This change list improves IME support on Linux. Many corner cases that were n...

chrome/browser/renderer_host/render_widget_host_view_gtk.cc

Index: chrome/browser/renderer_host/render_widget_host_view_gtk.cc
===================================================================
--- chrome/browser/renderer_host/render_widget_host_view_gtk.cc	（版本 21138）
+++ chrome/browser/renderer_host/render_widget_host_view_gtk.cc	（工作副本）
@@ -30,6 +30,569 @@
 
 using WebKit::WebInputEventFactory;
 
+// This class is a conveience wrapper for GtkIMContext.
+class RenderWidgetHostViewGtkIMContext {
+ public:
+  explicit RenderWidgetHostViewGtkIMContext(RenderWidgetHostViewGtk* host_view)
+      : host_view_(host_view),
+        context_(gtk_im_multicontext_new()),
+        context_simple_(gtk_im_context_simple_new()),
+        is_focused_(false),
+        is_composing_text_(false),
+        is_enabled_(false),
+        is_in_key_event_handler_(false),
+        preedit_cursor_position_(0),
+        is_preedit_changed_(false) {
+    DCHECK(context_);
+    DCHECK(context_simple_);
+
+    // context_ and context_simple_ share the same callback handlers.
+    // All data come from them are treated equally.
+    // context_ is for full input method support.
+    // context_simple_ is for supporting dead/compose keys when input method is
+    // disabled by webkit, eg. in password input box.
+    g_signal_connect(context_, "preedit_start",
+                     G_CALLBACK(HandlePreeditStartThunk), this);
+    g_signal_connect(context_, "preedit_end",
+                     G_CALLBACK(HandlePreeditEndThunk), this);
+    g_signal_connect(context_, "preedit_changed",
+                     G_CALLBACK(HandlePreeditChangedThunk), this);
+    g_signal_connect(context_, "commit",
+                     G_CALLBACK(HandleCommitThunk), this);
+
+    g_signal_connect(context_simple_, "preedit_start",
+                     G_CALLBACK(HandlePreeditStartThunk), this);
+    g_signal_connect(context_simple_, "preedit_end",
+                     G_CALLBACK(HandlePreeditEndThunk), this);
+    g_signal_connect(context_simple_, "preedit_changed",
+                     G_CALLBACK(HandlePreeditChangedThunk), this);
+    g_signal_connect(context_simple_, "commit",
+                     G_CALLBACK(HandleCommitThunk), this);
+  }
+
+  ~RenderWidgetHostViewGtkIMContext() {
+    if (context_)
+      g_object_unref(context_);
+    if (context_simple_)
+      g_object_unref(context_simple_);
+  }
+
+  void ProcessKeyEvent(GdkEventKey* event) {
+    // Indicates preedit-changed and commit signal handlers that we are
+    // processing a key event.
+    is_in_key_event_handler_ = true;
+    // Reset this flag so that we can know if preedit is changed after
+    // processing this key event.
+    is_preedit_changed_ = false;
+    // Clear it so that we can know if something needs committing after
+    // processing this key event.
+    commit_text_.clear();
+
+    // According to Document Object Model (DOM) Level 3 Events Specification
+    // Appendix A: Keyboard events and key identifiers
+    // http://www.w3.org/TR/DOM-Level-3-Events/keyset.html:
+    // The event sequence would be:
+    // 1. keydown
+    // 2. textInput
+    // 3. keyup
+    //
+    // So keydown must be sent to webkit before sending input method result,
+    // while keyup must be sent afterwards.
+    // However on Windows, if a keydown event has been processed by IME, its
+    // virtual keycode will be changed to VK_PROCESSKEY(0xE5) before being sent
+    // to application.
+    // To emulate the windows behavior as much as possible, we need to send the
+    // key event to the GtkIMContext object first, and decide whether or not to
+    // send the original key event to webkit according to the result from IME.
+    //
+    // If IME is enabled by WebKit, this event will be dispatched to context_
+    // to get full IME support. Otherwise it'll be dispatched to
+    // context_simple_, so that dead/compose keys can still work.
+    //
+    // It sends a "commit" signal when it has a character to be inserted
+    // even when we use a US keyboard so that we can send a Char event
+    // (or an IME event) to the renderer in our "commit"-signal handler.
+    // We should send a KeyDown (or a KeyUp) event before dispatching this
+    // event to the GtkIMContext object (and send a Char event) so that WebKit
+    // can dispatch the JavaScript events in the following order: onkeydown(),
+    // onkeypress(), and onkeyup(). (Many JavaScript pages assume this.)
+    gboolean filtered = false;
+    if (is_enabled_) {
+      filtered = gtk_im_context_filter_keypress(context_, event);
+    } else {
+      filtered = gtk_im_context_filter_keypress(context_simple_, event);
+    }
+
+    NativeWebKeyboardEvent wke(event);
+
+    // Send filtered keydown event before sending IME result.
+    if (event->type == GDK_KEY_PRESS && filtered)
