# -*- coding: utf-8 -*-
# vim:et sts=4 sw=4
#
# ibus-typing-booster - A completion input method for IBus
#
# Copyright (c) 2011-2013 Anish Patil <apatil@redhat.com>
# Copyright (c) 2012-2018 Mike FABIAN <mfabian@redhat.com>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>

'''
This file implements the ibus engine for ibus-typing-booster
'''

# “Use of super on an old style class”: pylint: disable=super-on-old-class
# “Wrong continued indentation”: pylint: disable=bad-continuation

import os
import sys
import unicodedata
import re
import time
import locale
from gettext import dgettext
from gi import require_version
require_version('IBus', '1.0')
from gi.repository import IBus
require_version('Gio', '2.0')
from gi.repository import Gio
require_version('GLib', '2.0')
from gi.repository import GLib
from m17n_translit import Transliterator
import itb_util
import itb_emoji

__all__ = (
    "TypingBoosterEngine",
)

_ = lambda a: dgettext("ibus-typing-booster", a)
N_ = lambda a: a

DEBUG_LEVEL = int(0)

# ☐ U+2610 BALLOT BOX
MODE_OFF_SYMBOL = '☐'
# ☑ U+2611 BALLOT BOX WITH CHECK
# 🗹 U+1F5F9 BALLOT_BOX WITH BOLD CHECK
MODE_ON_SYMBOL = '☑'

#  ☺ U+263A WHITE SMILING FACE
# 😃 U+1F603 SMILING FACE WITH OPEN MOUTH
# 🙂 U+1F642 SLIGHTLY SMILING FACE
EMOJI_PREDICTION_MODE_SYMBOL = '🙂'

# 🕶 U+1F576 DARK SUNGLASSES
# 😎 U+1F60E SMILING FACE WITH SUNGLASSES
# 🕵 U+1F575 SLEUTH OR SPY
OFF_THE_RECORD_MODE_SYMBOL = '🕵'

# ⏳ U+23F3 HOURGLASS WITH FLOWING SAND
BUSY_SYMBOL = '⏳'

# ✓ U+2713 CHECK MARK
SPELL_CHECKING_CANDIDATE_SYMBOL = '✓'

# ⭐ U+2B50 WHITE MEDIUM STAR
USER_DATABASE_CANDIDATE_SYMBOL = '⭐'

def argb(alpha, red, green, blue):
    '''Returns a 32bit ARGB value'''
    return (((alpha & 0xff) << 24)
            + ((red & 0xff) << 16)
            + ((green & 0xff) << 8)
            + (blue & 0xff))

def rgb(red, green, blue):
    '''Returns a 32bit ARGB value with the alpha value set to fully opaque'''
    return argb(255, red, green, blue)

class KeyEvent:
    '''Key event class used to make the checking of details of the key
    event easy
    '''
    def __init__(self, keyval, keycode, state):
        self.val = keyval
        self.code = keycode
        self.state = state
        self.name = IBus.keyval_name(self.val)
        self.unicode = IBus.keyval_to_unicode(self.val)
        self.msymbol = self.unicode
        self.shift = self.state & IBus.ModifierType.SHIFT_MASK != 0
        self.lock = self.state & IBus.ModifierType.LOCK_MASK != 0
        self.control = self.state & IBus.ModifierType.CONTROL_MASK != 0
        self.mod1 = self.state & IBus.ModifierType.MOD1_MASK != 0
        self.mod2 = self.state & IBus.ModifierType.MOD2_MASK != 0
        self.mod3 = self.state & IBus.ModifierType.MOD3_MASK != 0
        self.mod4 = self.state & IBus.ModifierType.MOD4_MASK != 0
        self.mod5 = self.state & IBus.ModifierType.MOD5_MASK != 0
        self.button1 = self.state & IBus.ModifierType.BUTTON1_MASK != 0
        self.button2 = self.state & IBus.ModifierType.BUTTON2_MASK != 0
        self.button3 = self.state & IBus.ModifierType.BUTTON3_MASK != 0
        self.button4 = self.state & IBus.ModifierType.BUTTON4_MASK != 0
        self.button5 = self.state & IBus.ModifierType.BUTTON5_MASK != 0
        self.super = self.state & IBus.ModifierType.SUPER_MASK != 0
        self.hyper = self.state & IBus.ModifierType.HYPER_MASK != 0
        self.meta = self.state & IBus.ModifierType.META_MASK != 0
        self.release = self.state & IBus.ModifierType.RELEASE_MASK != 0
        # MODIFIER_MASK: Modifier mask for the all the masks above
        self.modifier = self.state & IBus.ModifierType.MODIFIER_MASK != 0
        if itb_util.is_ascii(self.msymbol):
            if self.control:
                self.msymbol = 'C-' + self.msymbol
            if self.mod1:
                self.msymbol = 'A-' + self.msymbol
            if self.mod5:
                self.msymbol = 'G-' + self.msymbol
    def __str__(self):
        return (
            "val=%s code=%s state=0x%08x name='%s' unicode='%s' msymbol='%s' "
            % (self.val,
               self.code,
               self.state,
               self.name,
               self.unicode,
               self.msymbol)
            + "shift=%s control=%s mod1=%s mod5=%s release=%s\n"
            % (self.shift,
               self.control,
               self.mod1,
               self.mod5,
               self.release))

########################
### Engine Class #####
####################
class TypingBoosterEngine(IBus.Engine):
    '''The IBus Engine for ibus-typing-booster'''

    def __init__(self, bus, obj_path, db, unit_test=False):
        global DEBUG_LEVEL
        try:
            DEBUG_LEVEL = int(os.getenv('IBUS_TYPING_BOOSTER_DEBUG_LEVEL'))
        except (TypeError, ValueError):
            DEBUG_LEVEL = int(0)
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "TypingBoosterEngine.__init__(bus=%s, obj_path=%s, db=%s)\n"
                % (bus, obj_path, db))
        super(TypingBoosterEngine, self).__init__(
            connection=bus.get_connection(), object_path=obj_path)
        self._unit_test = unit_test
        self._input_purpose = 0
        self._has_input_purpose = False
        if hasattr(IBus, 'InputPurpose'):
            self._has_input_purpose = True
        self._lookup_table_is_invalid = False
        self._lookup_table_shows_related_candidates = False
        self._current_auxiliary_text = ''
        self._bus = bus
        self.db = db
        self._setup_pid = 0
        self._gsettings = Gio.Settings(
            schema='org.freedesktop.ibus.engine.typing-booster')
        self._gsettings.connect('changed', self.on_gsettings_value_changed)

        # Between some events sent to ibus like forward_key_event(),
        # delete_surrounding_text(), commit_text(), a sleep is necessary.
        # Without the sleep, these events may be processed out of order.
        self._ibus_event_sleep_seconds = 0.1

        self._emoji_predictions = itb_util.variant_to_value(
            self._gsettings.get_value('emojipredictions'))
        if self._emoji_predictions is None:
            self._emoji_predictions = False # default

        self._min_char_complete = itb_util.variant_to_value(
            self._gsettings.get_value('mincharcomplete'))
        if self._min_char_complete is None:
            self._min_char_complete = 1 # default
        if self._min_char_complete < 1:
            self._min_char_complete = 1 # minimum
        if self._min_char_complete > 9:
            self._min_char_complete = 9 # maximum

        self._page_size = itb_util.variant_to_value(
            self._gsettings.get_value('pagesize'))
        if self._page_size is None:
            self._page_size = 6 # reasonable default page size
        if self._page_size < 1:
            self._page_size = 1 # minimum page size supported
        if self._page_size > 9:
            self._page_size = 9 # maximum page size supported

        self._lookup_table_orientation = itb_util.variant_to_value(
            self._gsettings.get_value('lookuptableorientation'))
        if self._lookup_table_orientation is None:
            self._lookup_table_orientation = IBus.Orientation.VERTICAL

        self._show_number_of_candidates = itb_util.variant_to_value(
            self._gsettings.get_value('shownumberofcandidates'))
        if self._show_number_of_candidates is None:
            self._show_number_of_candidates = False

        self._show_status_info_in_auxiliary_text = itb_util.variant_to_value(
            self._gsettings.get_value('showstatusinfoinaux'))
        if self._show_status_info_in_auxiliary_text is None:
            self._show_status_info_in_auxiliary_text = False

        self._use_digits_as_select_keys = itb_util.variant_to_value(
            self._gsettings.get_value('usedigitsasselectkeys'))
        if self._use_digits_as_select_keys is None:
            self._use_digits_as_select_keys = True

        self._icon_dir = '%s%s%s%s' % (
            os.getenv('IBUS_TYPING_BOOSTER_LOCATION'),
            os.path.sep, 'icons', os.path.sep)

        self._status = '🚀' # FIXME: apparently not used anymore?

