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ime_input.h

// Copyright (c) 2006-2008 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 CHROME_BROWSER_IME_INPUT_H_
#define CHROME_BROWSER_IME_INPUT_H_

#include <windows.h>

#include <string>

#include "base/basictypes.h"
#include "gfx/rect.h"

// This header file defines a struct and a class used for encapsulating IMM32
// APIs, controls IMEs attached to a window, and enables the 'on-the-spot'
// input without deep knowledge about the APIs, i.e. knowledge about the
// language-specific and IME-specific behaviors.
// The following items enumerates the simplest steps for an (window)
// application to control its IMEs with the struct and the class defined
// this file.
// 1. Add an instance of the ImeInput class to its window class.
//    (The ImeInput class needs a window handle.)
// 2. Add messages handlers listed in the following subsections, follow the
//    instructions written in each subsection, and use the ImeInput class.
// 2.1. WM_IME_SETCONTEXT (0x0281)
//      Call the functions listed below:
//      - ImeInput::CreateImeWindow();
//      - ImeInput::CleanupComposition(), and;
//      - ImeInput::SetImeWindowStyle().
//      An application MUST prevent from calling ::DefWindowProc().
// 2.2. WM_IME_STARTCOMPOSITION (0x010D)
//      Call the functions listed below:
//      - ImeInput::CreateImeWindow(), and;
//      - ImeInput::ResetComposition().
//      An application MUST prevent from calling ::DefWindowProc().
// 2.3. WM_IME_COMPOSITION (0x010F)
//      Call the functions listed below:
//      - ImeInput::UpdateImeWindow();
//      - ImeInput::GetResult();
//      - ImeInput::GetComposition(), and;
//      - ImeInput::ResetComposition() (optional).
//      An application MUST prevent from calling ::DefWindowProc().
// 2.4. WM_IME_ENDCOMPOSITION (0x010E)
//      Call the functions listed below:
//      - ImeInput::ResetComposition(), and;
//      - ImeInput::DestroyImeWindow().
//      An application CAN call ::DefWindowProc().
// 2.5. WM_INPUTLANGCHANGE (0x0051)
//      Call the functions listed below:
//      - ImeInput::SetInputLanguage().
//      An application CAN call ::DefWindowProc().

// This struct represents the status of an ongoing composition.
struct ImeComposition {
  // Represents the cursor position in the IME composition.
  int cursor_position;

  // Represents the position of the beginning of the selection
  int target_start;

  // Represents the position of the end of the selection
  int target_end;

  // Represents the type of the string in the 'ime_string' parameter.
  // Its possible values and description are listed bwlow:
  //   Value         Description
  //   0             The parameter is not used.
  //   GCS_RESULTSTR The parameter represents a result string.
  //   GCS_COMPSTR   The parameter represents a composition string.
  int string_type;

  // Represents the string retrieved from IME (Input Method Editor)
  std::wstring ime_string;
};

// This class controls the IMM (Input Method Manager) through IMM32 APIs and
// enables it to retrieve the string being controled by the IMM. (I wrote
// a note to describe the reason why I do not use 'IME' but 'IMM' below.)
// NOTE(hbono):
//   Fortunately or unfortunately, TSF (Text Service Framework) and
//   CUAS (Cicero Unaware Application Support) allows IMM32 APIs for
//   retrieving not only the inputs from IMEs (Input Method Editors), used
//   only for inputting East-Asian language texts, but also the ones from
//   tablets (on Windows XP Tablet PC Edition and Windows Vista), voice
//   recognizers (e.g. ViaVoice and Microsoft Office), etc.
//   We can disable TSF and CUAS in Windows XP Tablet PC Edition. On the other
//   hand, we can NEVER disable either TSF or CUAS in Windows Vista, i.e.
//   THIS CLASS IS NOT ONLY USED ON THE INPUT CONTEXTS OF EAST-ASIAN
//   LANGUAGES BUT ALSO USED ON THE INPUT CONTEXTS OF ALL LANGUAGES.
class ImeInput {
 public:
  ImeInput();
  ~ImeInput();

  // Retrieves whether or not there is an ongoing composition.
  bool is_composing() const { return is_composing_; }

  // Retrieves the input language from Windows and update it.
  // Return values
  //   * true
  //     The given input language has IMEs.
  //   * false
  //     The given input language does not have IMEs.
  bool SetInputLanguage();

  // Create the IME windows, and allocate required resources for them.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void CreateImeWindow(HWND window_handle);

  // Update the style of the IME windows.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  //   * message [in] (UINT)
  //   * wparam [in] (WPARAM)
  //   * lparam [in] (LPARAM)
  //     Represent the windows message of the caller.
  //     These parameters are used for verifying if this function is called
  //     in a handler function for WM_IME_SETCONTEXT messages because this
  //     function uses ::DefWindowProc() to update the style.
  //     A caller just has to pass the input parameters for the handler
  //     function without modifications.
  //   * handled [out] (BOOL*)
  //     Returns ::DefWindowProc() is really called in this function.
  //     PLEASE DO NOT CALL ::DefWindowProc() IF THIS VALUE IS TRUE!
  //     All the window styles set in this function are over-written when
  //     calling ::DefWindowProc() after returning this function.
  void SetImeWindowStyle(HWND window_handle, UINT message,
                         WPARAM wparam, LPARAM lparam, BOOL* handled);

  // Destroy the IME windows and all the resources attached to them.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void DestroyImeWindow(HWND window_handle);

  // Update the position of the IME windows.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void UpdateImeWindow(HWND window_handle);

  // Clean up the all resources attached to the given ImeInput object, and
  // reset its composition status.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void CleanupComposition(HWND window_handle);