+      ProcessFilteredKeyPressEvent(&wke);
+
+    // Send IME results. In most cases, it's only available if the key event
+    // is filtered by IME. But in rare cases, an unfiltered key event may also
+    // generate IME results.
+    // Any IME results generated by a unfiltered key down event must be sent
+    // before the key down event, to avoid some tricky issues. For example,
+    // when using latin-post input method, pressing 'a' then Backspace, may
+    // generate following events in sequence:
+    //  1. keydown 'a' (filtered)
+    //  2. preedit changed to "a"
+    //  3. keyup 'a' (unfiltered)
+    //  4. keydown Backspace (unfiltered)
+    //  5. commit "a"
+    //  6. preedit end
+    //  7. keyup Backspace (unfiltered)
+    //
+    // In this case, the input box will be in a strange state if keydown
+    // Backspace is sent to webkit before commit "a" and preedit end.
+    ProcessInputMethodResult(event, filtered);
+
+    // Send unfiltered keydown and keyup events after sending IME result.
+    if (event->type == GDK_KEY_PRESS && !filtered)
+      ProcessUnfilteredKeyPressEvent(&wke);
+    else if (event->type == GDK_KEY_RELEASE)
+      host_view_->GetRenderWidgetHost()->ForwardKeyboardEvent(wke);
+
+    // End of key event processing.
+    is_in_key_event_handler_ = false;
+  }
+
+  void UpdateStatus(int control, const gfx::Rect& caret_rect) {
+    // The renderer has updated its IME status.
+    // Control the GtkIMContext object according to this status.
+    if (!context_ || !is_focused_)
+      return;
+
+    DCHECK(!is_in_key_event_handler_);
+
+    // TODO(james.su@gmail.com): Following code causes a side effect:
+    // When trying to move cursor from one text input box to another while
+    // composition text is still not confirmed, following CompleteComposition()
+    // calls will prevent the cursor from moving outside the first input box.
+    if (control == IME_DISABLE) {
+      if (is_enabled_) {
+        CompleteComposition();
+        gtk_im_context_reset(context_simple_);
+        gtk_im_context_focus_out(context_);
+        is_enabled_ = false;
+      }
+    } else {
+      // Enable the GtkIMContext object if it's not enabled yet.
+      if (!is_enabled_) {
+        // Reset context_simple_ to its initial state, in case it's currently
+        // in middle of a composition session inside a password box.
+        gtk_im_context_reset(context_simple_);
+        gtk_im_context_focus_in(context_);
+        // It might be true when switching from a password box in middle of a
+        // composition session.
+        is_composing_text_ = false;
+        is_enabled_ = true;
+      } else if (control == IME_COMPLETE_COMPOSITION) {
+        CompleteComposition();
+      }
+
+      // Updates the position of the IME candidate window.
+      // The position sent from the renderer is a relative one, so we need to
+      // attach the GtkIMContext object to this window before changing the
+      // position.
+      GdkRectangle cursor_rect(caret_rect.ToGdkRectangle());
+      gtk_im_context_set_cursor_location(context_, &cursor_rect);
+    }
+  }
+
+  void OnFocusIn() {
+    if (is_focused_)
+      return;
+
+    // Tracks the focused state so that we can give focus to the
+    // GtkIMContext object correctly later when IME is enabled by WebKit.
+    is_focused_ = true;
+
+    // We should call gtk_im_context_set_client_window() only when this window
+    // gain (or release) the window focus because an immodule may reset its
+    // internal status when processing this function.
+    gtk_im_context_set_client_window(context_,
+                                     host_view_->native_view()->window);
+
+    // Notify the GtkIMContext object of this focus-in event only if IME is
+    // enabled by WebKit.
+    if (is_enabled_)
+      gtk_im_context_focus_in(context_);
+
+    // Actually current GtkIMContextSimple implementation doesn't care about
+    // client window. This line is just for safe.
+    gtk_im_context_set_client_window(context_simple_,
+                                     host_view_->native_view()->window);
+
+    // context_simple_ is always enabled.
+    // Actually it doesn't care focus state at all.
+    gtk_im_context_focus_in(context_simple_);
+
+    // Enables RenderWidget's IME related events, so that we can be notified
+    // when WebKit wants to enable or disable IME.
+    host_view_->GetRenderWidgetHost()->ImeSetInputMode(true);
+  }
+
+  void OnFocusOut() {
+    if (!is_focused_)
+      return;
+
+    // Tracks the focused state so that we won't give focus to the
+    // GtkIMContext object unexpectly.
+    is_focused_ = false;
+
+    // Notify the GtkIMContext object of this focus-out event only if IME is
+    // enabled by WebKit.
+    if (is_enabled_) {
+      // To reset the GtkIMContext object and prevent data loss.
+      CompleteComposition();
+      gtk_im_context_focus_out(context_);
+    }
+