        self.is_lookup_table_enabled_by_tab = False
        self._tab_enable = itb_util.variant_to_value(
            self._gsettings.get_value('tabenable'))
        if self._tab_enable is None:
            self._tab_enable = False

        self._off_the_record = itb_util.variant_to_value(
            self._gsettings.get_value('offtherecord'))
        if self._off_the_record is None:
            self._off_the_record = False # default

        self._qt_im_module_workaround = itb_util.variant_to_value(
            self._gsettings.get_value('qtimmoduleworkaround'))
        if self._qt_im_module_workaround is None:
            self._qt_im_module_workaround = False # default

        self._arrow_keys_reopen_preedit = itb_util.variant_to_value(
            self._gsettings.get_value('arrowkeysreopenpreedit'))
        if self._arrow_keys_reopen_preedit is None:
            self._arrow_keys_reopen_preedit = False # default

        self._auto_commit_characters = itb_util.variant_to_value(
            self._gsettings.get_value('autocommitcharacters'))
        if not self._auto_commit_characters:
            self._auto_commit_characters = '' # default

        self._remember_last_used_preedit_ime = False
        self._remember_last_used_preedit_ime = itb_util.variant_to_value(
            self._gsettings.get_value('rememberlastusedpreeditime'))
        if self._remember_last_used_preedit_ime is None:
            self._remember_last_used_preedit_ime = False

        self._dictionary_names = []
        dictionary = itb_util.variant_to_value(
            self._gsettings.get_value('dictionary'))
        if dictionary:
            # There is a dictionary setting in Gsettings, use that:
            names = [x.strip() for x in dictionary.split(',')]
            for name in names:
                if name:
                    self._dictionary_names.append(name)
        else:
            # There is no dictionary setting in Gsettings. Get the default
            # dictionaries for the current effective value of
            # LC_CTYPE and save it to Gsettings:
            self._dictionary_names = itb_util.get_default_dictionaries(
                locale.getlocale(category=locale.LC_CTYPE)[0])
            self._gsettings.set_value(
                'dictionary',
                GLib.Variant.new_string(','.join(self._dictionary_names)))
        self.db.hunspell_obj.set_dictionary_names(self._dictionary_names[:])

        if  self._emoji_predictions:
            if DEBUG_LEVEL > 1:
                sys.stderr.write('Instantiate EmojiMatcher(languages = %s\n'
                                 %self._dictionary_names)
            self.emoji_matcher = itb_emoji.EmojiMatcher(
                languages=self._dictionary_names)
            if DEBUG_LEVEL > 1:
                sys.stderr.write('EmojiMatcher() instantiated.\n')
        else:
            self.emoji_matcher = None

        # The number of current imes needs to be limited to some fixed
        # maximum number because of the property menu to select the preëdit
        # ime. Unfortunately the number of sub-properties for such a menu
        # cannot be changed, as a workaround a fixed number can be used
        # and unused entries can be hidden.
        itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS = 10
        self._current_imes = []
        # Try to get the selected input methods from Gsettings:
        inputmethod = itb_util.variant_to_value(
            self._gsettings.get_value('inputmethod'))
        if inputmethod:
            inputmethods = [x.strip() for x in inputmethod.split(',')]
            for ime in inputmethods:
                if ime:
                    self._current_imes.append(ime)
        if self._current_imes == []:
            # There is no ime set in Gsettings, get a default list
            # of input methods for the current effective value of LC_CTYPE
            # and save it to Gsettings:
            self._current_imes = itb_util.get_default_input_methods(
                locale.getlocale(category=locale.LC_CTYPE)[0])
            self._gsettings.set_value(
                'inputmethod',
                GLib.Variant.new_string(','.join(self._current_imes)))
        if len(self._current_imes) > itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS:
            sys.stderr.write(
                'Trying to set more than the allowed maximum of %s '
                %itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS
                + 'input methods.\n'
                + 'Trying to set: %s\n' %self._current_imes
                + 'Really setting: %s\n'
                %self._current_imes[:itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS])
            self._current_imes = (
                self._current_imes[:itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS])

        self._commit_happened_after_focus_in = False

        self._typed_string = [] # A list of msymbols
        self._typed_string_cursor = 0
        self._p_phrase = ''
        self._pp_phrase = ''
        self._transliterated_strings = {}
        self._transliterators = {}
        self._init_transliterators()
        # self._candidates: hold candidates selected from database and hunspell
        self._candidates = []
        self._lookup_table = IBus.LookupTable()
        self._lookup_table.clear()
        self._lookup_table.set_page_size(self._page_size)
        self._lookup_table.set_orientation(self._lookup_table_orientation)
        self._lookup_table.set_cursor_visible(False)

        self.emoji_prediction_mode_properties = {
            'EmojiPredictionMode.Off': {
                'number': 0,
                'symbol': MODE_OFF_SYMBOL + EMOJI_PREDICTION_MODE_SYMBOL,
                'label': _('Off'),
            },
            'EmojiPredictionMode.On': {
                'number': 1,
                'symbol': MODE_ON_SYMBOL + EMOJI_PREDICTION_MODE_SYMBOL,
                'label': _('On'),
            }
        }
        self.emoji_prediction_mode_menu = {
            'key': 'EmojiPredictionMode',
            'label': _('Unicode symbols and emoji predictions'),
            'tooltip':
            _('Unicode symbols and emoji predictions'),
            'shortcut_hint': '(AltGr-F6, Control+RightMouse)',
            'sub_properties': self.emoji_prediction_mode_properties
        }
        self.off_the_record_mode_properties = {
            'OffTheRecordMode.Off': {
                'number': 0,
                'symbol': MODE_OFF_SYMBOL + OFF_THE_RECORD_MODE_SYMBOL,
                'label': _('Off'),
            },
            'OffTheRecordMode.On': {
                'number': 1,
                'symbol': MODE_ON_SYMBOL + OFF_THE_RECORD_MODE_SYMBOL,
                'label': _('On'),
            }
        }
        self.off_the_record_mode_menu = {
            'key': 'OffTheRecordMode',
            'label': _('Off the record mode'),
            'tooltip': _('Off the record mode'),
            'shortcut_hint': '(AltGr-F9, Alt+RightMouse)',
            'sub_properties': self.off_the_record_mode_properties
        }
        self._prop_dict = {}
        self._sub_props_dict = {}
        self.main_prop_list = []
        self.preedit_ime_menu = {}
        self.preedit_ime_properties = {}
        self.preedit_ime_sub_properties_prop_list = []
        self._update_preedit_ime_menu_dicts()
        self._setup_property = None
        self._init_properties()

        sys.stderr.write(
            '--- Initialized and ready for input: %s ---\n'
            %time.strftime('%Y-%m-%d: %H:%M:%S'))
        self.reset()

    def _init_transliterators(self):
        '''Initialize the dictionary of m17n-db transliterator objects'''
        self._transliterators = {}
        for ime in self._current_imes:
            # using m17n transliteration
            try:
                if DEBUG_LEVEL > 1:
                    sys.stderr.write(
                        "instantiating Transliterator(%(ime)s)\n"
                        %{'ime': ime})
                self._transliterators[ime] = Transliterator(ime)
            except ValueError as error:
                sys.stderr.write(
                    'Error initializing Transliterator %s:\n' %ime
                    + '%s\n' %error
                    + 'Maybe /usr/share/m17n/%s.mim is not installed?\n'
                    %ime)
                # Use dummy transliterator “NoIme” as a fallback:
                self._transliterators[ime] = Transliterator('NoIme')
        self._update_transliterated_strings()

    def is_empty(self):
        '''Checks whether the preëdit is empty

        Returns True if the preëdit is empty, False if not.

