &mCompositionString);
+
+    if (!IS_COMPOSING_LPARAM(lParam)) {
+      return ShouldDrawCompositionStringOurselves();
+    }
+  }
+
+  //
+  // This provides us with a composition string
+  //
+  if (!mIsComposing) {
+    HandleStartComposition(aWindow, aContext);
+  }
+
+  //--------------------------------------------------------
+  // 1. Get GCS_COMPSTR
+  //--------------------------------------------------------
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleComposition, GCS_COMPSTR"));
+
+  nsAutoString previousCompositionString(mCompositionString);
+  GetCompositionString(aContext, GCS_COMPSTR, mCompositionString);
+
+  if (!IS_COMPOSING_LPARAM(lParam)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("  IMMHandler::HandleComposition, lParam doesn't indicate composing, "
+         "mCompositionString=\"%s\", previousCompositionString=\"%s\"",
+         NS_ConvertUTF16toUTF8(mCompositionString).get(),
+         NS_ConvertUTF16toUTF8(previousCompositionString).get()));
+
+    // If composition string isn't changed, we can trust the lParam.
+    // So, we need to do nothing.
+    if (previousCompositionString == mCompositionString) {
+      return ShouldDrawCompositionStringOurselves();
+    }
+
+    // IME may send WM_IME_COMPOSITION without composing lParam values
+    // when composition string becomes empty (e.g., using Backspace key).
+    // If composition string is empty, we should dispatch a compositionchange
+    // event with empty string and clear the clause information.
+    if (mCompositionString.IsEmpty()) {
+      mClauseArray.Clear();
+      mAttributeArray.Clear();
+      mCursorPosition = 0;
+      DispatchCompositionChangeEvent(aWindow, aContext);
+      return ShouldDrawCompositionStringOurselves();
+    }
+
+    // Otherwise, we cannot trust the lParam value.  We might need to
+    // dispatch compositionchange event with the latest composition string
+    // information.
+  }
+
+  // See https://bugzilla.mozilla.org/show_bug.cgi?id=296339
+  if (mCompositionString.IsEmpty() && !startCompositionMessageHasBeenSent) {
+    // In this case, maybe, the sender is MSPinYin. That sends *only*
+    // WM_IME_COMPOSITION with GCS_COMP* and GCS_RESULT* when
+    // user inputted the Chinese full stop. So, that doesn't send
+    // WM_IME_STARTCOMPOSITION and WM_IME_ENDCOMPOSITION.
+    // If WM_IME_STARTCOMPOSITION was not sent and the composition
+    // string is null (it indicates the composition transaction ended),
+    // WM_IME_ENDCOMPOSITION may not be sent. If so, we cannot run
+    // HandleEndComposition() in other place.
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("    IMMHandler::HandleComposition, Aborting GCS_COMPSTR"));
+    HandleEndComposition(aWindow);
+    return IS_COMMITTING_LPARAM(lParam);
+  }
+
+  //--------------------------------------------------------
+  // 2. Get GCS_COMPCLAUSE
+  //--------------------------------------------------------
+  long clauseArrayLength =
+      ::ImmGetCompositionStringW(aContext.get(), GCS_COMPCLAUSE, nullptr, 0);
+  clauseArrayLength /= sizeof(uint32_t);
+
+  if (clauseArrayLength > 0) {
+    nsresult rv = EnsureClauseArray(clauseArrayLength);
+    NS_ENSURE_SUCCESS(rv, false);
+
+    // Intelligent ABC IME (Simplified Chinese IME, the code page is 936)
+    // will crash in ImmGetCompositionStringW for GCS_COMPCLAUSE (bug 424663).
+    // See comment 35 of the bug for the detail. Therefore, we should use A
+    // API for it, however, we should not kill Unicode support on all IMEs.
+    bool useA_API = !(sIMEProperty & IME_PROP_UNICODE);
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::HandleComposition, GCS_COMPCLAUSE, useA_API=%s",
+             useA_API ? "TRUE" : "FALSE"));
+
+    long clauseArrayLength2 =
+        useA_API ? ::ImmGetCompositionStringA(
+                       aContext.get(), GCS_COMPCLAUSE, mClauseArray.Elements(),
+                       mClauseArray.Capacity() * sizeof(uint32_t))
+                 : ::ImmGetCompositionStringW(
+                       aContext.get(), GCS_COMPCLAUSE, mClauseArray.Elements(),
+                       mClauseArray.Capacity() * sizeof(uint32_t));
+    clauseArrayLength2 /= sizeof(uint32_t);
+
+    if (clauseArrayLength != clauseArrayLength2) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("    IMMHandler::HandleComposition, GCS_COMPCLAUSE, "
+               "clauseArrayLength=%ld but clauseArrayLength2=%ld",
+               clauseArrayLength, clauseArrayLength2));
+      if (clauseArrayLength > clauseArrayLength2)
+        clauseArrayLength = clauseArrayLength2;
+    }
+
+    if (useA_API && clauseArrayLength > 0) {
+      // Convert each values of sIMECompClauseArray. The values mean offset of
+      // the clauses in ANSI string. But we need the values in Unicode string.
+      nsAutoCString compANSIStr;
+      if (ConvertToANSIString(mCompositionString, GetKeyboardCodePage(),
+                              compANSIStr)) {
+        uint32_t maxlen = compANSIStr.Length();
+        mClauseArray.SetLength(clauseArrayLength);
+        mClauseArray[0] = 0;  // first value must be 0
+        for (int32_t i = 1; i < clauseArrayLength; i++) {
+          uint32_t len = std::min(mClauseArray[i], maxlen);
+          mClauseArray[i] =
+              ::MultiByteToWideChar(GetKeyboardCodePage(), MB_PRECOMPOSED,
+                                    (LPCSTR)compANSIStr.get(), len, nullptr, 0);
+        }
+      }
+    }
+  }
+  // compClauseArrayLength may be negative. I.e., ImmGetCompositionStringW
+  // may return an error code.
+  mClauseArray.SetLength(std::max<long>(0, clauseArrayLength));
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::HandleComposition, GCS_COMPCLAUSE, mClauseLength=%zu",
+           mClauseArray.Length()));
+
+  //--------------------------------------------------------
+  // 3. Get GCS_COMPATTR
+  //--------------------------------------------------------
+  // This provides us with the attribute string necessary
+  // for doing hiliting
+  long attrArrayLength =
+      ::ImmGetCompositionStringW(aContext.get(), GCS_COMPATTR, nullptr, 0);
+  attrArrayLength /= sizeof(uint8_t);
+
+  if (attrArrayLength > 0) {
+    nsresult rv = EnsureAttributeArray(attrArrayLength);
+    NS_ENSURE_SUCCESS(rv, false);
+    attrArrayLength = ::ImmGetCompositionStringW(
+        aContext.get(), GCS_COMPATTR, mAttributeArray.Elements(),
+        mAttributeArray.Capacity() * sizeof(uint8_t));
+  }
+
+  // attrStrLen may be negative. I.e., ImmGetCompositionStringW may return an
+  // error code.
+  mAttributeArray.SetLength(std::max<long>(0, attrArrayLength));
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("  IMMHandler::HandleComposition, GCS_COMPATTR, mAttributeLength=%zu",
+       mAttributeArray.Length()));
+
+  //--------------------------------------------------------
+  // 4. Get GCS_CURSOPOS
+  //--------------------------------------------------------
+  // Some IMEs (e.g., the standard IME for Korean) don't have caret position.