+    // Detach this GtkIMContext object from this window.
+    gtk_im_context_set_client_window(context_, NULL);
+
+    // To make sure it'll be in correct state when focused in again.
+    gtk_im_context_reset(context_simple_);
+    gtk_im_context_focus_out(context_simple_);
+    gtk_im_context_set_client_window(context_simple_, NULL);
+
+    // Reset stored IME status.
+    is_composing_text_ = false;
+    preedit_text_.clear();
+    preedit_cursor_position_ = 0;
+
+    // Disable RenderWidget's IME related events to save bandwidth.
+    host_view_->GetRenderWidgetHost()->ImeSetInputMode(false);
+  }
+
+ private:
+  // Check if a text needs commit by forwarding a char event instead of
+  // by confirming as a composition text.
+  bool NeedCommitByForwardingCharEvent() {
+    // If there is no composition text and has only one character to be
+    // committed, then the character will be send to webkit as a Char event
+    // instead of a confirmed composition text.
+    // It should be fine to handle BMP character only, as non-BMP characters
+    // can always be committed as confirmed composition text.
+    return !is_composing_text_ && commit_text_.length() == 1;
+  }
+
+  void ProcessFilteredKeyPressEvent(NativeWebKeyboardEvent* wke) {
+    // Copied from third_party/WebKit/WebCore/page/EventHandler.cpp
+    //
+    // Match key code of composition keydown event on windows.
+    // IE sends VK_PROCESSKEY which has value 229;
+    //
+    // Please refer to following documents for detals:
+    // - Virtual-Key Codes
+    //   http://msdn.microsoft.com/en-us/library/ms645540(VS.85).aspx
+    // - How the IME System Works
+    //   http://msdn.microsoft.com/en-us/library/cc194848.aspx
+    // - ImmGetVirtualKey Function
+    //   http://msdn.microsoft.com/en-us/library/dd318570(VS.85).aspx
+    const int kCompositionEventKeyCode = 229;
+
+    // If IME has filtered this event, then replace virtual key code with
+    // VK_PROCESSKEY. See comment in ProcessKeyEvent() for details.
+    // It's only required for keydown events.
+    // To emulate windows behavior, when input method is enabled, if the commit
+    // text can be emulated by a Char event, then don't do this replacement.
+    if (!NeedCommitByForwardingCharEvent()) {
+      wke->windowsKeyCode = kCompositionEventKeyCode;
+      // Prevent RenderView::UnhandledKeyboardEvent() from processing it.
+      // Otherwise unexpected result may occur. For example if it's a
+      // Backspace key event, the browser may go back to previous page.
+      if (wke->os_event) {
+        wke->os_event->keyval = GDK_VoidSymbol;
+        wke->os_event->state = 0;
+      }
+    }
+    host_view_->GetRenderWidgetHost()->ForwardKeyboardEvent(*wke);
+  }
+
+  void ProcessUnfilteredKeyPressEvent(NativeWebKeyboardEvent* wke) {
+    RenderWidgetHost* host = host_view_->GetRenderWidgetHost();
+
+    // Send keydown event as it, because it's not filtered by IME.
+    host->ForwardKeyboardEvent(*wke);
+
+    // IME is disabled by WebKit or the GtkIMContext object cannot handle
+    // this key event.
+    // This case is caused by two reasons:
+    // 1. The given key event is a control-key event, (e.g. return, page up,
+    //    page down, tab, arrows, etc.) or;
+    // 2. The given key event is not a control-key event but printable
+    //    characters aren't assigned to the event, (e.g. alt+d, etc.)
+    // Create a Char event manually from this key event and send it to the
+    // renderer when this Char event contains a printable character which
+    // should be processed by WebKit.
+    // isSystemKey will be set to true if this key event has Alt modifier,
+    // see WebInputEventFactory::keyboardEvent() for details.
+    if (wke->text[0]) {
+      wke->type = WebKit::WebInputEvent::Char;
+      host->ForwardKeyboardEvent(*wke);
+    }
+  }
+
+  // Processes result returned from input method after filtering a key event.
+  // |filtered| indicates if the key event was filtered by the input method.
+  void ProcessInputMethodResult(const GdkEventKey* event, bool filtered) {
+    RenderWidgetHost* host = host_view_->GetRenderWidgetHost();
+    bool committed = false;
+    // We do commit before preedit change, so that we can optimize some
+    // unnecessary preedit changes.
+    if (commit_text_.length()) {
+      if (filtered && NeedCommitByForwardingCharEvent()) {
+        // Send a Char event when we input a composed character without IMEs
+        // so that this event is to be dispatched to onkeypress() handlers,
+        // autofill, etc.
+        // Only commit text generated by a filtered key down event can be sent
+        // as a Char event, because a unfiltered key down event will probably
+        // generate another Char event.
+        // TODO(james.su@gmail.com): Is it necessary to support non BMP chars
+        // here?
+        NativeWebKeyboardEvent char_event(commit_text_[0],