        :rtype: boolean
        '''
        return len(self._typed_string) == 0

    def _clear_input(self):
        '''Clear all input'''
        self._lookup_table.clear()
        self._lookup_table.set_cursor_visible(False)
        self._candidates = []
        self._typed_string = []
        self._typed_string_cursor = 0
        for ime in self._current_imes:
            self._transliterated_strings[ime] = ''

    def _insert_string_at_cursor(self, string_to_insert):
        '''Insert typed string at cursor position'''
        if DEBUG_LEVEL > 1:
            sys.stderr.write("_insert_string_at_cursor() string_to_insert=%s\n"
                             %string_to_insert)
            sys.stderr.write("_insert_string_at_cursor() "
                             + "self._typed_string=%s\n"
                             %self._typed_string)
            sys.stderr.write("_insert_string_at_cursor() "
                             + "self._typed_string_cursor=%s\n"
                             %self._typed_string_cursor)
        self._typed_string = self._typed_string[:self._typed_string_cursor] \
                             +string_to_insert \
                             +self._typed_string[self._typed_string_cursor:]
        self._typed_string_cursor += len(string_to_insert)
        self._update_transliterated_strings()

    def _remove_string_before_cursor(self):
        '''Remove typed string before cursor'''
        if self._typed_string_cursor > 0:
            self._typed_string = self._typed_string[self._typed_string_cursor:]
            self._typed_string_cursor = 0
            self._update_transliterated_strings()

    def _remove_string_after_cursor(self):
        '''Remove typed string after cursor'''
        if self._typed_string_cursor < len(self._typed_string):
            self._typed_string = self._typed_string[:self._typed_string_cursor]
            self._update_transliterated_strings()

    def _remove_character_before_cursor(self):
        '''Remove typed character before cursor'''
        if self._typed_string_cursor > 0:
            self._typed_string = (
                self._typed_string[:self._typed_string_cursor-1]
                +self._typed_string[self._typed_string_cursor:])
            self._typed_string_cursor -= 1
            self._update_transliterated_strings()

    def _remove_character_after_cursor(self):
        '''Remove typed character after cursor'''
        if self._typed_string_cursor < len(self._typed_string):
            self._typed_string = (
                self._typed_string[:self._typed_string_cursor]
                +self._typed_string[self._typed_string_cursor+1:])
            self._update_transliterated_strings()

    def get_caret(self):
        '''
        Get caret position in preëdit string

        The preëdit contains the transliterated string, the caret
        position can only be approximated from the cursor position in
        the typed string.

        For example, if the typed string is “gru"n” and the
        transliteration method used is “Latin Postfix”, this
        transliterates to “grün”. Now if the cursor position in the
        typed string is “3”, then the cursor is between the “u”
        and the “"”.  In the transliterated string, this would be in the
        middle of the “ü”. But the caret cannot be shown there of course.

        So the caret position is approximated by transliterating the
        string up to the cursor, i.e. transliterating “gru” which
        gives “gru” and return the length of that
        transliteration as the caret position. Therefore, the caret
        is displayed after the “ü” instead of in the middle of the “ü”.

        This has the effect that when typing “arrow left” over a
        preëdit string “grün” which has been typed as “gru"n”
        using Latin Postfix translation, one needs to type “arrow
        left” two times to get over the “ü”.

        If the cursor is at position 3 in the input string “gru"n”,
        and one types an “a” there, the input string becomes
        “grua"n” and the transliterated string, i.e. the preëdit,
        becomes “gruän”, which might be a bit surprising, but that
        is at least consistent and better then nothing at the moment.

        This problem is certainly worse in languages like Marathi where
        these length differences between the input and the transliteration
        are worse.

        But until this change, the code to move around and edit in
        the preëdit did not work at all. Now it works fine if
        no transliteration is used and works better than nothing
        even if transliteration is used.
        '''
        preedit_ime = self._current_imes[0]
        transliterated_string_up_to_cursor = (
            self._transliterators[preedit_ime].transliterate(
                self._typed_string[:self._typed_string_cursor]))
        if preedit_ime in ['ko-romaja', 'ko-han2']:
            transliterated_string_up_to_cursor = unicodedata.normalize(
                'NFKD', transliterated_string_up_to_cursor)
        transliterated_string_up_to_cursor = unicodedata.normalize(
            'NFC', transliterated_string_up_to_cursor)
        return len(transliterated_string_up_to_cursor)

    def _append_candidate_to_lookup_table(
            self, phrase='', user_freq=0, comment='',
            from_user_db=False, spell_checking=False):
        '''append candidate to lookup_table'''
        if not phrase:
            return
        phrase = unicodedata.normalize('NFC', phrase)
        # U+2028 LINE SEPARATOR and U+2029 PARAGRAPH SEPARATOR make
        # the line spacing in the lookup table huge, which looks ugly.
        # Remove them to make the lookup table look better.
        # Selecting them does still work because the string which
        # is committed is not read from the lookup table but
        # from self._candidates[index][0].
        phrase = phrase.replace(' ','').replace(' ','')
        # Embed “phrase” and “comment” separately with “Explicit
        # Directional Embeddings” (RLE, LRE, PDF).
        #
        # Using “Explicit Directional Isolates” (FSI, PDI) would be
        # better, but they don’t seem to work yet. Maybe not
        # implemented yet?
        #
        # This embedding can be necessary when “phrase” and “comment”
        # have different bidi directions.
        #
        # For example, the currency symbol ﷼ U+FDFC RIAL SIGN is a
        # strong right-to-left character. When looking up related
        # symbols for another currency symbol, U+FDFC RIAL SIGN should
        # be among the candidates. But the comment is just the name
        # from UnicodeData.txt. Without adding any directional
        # formatting characters, the candidate would look like:
        #
        #     1. ['rial sign ['sc ﷼
        #
        # But it should look like:
        #
        #     1.  rial sign ['sc'] ﷼
        #
        # Without the embedding, similar problems happen when “comment”
        # is right-to-left but “phrase” is not.
        phrase = itb_util.bidi_embed(phrase)
        attrs = IBus.AttrList()
        if comment:
            phrase += ' ' + itb_util.bidi_embed(comment)
        if DEBUG_LEVEL > 0:
            if spell_checking: # spell checking suggestion
                phrase = phrase + ' ' + SPELL_CHECKING_CANDIDATE_SYMBOL
                if  DEBUG_LEVEL > 1:
                    attrs.append(IBus.attr_foreground_new(
                        rgb(0xff, 0x00, 0x00), 0, len(phrase)))
            elif from_user_db:
                # This was found in the user database.  So it is
                # possible to delete it with a key binding or
                # mouse-click, if the user desires. Mark it
                # differently to show that it is deletable:
                phrase = phrase + ' ' + USER_DATABASE_CANDIDATE_SYMBOL
                if  DEBUG_LEVEL > 1:
                    attrs.append(IBus.attr_foreground_new(
                        rgb(0xff, 0x7f, 0x00), 0, len(phrase)))
            else:
                # This is a (possibly accent insensitive) match in a
                # hunspell dictionary or an emoji matched by
                # EmojiMatcher.
                if  DEBUG_LEVEL > 1:
                    attrs.append(IBus.attr_foreground_new(
                        rgb(0x00, 0x00, 0x00), 0, len(phrase)))
        if DEBUG_LEVEL > 1:
            phrase += ' ' + str(user_freq)
            attrs.append(IBus.attr_foreground_new(
                rgb(0x00, 0xff, 0x00),
                len(phrase) - len(str(user_freq)),
                len(phrase)))
        text = IBus.Text.new_from_string(phrase)
        i = 0
        while attrs.get(i) != None:
            attr = attrs.get(i)
            text.append_attribute(attr.get_attr_type(),
                                  attr.get_value(),
                                  attr.get_start_index(),
                                  attr.get_end_index())
            i += 1
        self._lookup_table.append_candidate(text)
        self._lookup_table.set_cursor_visible(False)