+  if (lParam & GCS_CURSORPOS) {
+    mCursorPosition =
+        ::ImmGetCompositionStringW(aContext.get(), GCS_CURSORPOS, nullptr, 0);
+    if (mCursorPosition < 0) {
+      mCursorPosition = NO_IME_CARET;  // The result is error
+    }
+  } else {
+    mCursorPosition = NO_IME_CARET;
+  }
+
+  NS_ASSERTION(mCursorPosition <= (long)mCompositionString.Length(),
+               "illegal pos");
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("  IMMHandler::HandleComposition, GCS_CURSORPOS, mCursorPosition=%d",
+           mCursorPosition));
+
+  //--------------------------------------------------------
+  // 5. Send the compositionchange event
+  //--------------------------------------------------------
+  DispatchCompositionChangeEvent(aWindow, aContext);
+
+  return ShouldDrawCompositionStringOurselves();
+}
+
+void IMMHandler::HandleEndComposition(nsWindow* aWindow,
+                                      const nsAString* aCommitString) {
+  MOZ_ASSERT(mIsComposing,
+             "HandleEndComposition is called but mIsComposing is FALSE");
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleEndComposition(aWindow=0x%p, aCommitString=0x%p "
+           "(\"%s\"))",
+           aWindow, aCommitString,
+           aCommitString ? NS_ConvertUTF16toUTF8(*aCommitString).get() : ""));
+
+  IMEHandler::MaybeDestroyNativeCaret();
+
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleEndComposition, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->CommitComposition(status, aCommitString, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleStartComposition, FAILED, due to "
+             "TextEventDispatcher::CommitComposition() failure"));
+    return;
+  }
+  mIsComposing = false;
+  // XXX aWindow and mComposingWindow are always same??
+  mComposingWindow = nullptr;
+  mDispatcher = nullptr;
+}
+
+bool IMMHandler::HandleReconvert(nsWindow* aWindow, LPARAM lParam,
+                                 LRESULT* oResult) {
+  *oResult = 0;
+  RECONVERTSTRING* pReconv = reinterpret_cast<RECONVERTSTRING*>(lParam);
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return false;
+  }
+
+  const uint32_t len = contentSelection->HasRange()
+                           ? contentSelection->OffsetAndDataRef().Length()
+                           : 0u;
+  uint32_t needSize = sizeof(RECONVERTSTRING) + len * sizeof(WCHAR);
+
+  if (!pReconv) {
+    // Return need size to reconvert.
+    if (len == 0) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleReconvert, There are not selected text"));
+      return false;
+    }
+    *oResult = needSize;
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleReconvert, succeeded, result=%" PRIdLPTR,
+             *oResult));
+    return true;
+  }
+
+  if (pReconv->dwSize < needSize) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleReconvert, FAILED, pReconv->dwSize=%ld, "
+             "needSize=%u",
+             pReconv->dwSize, needSize));
+    return false;
+  }
+
+  *oResult = needSize;
+
+  // Fill reconvert struct
+  pReconv->dwVersion = 0;
+  pReconv->dwStrLen = len;
+  pReconv->dwStrOffset = sizeof(RECONVERTSTRING);
+  pReconv->dwCompStrLen = len;
+  pReconv->dwCompStrOffset = 0;
+  pReconv->dwTargetStrLen = len;
+  pReconv->dwTargetStrOffset = 0;
+
+  if (len) {
+    ::CopyMemory(reinterpret_cast<LPVOID>(lParam + sizeof(RECONVERTSTRING)),
+                 contentSelection->OffsetAndDataRef().DataRef().get(),
+                 len * sizeof(WCHAR));
+  }
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::HandleReconvert, SUCCEEDED, pReconv=%s, result=%" PRIdLPTR,
+       GetReconvertStringLog(pReconv).get(), *oResult));
+
+  return true;
+}
+
+bool IMMHandler::HandleQueryCharPosition(nsWindow* aWindow, LPARAM lParam,
+                                         LRESULT* oResult) {
+  uint32_t len = mIsComposing ? mCompositionString.Length() : 0;
+  *oResult = false;
+  IMECHARPOSITION* pCharPosition = reinterpret_cast<IMECHARPOSITION*>(lParam);
+  if (!pCharPosition) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleQueryCharPosition, FAILED, due to "
+             "pCharPosition is null"));
+    return false;
+  }
+  if (pCharPosition->dwSize < sizeof(IMECHARPOSITION)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, pCharPosition->dwSize=%lu, "
+             "sizeof(IMECHARPOSITION)=%zu",
+             pCharPosition->dwSize, sizeof(IMECHARPOSITION)));
+    return false;
+  }
+  if (::GetFocus() != aWindow->GetWindowHandle()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleReconvert, FAILED, ::GetFocus()=%p, "
+             "OurWindowHandle=%p",
+             ::GetFocus(), aWindow->GetWindowHandle()));
+    return false;
+  }
+  if (pCharPosition->dwCharPos > len) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleQueryCharPosition, FAILED, "
+             "pCharPosition->dwCharPos=%ld, len=%u",
+             pCharPosition->dwCharPos, len));
+    return false;
+  }
+
+  LayoutDeviceIntRect r;
+  bool ret =
+      GetCharacterRectOfSelectedTextAt(aWindow, pCharPosition->dwCharPos, r);
+  NS_ENSURE_TRUE(ret, false);
+
+  LayoutDeviceIntRect screenRect;
+  // We always need top level window that is owner window of the popup window
+  // even if the content of the popup window has focus.
+  ResolveIMECaretPos(aWindow->GetTopLevelWindow(false), r, nullptr, screenRect);
+
+  // XXX This might need to check writing mode.  However, MSDN doesn't explain
+  //     how to set the values in vertical writing mode. Additionally, IME
+  //     doesn't work well with top-left of the character (this is explicitly
+  //     documented) and its horizontal width.  So, it might be better to set
+  //     top-right corner of the character and horizontal width, but we're not
+  //     sure if it doesn't cause any problems with a lot of IMEs...