+                                          event->state,
+                                          base::Time::Now().ToDoubleT());
+        host->ForwardKeyboardEvent(char_event);
+      } else {
+        committed = true;
+        // Send an IME event.
+        // Unlike a Char event, an IME event is NOT dispatched to onkeypress()
+        // handlers or autofill.
+        host->ImeConfirmComposition(commit_text_);
+        // Set this flag to false, as this composition session has been
+        // finished.
+        is_composing_text_ = false;
+      }
+    }
+
+    // Send preedit text only if it's changed.
+    // If a text has been committed, then we don't need to send the empty
+    // preedit text again.
+    if (is_preedit_changed_) {
+      if (preedit_text_.length()) {
+        host->ImeSetComposition(preedit_text_, preedit_cursor_position_,
+                                -1, -1);
+      } else if (!committed) {
+        host->ImeCancelComposition();
+      }
+    }
+  }
+
+  void CompleteComposition() {
+    if (!is_enabled_)
+      return;
+
+    // If WebKit requires to complete current composition, then we need commit
+    // existing preedit text and reset the GtkIMContext object.
+
+    // Backup existing preedit text to avoid it's being cleared when resetting
+    // the GtkIMContext object.
+    string16 old_preedit_text = preedit_text_;
+
+    // Clear it so that we can know if anything is committed by following
+    // line.
+    commit_text_.clear();
+
+    // Resetting the GtkIMContext. Input method may commit something at this
+    // point. In this case, we shall not commit the preedit text again.
+    gtk_im_context_reset(context_);
+
+    // If nothing was committed by above line, then commit stored preedit text
+    // to prevent data loss.
+    if (old_preedit_text.length() && commit_text_.length() == 0) {
+      host_view_->GetRenderWidgetHost()->ImeConfirmComposition(
+          old_preedit_text);
+    }
+
+    is_composing_text_ = false;
+    preedit_text_.clear();
+    preedit_cursor_position_ = 0;
+  }
+
+  // Real code of "commit" signal handler.
+  void HandleCommit(const string16& text) {
+    // Append the text to the buffer, because commit signal might be fired
+    // multiple times when processing a key event.
+    commit_text_.append(text);
+    // Nothing needs to do, if it's currently in ProcessKeyEvent()
+    // handler, which will send commit text to webkit later. Otherwise,
+    // we need send it here.
+    // It's possible that commit signal is fired without a key event, for
+    // example when user input via a voice or handwriting recognition software.
+    // In this case, the text must be committed directly.
+    if (!is_in_key_event_handler_) {
+      host_view_->GetRenderWidgetHost()->ImeConfirmComposition(text);
+    }
+  }
+
+  // Real code of "preedit-start" signal handler.
+  void HandlePreeditStart() {
+    is_composing_text_ = true;
+  }
+
+  // Real code of "preedit-changed" signal handler.
+  void HandlePreeditChanged(const string16& text, int cursor_position) {
+    bool changed = false;
+    // If preedit text or cursor position is not changed since last time,
+    // then it's not necessary to update it again.
+    // Preedit text is always stored, so that we can commit it when webkit
+    // requires.
+    // Don't set is_preedit_changed_ to false if there is no change, because
+    // this handler might be called multiple times with the same data.
+    if (cursor_position != preedit_cursor_position_ || text != preedit_text_) {
+      preedit_text_ = text;
+      preedit_cursor_position_ = cursor_position;
+      is_preedit_changed_ = true;
+      changed = true;
+    }
+
+    // In case we are using a buggy input method which doesn't fire
+    // "preedit_start" signal.
+    if (text.length())
+      is_composing_text_ = true;
+
+    // Nothing needs to do, if it's currently in ProcessKeyEvent()
+    // handler, which will send preedit text to webkit later.
+    // Otherwise, we need send it here if it's been changed.
+    if (!is_in_key_event_handler_ && changed) {
+      if (text.length()) {
+        host_view_->GetRenderWidgetHost()->ImeSetComposition(
+            text, cursor_position, -1, -1);
+      } else {
+        host_view_->GetRenderWidgetHost()->ImeCancelComposition();
+      }
+    }
+  }
+
+  // Real code of "preedit-end" signal handler.
+  void HandlePreeditEnd() {
+    bool changed = false;
+    if (preedit_text_.length()) {
+      // The composition session has been finished.
+      preedit_text_.clear();
+      preedit_cursor_position_ = 0;
+      is_preedit_changed_ = true;
+      changed = true;
+    }
+
+    // If there is still a preedit text when firing "preedit-end" signal,
+    // we need inform webkit to clear it.
+    // It's only necessary when it's not in ProcessKeyEvent ().
+    if (!is_in_key_event_handler_ && changed) {
+      host_view_->GetRenderWidgetHost()->ImeCancelComposition();