    def _update_candidates(self):
        '''Update the list of candidates and fill the lookup table with the
        candidates
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write("_update_candidates() self._typed_string=%s\n"
                             %self._typed_string)
        self._lookup_table.clear()
        self._lookup_table.set_cursor_visible(False)
        if self.is_empty():
            # Nothing to do when there is no input available.
            # One can accidentally end up here even though the
            # input is empty because this is called by GLib.idle_add().
            # Better make sure that calling this function with
            # empty input does not pointlessly try to find candidates.
            return
        self._candidates = []
        phrase_frequencies = {}
        for ime in self._current_imes:
            if self._transliterated_strings[ime]:
                candidates = []
                prefix_length = 0
                prefix = ''
                stripped_transliterated_string = (
                    itb_util.lstrip_token(self._transliterated_strings[ime]))
                if (stripped_transliterated_string
                        and ((len(stripped_transliterated_string)
                              >= self._min_char_complete)
                             or self._tab_enable)):
                    prefix_length = (
                        len(self._transliterated_strings[ime])
                        - len(stripped_transliterated_string))
                    if prefix_length:
                        prefix = (
                            self._transliterated_strings[ime][0:prefix_length])
                    try:
                        candidates = self.db.select_words(
                            stripped_transliterated_string,
                            p_phrase=self._p_phrase,
                            pp_phrase=self._pp_phrase)
                    except:
                        import traceback
                        traceback.print_exc()
                if candidates and prefix:
                    candidates = [(prefix+x[0], x[1]) for x in candidates]
                for cand in candidates:
                    if cand[0] in phrase_frequencies:
                        phrase_frequencies[cand[0]] = max(
                            phrase_frequencies[cand[0]], cand[1])
                    else:
                        phrase_frequencies[cand[0]] = cand[1]
        phrase_candidates = self.db.best_candidates(phrase_frequencies)
        if (self._emoji_predictions
            or self._typed_string[0] in (' ', '_')
            or self._typed_string[-1] in (' ', '_')):
            # If emoji mode is off and the emoji predictions are
            # triggered here because the typed string starts with a '
            # ' or a '_', the emoji matcher might not have been
            # initialized yet.  Make sure it is initialized now:
            if (not self.emoji_matcher
                or
                self.emoji_matcher.get_languages()
                != self._dictionary_names):
                self.emoji_matcher = itb_emoji.EmojiMatcher(
                    languages=self._dictionary_names)
            emoji_scores = {}
            for ime in self._current_imes:
                if (self._transliterated_strings[ime]
                        and ((len(self._transliterated_strings[ime])
                              >= self._min_char_complete)
                             or self._tab_enable)):
                    emoji_candidates = self.emoji_matcher.candidates(
                        self._transliterated_strings[ime])
                    for cand in emoji_candidates:
                        if (cand[0] not in emoji_scores
                                or cand[2] > emoji_scores[cand[0]][0]):
                            emoji_scores[cand[0]] = (cand[2], cand[1])
            phrase_candidates_emoji_name = []
            for cand in phrase_candidates:
                if cand[0] in emoji_scores:
                    phrase_candidates_emoji_name.append((
                        cand[0], cand[1], emoji_scores[cand[0]][1],
                        cand[1] > 0, cand[1] < 0))
                    # avoid duplicates in the lookup table:
                    del emoji_scores[cand[0]]
                else:
                    phrase_candidates_emoji_name.append((
                        cand[0], cand[1], self.emoji_matcher.name(cand[0]),
                        cand[1] > 0, cand[1] < 0))
            emoji_candidates = []
            for (key, value) in sorted(
                    emoji_scores.items(),
                    key=lambda x: (
                        - x[1][0],   # score
                        - len(x[0]), # length of emoji string
                        x[1][1]      # name of emoji
                    ))[:20]:
                emoji_candidates.append((key, value[0], value[1]))
            page_size = self._lookup_table.get_page_size()
            phrase_candidates_top = phrase_candidates_emoji_name[:page_size-1]
            phrase_candidates_rest = phrase_candidates_emoji_name[page_size-1:]
            emoji_candidates_top = emoji_candidates[:page_size]
            emoji_candidates_rest = emoji_candidates[page_size:]
            for cand in phrase_candidates_top:
                self._candidates.append(
                    (cand[0], cand[1], cand[2], cand[3], cand[4]))
            for cand in emoji_candidates_top:
                self._candidates.append(
                    (cand[0], cand[1], cand[2], False, False))
            for cand in phrase_candidates_rest:
                self._candidates.append(
                    (cand[0], cand[1], cand[2], cand[3], cand[4]))
            for cand in emoji_candidates_rest:
                self._candidates.append(
                    (cand[0], cand[1], cand[2], False, False))
        else:
            for cand in phrase_candidates:
                self._candidates.append(
                    (cand[0], cand[1], '', cand[1] > 0, cand[1] < 0))
        for cand in self._candidates:
            self._append_candidate_to_lookup_table(
                phrase=cand[0], user_freq=cand[1], comment=cand[2],
                from_user_db=cand[3], spell_checking=cand[4])
        return True

    def _arrow_down(self):
        '''Process Arrow Down Key Event
        Move Lookup Table cursor down'''
        if not self._lookup_table.cursor_visible:
            self._lookup_table.set_cursor_visible(True)
            return True
        elif self._lookup_table.cursor_down():
            return True
        return False

    def _arrow_up(self):
        '''Process Arrow Up Key Event
        Move Lookup Table cursor up'''
        self._lookup_table.set_cursor_visible(True)
        if self._lookup_table.cursor_up():
            return True
        return False

    def _page_down(self):
        '''Process Page Down Key Event
        Move Lookup Table page down'''
        self._lookup_table.set_cursor_visible(True)
        if self._lookup_table.page_down():
            return True
        return False

    def _page_up(self):
        '''Process Page Up Key Event
        move Lookup Table page up'''
        self._lookup_table.set_cursor_visible(True)
        if self._lookup_table.page_up():
            return True
        return False

    def _set_lookup_table_cursor_pos_in_current_page(self, index):
        '''Sets the cursor in the lookup table to index in the current page

        Returns True if successful, False if not.

        The topmost candidate has the index 0 and the label “1”.
        '''
        page_size = self._lookup_table.get_page_size()
        if index > page_size:
            return False
        page, dummy_pos_in_page = divmod(self._lookup_table.get_cursor_pos(),
                                         page_size)
        new_pos = page * page_size + index
        if new_pos > self._lookup_table.get_number_of_candidates():
            return False
        self._lookup_table.set_cursor_pos(new_pos)
        return True

    def get_string_from_lookup_table_cursor_pos(self):
        '''
        Get the candidate at the current cursor position in the lookup
        table.
        '''
        if not self._candidates:
            return ''
        index = self._lookup_table.get_cursor_pos()
        if index >= len(self._candidates):
            # the index given is out of range
            return ''
        return self._candidates[index][0]

    def get_string_from_lookup_table_current_page(self, index):
        '''
        Get the candidate at “index” in the currently visible
        page of the lookup table. The topmost candidate
        has the index 0 and has the label “1.”.
        '''
        if not self._set_lookup_table_cursor_pos_in_current_page(index):
            return ''
        return self.get_string_from_lookup_table_cursor_pos()

    def remove_candidate_from_user_database(self, index):
        '''Remove the candidate shown at index in the candidate list
        from the user database.

        The index parameter should start from 0.

        The removal is done independent of the input phrase, all
        rows in the user database for that phrase are deleted.

        It does not matter either whether this is a user defined
        phrase or a phrase which can be found in the hunspell
        dictionaries.  In both cases, it is removed from the user
        database.

        In case of a system phrase, which can be found in the hunspell
        dictionaries, this means that the phrase could still appear in
        the suggestions after removing it from the user database
        because it still can be suggested by the hunspell
        dictionaries. But it becomes less likely because removing a
        system phrase from the user database resets its user frequency
        to 0 again.

        So the user can always try to delete a phrase if he does not
        want the phrase to be suggested wich such a high priority, no
        matter whether it is a system phrase or a user defined phrase.
        '''
        if not self._set_lookup_table_cursor_pos_in_current_page(index):
            return False
        phrase = self.get_string_from_lookup_table_cursor_pos()
        if not phrase:
            return False
        # If the candidate to be removed from the user database starts
        # with characters which are stripped from tokens, we probably
        # want to delete the stripped candidate.  I.e. if the
        # candidate is “_somestuff” we should delete “somestuff” from
        # the user database. Especially when triggering an emoji
        # search with the prefix “_” this is the case. For example,
        # when one types “_ca” one could get the flag of Canada “_🇨🇦”
        # or the castle emoji “_🏰” as suggestions from the user
        # database if one has typed these emoji before. But only the
        # emoji came from the database, not the prefix “_”, because it
        # is one of the prefixes stripped from tokens.  Trying to
        # delete the complete candidate from the user database won’t
        # achieve anything, only the stripped token is in the
        # database.
        stripped_phrase = itb_util.lstrip_token(phrase)
        if stripped_phrase:
            self.db.remove_phrase(phrase=stripped_phrase, commit=True)
        # Try to remove the whole candidate as well from the database.
        # Probably this won’t do anything, just to make sure that it
        # is really removed even if the prefix also ended up in the
        # database for whatever reason (It could be because the list
        # of prefixes to strip from tokens has changed compared to a
        # an older release of ibus-typing-booster).
        self.db.remove_phrase(phrase=phrase, commit=True)
        return True

    def get_cursor_pos(self):
        '''get lookup table cursor position'''
        return self._lookup_table.get_cursor_pos()

    def get_lookup_table(self):
        '''Get lookup table'''
        return self._lookup_table

    def set_lookup_table(self, lookup_table):
        '''Set lookup table'''
        self._lookup_table = lookup_table

    def get_p_phrase(self):
        '''Get previous word'''
        return self._p_phrase

    def get_pp_phrase(self):
        '''Get word before previous word'''
        return self._pp_phrase

    def push_context(self, phrase):
        '''Pushes a word on the context stack which remembers the last two
        words typed.
        '''
        self._pp_phrase = self._p_phrase
        self._p_phrase = phrase

    def clear_context(self):
        '''Clears the context stack which remembers the last two words typed
        '''
        self._pp_phrase = ''
        self._p_phrase = ''

    def _update_transliterated_strings(self):
        '''Transliterates the current input (list of msymbols) for all current
        input methods and stores the results in a dictionary.
        '''
        self._transliterated_strings = {}
        for ime in self._current_imes:
            self._transliterated_strings[ime] = (
                self._transliterators[ime].transliterate(
                    self._typed_string))
            if ime in ['ko-romaja', 'ko-han2']:
                self._transliterated_strings[ime] = unicodedata.normalize(
                    'NFKD', self._transliterated_strings[ime])
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "_update_transliterated_strings() self._typed_string=%s\n"
                %self._typed_string)
            sys.stderr.write(
                "_update_transliterated_strings() "
                + "self._transliterated_strings=%s\n"
                %self._transliterated_strings)

    def get_current_imes(self):
        '''Get current list of input methods

        It is important to return a copy, we do not want to change
        the private member variable directly.