  // Reset the composition status.
  // Cancel the ongoing composition if it exists.
  // NOTE(hbono): This method does not release the allocated resources.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void ResetComposition(HWND window_handle);

  // Retrieve a composition result of the ongoing composition if it exists.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  //   * lparam [in] (LPARAM)
  //     Specifies the updated members of the ongoing composition, and must be
  //     the same parameter of a WM_IME_COMPOSITION message handler.
  //     This parameter is used for checking if the ongoing composition has
  //     its result string,
  //   * composition [out] (ImeComposition)
  //     Represents the struct contains the composition result.
  // Return values
  //   * true
  //     The ongoing composition has a composition result.
  //   * false
  //     The ongoing composition does not have composition results.
  // Remarks
  //   This function is designed for being called from WM_IME_COMPOSITION
  //   message handlers.
  bool GetResult(HWND window_handle, LPARAM lparam,
                 ImeComposition* composition);

  // Retrieve the current composition status of the ongoing composition.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  //   * lparam [in] (LPARAM)
  //     Specifies the updated members of the ongoing composition, and must be
  //     the same parameter of a WM_IME_COMPOSITION message handler.
  //     This parameter is used for checking if the ongoing composition has
  //     its result string,
  //   * composition [out] (ImeComposition)
  //     Represents the struct contains the composition status.
  // Return values
  //   * true
  //     The status of the ongoing composition is updated.
  //   * false
  //     The status of the ongoing composition is not updated.
  // Remarks
  //   This function is designed for being called from WM_IME_COMPOSITION
  //   message handlers.
  bool GetComposition(HWND window_handle, LPARAM lparam,
                      ImeComposition* composition);

  // Enable the IME attached to the given window, i.e. allows user-input
  // events to be dispatched to the IME.
  // In Chrome, this function is used when:
  //   * a renderer process moves its input focus to another edit control, or;
  //   * a renrerer process moves the position of the focused edit control.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  //   * caret_rect [in] (const gfx::Rect&)
  //     Represent the rectangle of the input caret.
  //     This rectangle is used for controlling the positions of IME windows.
  //   * complete [in] (bool)
  //     Represents whether or not to complete the ongoing composition.
  //     + true
  //       After finishing the ongoing composition and close its IME windows,
  //       start another composition and display its IME windows to the given
  //       position.
  //     + false
  //       Just move the IME windows of the ongoing composition to the given
  //       position without finishing it.
  void EnableIME(HWND window_handle,
                 const gfx::Rect& caret_rect,
                 bool complete);

  // Disable the IME attached to the given window, i.e. prohibits any user-input
  // events from being dispatched to the IME.
  // In Chrome, this function is used when:
  //   * a renreder process sets its input focus to a password input.
  // Parameters
  //   * window_handle [in] (HWND)
  //     Represents the window handle of the caller.
  void DisableIME(HWND window_handle);

 protected:
  // Determines whether or not the given attribute represents a target
  // (a.k.a. a selection).
  bool IsTargetAttribute(char attribute) const {
    return (attribute == ATTR_TARGET_CONVERTED ||
            attribute == ATTR_TARGET_NOTCONVERTED);
  }

  // Retrieve the target area.
  void GetCaret(HIMC imm_context, LPARAM lparam,
                ImeComposition* composition);

  // Update the position of the IME windows.
  void MoveImeWindow(HWND window_handle, HIMC imm_context);

  // Complete the ongoing composition if it exists.
  void CompleteComposition(HWND window_handle, HIMC imm_context);

  // Retrieve a string from the IMM.
  bool GetString(HIMC imm_context, WPARAM lparam, int type,
                 ImeComposition* composition);

 private:
  // Represents whether or not there is an ongoing composition in a browser
  // process, i.e. whether or not a browser process is composing a text.
  bool is_composing_;

  // This value represents whether or not the current input context has IMEs.
  // The following table shows the list of IME status:
  //   Value  Description
  //   false  The current input language does not have IMEs.
  //   true   The current input language has IMEs.
  bool ime_status_;

  // The current input Language ID retrieved from Windows, which consists of:
  //   * Primary Language ID (bit 0 to bit 9), which shows a natunal language
  //     (English, Korean, Chinese, Japanese, etc.) and;
  //   * Sub-Language ID (bit 10 to bit 15), which shows a geometrical region
  //     the language is spoken (For English, United States, United Kingdom,
  //     Australia, Canada, etc.)
  // The following list enumerates some examples for the Language ID:
  //   * "en-US" (0x0409)
  //     MAKELANGID(LANG_ENGLISH, SUBLANG_ENGLISH_US);
  //   * "ko-KR" (0x0412)
  //     MAKELANGID(LANG_KOREAN,  SUBLANG_KOREAN);
  //   * "zh-TW" (0x0404)
  //     MAKELANGID(LANG_CHINESE, SUBLANG_CHINESE_TRADITIONAL);
  //   * "zh-CN" (0x0804)
  //     MAKELANGID(LANG_CHINESE, SUBLANG_CHINESE_SIMPLIFIED);
  //   * "ja-JP" (0x0411)
  //     MAKELANGID(LANG_JAPANESE, SUBLANG_JAPANESE_JAPAN), etc.
  //   (See <winnt.h> for other available values.)
  // This Language ID is used for processing language-specific operations in
  // IME functions.
  LANGID input_language_id_;

  // Represents whether or not the current input context has created a system
  // caret to set the position of its IME candidate window.
  //   * true: it creates a system caret.
  //   * false: it does not create a system caret.
  bool system_caret_;

  // The rectangle of the input caret retrieved from a renderer process.
  gfx::Rect caret_rect_;

  DISALLOW_EVIL_CONSTRUCTORS(ImeInput);
};

#endif  // CHROME_BROWSER_IME_INPUT_H_

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