+    }
+
+    // Don't set is_composing_text_ to false here, because "preedit_end"
+    // signal may be fired before "commit" signal.
+  }
+
+ private:
+  // Signal handlers of GtkIMContext object.
+  static void HandleCommitThunk(GtkIMContext* context, gchar* text,
+                                RenderWidgetHostViewGtkIMContext* self) {
+    self->HandleCommit(UTF8ToUTF16(text));
+  }
+
+  static void HandlePreeditStartThunk(GtkIMContext* context,
+                                      RenderWidgetHostViewGtkIMContext* self) {
+    self->HandlePreeditStart();
+  }
+
+  static void HandlePreeditChangedThunk(
+      GtkIMContext* context, RenderWidgetHostViewGtkIMContext* self) {
+    gchar* text = NULL;
+    gint cursor_position = 0;
+    gtk_im_context_get_preedit_string(context, &text, NULL, &cursor_position);
+    self->HandlePreeditChanged(UTF8ToUTF16(text), cursor_position);
+    g_free(text);
+  }
+
+  static void HandlePreeditEndThunk(GtkIMContext* context,
+                                    RenderWidgetHostViewGtkIMContext* self) {
+    self->HandlePreeditEnd();
+  }
+
+ private:
+  // The parent object.
+  RenderWidgetHostViewGtk* host_view_;
+
+  // The GtkIMContext object.
+  // In terms of the DOM event specification Appendix A
+  //   <http://www.w3.org/TR/DOM-Level-3-Events/keyset.html>,
+  // GTK uses a GtkIMContext object for the following two purposes:
+  //  1. Composing Latin characters (A.1.2), and;
+  //  2. Composing CJK characters with an IME (A.1.3).
+  // Many JavaScript pages assume composed Latin characters are dispatched to
+  // their onkeypress() handlers but not dispatched CJK characters composed
+  // with an IME. To emulate this behavior, we should monitor the status of
+  // this GtkIMContext object and prevent sending Char events when a
+  // GtkIMContext object sends a "commit" signal with the CJK characters
+  // composed by an IME.
+  GtkIMContext* context_;
+
+  // A GtkIMContextSimple object, for supporting dead/compose keys when input
+  // method is disabled, eg. in password input box.
+  GtkIMContext* context_simple_;
+
+  // Whether or not this widget is focused.
+  bool is_focused_;
+
+  // Whether or not the above GtkIMContext is composing a text with an IME.
+  // This flag is used in "commit" signal handler of the GtkIMContext object,
+  // which determines how to submit the result text to WebKit according to this
+  // flag.
+  // If this flag is true or there are more than one characters in the result,
+  // then the result text will be committed to WebKit as a confirmed
+  // composition. Otherwise, it'll be forwarded as a key event.
+  //
+  // The GtkIMContext object sends a "preedit_start" before it starts composing
+  // a text and a "preedit_end" signal after it finishes composing it.
+  // "preedit_start" signal is monitored to turn it on.
+  // We don't monitor "preedit_end" signal to turn it off, because an input
+  // method may fire "preedit_end" signal before "commit" signal.
+  // A buggy input method may not fire "preedit_start" and/or "preedit_end"
+  // at all, so this flag will also be set to true when "preedit_changed" signal
+  // is fired with non-empty preedit text.
+  bool is_composing_text_;
+
+  // Whether or not the IME is enabled.
+  // This flag is actually controlled by RenderWidget.
+  // It shall be set to false when an ImeUpdateStatus message with control ==
+  // IME_DISABLE is received, and shall be set to true if control ==
+  // IME_COMPLETE_COMPOSITION or IME_MOVE_WINDOWS.
+  // When this flag is false, keyboard events shall be dispatched directly
+  // instead of sending to context_.
+  bool is_enabled_;
+
+  // Whether or not it's currently running inside key event handler.
+  // If it's true, then preedit-changed and commit handler will backup the
+  // preedit or commit text instead of sending them down to webkit.
+  // key event handler will send them later.
+  bool is_in_key_event_handler_;
+
+  // Stores a copy of the most recent preedit text retrieved from context_.
+  // When an ImeUpdateStatus message with control == IME_COMPLETE_COMPOSITION
+  // is received, this stored preedit text (if not empty) shall be committed,
+  // and context_ shall be reset.
+  string16 preedit_text_;
+
+  // Stores the cursor position in the stored preedit text.
+  int preedit_cursor_position_;
+
+  // Whether or not the preedit has been changed since last key event.
+  bool is_preedit_changed_;
+
+  // Stores a copy of the most recent commit text received by commit signal
+  // handler.
+  string16 commit_text_;
+
+  DISALLOW_COPY_AND_ASSIGN(RenderWidgetHostViewGtkIMContext);
+};
+
 // This class is a simple convenience wrapper for Gtk functions. It has only
 // static methods.
 class RenderWidgetHostViewGtkWidget {
@@ -78,16 +641,9 @@
     g_signal_connect_after(widget, "scroll-event",
                            G_CALLBACK(MouseScrollEvent), host_view);
 