        :rtype: List of strings
        '''
        return self._current_imes[:]

    def set_current_imes(self, imes, update_gsettings=True):
        '''Set current list of input methods

        :param imes: List of input methods
        :type imes: List of strings
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if imes == self._current_imes: # nothing to do
            return
        if len(imes) > itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS:
            sys.stderr.write(
                'Trying to set more than the allowed maximum of %s '
                %itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS
                + 'input methods.\n'
                + 'Trying to set: %s\n' %imes
                + 'Really setting: %s\n'
                %imes[:itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS])
            imes = imes[:itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS]
        if set(imes) != set(self._current_imes):
            # Input methods have been added or removed from the list
            # of current input methods. Initialize the
            # transliterators. If only the order of the input methods
            # has changed, initialising the transliterators is not
            # necessary (and neither is updating the transliterated
            # strings necessary).
            self._current_imes = imes
            self._init_transliterators()
        else:
            self._current_imes = imes
        self._update_preedit_ime_menu_dicts()
        self._init_or_update_property_menu_preedit_ime(
            self.preedit_ime_menu, current_mode=0)
        if not self.is_empty():
            self._update_ui()
        if update_gsettings:
            self._gsettings.set_value(
                'inputmethod',
                GLib.Variant.new_string(','.join(imes)))

    def set_dictionary_names(self, dictionary_names, update_gsettings=True):
        '''Set current dictionary names

        :param dictionary_names: List of names of dictionaries to use
        :type dictionary_names: List of strings
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if dictionary_names == self._dictionary_names: # nothing to do
            return
        self._dictionary_names = dictionary_names
        self.db.hunspell_obj.set_dictionary_names(dictionary_names)
        if self._emoji_predictions:
            if (not self.emoji_matcher
                    or
                    self.emoji_matcher.get_languages()
                    != dictionary_names):
                self.emoji_matcher = itb_emoji.EmojiMatcher(
                    languages=dictionary_names)
        if not self.is_empty():
            self._update_ui()
        if update_gsettings:
            self._gsettings.set_value(
                'dictionary',
                GLib.Variant.new_string(','.join(dictionary_names)))

    def get_dictionary_names(self):
        '''Get current list of dictionary names

        :rtype: list of strings
        '''
        # It is important to return a copy, we do not want to change
        # the private member variable directly.
        return self._dictionary_names[:]

    def _update_preedit_ime_menu_dicts(self):
        '''
        Update the dictionary for the preëdit ime menu.
        '''
        self.preedit_ime_properties = {}
        current_imes = self.get_current_imes()
        current_imes_max = itb_util.MAXIMUM_NUMBER_OF_INPUT_METHODS
        for i in range(0, current_imes_max):
            if i < len(current_imes):
                self.preedit_ime_properties[
                    'PreeditIme.' + str(i)
                ] = {'number': i,
                     'symbol': current_imes[i],
                     'label': current_imes[i],
                     'tooltip': '', # tooltips do not work in sub-properties
                }
            else:
                self.preedit_ime_properties[
                    'PreeditIme.'+str(i)
                ] = {'number': i, 'symbol': '', 'label': '', 'tooltip': ''}
        self.preedit_ime_menu = {
            'key': 'PreeditIme',
            'label': _('Preedit input method'),
            'tooltip': _('Switch preedit input method'),
            'shortcut_hint': '(Ctrl+ArrowUp, Ctrl+ArrowDown)',
            'sub_properties': self.preedit_ime_properties}

    def _init_or_update_property_menu_preedit_ime(self, menu, current_mode=0):
        '''
        Initialize or update the ibus property menu for
        the preëdit input method.
        '''
        key = menu['key']
        sub_properties = menu['sub_properties']
        for prop in sub_properties:
            if sub_properties[prop]['number'] == int(current_mode):
                symbol = sub_properties[prop]['symbol']
                label = '%(label)s (%(symbol)s) %(shortcut_hint)s' % {
                    'label': menu['label'],
                    'symbol': symbol,
                    'shortcut_hint': menu['shortcut_hint']}
                tooltip = '%(tooltip)s\n%(shortcut_hint)s' % {
                    'tooltip': menu['tooltip'],
                    'shortcut_hint': menu['shortcut_hint']}
        visible = len(self.get_current_imes()) > 1
        self._init_or_update_sub_properties_preedit_ime(
            sub_properties, current_mode=current_mode)
        if not key in self._prop_dict: # initialize property
            self._prop_dict[key] = IBus.Property(
                key=key,
                prop_type=IBus.PropType.MENU,
                label=IBus.Text.new_from_string(label),
                symbol=IBus.Text.new_from_string(symbol),
                tooltip=IBus.Text.new_from_string(tooltip),
                sensitive=visible,
                visible=visible,
                state=IBus.PropState.UNCHECKED,
                sub_props=self.preedit_ime_sub_properties_prop_list)
            self.main_prop_list.append(self._prop_dict[key])
        else:  # update the property
            self._prop_dict[key].set_label(
                IBus.Text.new_from_string(label))
            self._prop_dict[key].set_symbol(
                IBus.Text.new_from_string(symbol))
            self._prop_dict[key].set_tooltip(
                IBus.Text.new_from_string(tooltip))
            self._prop_dict[key].set_sensitive(visible)
            self._prop_dict[key].set_visible(visible)
            self.update_property(self._prop_dict[key]) # important!

    def _init_or_update_sub_properties_preedit_ime(
            self, modes, current_mode=0):
        '''
        Initialize or update the sub-properties of the property menu
        for the preëdit input method.
        '''
        if not self.preedit_ime_sub_properties_prop_list:
            update = False
            self.preedit_ime_sub_properties_prop_list = IBus.PropList()
        else:
            update = True
        number_of_current_imes = len(self.get_current_imes())
        for mode in sorted(modes, key=lambda x: (modes[x]['number'])):
            visible = modes[mode]['number'] < number_of_current_imes
            if modes[mode]['number'] == int(current_mode):
                state = IBus.PropState.CHECKED
            else:
                state = IBus.PropState.UNCHECKED
            label = modes[mode]['label']
            if 'tooltip' in modes[mode]:
                tooltip = modes[mode]['tooltip']
            else:
                tooltip = ''
            if not update: # initialize property
                self._prop_dict[mode] = IBus.Property(
                    key=mode,
                    prop_type=IBus.PropType.RADIO,
                    label=IBus.Text.new_from_string(label),
                    tooltip=IBus.Text.new_from_string(tooltip),
                    sensitive=visible,
                    visible=visible,
                    state=state,
                    sub_props=None)
                self.preedit_ime_sub_properties_prop_list.append(
                    self._prop_dict[mode])
            else: # update property
                self._prop_dict[mode].set_label(
                    IBus.Text.new_from_string(label))
                self._prop_dict[mode].set_tooltip(
                    IBus.Text.new_from_string(tooltip))
                self._prop_dict[mode].set_sensitive(visible)
                self._prop_dict[mode].set_visible(visible)
                self.update_property(self._prop_dict[mode]) # important!