+  pCharPosition->pt.x = screenRect.X();
+  pCharPosition->pt.y = screenRect.Y();
+
+  pCharPosition->cLineHeight = r.Height();
+
+  WidgetQueryContentEvent queryEditorRectEvent(true, eQueryEditorRect, aWindow);
+  aWindow->InitEvent(queryEditorRectEvent);
+  DispatchEvent(aWindow, queryEditorRectEvent);
+  if (NS_WARN_IF(queryEditorRectEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleQueryCharPosition, eQueryEditorRect failed"));
+    ::GetWindowRect(aWindow->GetWindowHandle(), &pCharPosition->rcDocument);
+  } else {
+    LayoutDeviceIntRect editorRectInWindow = queryEditorRectEvent.mReply->mRect;
+    nsWindow* window = !!queryEditorRectEvent.mReply->mFocusedWidget
+                           ? static_cast<nsWindow*>(
+                                 queryEditorRectEvent.mReply->mFocusedWidget)
+                           : aWindow;
+    LayoutDeviceIntRect editorRectInScreen;
+    ResolveIMECaretPos(window, editorRectInWindow, nullptr, editorRectInScreen);
+    ::SetRect(&pCharPosition->rcDocument, editorRectInScreen.X(),
+              editorRectInScreen.Y(), editorRectInScreen.XMost(),
+              editorRectInScreen.YMost());
+  }
+
+  *oResult = TRUE;
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::HandleQueryCharPosition, SUCCEEDED, pCharPosition={ "
+       "pt={ x=%ld, y=%ld }, cLineHeight=%d, rcDocument={ left=%ld, top=%ld, "
+       "right=%ld, bottom=%ld } }",
+       pCharPosition->pt.x, pCharPosition->pt.y, pCharPosition->cLineHeight,
+       pCharPosition->rcDocument.left, pCharPosition->rcDocument.top,
+       pCharPosition->rcDocument.right, pCharPosition->rcDocument.bottom));
+  return true;
+}
+
+bool IMMHandler::HandleDocumentFeed(nsWindow* aWindow, LPARAM lParam,
+                                    LRESULT* oResult) {
+  *oResult = 0;
+  RECONVERTSTRING* pReconv = reinterpret_cast<RECONVERTSTRING*>(lParam);
+
+  LayoutDeviceIntPoint point(0, 0);
+
+  bool hasCompositionString =
+      mIsComposing && ShouldDrawCompositionStringOurselves();
+
+  int32_t targetOffset, targetLength;
+  if (!hasCompositionString) {
+    const Maybe<ContentSelection>& contentSelection =
+        GetContentSelectionWithQueryIfNothing(aWindow);
+    if (contentSelection.isNothing()) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleDocumentFeed, FAILED, due to "
+               "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+      return false;
+    }
+    if (contentSelection->HasRange()) {
+      targetOffset = static_cast<int32_t>(
+          contentSelection->OffsetAndDataRef().StartOffset());
+      targetLength =
+          static_cast<int32_t>(contentSelection->OffsetAndDataRef().Length());
+    } else {
+      // If there is no selection range, let's return all text in the editor.
+      targetOffset = 0;
+      targetLength = INT32_MAX;
+    }
+  } else {
+    targetOffset = int32_t(mCompositionStart);
+    targetLength = int32_t(mCompositionString.Length());
+  }
+
+  // XXX nsString::Find and nsString::RFind take int32_t for offset, so,
+  //     we cannot support this message when the current offset is larger than
+  //     INT32_MAX.
+  if (targetOffset < 0 || targetLength < 0 || targetOffset + targetLength < 0) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to the selection is out of range"));
+    return false;
+  }
+
+  // Get all contents of the focused editor.
+  WidgetQueryContentEvent queryTextContentEvent(true, eQueryTextContent,
+                                                aWindow);
+  queryTextContentEvent.InitForQueryTextContent(0, UINT32_MAX);
+  aWindow->InitEvent(queryTextContentEvent, &point);
+  DispatchEvent(aWindow, queryTextContentEvent);
+  if (NS_WARN_IF(queryTextContentEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to eQueryTextContent failure"));
+    return false;
+  }
+
+  nsAutoString str(queryTextContentEvent.mReply->DataRef());
+  if (targetOffset > static_cast<int32_t>(str.Length())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::HandleDocumentFeed, FAILED, "
+             "due to the caret offset is invalid"));
+    return false;
+  }
+
+  // Get the focused paragraph, we decide that it starts from the previous CRLF
+  // (or start of the editor) to the next one (or the end of the editor).
+  int32_t paragraphStart = 0;
+  if (targetOffset > 0) {
+    paragraphStart = Substring(str, 0, targetOffset).RFind(u"\n") + 1;
+  }
+  int32_t paragraphEnd = str.Find(u"\r", targetOffset + targetLength);
+  if (paragraphEnd < 0) {
+    paragraphEnd = str.Length();
+  }
+  nsDependentSubstring paragraph(str, paragraphStart,
+                                 paragraphEnd - paragraphStart);
+
+  uint32_t len = paragraph.Length();
+  uint32_t needSize = sizeof(RECONVERTSTRING) + len * sizeof(WCHAR);
+
+  if (!pReconv) {
+    *oResult = needSize;
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::HandleDocumentFeed, succeeded, result=%" PRIdLPTR,
+             *oResult));
+    return true;
+  }
+
+  if (pReconv->dwSize < needSize) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::HandleDocumentFeed, FAILED, "
+             "pReconv->dwSize=%ld, needSize=%u",
+             pReconv->dwSize, needSize));
+    return false;
+  }
+
+  // Fill reconvert struct
+  pReconv->dwVersion = 0;
+  pReconv->dwStrLen = len;
+  pReconv->dwStrOffset = sizeof(RECONVERTSTRING);
+  if (hasCompositionString) {
+    pReconv->dwCompStrLen = targetLength;
+    pReconv->dwCompStrOffset = (targetOffset - paragraphStart) * sizeof(WCHAR);
+    // Set composition target clause information
+    uint32_t offset, length;
+    if (!GetTargetClauseRange(&offset, &length)) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("IMMHandler::HandleDocumentFeed, FAILED, "
+               "due to IMMHandler::GetTargetClauseRange() failure"));
+      return false;
+    }
+    pReconv->dwTargetStrLen = length;
+    pReconv->dwTargetStrOffset = (offset - paragraphStart) * sizeof(WCHAR);
+  } else {
+    pReconv->dwTargetStrLen = targetLength;
+    pReconv->dwTargetStrOffset =
+        (targetOffset - paragraphStart) * sizeof(WCHAR);
+    // There is no composition string, so, the length is zero but we should
+    // set the cursor offset to the composition str offset.
+    pReconv->dwCompStrLen = 0;
+    pReconv->dwCompStrOffset = pReconv->dwTargetStrOffset;
+  }
+
+  *oResult = needSize;
+  ::CopyMemory(reinterpret_cast<LPVOID>(lParam + sizeof(RECONVERTSTRING)),
+               paragraph.BeginReading(), len * sizeof(WCHAR));
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::HandleDocumentFeed, SUCCEEDED, pReconv=%s, "
+           "result=%" PRIdLPTR,
+           GetReconvertStringLog(pReconv).get(), *oResult));
+
+  return true;
+}
+
+bool IMMHandler::CommitCompositionOnPreviousWindow(nsWindow* aWindow) {
+  if (!mComposingWindow || mComposingWindow == aWindow) {
+    return false;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::CommitCompositionOnPreviousWindow, mIsComposing=%s",
+           GetBoolName(mIsComposing)));
+
+  // If we have composition, we should dispatch composition events internally.