-    // Create a GtkIMContext instance and attach its signal handlers.
-    host_view->im_context_ = gtk_im_multicontext_new();
-    g_signal_connect(host_view->im_context_, "preedit_start",
-                     G_CALLBACK(InputMethodPreeditStart), host_view);
-    g_signal_connect(host_view->im_context_, "preedit_end",
-                     G_CALLBACK(InputMethodPreeditEnd), host_view);
-    g_signal_connect(host_view->im_context_, "preedit_changed",
-                     G_CALLBACK(InputMethodPreeditChanged), host_view);
-    g_signal_connect(host_view->im_context_, "commit",
-                     G_CALLBACK(InputMethodCommit), host_view);
+    // Create GtkIMContext wrapper object.
+    host_view->im_context_.reset(
+        new RenderWidgetHostViewGtkIMContext(host_view));
 
     return widget;
   }
@@ -114,46 +670,10 @@
       // allows us to release our keyboard grab.
       host_view->host_->Shutdown();
     } else {
-      NativeWebKeyboardEvent wke(event);
-      host_view->GetRenderWidgetHost()->ForwardKeyboardEvent(wke);
+      // Send key event to input method.
+      host_view->im_context_->ProcessKeyEvent(event);
     }
 
-    // Save the current modifier-key state before dispatching this event to the
-    // GtkIMContext object so its event handlers can use this state to create
-    // Char events.
-    host_view->im_modifier_state_ = event->state;
-
-    // Dispatch this event to the GtkIMContext object.
-    // It sends a "commit" signal when it has a character to be inserted
-    // even when we use a US keyboard so that we can send a Char event
-    // (or an IME event) to the renderer in our "commit"-signal handler.
-    // We should send a KeyDown (or a KeyUp) event before dispatching this
-    // event to the GtkIMContext object (and send a Char event) so that WebKit
-    // can dispatch the JavaScript events in the following order: onkeydown(),
-    // onkeypress(), and onkeyup(). (Many JavaScript pages assume this.)
-    // TODO(hbono): we should not dispatch a key event when the input focus
-    // is in a password input?
-    if (!gtk_im_context_filter_keypress(host_view->im_context_, event)) {
-      // The GtkIMContext object cannot handle this key event.
-      // This case is caused by two reasons:
-      // 1. The given key event is a control-key event, (e.g. return, page up,
-      //    page down, tab, arrows, etc.) or;
-      // 2. The given key event is not a control-key event but printable
-      //    characters aren't assigned to the event, (e.g. alt+d, etc.)
-      // Create a Char event manually from this key event and send it to the
-      // renderer when this Char event contains a printable character which
-      // should be processed by WebKit.
-      // TODO(hbono): Windows Chrome sends a Char event with its isSystemKey
-      // value true for the above case 2. We should emulate this behavior?
-      if (event->type == GDK_KEY_PRESS &&
-          !gdk_keyval_to_unicode(event->keyval)) {
-        NativeWebKeyboardEvent wke(event);
-        wke.type = WebKit::WebInputEvent::Char;
-        if (wke.text[0])
-          host_view->GetRenderWidgetHost()->ForwardKeyboardEvent(wke);
-      }
-    }
-
     // We return TRUE because we did handle the event. If it turns out webkit
     // can't handle the event, we'll deal with it in
     // RenderView::UnhandledKeyboardEvent().
@@ -188,14 +708,10 @@
     host_view->ShowCurrentCursor();
     host_view->GetRenderWidgetHost()->Focus();
 