    def _init_or_update_property_menu(self, menu, current_mode=0):
        '''
        Initialize or update a ibus property menu
        '''
        menu_key = menu['key']
        sub_properties_dict = menu['sub_properties']
        for prop in sub_properties_dict:
            if sub_properties_dict[prop]['number'] == int(current_mode):
                symbol = sub_properties_dict[prop]['symbol']
                label = '%(symbol)s %(label)s %(shortcut_hint)s' % {
                    'label': menu['label'],
                    'symbol': symbol,
                    'shortcut_hint': menu['shortcut_hint']}
                tooltip = '%(tooltip)s\n%(shortcut_hint)s' % {
                    'tooltip': menu['tooltip'],
                    'shortcut_hint': menu['shortcut_hint']}
        self._init_or_update_sub_properties(
            menu_key, sub_properties_dict, current_mode=current_mode)
        if not menu_key in self._prop_dict: # initialize property
            self._prop_dict[menu_key] = IBus.Property(
                key=menu_key,
                prop_type=IBus.PropType.MENU,
                label=IBus.Text.new_from_string(label),
                symbol=IBus.Text.new_from_string(symbol),
                tooltip=IBus.Text.new_from_string(tooltip),
                sensitive=True,
                visible=True,
                state=IBus.PropState.UNCHECKED,
                sub_props=self._sub_props_dict[menu_key])
            self.main_prop_list.append(self._prop_dict[menu_key])
        else: # update the property
            self._prop_dict[menu_key].set_label(
                IBus.Text.new_from_string(label))
            self._prop_dict[menu_key].set_symbol(
                IBus.Text.new_from_string(symbol))
            self._prop_dict[menu_key].set_tooltip(
                IBus.Text.new_from_string(tooltip))
            self._prop_dict[menu_key].set_sensitive(True)
            self._prop_dict[menu_key].set_visible(True)
            self.update_property(self._prop_dict[menu_key]) # important!

    def _init_or_update_sub_properties(self, menu_key, modes, current_mode=0):
        '''
        Initialize or update the sub-properties of a property menu entry.
        '''
        if not menu_key in self._sub_props_dict:
            update = False
            self._sub_props_dict[menu_key] = IBus.PropList()
        else:
            update = True
        for mode in sorted(modes, key=lambda x: (modes[x]['number'])):
            if modes[mode]['number'] == int(current_mode):
                state = IBus.PropState.CHECKED
            else:
                state = IBus.PropState.UNCHECKED
            label = modes[mode]['label']
            if 'tooltip' in modes[mode]:
                tooltip = modes[mode]['tooltip']
            else:
                tooltip = ''
            if not update: # initialize property
                self._prop_dict[mode] = IBus.Property(
                    key=mode,
                    prop_type=IBus.PropType.RADIO,
                    label=IBus.Text.new_from_string(label),
                    tooltip=IBus.Text.new_from_string(tooltip),
                    sensitive=True,
                    visible=True,
                    state=state,
                    sub_props=None)
                self._sub_props_dict[menu_key].append(
                    self._prop_dict[mode])
            else: # update property
                self._prop_dict[mode].set_label(
                    IBus.Text.new_from_string(label))
                self._prop_dict[mode].set_tooltip(
                    IBus.Text.new_from_string(tooltip))
                self._prop_dict[mode].set_sensitive(True)
                self._prop_dict[mode].set_visible(True)
                self._prop_dict[mode].set_state(state)
                self.update_property(self._prop_dict[mode]) # important!

    def _init_properties(self):
        '''
        Initialize the ibus property menus
        '''
        self._prop_dict = {}
        self.main_prop_list = IBus.PropList()

        self._init_or_update_property_menu(
            self.emoji_prediction_mode_menu,
            self._emoji_predictions)

        self._init_or_update_property_menu(
            self.off_the_record_mode_menu,
            self._off_the_record)

        self._init_or_update_property_menu_preedit_ime(
            self.preedit_ime_menu, current_mode=0)

        self._setup_property = IBus.Property(
            key='setup',
            label=IBus.Text.new_from_string(_('Setup')),
            icon='gtk-preferences',
            tooltip=IBus.Text.new_from_string(
                _('Preferences for ibus-typing-booster')),
            sensitive=True,
            visible=True)
        self.main_prop_list.append(self._setup_property)
        self.register_properties(self.main_prop_list)

    def do_property_activate(
            self, ibus_property, prop_state=IBus.PropState.UNCHECKED):
        '''
        Handle clicks on properties
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "do_property_activate() ibus_property=%s prop_state=%s\n"
                %(ibus_property, prop_state))
        if ibus_property == "setup":
            self._start_setup()
            return
        if prop_state != IBus.PropState.CHECKED:
            # If the mouse just hovered over a menu button and
            # no sub-menu entry was clicked, there is nothing to do:
            return
        if ibus_property.startswith(self.preedit_ime_menu['key']+'.'):
            number = self.preedit_ime_properties[ibus_property]['number']
            if number != 0:
                # If number 0 has been clicked, there is nothing to
                # do, the first one is already the preedit input
                # method
                imes = self.get_current_imes()
                self.set_current_imes(
                    [imes[number]] + imes[number+1:] + imes[:number],
                    update_gsettings=self._remember_last_used_preedit_ime)
            return
        if ibus_property.startswith(
                self.emoji_prediction_mode_menu['key'] + '.'):
            self.set_emoji_prediction_mode(
                bool(self.emoji_prediction_mode_properties
                     [ibus_property]['number']))
            return
        if ibus_property.startswith(
                self.off_the_record_mode_menu['key'] + '.'):
            self.set_off_the_record_mode(
                bool(self.off_the_record_mode_properties
                     [ibus_property]['number']))
            return

    def _start_setup(self):
        '''Start the setup tool if it is not running yet'''
        if self._setup_pid != 0:
            pid, dummy_state = os.waitpid(self._setup_pid, os.P_NOWAIT)
            if pid != self._setup_pid:
                # If the last setup tool started from here is still
                # running the pid returned by the above os.waitpid()
                # is 0. In that case just return, don’t start a
                # second setup tool.
                return
            self._setup_pid = 0
        setup_cmd = os.path.join(
            os.getenv('IBUS_TYPING_BOOSTER_LIB_LOCATION'),
            'ibus-setup-typing-booster')
        self._setup_pid = os.spawnl(
            os.P_NOWAIT,
            setup_cmd,
            'ibus-setup-typing-booster')

    def reset(self):
        '''Clear the preëdit and close the lookup table
        '''
        self._clear_input()
        self._update_ui()

    def do_destroy(self):
        '''Called when this input engine is destroyed
        '''
        self.reset()
        self.do_focus_out()
        super(TypingBoosterEngine, self).destroy()

    def _update_preedit(self):
        '''Update Preedit String in UI'''
        # get_caret() should also use NFC!
        _str = unicodedata.normalize(
            'NFC', self._transliterated_strings[
                self.get_current_imes()[0]])
        if _str == '':
            super(TypingBoosterEngine, self).update_preedit_text(
                IBus.Text.new_from_string(''), 0, False)
        else:
            attrs = IBus.AttrList()
            attrs.append(IBus.attr_underline_new(
                IBus.AttrUnderline.SINGLE, 0, len(_str)))
            text = IBus.Text.new_from_string(_str)
            i = 0
            while attrs.get(i) != None:
                attr = attrs.get(i)
                text.append_attribute(attr.get_attr_type(),
                                      attr.get_value(),
                                      attr.get_start_index(),
                                      attr.get_end_index())
                i += 1
            super(TypingBoosterEngine, self).update_preedit_text(
                text, self.get_caret(), True)

    def _update_aux(self):
        '''Update auxiliary text'''
        aux_string = ''
        if self._show_number_of_candidates:
            aux_string = '(%d / %d) ' % (
                self.get_lookup_table().get_cursor_pos() + 1,
                self.get_lookup_table().get_number_of_candidates())
        if self._show_status_info_in_auxiliary_text:
            preedit_ime = self.get_current_imes()[0]
            if preedit_ime != 'NoIme':
                aux_string += preedit_ime + ' '
            if self._emoji_predictions:
                aux_string += (
                    MODE_ON_SYMBOL + EMOJI_PREDICTION_MODE_SYMBOL + ' ')
            else:
                aux_string += (
                    MODE_OFF_SYMBOL + EMOJI_PREDICTION_MODE_SYMBOL + ' ')
            if self._off_the_record:
                aux_string += (
                    MODE_ON_SYMBOL + OFF_THE_RECORD_MODE_SYMBOL + ' ')
            else:
                aux_string += (
                    MODE_OFF_SYMBOL + OFF_THE_RECORD_MODE_SYMBOL + ' ')
        # Colours do not work at the moment in the auxiliary text!
        # Needs fix in ibus.
        attrs = IBus.AttrList()
        attrs.append(IBus.attr_foreground_new(
            rgb(0x95, 0x15, 0xb5),
            0,
            len(aux_string)))
        if DEBUG_LEVEL > 0:
            context = (
                'Context: ' + self.get_pp_phrase()
                + ' ' + self.get_p_phrase())
            aux_string += context
            attrs.append(IBus.attr_foreground_new(
                rgb(0x00, 0xff, 0x00),
                len(aux_string)-len(context),
                len(aux_string)))
        text = IBus.Text.new_from_string(aux_string)
        i = 0
        while attrs.get(i) != None:
            attr = attrs.get(i)
            text.append_attribute(attr.get_attr_type(),
                                  attr.get_value(),
                                  attr.get_start_index(),
                                  attr.get_end_index())
            i += 1
        visible = True
        if (self.get_lookup_table().get_number_of_candidates() == 0
            or (self._tab_enable
                and not self.is_lookup_table_enabled_by_tab)
            or not aux_string):
            visible = False
        super(TypingBoosterEngine, self).update_auxiliary_text(text, visible)
        self._current_auxiliary_text = text