+  if (mIsComposing) {
+    IMEContext context(mComposingWindow);
+    NS_ASSERTION(context.IsValid(), "IME context must be valid");
+
+    HandleEndComposition(mComposingWindow);
+    return true;
+  }
+
+  return false;
+}
+
+static TextRangeType PlatformToNSAttr(uint8_t aAttr) {
+  switch (aAttr) {
+    case ATTR_INPUT_ERROR:
+    // case ATTR_FIXEDCONVERTED:
+    case ATTR_INPUT:
+      return TextRangeType::eRawClause;
+    case ATTR_CONVERTED:
+      return TextRangeType::eConvertedClause;
+    case ATTR_TARGET_NOTCONVERTED:
+      return TextRangeType::eSelectedRawClause;
+    case ATTR_TARGET_CONVERTED:
+      return TextRangeType::eSelectedClause;
+    default:
+      NS_ASSERTION(false, "unknown attribute");
+      return TextRangeType::eCaret;
+  }
+}
+
+// static
+void IMMHandler::DispatchEvent(nsWindow* aWindow, WidgetGUIEvent& aEvent) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::DispatchEvent(aWindow=0x%p, aEvent={ mMessage=%s }, "
+       "aWindow->Destroyed()=%s",
+       aWindow, ToChar(aEvent.mMessage), GetBoolName(aWindow->Destroyed())));
+
+  if (aWindow->Destroyed()) {
+    return;
+  }
+
+  aWindow->DispatchWindowEvent(aEvent);
+}
+
+void IMMHandler::DispatchCompositionChangeEvent(nsWindow* aWindow,
+                                                const IMEContext& aContext) {
+  NS_ASSERTION(mIsComposing, "conflict state");
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::DispatchCompositionChangeEvent"));
+
+  // If we don't need to draw composition string ourselves, we don't need to
+  // fire compositionchange event during composing.
+  if (!ShouldDrawCompositionStringOurselves()) {
+    // But we need to adjust composition window pos and native caret pos, here.
+    SetIMERelatedWindowsPos(aWindow, aContext);
+    return;
+  }
+
+  RefPtr<nsWindow> kungFuDeathGrip(aWindow);
+  RefPtr<TextEventDispatcher> dispatcher = GetTextEventDispatcherFor(aWindow);
+  nsresult rv = dispatcher->BeginNativeInputTransaction();
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to "
+             "TextEventDispatcher::BeginNativeInputTransaction() failure"));
+    return;
+  }
+
+  // NOTE: Calling SetIMERelatedWindowsPos() from this method will be failure
+  //       in e10s mode.  compositionchange event will notify this of
+  //       NOTIFY_IME_OF_COMPOSITION_EVENT_HANDLED, then
+  //       SetIMERelatedWindowsPos() will be called.
+
+  // XXX Sogou (Simplified Chinese IME) returns contradictory values:
+  //     The cursor position is actual cursor position. However, other values
+  //     (composition string and attributes) are empty.
+
+  if (mCompositionString.IsEmpty()) {
+    // Don't append clause information if composition string is empty.
+  } else if (mClauseArray.IsEmpty()) {
+    // Some IMEs don't return clause array information, then, we assume that
+    // all characters in the composition string are in one clause.
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::DispatchCompositionChangeEvent, "
+             "mClauseArray.Length()=0"));
+    rv = dispatcher->SetPendingComposition(mCompositionString, nullptr);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+               "TextEventDispatcher::SetPendingComposition() failure"));
+      return;
+    }
+  } else {
+    // iterate over the attributes
+    rv = dispatcher->SetPendingCompositionString(mCompositionString);
+    if (NS_WARN_IF(NS_FAILED(rv))) {
+      MOZ_LOG(gIMELog, LogLevel::Error,
+              ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+               "TextEventDispatcher::SetPendingCompositionString() failure"));
+      return;
+    }
+    uint32_t lastOffset = 0;
+    for (uint32_t i = 0; i < mClauseArray.Length() - 1; i++) {
+      uint32_t current = mClauseArray[i + 1];
+      if (current > mCompositionString.Length()) {
+        MOZ_LOG(gIMELog, LogLevel::Info,
+                ("  IMMHandler::DispatchCompositionChangeEvent, "
+                 "mClauseArray[%u]=%u. "
+                 "This is larger than mCompositionString.Length()=%zu",
+                 i + 1, current, mCompositionString.Length()));
+        current = int32_t(mCompositionString.Length());
+      }
+
+      uint32_t length = current - lastOffset;
+      if (NS_WARN_IF(lastOffset >= mAttributeArray.Length())) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to "
+                 "invalid data of mClauseArray or mAttributeArray"));
+        return;
+      }
+      TextRangeType textRangeType =
+          PlatformToNSAttr(mAttributeArray[lastOffset]);
+      rv = dispatcher->AppendClauseToPendingComposition(length, textRangeType);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+                 "TextEventDispatcher::AppendClauseToPendingComposition() "
+                 "failure"));
+        return;
+      }
+
+      lastOffset = current;
+
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::DispatchCompositionChangeEvent, index=%u, "
+               "rangeType=%s, range length=%u",
+               i, ToChar(textRangeType), length));
+    }
+  }
+
+  if (mCursorPosition == NO_IME_CARET) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::DispatchCompositionChangeEvent, no caret"));
+  } else {
+    uint32_t cursor = static_cast<uint32_t>(mCursorPosition);
+    if (cursor > mCompositionString.Length()) {
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::CreateTextRangeArray, mCursorPosition=%d. "
+               "This is larger than mCompositionString.Length()=%zu",
+               mCursorPosition, mCompositionString.Length()));
+      cursor = mCompositionString.Length();
+    }
+
+    // If caret is in the target clause, the target clause will be painted as
+    // normal selection range.  Since caret shouldn't be in selection range on
+    // Windows, we shouldn't append caret range in such case.
+    const TextRangeArray* clauses = dispatcher->GetPendingCompositionClauses();
+    const TextRange* targetClause =
+        clauses ? clauses->GetTargetClause() : nullptr;
+    if (targetClause && cursor >= targetClause->mStartOffset &&
+        cursor <= targetClause->mEndOffset) {
+      // Forget the caret position specified by IME since Gecko's caret position
+      // will be at the end of composition string.
+      mCursorPosition = NO_IME_CARET;
+      MOZ_LOG(gIMELog, LogLevel::Info,
+              ("  IMMHandler::CreateTextRangeArray, no caret due to it's in "
+               "the target clause, now, mCursorPosition is NO_IME_CARET"));
+    }
+
+    if (mCursorPosition != NO_IME_CARET) {
+      rv = dispatcher->SetCaretInPendingComposition(cursor, 0);
+      if (NS_WARN_IF(NS_FAILED(rv))) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+             "TextEventDispatcher::SetCaretInPendingComposition() failure"));
+        return;
+      }
+    }
+  }
+
+  WidgetEventTime eventTime = aWindow->CurrentMessageWidgetEventTime();
+  nsEventStatus status;
+  rv = dispatcher->FlushPendingComposition(status, &eventTime);
+  if (NS_WARN_IF(NS_FAILED(rv))) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::DispatchCompositionChangeEvent, FAILED due to"
+             "TextEventDispatcher::FlushPendingComposition() failure"));
+    return;
+  }
+}
+
+void IMMHandler::GetCompositionString(const IMEContext& aContext, DWORD aIndex,
+                                      nsAString& aCompositionString) const {
+  aCompositionString.Truncate();
+
+  // Retrieve the size of the required output buffer.
+  long lRtn = ::ImmGetCompositionStringW(aContext.get(), aIndex, nullptr, 0);
+  if (lRtn < 0 || !aCompositionString.SetLength((lRtn / sizeof(WCHAR)) + 1,
+                                                mozilla::fallible)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::GetCompositionString, FAILED, due to OOM"));
+    return;  // Error or out of memory.
+  }
+
+  // Actually retrieve the composition string information.
