text: // Copyright 2013 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #ifndef UI_BASE_IME_CHROMEOS_CHARACTER_COMPOSER_H_
  #define UI_BASE_IME_CHROMEOS_CHARACTER_COMPOSER_H_
  
  #include <vector>
  
  #include "base/strings/string_util.h"
  #include "ui/base/ui_export.h"
  
  namespace ui {
  class KeyEvent;
  
  // A class to recognize compose and dead key sequence.
  // Outputs composed character.
  class UI_EXPORT CharacterComposer {
   public:
    CharacterComposer();
    ~CharacterComposer();
  
    void Reset();
  
    // Filters keypress.
    // Returns true if the keypress is recognized as a part of composition
    // sequence.
    // Fabricated events which don't have the native event, are not supported.
    bool FilterKeyPress(const ui::KeyEvent& event);
  
    // Returns a string consisting of composed character.
    // Empty string is returned when there is no composition result.
    const string16& composed_character() const { return composed_character_; }
  
    // Returns the preedit string.
    const string16& preedit_string() const { return preedit_string_; }
  
   private:
    friend class CharacterComposerTest;
  
    // An enum to describe composition mode.
    enum CompositionMode {
      // This is the initial state.
      // Composite a character with dead-keys and compose-key.
      KEY_SEQUENCE_MODE,
      // Composite a character with a hexadecimal unicode sequence.
      HEX_MODE,
    };
  
    // Filters keypress using IBus defined value.
    // Returns true if the keypress is recognized as a part of composition
    // sequence.
    // |keyval| must be a GDK_KEY_* constant.
    // |keycode| must be a X key code.
    // |flags| must be a combination of ui::EF_* flags.
    //
    // composed_character() returns non empty string when there is a character
    // composed after this method returns true.
    // preedit_string() returns non empty string when there is a preedit string
    // after this method returns true.
    // Return values of preedit_string() is empty after this method returns false.
    // composed_character() may have some characters which are consumed in this
    // composing session.
    //
    //
    // TODO(nona): Actually a X KeySym is passed to |keyval|, so we should use
    // XK_* rather than GDK_KEY_*.
    bool FilterKeyPressInternal(unsigned int keyval, unsigned int keycode,
                                int flags);
  
    // Filters keypress in key sequence mode.
    bool FilterKeyPressSequenceMode(unsigned int keyval, int flags);
  
    // Filters keypress in hexadecimal mode.
    bool FilterKeyPressHexMode(unsigned int keyval, unsigned int keycode,
                               int flags);
  
    // Commit a character composed from hexadecimal uncode sequence
    void CommitHex();
  
    // Updates preedit string in hexadecimal mode.
    void UpdatePreeditStringHexMode();
  
    // Remembers keypresses previously filtered.
    std::vector<unsigned int> compose_buffer_;
  
    // A string representing the composed character.
    string16 composed_character_;
  
    // Preedit string.
    string16 preedit_string_;
  
    // Composition mode which this instance is in.
    CompositionMode composition_mode_;
  
    DISALLOW_COPY_AND_ASSIGN(CharacterComposer);
  };
  
  }  // namespace ui
  
  #endif  // UI_BASE_IME_CHROMEOS_CHARACTER_COMPOSER_H_
  