    def _update_lookup_table(self):
        '''Update the lookup table

        Show it if it is not empty and not disabled, otherwise hide it.
        '''
        # Also make sure to hide lookup table if there are
        # no candidates to display. On f17, this makes no
        # difference but gnome-shell in f18 will display
        # an empty suggestion popup if the number of candidates
        # is zero!
        if (self.is_empty()
            or self.get_lookup_table().get_number_of_candidates() == 0
            or (self._tab_enable and not self.is_lookup_table_enabled_by_tab)):
            self.hide_lookup_table()
        else:
            self.update_lookup_table(self.get_lookup_table(), True)

    def _update_lookup_table_and_aux(self):
        '''Update the lookup table and the auxiliary text'''
        self._update_lookup_table()
        self._update_aux()
        self._lookup_table_is_invalid = False

    def _update_candidates_and_lookup_table_and_aux(self):
        '''Update the candidates, the lookup table and the auxiliary text'''
        self._update_candidates()
        self._update_lookup_table_and_aux()

    def _update_ui(self):
        '''Update User Interface'''
        self._update_preedit()
        if self.is_empty():
            # Hide lookup table again if preëdit became empty and
            # suggestions are only enabled by Tab key:
            self.is_lookup_table_enabled_by_tab = False
        if (self.is_empty()
            or (self._tab_enable and not self.is_lookup_table_enabled_by_tab)):
            # If the lookup table would be hidden anyway, there is no
            # point in updating the candidates, save some time by making
            # sure the lookup table and the auxiliary text are really
            # hidden and return immediately:
            self.hide_lookup_table()
            self._current_auxiliary_text = IBus.Text.new_from_string('')
            super(TypingBoosterEngine, self).update_auxiliary_text(
                self._current_auxiliary_text, False)
            return
        self._lookup_table_shows_related_candidates = False
        if self._lookup_table_is_invalid:
            return
        self._lookup_table_is_invalid = True
        # Don’t show the lookup table if it is invalid anway
        self.get_lookup_table().clear()
        self.get_lookup_table().set_cursor_visible(False)
        self.hide_lookup_table()
        # Show an hourglass with moving sand in the auxiliary text to
        # indicate that the lookup table is being updated:
        super(TypingBoosterEngine, self).update_auxiliary_text(
            IBus.Text.new_from_string(BUSY_SYMBOL), True)
        if self._unit_test:
            self._update_candidates_and_lookup_table_and_aux()
        else:
            GLib.idle_add(self._update_candidates_and_lookup_table_and_aux)

    def _lookup_related_candidates(self):
        '''Lookup related (similar) emoji or related words (synonyms,
        hyponyms, hypernyms).
        '''
        # We might end up here by typing a shortcut key like
        # AltGr+F12.  This should also work when suggestions are only
        # enabled by Tab and are currently disabled.  Typing such a
        # shortcut key explicitly requests looking up related
        # candidates, so it should have the same effect as Tab and
        # enable the lookup table:
        if self._tab_enable and not self.is_lookup_table_enabled_by_tab:
            self.is_lookup_table_enabled_by_tab = True
        phrase = ''
        if (self.get_lookup_table().get_number_of_candidates()
            and  self.get_lookup_table().cursor_visible):
            phrase = self.get_string_from_lookup_table_cursor_pos()
        else:
            phrase = self._transliterated_strings[
                self.get_current_imes()[0]]
        if not phrase:
            return
        # Hide lookup table and show an hourglass with moving sand in
        # the auxiliary text to indicate that the lookup table is
        # being updated. Don’t clear the lookup table here because we
        # might want to show it quickly again if nothing related is
        # found:
        if self.get_lookup_table().get_number_of_candidates():
            self.hide_lookup_table()
        super(TypingBoosterEngine, self).update_auxiliary_text(
            IBus.Text.new_from_string(BUSY_SYMBOL), True)
        related_candidates = []
        # Try to find similar emoji even if emoji predictions are
        # turned off.  Even when they are turned off, an emoji might
        # show up in the candidate list because it was found in the
        # user database. But when emoji predictions are turned off,
        # it is possible that they never been turned on in this session
        # and then the emoji matcher has not been initialized. Or,
        # the languages have been changed while emoji matching was off.
        # So make sure that the emoji matcher is available for the
        # correct list of languages before searching for similar
        # emoji:
        if (not self.emoji_matcher
            or
            self.emoji_matcher.get_languages()
            != self._dictionary_names):
            self.emoji_matcher = itb_emoji.EmojiMatcher(
                languages=self._dictionary_names)
        related_candidates = self.emoji_matcher.similar(phrase)
        try:
            import itb_nltk
            for synonym in itb_nltk.synonyms(phrase, keep_original=False):
                related_candidates.append((synonym, '[synonym]', 0))
            for hypernym in itb_nltk.hypernyms(phrase, keep_original=False):
                related_candidates.append((hypernym, '[hypernym]', 0))
            for hyponym in itb_nltk.hyponyms(phrase, keep_original=False):
                related_candidates.append((hyponym, '[hyponym]', 0))
        except (ImportError, LookupError):
            pass
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                '_lookup_related_candidates():'
                +  ' related_candidates of “%s” = %s\n'
                %(phrase, related_candidates))
        if not related_candidates:
            # Nothing related found, show the original lookup table
            # and original auxiliary text again:
            if self._current_auxiliary_text:
                super(TypingBoosterEngine, self).update_auxiliary_text(
                    self._current_auxiliary_text, True)
            else:
                super(TypingBoosterEngine, self).update_auxiliary_text(
                    IBus.Text.new_from_string(''), False)
            if self.get_lookup_table().get_number_of_candidates():
                self.update_lookup_table(self.get_lookup_table(), True)
            return
        self._candidates = []
        self.get_lookup_table().clear()
        self.get_lookup_table().set_cursor_visible(False)
        for cand in related_candidates:
            self._candidates.append((cand[0], cand[2], cand[1]))
            self._append_candidate_to_lookup_table(
                phrase=cand[0], user_freq=cand[2], comment=cand[1])
        self._update_lookup_table_and_aux()
        self._lookup_table_shows_related_candidates = True

    def _has_transliteration(self, msymbol_list):
        '''Check whether the current input (list of msymbols) has a
        (non-trivial, i.e. not transliterating to itself)
        transliteration in any of the current input methods.
        '''
        for ime in self.get_current_imes():
            if self._transliterators[ime].transliterate(
                    msymbol_list) != ''.join(msymbol_list):
                if DEBUG_LEVEL > 1:
                    sys.stderr.write(
                        "_has_transliteration(%s) == True\n" %msymbol_list)
                return True
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "_has_transliteration(%s) == False\n" %msymbol_list)
        return False

    def _commit_string(self, commit_phrase, input_phrase=''):
        '''Commits a string

        Also updates the context and the user database of learned
        input.