+  lRtn = ::ImmGetCompositionStringW(aContext.get(), aIndex,
+                                    (LPVOID)aCompositionString.BeginWriting(),
+                                    lRtn + sizeof(WCHAR));
+  aCompositionString.SetLength(lRtn / sizeof(WCHAR));
+
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::GetCompositionString, succeeded, aCompositionString=\"%s\"",
+       NS_ConvertUTF16toUTF8(aCompositionString).get()));
+}
+
+bool IMMHandler::GetTargetClauseRange(uint32_t* aOffset, uint32_t* aLength) {
+  NS_ENSURE_TRUE(aOffset, false);
+  NS_ENSURE_TRUE(mIsComposing, false);
+  NS_ENSURE_TRUE(ShouldDrawCompositionStringOurselves(), false);
+
+  bool found = false;
+  *aOffset = mCompositionStart;
+  for (uint32_t i = 0; i < mAttributeArray.Length(); i++) {
+    if (mAttributeArray[i] == ATTR_TARGET_NOTCONVERTED ||
+        mAttributeArray[i] == ATTR_TARGET_CONVERTED) {
+      *aOffset = mCompositionStart + i;
+      found = true;
+      break;
+    }
+  }
+
+  if (!aLength) {
+    return true;
+  }
+
+  if (!found) {
+    // The all composition string is targetted when there is no ATTR_TARGET_*
+    // clause. E.g., there is only ATTR_INPUT
+    *aLength = mCompositionString.Length();
+    return true;
+  }
+
+  uint32_t offsetInComposition = *aOffset - mCompositionStart;
+  *aLength = mCompositionString.Length() - offsetInComposition;
+  for (uint32_t i = offsetInComposition; i < mAttributeArray.Length(); i++) {
+    if (mAttributeArray[i] != ATTR_TARGET_NOTCONVERTED &&
+        mAttributeArray[i] != ATTR_TARGET_CONVERTED) {
+      *aLength = i - offsetInComposition;
+      break;
+    }
+  }
+  return true;
+}
+
+bool IMMHandler::ConvertToANSIString(const nsString& aStr, UINT aCodePage,
+                                     nsACString& aANSIStr) {
+  int len = ::WideCharToMultiByte(aCodePage, 0, (LPCWSTR)aStr.get(),
+                                  aStr.Length(), nullptr, 0, nullptr, nullptr);
+  NS_ENSURE_TRUE(len >= 0, false);
+
+  if (!aANSIStr.SetLength(len, mozilla::fallible)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::ConvertToANSIString, FAILED, due to OOM"));
+    return false;
+  }
+  ::WideCharToMultiByte(aCodePage, 0, (LPCWSTR)aStr.get(), aStr.Length(),
+                        (LPSTR)aANSIStr.BeginWriting(), len, nullptr, nullptr);
+  return true;
+}
+
+bool IMMHandler::GetCharacterRectOfSelectedTextAt(
+    nsWindow* aWindow, uint32_t aOffset, LayoutDeviceIntRect& aCharRect,
+    WritingMode* aWritingMode) {
+  LayoutDeviceIntPoint point(0, 0);
+
+  const Maybe<ContentSelection>& contentSelection =
+      GetContentSelectionWithQueryIfNothing(aWindow);
+  if (contentSelection.isNothing()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+             "Selection::GetContentSelectionWithQueryIfNothing() failure"));
+    return false;
+  }
+
+  // If there is neither a selection range nor composition string, cannot return
+  // character rect, of course.
+  if (!contentSelection->HasRange() && !mIsComposing) {
+    MOZ_LOG(gIMELog, LogLevel::Warning,
+            ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+             "there is neither a selection range nor composition string"));
+    return false;
+  }
+
+  // If the offset is larger than the end of composition string or selected
+  // string, we should return false since such case must be a bug of the caller
+  // or the active IME.  If it's an IME's bug, we need to set targetLength to
+  // aOffset.
+  const uint32_t targetLength =
+      mIsComposing ? mCompositionString.Length()
+                   : contentSelection->OffsetAndDataRef().Length();
+  if (NS_WARN_IF(aOffset > targetLength)) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("IMMHandler::GetCharacterRectOfSelectedTextAt, FAILED, due to "
+         "aOffset is too large (aOffset=%u, targetLength=%u, mIsComposing=%s)",
+         aOffset, targetLength, GetBoolName(mIsComposing)));
+    return false;
+  }
+
+  // If there is caret, we might be able to use caret rect.
+  uint32_t caretOffset = UINT32_MAX;
+  // There is a caret only when the normal selection is collapsed.
+  if (contentSelection.isNothing() ||
+      contentSelection->OffsetAndDataRef().IsDataEmpty()) {
+    if (mIsComposing) {
+      // If it's composing, mCursorPosition is the offset to caret in
+      // the composition string.
+      if (mCursorPosition != NO_IME_CARET) {
+        MOZ_ASSERT(mCursorPosition >= 0);
+        caretOffset = mCursorPosition;
+      } else if (!ShouldDrawCompositionStringOurselves() ||
+                 mCompositionString.IsEmpty()) {
+        // Otherwise, if there is no composition string, we should assume that
+        // there is a caret at the start of composition string.
+        caretOffset = 0;
+      }
+    } else {
+      // If there is no composition, the selection offset is the caret offset.
+      caretOffset = 0;
+    }
+  }
+
+  // If there is a caret and retrieving offset is same as the caret offset,
+  // we should use the caret rect.
+  if (aOffset != caretOffset) {
+    WidgetQueryContentEvent queryTextRectEvent(true, eQueryTextRect, aWindow);
+    WidgetQueryContentEvent::Options options;
+    options.mRelativeToInsertionPoint = true;
+    queryTextRectEvent.InitForQueryTextRect(aOffset, 1, options);
+    aWindow->InitEvent(queryTextRectEvent, &point);
+    DispatchEvent(aWindow, queryTextRectEvent);
+    if (queryTextRectEvent.Succeeded()) {
+      aCharRect = queryTextRectEvent.mReply->mRect;
+      if (aWritingMode) {
+        *aWritingMode = queryTextRectEvent.mReply->WritingModeRef();
+      }
+      MOZ_LOG(
+          gIMELog, LogLevel::Debug,
+          ("IMMHandler::GetCharacterRectOfSelectedTextAt, Succeeded, "
+           "aOffset=%u, aCharRect={ x: %d, y: %d, width: %d, height: %d }, "
+           "queryTextRectEvent={ mReply=%s }",
+           aOffset, aCharRect.X(), aCharRect.Y(), aCharRect.Width(),
+           aCharRect.Height(), ToString(queryTextRectEvent.mReply).c_str()));
+      return true;
+    }
+  }
+
+  return GetCaretRect(aWindow, aCharRect, aWritingMode);
+}
+
+bool IMMHandler::GetCaretRect(nsWindow* aWindow,
+                              LayoutDeviceIntRect& aCaretRect,
+                              WritingMode* aWritingMode) {
+  LayoutDeviceIntPoint point(0, 0);
+
+  WidgetQueryContentEvent queryCaretRectEvent(true, eQueryCaretRect, aWindow);
+  WidgetQueryContentEvent::Options options;
+  options.mRelativeToInsertionPoint = true;
+  queryCaretRectEvent.InitForQueryCaretRect(0, options);
+  aWindow->InitEvent(queryCaretRectEvent, &point);
+  DispatchEvent(aWindow, queryCaretRectEvent);
+  if (queryCaretRectEvent.Failed()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Info,
+        ("IMMHandler::GetCaretRect, FAILED, due to eQueryCaretRect failure"));
+    return false;
+  }
+  aCaretRect = queryCaretRectEvent.mReply->mRect;
+  if (aWritingMode) {
+    *aWritingMode = queryCaretRectEvent.mReply->WritingModeRef();
+  }
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::GetCaretRect, SUCCEEDED, "
+           "aCaretRect={ x: %d, y: %d, width: %d, height: %d }, "
+           "queryCaretRectEvent={ mReply=%s }",
+           aCaretRect.X(), aCaretRect.Y(), aCaretRect.Width(),
+           aCaretRect.Height(), ToString(queryCaretRectEvent.mReply).c_str()));
+  return true;
+}
+
+bool IMMHandler::SetIMERelatedWindowsPos(nsWindow* aWindow,
+                                         const IMEContext& aContext) {
+  // Get first character rect of current a normal selected text or a composing
+  // string.