-    // Notify the GtkIMContext object of this focus-in event and
-    // attach this GtkIMContext object to this window.
-    // We should call gtk_im_context_set_client_window() only when this window
-    // gain (or release) the window focus because an immodule may reset its
-    // internal status when processing this function.
-    gtk_im_context_focus_in(host_view->im_context_);
-    gtk_im_context_set_client_window(host_view->im_context_,
-                                     host_view->native_view()->window);
+    // The only way to enable a GtkIMContext object is to call its focus in
+    // handler.
+    host_view->im_context_->OnFocusIn();
+
     return FALSE;
   }
 
@@ -211,10 +727,9 @@
     if (!host_view->is_showing_context_menu_)
       host_view->GetRenderWidgetHost()->Blur();
 
-    // Notify the GtkIMContext object of this focus-in event and
-    // detach this GtkIMContext object from this window.
-    gtk_im_context_focus_out(host_view->im_context_);
-    gtk_im_context_set_client_window(host_view->im_context_, NULL);
+    // Disable the GtkIMContext object.
+    host_view->im_context_->OnFocusOut();
+
     return FALSE;
   }
 
@@ -224,10 +739,14 @@
   // shown, and must rely on this signal instead.
   static void OnGrabNotify(GtkWidget* widget, gboolean was_grabbed,
                            RenderWidgetHostViewGtk* host_view) {
-    if (was_grabbed)
-      OnFocusIn(widget, NULL, host_view);
-    else
-      OnFocusOut(widget, NULL, host_view);
+    if (was_grabbed) {
+      if (host_view->was_focused_before_grab_)
+        OnFocusIn(widget, NULL, host_view);
+    } else {
+      host_view->was_focused_before_grab_ = host_view->HasFocus();
+      if (host_view->was_focused_before_grab_)
+        OnFocusOut(widget, NULL, host_view);
+    }
   }
 
   static gboolean ButtonPressReleaseEvent(
@@ -309,69 +828,6 @@
     return FALSE;
   }
 
