IME (input method editor) support for Aura, part 1 of 3: Add ui/base/ime/ classes

ui/base/ime/input_method.h

Index: ui/base/ime/input_method.h
diff --git a/ui/base/ime/input_method.h b/ui/base/ime/input_method.h
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+// Copyright (c) 2011 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_BASE_IME_INPUT_METHOD_H_
+#define UI_BASE_IME_INPUT_METHOD_H_
+#pragma once
+
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/event_types.h"
+#include "base/i18n/rtl.h"
+#include "ui/base/ime/text_input_type.h"
+#include "ui/base/keycodes/keyboard_codes.h"
+#include "ui/base/ui_export.h"
+
+namespace ui {
+
+namespace internal {
+class InputMethodDelegate;
+}  // namespace internal
+
+class TextInputClient;
+
+// An interface implemented by an object that encapsulates a native input method
+// service provided by the underlying operating system, and acts as a "system
+// wide" input method for all Chrome windows. A class that implements this
+// interface should behave as follows:
+// - Receives a keyboard event directly from a message dispatcher for the
+//   system through the InputMethod::DispatchKeyEvent API, and forwards it to
+//   an underlying input method for the OS.
+// - The input method should handle the key event either of the following ways:
+//   1) Send the original key down event to the focused window, which is e.g.
+//      a NativeWidgetAura (NWA) or a RenderWidgetHostViewAura (RWHVA), using
+//      internal::InputMethodDelegate::DispatchKeyEventPostIME API, then send
+//      a Char event using TextInputClient::InsertChar API to a text input
+//      client, which is, again, e.g. NWA or RWHVA, and then send the original
+//      key up event to the same window.
+//   2) Send VKEY_PROCESSKEY event to the window using the DispatchKeyEvent API,
+//      then update IME status (e.g. composition text) using TextInputClient,
+//      and then send the original key up event to the window.
+// - Keeps track of the focused TextInputClient to see which client can call
+//   APIs, OnTextInputTypeChanged, OnCaretBoundsChanged, and CancelComposition,
+//   that change the state of the input method.
+// In Aura environment, aura::DesktopHost creates an instance of ui::InputMethod
+// and owns it.
+class UI_EXPORT InputMethod {
+ public:
+  virtual ~InputMethod() {}
+
+  // Sets the delegate used by this InputMethod instance. It should only be
+  // called by an object which manages the whole UI (e.g. aura::DesktopHost).
+  virtual void SetDelegate(internal::InputMethodDelegate* delegate) = 0;
+
+  // Initializes the InputMethod object. Pass true if the system toplevel window
+  // already has keyboard focus.
+  virtual void Init(bool focused) = 0;
+
+  // Called when the top-level system window gets keyboard focus.
+  virtual void OnFocus() = 0;
+
+  // Called when the top-level system window loses keyboard focus.
+  virtual void OnBlur() = 0;
+
+  // Sets the text input client which receives text input events such as
+  // SetCompositionText(). |client| can be NULL. A gfx::NativeWindow which
+  // implementes TextInputClient interface, e.g. NWA and RWHVA, should register
+  // itself by calling the method when it is focused, and unregister itself by
+  // calling the metho with NULL when it is unfocused.
+  virtual void SetFocusedTextInputClient(TextInputClient* client) = 0;
+
+  // Gets the current text input client. Returns NULL when no client is set.
+  virtual TextInputClient* GetTextInputClient() const = 0;
+
+  // Dispatches a key event to the input method. The key event will be
+  // dispatched back to the caller via
+  // ui::InputMethodDelegate::DispatchKeyEventPostIME(), once it's processed by
+  // the input method. It should only be called by a message dispatcher.
+  virtual void DispatchKeyEvent(const base::NativeEvent& native_key_event) = 0;
+
+  // TODO(yusukes): Add DispatchFabricatedKeyEvent to support virtual keyboards.
+
+  // Called by the focused client whenever its text input type is changed.
+  // Before calling this method, the focused client must confirm or clear
+  // existing composition text and call InputMethod::CancelComposition() when
+  // necessary. Otherwise unexpected behavior may happen. This method has no
+  // effect if the client is not the focused client.
+  virtual void OnTextInputTypeChanged(const TextInputClient* client) = 0;
+
+  // Called by the focused client whenever its caret bounds is changed.
+  // This method has no effect if the client is not the focused client.
+  virtual void OnCaretBoundsChanged(const TextInputClient* client) = 0;
+
+  // Called by the focused client to ask the input method cancel the ongoing
+  // composition session. This method has no effect if the client is not the
+  // focused client.
+  virtual void CancelComposition(const TextInputClient* client) = 0;
+
+  // Returns the locale of current keyboard layout or input method, as a BCP-47
+  // tag, or an empty string if the input method cannot provide it.
+  virtual std::string GetInputLocale() = 0;
+
+  // Returns the text direction of current keyboard layout or input method, or
+  // base::i18n::UNKNOWN_DIRECTION if the input method cannot provide it.
+  virtual base::i18n::TextDirection GetInputTextDirection() = 0;
+
+  // Checks if the input method is active, i.e. if it's ready for processing
+  // keyboard event and generate composition or text result.
+  // If the input method is inactive, then it's not necessary to inform it the
+  // changes of caret bounds and text input type.
+  // Note: character results may still be generated and sent to the text input
+  // client by calling TextInputClient::InsertChar(), even if the input method
+  // is not active.
+  virtual bool IsActive() = 0;
+
+  // Gets the text input type of the focused text input client. Returns
+  // ui::TEXT_INPUT_TYPE_NONE if there is no focused client.
+  virtual TextInputType GetTextInputType() const = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_BASE_IME_INPUT_METHOD_H_