+  WritingMode writingMode;
+  LayoutDeviceIntRect firstSelectedCharRectRelativeToWindow;
+  bool ret = GetCharacterRectOfSelectedTextAt(
+      aWindow, 0, firstSelectedCharRectRelativeToWindow, &writingMode);
+  NS_ENSURE_TRUE(ret, false);
+  nsWindow* toplevelWindow = aWindow->GetTopLevelWindow(false);
+  LayoutDeviceIntRect firstSelectedCharRect;
+  ResolveIMECaretPos(toplevelWindow, firstSelectedCharRectRelativeToWindow,
+                     aWindow, firstSelectedCharRect);
+
+  // Set native caret size/position to our caret. Some IMEs honor it. E.g.,
+  // "Intelligent ABC" (Simplified Chinese) and "MS PinYin 3.0" (Simplified
+  // Chinese) on XP.  But if a11y module is handling native caret, we shouldn't
+  // touch it.
+  if (!IMEHandler::IsA11yHandlingNativeCaret()) {
+    LayoutDeviceIntRect caretRect(firstSelectedCharRect),
+        caretRectRelativeToWindow;
+    if (GetCaretRect(aWindow, caretRectRelativeToWindow)) {
+      ResolveIMECaretPos(toplevelWindow, caretRectRelativeToWindow, aWindow,
+                         caretRect);
+    } else {
+      NS_WARNING("failed to get caret rect");
+      caretRect.SetWidth(1);
+    }
+    IMEHandler::CreateNativeCaret(aWindow, caretRect);
+  }
+
+  if (ShouldDrawCompositionStringOurselves()) {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::SetIMERelatedWindowsPos, Set candidate window"));
+
+    // Get a rect of first character in current target in composition string.
+    LayoutDeviceIntRect firstTargetCharRect, lastTargetCharRect;
+    if (mIsComposing && !mCompositionString.IsEmpty()) {
+      // If there are no targetted selection, we should use it's first character
+      // rect instead.
+      uint32_t offset, length;
+      if (!GetTargetClauseRange(&offset, &length)) {
+        MOZ_LOG(gIMELog, LogLevel::Error,
+                ("  IMMHandler::SetIMERelatedWindowsPos, FAILED, due to "
+                 "GetTargetClauseRange() failure"));
+        return false;
+      }
+      ret =
+          GetCharacterRectOfSelectedTextAt(aWindow, offset - mCompositionStart,
+                                           firstTargetCharRect, &writingMode);
+      NS_ENSURE_TRUE(ret, false);
+      if (length) {
+        ret = GetCharacterRectOfSelectedTextAt(
+            aWindow, offset + length - 1 - mCompositionStart,
+            lastTargetCharRect);
+        NS_ENSURE_TRUE(ret, false);
+      } else {
+        lastTargetCharRect = firstTargetCharRect;
+      }
+    } else {
+      // If there are no composition string, we should use a first character
+      // rect.
+      ret = GetCharacterRectOfSelectedTextAt(aWindow, 0, firstTargetCharRect,
+                                             &writingMode);
+      NS_ENSURE_TRUE(ret, false);
+      lastTargetCharRect = firstTargetCharRect;
+    }
+    ResolveIMECaretPos(toplevelWindow, firstTargetCharRect, aWindow,
+                       firstTargetCharRect);
+    ResolveIMECaretPos(toplevelWindow, lastTargetCharRect, aWindow,
+                       lastTargetCharRect);
+    LayoutDeviceIntRect targetClauseRect;
+    targetClauseRect.UnionRect(firstTargetCharRect, lastTargetCharRect);
+
+    // Move the candidate window to proper position from the target clause as
+    // far as possible.
+    CANDIDATEFORM candForm;
+    candForm.dwIndex = 0;
+    if (!writingMode.IsVertical() || IsVerticalWritingSupported()) {
+      candForm.dwStyle = CFS_EXCLUDE;
+      // Candidate window shouldn't overlap the target clause in any writing
+      // mode.
+      candForm.rcArea.left = targetClauseRect.X();
+      candForm.rcArea.right = targetClauseRect.XMost();
+      candForm.rcArea.top = targetClauseRect.Y();
+      candForm.rcArea.bottom = targetClauseRect.YMost();
+      if (!writingMode.IsVertical()) {
+        // In horizontal layout, current point of interest should be top-left
+        // of the first character.
+        candForm.ptCurrentPos.x = firstTargetCharRect.X();
+        candForm.ptCurrentPos.y = firstTargetCharRect.Y();
+      } else if (writingMode.IsVerticalRL()) {
+        // In vertical layout (RL), candidate window should be positioned right
+        // side of target clause.  However, we don't set vertical writing font
+        // to the IME.  Therefore, the candidate window may be positioned
+        // bottom-left of target clause rect with these information.
+        candForm.ptCurrentPos.x = targetClauseRect.X();
+        candForm.ptCurrentPos.y = targetClauseRect.Y();
+      } else {
+        MOZ_ASSERT(writingMode.IsVerticalLR(), "Did we miss some causes?");
+        // In vertical layout (LR), candidate window should be poisitioned left
+        // side of target clause.  Although, we don't set vertical writing font
+        // to the IME, the candidate window may be positioned bottom-right of
+        // the target clause rect with these information.
+        candForm.ptCurrentPos.x = targetClauseRect.XMost();
+        candForm.ptCurrentPos.y = targetClauseRect.Y();
+      }
+    } else {
+      // If vertical writing is not supported by IME, let's set candidate
+      // window position to the bottom-left of the target clause because
+      // the position must be the safest position to prevent the candidate
+      // window to overlap with the target clause.
+      candForm.dwStyle = CFS_CANDIDATEPOS;
+      candForm.ptCurrentPos.x = targetClauseRect.X();
+      candForm.ptCurrentPos.y = targetClauseRect.YMost();
+    }
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::SetIMERelatedWindowsPos, Calling "
+             "ImmSetCandidateWindow()... ptCurrentPos={ x=%ld, y=%ld }, "
+             "rcArea={ left=%ld, top=%ld, right=%ld, bottom=%ld }, "
+             "writingMode=%s",
+             candForm.ptCurrentPos.x, candForm.ptCurrentPos.y,
+             candForm.rcArea.left, candForm.rcArea.top, candForm.rcArea.right,
+             candForm.rcArea.bottom, ToString(writingMode).c_str()));
+    ::ImmSetCandidateWindow(aContext.get(), &candForm);
+  } else {
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("IMMHandler::SetIMERelatedWindowsPos, Set composition window"));
+
+    // Move the composition window to caret position (if selected some
+    // characters, we should use first character rect of them).