-  static void InputMethodCommit(GtkIMContext* im_context,
-                                gchar* text,
-                                RenderWidgetHostViewGtk* host_view) {
-    const string16& im_text = UTF8ToUTF16(text);
-    if (!host_view->im_is_composing_cjk_text_ && im_text.length() == 1) {
-      // Send a Char event when we input a composed character without IMEs so
-      // that this event is to be dispatched to onkeypress() handlers,
-      // autofill, etc.
-      ForwardCharEvent(host_view, im_text[0]);
-    } else {
-      // Send an IME event.
-      // Unlike a Char event, an IME event is NOT dispatched to onkeypress()
-      // handlers or autofill.
-      host_view->GetRenderWidgetHost()->ImeConfirmComposition(im_text);
-    }
-  }
-
-  static void InputMethodPreeditStart(GtkIMContext* im_context,
-                                      RenderWidgetHostViewGtk* host_view) {
-    // Start monitoring IME events of the renderer.
-    // TODO(hbono): a renderer sends these IME events not only for sending the
-    // caret position, but also for enabling/disabling IMEs. If we need to
-    // enable/disable IMEs, we should move this code to a better place.
-    // (This signal handler is called only when an IME is enabled. So, once
-    // we disable an IME, we cannot receive any IME events from the renderer,
-    // i.e. we cannot re-enable the IME any longer.)
-    host_view->GetRenderWidgetHost()->ImeSetInputMode(true);
-    host_view->im_is_composing_cjk_text_ = true;
-  }
-
-  static void InputMethodPreeditEnd(GtkIMContext* im_context,
-                                    RenderWidgetHostViewGtk* host_view) {
-    // End monitoring IME events.
-    host_view->GetRenderWidgetHost()->ImeSetInputMode(false);
-    host_view->im_is_composing_cjk_text_ = false;
-  }
-
-  static void InputMethodPreeditChanged(GtkIMContext* im_context,
-                                        RenderWidgetHostViewGtk* host_view) {
-    // Send an IME event to update the composition node of the renderer.
-    // TODO(hbono): an IME intercepts all key events while composing a text,
-    // i.e. we cannot receive any GDK_KEY_PRESS (or GDK_KEY_UP) events.
-    // Should we send pseudo KeyDown (and KeyUp) events to emulate Windows?
-    gchar* preedit_text = NULL;
-    gint cursor_position = 0;
-    gtk_im_context_get_preedit_string(im_context, &preedit_text, NULL,
-                                      &cursor_position);
-    host_view->GetRenderWidgetHost()->ImeSetComposition(
-        UTF8ToUTF16(preedit_text), cursor_position, -1, -1);
-    g_free(preedit_text);
-  }
-
-  static void ForwardCharEvent(RenderWidgetHostViewGtk* host_view,
-                               wchar_t im_character) {
-    if (!im_character)
-      return;
-
-    NativeWebKeyboardEvent char_event(im_character,
-                                      host_view->im_modifier_state_,
-                                      base::Time::Now().ToDoubleT());
-    host_view->GetRenderWidgetHost()->ForwardKeyboardEvent(char_event);
-  }
-
   DISALLOW_IMPLICIT_CONSTRUCTORS(RenderWidgetHostViewGtkWidget);
 };
 
@@ -390,15 +846,11 @@
       parent_host_view_(NULL),
       parent_(NULL),
       is_popup_first_mouse_release_(true),
-      im_context_(NULL),
-      im_is_composing_cjk_text_(false),
-      im_modifier_state_(0) {
+      was_focused_before_grab_(false) {
   host_->set_view(this);
 }
 
 RenderWidgetHostViewGtk::~RenderWidgetHostViewGtk() {
-  if (im_context_)
-    g_object_unref(im_context_);
   view_.Destroy();
 }
 
@@ -559,28 +1011,7 @@
 
 void RenderWidgetHostViewGtk::IMEUpdateStatus(int control,
                                               const gfx::Rect& caret_rect) {
-  // The renderer has updated its IME status.
-  // Control the GtkIMContext object according to this status.
-  if (!im_context_)
-    return;
-
-  if (control == IME_DISABLE) {
-    // TODO(hbono): this code just resets the GtkIMContext object.
-    // Should we prevent sending key events to the GtkIMContext object
-    // (or unref it) when we disable IMEs?
-    gtk_im_context_reset(im_context_);
-    gtk_im_context_set_cursor_location(im_context_, NULL);
-  } else {
-    // TODO(hbono): we should finish (not reset) an ongoing composition
-    // when |control| is IME_COMPLETE_COMPOSITION.
-
-    // Updates the position of the IME candidate window.
-    // The position sent from the renderer is a relative one, so we need to
-    // attach the GtkIMContext object to this window before changing the
-    // position.
-    GdkRectangle cursor_rect(caret_rect.ToGdkRectangle());
-    gtk_im_context_set_cursor_location(im_context_, &cursor_rect);
-  }
+  im_context_->UpdateStatus(control, caret_rect);
 }
 
 void RenderWidgetHostViewGtk::DidPaintRect(const gfx::Rect& rect) {