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// 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.
#include <stddef.h>
#include <stdint.h>
#include <vector>
#include "base/macros.h"
#include "base/strings/string_util.h"
#include "ui/base/ime/ui_base_ime_export.h"
#include "ui/events/keycodes/dom/dom_key.h"
namespace ui {
class KeyEvent;
// A class to recognize compose and dead key sequence.
// Outputs composed character.
class UI_BASE_IME_EXPORT CharacterComposer {
using ComposeBuffer = std::vector<DomKey>;
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 base::string16& composed_character() const {
return composed_character_;
// Returns the preedit string.
const base::string16& preedit_string() const { return preedit_string_; }
// An enum to describe composition mode.
enum CompositionMode {
// This is the initial state.
// Composite a character with dead-keys and compose-key.
// Composite a character with a hexadecimal unicode sequence.
// Filters keypress in key sequence mode.
bool FilterKeyPressSequenceMode(const ui::KeyEvent& event);
// Filters keypress in hexadecimal mode.
bool FilterKeyPressHexMode(const ui::KeyEvent& event);
// Commit a character composed from hexadecimal uncode sequence
void CommitHex();
// Updates preedit string in hexadecimal mode.
void UpdatePreeditStringHexMode();
// Remembers keypresses previously filtered.
std::vector<DomKey> compose_buffer_;
// Records hexadecimal digits previously filtered.
std::vector<unsigned int> hex_buffer_;
// A string representing the composed character.
base::string16 composed_character_;
// Preedit string.
base::string16 preedit_string_;
// Composition mode which this instance is in.
CompositionMode composition_mode_;
// Abstract class for determining whether a ComposeBuffer forms a valid
// character composition sequence.
class ComposeChecker {
enum class CheckSequenceResult {
// The sequence is not a composition sequence or the prefix of any
// composition sequence.
// The sequence is a prefix of one or more composition sequences.
// The sequence matches a composition sequence.
ComposeChecker() {}
virtual ~ComposeChecker() {}
virtual CheckSequenceResult CheckSequence(
const ui::CharacterComposer::ComposeBuffer& sequence,
uint32_t* composed_character) const = 0;
// Implementation of |ComposeChecker| using a compact generated tree.
class TreeComposeChecker : public ComposeChecker {
struct CompositionData {
size_t maximum_sequence_length;
int tree_entries;
const uint16_t* tree;
TreeComposeChecker(const CompositionData& data) : data_(data) {}
CheckSequenceResult CheckSequence(
const ui::CharacterComposer::ComposeBuffer& sequence,
uint32_t* composed_character) const override;
bool Find(uint16_t index, uint16_t size, uint16_t key, uint16_t* value) const;
const CompositionData& data_;
} // namespace ui