+    // And in this mode, IME adjusts the candidate window position
+    // automatically. So, we don't need to set it.
+    COMPOSITIONFORM compForm;
+    compForm.dwStyle = CFS_POINT;
+    compForm.ptCurrentPos.x = !writingMode.IsVerticalLR()
+                                  ? firstSelectedCharRect.X()
+                                  : firstSelectedCharRect.XMost();
+    compForm.ptCurrentPos.y = firstSelectedCharRect.Y();
+    ::ImmSetCompositionWindow(aContext.get(), &compForm);
+  }
+
+  return true;
+}
+
+void IMMHandler::ResolveIMECaretPos(nsIWidget* aReferenceWidget,
+                                    LayoutDeviceIntRect& aCursorRect,
+                                    nsIWidget* aNewOriginWidget,
+                                    LayoutDeviceIntRect& aOutRect) {
+  aOutRect = aCursorRect;
+
+  if (aReferenceWidget == aNewOriginWidget) return;
+
+  if (aReferenceWidget)
+    aOutRect.MoveBy(aReferenceWidget->WidgetToScreenOffset());
+
+  if (aNewOriginWidget)
+    aOutRect.MoveBy(-aNewOriginWidget->WidgetToScreenOffset());
+}
+
+static void SetHorizontalFontToLogFont(const nsAString& aFontFace,
+                                       LOGFONTW& aLogFont) {
+  aLogFont.lfEscapement = aLogFont.lfOrientation = 0;
+  if (NS_WARN_IF(aFontFace.Length() > LF_FACESIZE - 1)) {
+    memcpy(aLogFont.lfFaceName, L"System", sizeof(L"System"));
+    return;
+  }
+  memcpy(aLogFont.lfFaceName, aFontFace.BeginReading(),
+         aFontFace.Length() * sizeof(wchar_t));
+  aLogFont.lfFaceName[aFontFace.Length()] = 0;
+}
+
+static void SetVerticalFontToLogFont(const nsAString& aFontFace,
+                                     LOGFONTW& aLogFont) {
+  aLogFont.lfEscapement = aLogFont.lfOrientation = 2700;
+  if (NS_WARN_IF(aFontFace.Length() > LF_FACESIZE - 2)) {
+    memcpy(aLogFont.lfFaceName, L"@System", sizeof(L"@System"));
+    return;
+  }
+  aLogFont.lfFaceName[0] = '@';
+  memcpy(&aLogFont.lfFaceName[1], aFontFace.BeginReading(),
+         aFontFace.Length() * sizeof(wchar_t));
+  aLogFont.lfFaceName[aFontFace.Length() + 1] = 0;
+}
+
+void IMMHandler::AdjustCompositionFont(nsWindow* aWindow,
+                                       const IMEContext& aContext,
+                                       const WritingMode& aWritingMode,
+                                       bool aForceUpdate) {
+  // An instance of IMMHandler is destroyed when active IME is changed.
+  // Therefore, we need to store the information which are set to the IM
+  // context to static variables since IM context is never recreated.
+  static bool sCompositionFontsInitialized = false;
+  static nsString sCompositionFont;
+  static bool sCompositionFontPrefDone = false;
+  if (!sCompositionFontPrefDone) {
+    sCompositionFontPrefDone = true;
+    Preferences::GetString("intl.imm.composition_font", sCompositionFont);
+  }
+
+  // If composition font is customized by pref, we need to modify the
+  // composition font of the IME context at first time even if the writing mode
+  // is horizontal.
+  bool setCompositionFontForcibly =
+      aForceUpdate ||
+      (!sCompositionFontsInitialized && !sCompositionFont.IsEmpty());
+
+  static WritingMode sCurrentWritingMode;
+  static nsString sCurrentIMEName;
+  if (!setCompositionFontForcibly &&
+      sWritingModeOfCompositionFont == aWritingMode &&
+      sCurrentIMEName == sIMEName) {
+    // Nothing to do if writing mode isn't being changed.
+    return;
+  }
+
+  // Decide composition fonts for both horizontal writing mode and vertical
+  // writing mode.  If the font isn't specified by the pref, use default
+  // font which is already set to the IM context.  And also in vertical writing
+  // mode, insert '@' to the start of the font.
+  if (!sCompositionFontsInitialized) {
+    sCompositionFontsInitialized = true;
+    // sCompositionFontH must not start with '@' and its length is less than
+    // LF_FACESIZE since it needs to end with null terminating character.
+    if (sCompositionFont.IsEmpty() ||
+        sCompositionFont.Length() > LF_FACESIZE - 1 ||
+        sCompositionFont[0] == '@') {
+      LOGFONTW defaultLogFont;
+      if (NS_WARN_IF(
+              !::ImmGetCompositionFont(aContext.get(), &defaultLogFont))) {
+        MOZ_LOG(
+            gIMELog, LogLevel::Error,
+            ("  IMMHandler::AdjustCompositionFont, ::ImmGetCompositionFont() "
+             "failed"));
+        sCompositionFont.AssignLiteral("System");
+      } else {
+        // The font face is typically, "System".
+        sCompositionFont.Assign(defaultLogFont.lfFaceName);
+      }
+    }
+
+    MOZ_LOG(gIMELog, LogLevel::Info,
+            ("  IMMHandler::AdjustCompositionFont, sCompositionFont=\"%s\" is "
+             "initialized",
+             NS_ConvertUTF16toUTF8(sCompositionFont).get()));
+  }
+
+  static nsString sCompositionFontForJapanist2003;
+  if (IsJapanist2003Active() && sCompositionFontForJapanist2003.IsEmpty()) {
+    const char* kCompositionFontForJapanist2003 =
+        "intl.imm.composition_font.japanist_2003";
+    Preferences::GetString(kCompositionFontForJapanist2003,
+                           sCompositionFontForJapanist2003);
+    // If the font name is not specified properly, let's use
+    // "MS PGothic" instead.
+    if (sCompositionFontForJapanist2003.IsEmpty() ||
+        sCompositionFontForJapanist2003.Length() > LF_FACESIZE - 2 ||
+        sCompositionFontForJapanist2003[0] == '@') {
+      sCompositionFontForJapanist2003.AssignLiteral("MS PGothic");
+    }
+  }
+
+  sWritingModeOfCompositionFont = aWritingMode;
+  sCurrentIMEName = sIMEName;
+
+  LOGFONTW logFont;
+  memset(&logFont, 0, sizeof(logFont));
+  if (!::ImmGetCompositionFont(aContext.get(), &logFont)) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::AdjustCompositionFont, ::ImmGetCompositionFont() "
+             "failed"));
+    logFont.lfFaceName[0] = 0;
+  }
+  // Need to reset some information which should be recomputed with new font.
+  logFont.lfWidth = 0;
+  logFont.lfWeight = FW_DONTCARE;
+  logFont.lfOutPrecision = OUT_DEFAULT_PRECIS;
+  logFont.lfClipPrecision = CLIP_DEFAULT_PRECIS;
+  logFont.lfPitchAndFamily = DEFAULT_PITCH;
+
+  if (aWritingMode.IsVertical() && IsVerticalWritingSupported()) {
+    SetVerticalFontToLogFont(IsJapanist2003Active()
+                                 ? sCompositionFontForJapanist2003
+                                 : sCompositionFont,
+                             logFont);
+  } else {
+    SetHorizontalFontToLogFont(IsJapanist2003Active()
+                                   ? sCompositionFontForJapanist2003
+                                   : sCompositionFont,
+                               logFont);
+  }
+  MOZ_LOG(gIMELog, LogLevel::Warning,
+          ("  IMMHandler::AdjustCompositionFont, calling "
+           "::ImmSetCompositionFont(\"%s\")",
+           NS_ConvertUTF16toUTF8(nsDependentString(logFont.lfFaceName)).get()));
+  ::ImmSetCompositionFontW(aContext.get(), &logFont);
+}
+
+// static
+nsresult IMMHandler::OnMouseButtonEvent(
+    nsWindow* aWindow, const IMENotification& aIMENotification) {
+  // We don't need to create the instance of the handler here.
+  if (!gIMMHandler) {
+    return NS_OK;
+  }
+
+  if (!sWM_MSIME_MOUSE || !IsComposingOnOurEditor() ||
+      !ShouldDrawCompositionStringOurselves()) {
+    return NS_OK;
+  }
+
+  // We need to handle only mousedown event.
+  if (aIMENotification.mMouseButtonEventData.mEventMessage != eMouseDown) {
+    return NS_OK;
+  }
+
+  // If the character under the cursor is not in the composition string,
+  // we don't need to notify IME of it.
+  uint32_t compositionStart = gIMMHandler->mCompositionStart;
+  uint32_t compositionEnd =
+      compositionStart + gIMMHandler->mCompositionString.Length();
+  if (aIMENotification.mMouseButtonEventData.mOffset < compositionStart ||
+      aIMENotification.mMouseButtonEventData.mOffset >= compositionEnd) {
+    return NS_OK;
+  }
+
+  BYTE button;
+  switch (aIMENotification.mMouseButtonEventData.mButton) {
+    case MouseButton::ePrimary:
+      button = IMEMOUSE_LDOWN;
+      break;
+    case MouseButton::eMiddle:
+      button = IMEMOUSE_MDOWN;
+      break;
+    case MouseButton::eSecondary:
+      button = IMEMOUSE_RDOWN;
+      break;
+    default:
+      return NS_OK;
+  }
+
+  // calcurate positioning and offset
+  // char :            JCH1|JCH2|JCH3
+  // offset:           0011 1122 2233
+  // positioning:      2301 2301 2301
+  LayoutDeviceIntPoint cursorPos =
+      aIMENotification.mMouseButtonEventData.mCursorPos;
+  LayoutDeviceIntRect charRect =
+      aIMENotification.mMouseButtonEventData.mCharRect;
+  int32_t cursorXInChar = cursorPos.x - charRect.X();
+  // The event might hit to zero-width character, see bug 694913.
+  // The reason might be:
+  // * There are some zero-width characters are actually.
+  // * font-size is specified zero.
+  // But nobody reproduced this bug actually...
+  // We should assume that user clicked on right most of the zero-width
+  // character in such case.
+  int positioning = 1;
+  if (charRect.Width() > 0) {
+    positioning = cursorXInChar * 4 / charRect.Width();
+    positioning = (positioning + 2) % 4;
+  }
+
+  int offset =
+      aIMENotification.mMouseButtonEventData.mOffset - compositionStart;
+  if (positioning < 2) {
+    offset++;
+  }
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::OnMouseButtonEvent, x,y=%d,%d, offset=%d, "
+           "positioning=%d",
+           cursorPos.x.value, cursorPos.y.value, offset, positioning));
+
+  // send MS_MSIME_MOUSE message to default IME window.
+  HWND imeWnd = ::ImmGetDefaultIMEWnd(aWindow->GetWindowHandle());
+  IMEContext context(aWindow);
+  if (::SendMessageW(imeWnd, sWM_MSIME_MOUSE,
+                     MAKELONG(MAKEWORD(button, positioning), offset),
+                     (LPARAM)context.get()) == 1) {
+    return NS_SUCCESS_EVENT_CONSUMED;
+  }
+  return NS_OK;
+}
+
+// static
+bool IMMHandler::OnKeyDownEvent(nsWindow* aWindow, WPARAM wParam, LPARAM lParam,
+                                MSGResult& aResult) {
+  MOZ_LOG(
+      gIMELog, LogLevel::Info,
+      ("IMMHandler::OnKeyDownEvent, hWnd=%p, wParam=%08zx, lParam=%08" PRIxLPTR,
+       aWindow->GetWindowHandle(), wParam, lParam));
+  aResult.mConsumed = false;
+  switch (wParam) {
+    case VK_TAB:
+    case VK_PRIOR:
+    case VK_NEXT:
+    case VK_END:
+    case VK_HOME:
+    case VK_LEFT:
+    case VK_UP:
+    case VK_RIGHT:
+    case VK_DOWN:
+    case VK_RETURN:
+      // If IME didn't process the key message (the virtual key code wasn't
+      // converted to VK_PROCESSKEY), and the virtual key code event causes
+      // moving caret or editing text with keeping composing state, we should
+      // cancel the composition here because we cannot support moving
+      // composition string with DOM events (IE also cancels the composition
+      // in same cases).  Then, this event will be dispatched.
+      if (IsComposingOnOurEditor()) {
+        // NOTE: We don't need to cancel the composition on another window.
+        CancelComposition(aWindow, false);
+      }
+      return false;
+    default:
+      return false;
+  }
+}
+
+Maybe<ContentSelection> IMMHandler::QueryContentSelection(nsWindow* aWindow) {
+  WidgetQueryContentEvent querySelectedTextEvent(true, eQuerySelectedText,
+                                                 aWindow);
+  LayoutDeviceIntPoint point(0, 0);
+  aWindow->InitEvent(querySelectedTextEvent, &point);
+  DispatchEvent(aWindow, querySelectedTextEvent);
+  if (NS_WARN_IF(querySelectedTextEvent.Failed())) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::Selection::Init, FAILED, due to eQuerySelectedText "
+             "failure"));
+    return Nothing();
+  }
+  // If the window is destroyed during querying selected text, we shouldn't
+  // do anymore.
+  if (aWindow->Destroyed()) {
+    MOZ_LOG(
+        gIMELog, LogLevel::Error,
+        ("  IMMHandler::Selection::Init, FAILED, due to the widget destroyed"));
+    return Nothing();
+  }
+
+  ContentSelection contentSelection(querySelectedTextEvent);
+
+  MOZ_LOG(gIMELog, LogLevel::Info,
+          ("IMMHandler::Selection::Init, querySelectedTextEvent={ mReply=%s }",
+           ToString(querySelectedTextEvent.mReply).c_str()));
+
+  if (contentSelection.HasRange() &&
+      !contentSelection.OffsetAndDataRef().IsValid()) {
+    MOZ_LOG(gIMELog, LogLevel::Error,
+            ("  IMMHandler::Selection::Init, FAILED, due to invalid range"));
+    return Nothing();
+  }
+  return Some(contentSelection);
+}
+
+}  // namespace widget
+}  // namespace mozilla