        May remove whitespace before the committed string if
        the committed string ended a sentence.
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                '_commit_string(%s, %s)\n' %(commit_phrase, input_phrase))
        # If the suggestions are only enabled by Tab key, i.e. the
        # lookup table is not shown until Tab has been typed, hide
        # the lookup table again after each commit. That means
        # that after each commit, when typing continues the
        # lookup table is first hidden again and one has to type
        # Tab again to show it.
        self.is_lookup_table_enabled_by_tab = False
        if not input_phrase:
            input_phrase = self._transliterated_strings[
                self.get_current_imes()[0]]
        # commit always in NFC:
        commit_phrase = unicodedata.normalize('NFC', commit_phrase)
        if self.client_capabilities & IBus.Capabilite.SURROUNDING_TEXT:
            # If a character ending a sentence is committed (possibly
            # followed by whitespace) remove trailing white space
            # before the committed string. For example if
            # commit_phrase is “!”, and the context before is “word ”,
            # make the result “word!”.  And if the commit_phrase is “!
            # ” and the context before is “word ” make the result
            # “word! ”.
            pattern_sentence_end = re.compile(
                r'^['
                + re.escape(itb_util.SENTENCE_END_CHARACTERS)
                + r']+[\s]*$')
            if pattern_sentence_end.search(commit_phrase):
                surrounding_text = self.get_surrounding_text()
                text = surrounding_text[0].get_text()
                cursor_pos = surrounding_text[1]
                anchor_pos = surrounding_text[2]
                if DEBUG_LEVEL > 1:
                    sys.stderr.write(
                        'Checking for whitespace before sentence end char. '
                        + 'surrounding_text = '
                        + '[text = "%s", cursor_pos = %s, anchor_pos = %s]'
                        %(text, cursor_pos, anchor_pos) + '\n')
                # The commit_phrase is *not* yet in the surrounding text,
                # it will show up there only when the next key event is
                # processed:
                pattern = re.compile(r'(?P<white_space>[\s]+)$')
                match = pattern.search(text[:cursor_pos])
                if match:
                    nchars = len(match.group('white_space'))
                    self.delete_surrounding_text(-nchars, nchars)
                    if DEBUG_LEVEL > 1:
                        surrounding_text = self.get_surrounding_text()
                        text = surrounding_text[0].get_text()
                        cursor_pos = surrounding_text[1]
                        anchor_pos = surrounding_text[2]
                        sys.stderr.write(
                            'Removed whitespace before sentence end char. '
                            + 'surrounding_text = '
                            + '[text = "%s", cursor_pos = %s, anchor_pos = %s]'
                            %(text, cursor_pos, anchor_pos) + '\n')
        super(TypingBoosterEngine, self).commit_text(
            IBus.Text.new_from_string(commit_phrase))
        self._clear_input()
        self._update_ui()
        self._commit_happened_after_focus_in = True
        stripped_input_phrase = itb_util.strip_token(input_phrase)
        stripped_commit_phrase = itb_util.strip_token(commit_phrase)
        if not self._off_the_record:
            self.db.check_phrase_and_update_frequency(
                input_phrase=stripped_input_phrase,
                phrase=stripped_commit_phrase,
                p_phrase=self.get_p_phrase(),
                pp_phrase=self.get_pp_phrase())
        self.push_context(stripped_commit_phrase)

    def _reopen_preedit_or_return_false(self, key):
        '''Backspace or arrow left has been typed.

        If the end of a word has been reached again and if it is
        possible to get that word back into preëdit, do that and
        return True.

        If not end of a word has been reached or it is impossible to
        get the word back into preëdit, use _return_false(key.val,
        key.code, key.state) to pass the key to the application.

        :rtype: Boolean

        '''
        if not (self.client_capabilities
                & IBus.Capabilite.SURROUNDING_TEXT):
            return self._return_false(key.val, key.code, key.state)
        surrounding_text = self.get_surrounding_text()
        text = surrounding_text[0].get_text()
        cursor_pos = surrounding_text[1]
        dummy_anchor_pos = surrounding_text[2]
        if not surrounding_text:
            return self._return_false(key.val, key.code, key.state)
        if not self._commit_happened_after_focus_in:
            # Before the first commit or cursor movement, the
            # surrounding text is probably from the previously
            # focused window (bug!), don’t use it.
            return self._return_false(key.val, key.code, key.state)
        if (not self._arrow_keys_reopen_preedit
                and key.val in (IBus.KEY_Left, IBus.KEY_KP_Left,
                                IBus.KEY_Right, IBus.KEY_KP_Right,
                                IBus.KEY_BackSpace)):
            # using arrows key to reopen the preëdit is disabled
            return self._return_false(key.val, key.code, key.state)
        if (key.shift
            or key.control
            or key.mod1
            or key.mod2
            or key.mod3
            or key.mod4
            or key.mod5
            or key.button1
            or key.button2
            or key.button3
            or key.button4
            or key.button5
            or key.super
            or key.hyper
            or key.meta):
            # “Control+Left” usually positions the cursor one word to
            # the left in most programs.  I.e. after Control+Left the
            # cursor usually ends up at the left side of a word.
            # Therefore, one cannot use the same code for reopening
            # the preëdit as for just “Left”. There are similar
            # problems with “Alt+Left”, “Shift+Left”.
            #
            # “Left”, “Right”, “Backspace”, “Delete” also have similar
            # problems together with “Control”, “Alt”, or “Shift” in
            # many programs.  For example “Shift+Left” marks (selects)
            # a region in gedit.
            #
            # Maybe better don’t try to reopen the preëdit at all if
            # any modifier key is on.
            #
            # *Except* for CapsLock. CapsLock causes no problems at
            # all for reopening the preëdit, so we don’t want to check
            # for key.modifier which would include key.lock but check
            # for the modifiers which cause problems individually.
            return self._return_false(key.val, key.code, key.state)
        if key.val in (IBus.KEY_BackSpace, IBus.KEY_Left, IBus.KEY_KP_Left):
            pattern = re.compile(
                r'(^|.*[\s]+)(?P<token>[\S]+)[\s]$')
            match = pattern.match(text[:cursor_pos])
            if not match:
                return self._return_false(key.val, key.code, key.state)
            # The pattern has matched, i.e. left of the cursor is
            # a single whitespace and left of that a token was
            # found.
            token = match.group('token')
            # Delete the whitespace and the token from the
            # application.
            if key.val in (IBus.KEY_BackSpace,):
                self.delete_surrounding_text(-1-len(token), 1+len(token))
            else:
                self.forward_key_event(key.val, key.code, key.state)
                # The sleep is needed because this is racy, without the
                # sleep it works unreliably.
                time.sleep(self._ibus_event_sleep_seconds)
                self.delete_surrounding_text(-len(token), len(token))
            # get the context to the left of the token:
            self.get_context()
            # put the token into the preedit again
            self._insert_string_at_cursor(list(token))
            # update the candidates.
            self._update_ui()
            return True
        elif key.val in (IBus.KEY_Delete, IBus.KEY_Right, IBus.KEY_KP_Right):
            pattern = re.compile(
                r'^[\s](?P<token>[\S]+)($|[\s]+.*)')
            match = pattern.match(text[cursor_pos:])
            if not match:
                return self._return_false(key.val, key.code, key.state)
            token = match.group('token')
            if key.val in (IBus.KEY_Delete,):
                self.delete_surrounding_text(0, len(token) + 1)
            else:
                self.forward_key_event(key.val, key.code, key.state)
                # The sleep is needed because this is racy, without the
                # sleep it works unreliably.
                time.sleep(self._ibus_event_sleep_seconds)
                self.delete_surrounding_text(0, len(token))
            # get the context to the left of the token:
            self.get_context()
            # put the token into the preedit again
            self._insert_string_at_cursor(list(token))
            self._typed_string_cursor = 0
            # update the candidates.
            self._update_ui()
            return True
        else:
            return self._return_false(key.val, key.code, key.state)

    def get_context(self):
        '''Try to get the context from the application using the “surrounding
        text” feature, if possible. If this works, it is much better
        than just using the last two words which were
        committed. Because the cursor position could have changed
        since the last two words were committed, one might have moved
        the cursor with the mouse or the arrow keys.  Unfortunately
        surrounding text is not supported by many applications.
        Basically it only seems to work reasonably well in Gnome
        applications.

        '''
        if not self.client_capabilities & IBus.Capabilite.SURROUNDING_TEXT:
            # If getting the surrounding text is not supported, leave
            # the context as it is, i.e. rely on remembering what was
            # typed last.
            return
        surrounding_text = self.get_surrounding_text()
        text = surrounding_text[0].get_text()
        cursor_pos = surrounding_text[1]
        dummy_anchor_pos = surrounding_text[2]
        if not surrounding_text:
            return
        if not self._commit_happened_after_focus_in:
            # Before the first commit or cursor movement, the
            # surrounding text is probably from the previously
            # focused window (bug!), don’t use it.
            return
        tokens = ([
            itb_util.strip_token(token)
            for token in itb_util.tokenize(text[:cursor_pos])])
        if len(tokens):
            self._p_phrase = tokens[-1]
        if len(tokens) > 1:
            self._pp_phrase = tokens[-2]

    def set_qt_im_module_workaround(self, mode, update_gsettings=True):
        '''Sets whether the workaround for the qt im module is used or not

        :param mode: Whether to use the workaround for the qt im module or not
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_qt_im_module_workaround(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._qt_im_module_workaround:
            return
        self._qt_im_module_workaround = mode
        if update_gsettings:
            self._gsettings.set_value(
                'qtimmoduleworkaround',
                GLib.Variant.new_boolean(mode))

    def toggle_qt_im_module_workaround(self, update_gsettings=True):
        '''Toggles whether the workaround for the qt im module is used or not

        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        self.set_qt_im_module_workaround(
            not self._qt_im_module_workaround, update_gsettings)

    def get_qt_im_module_workaround(self):
        '''Returns the current value of the flag to enable
        a workaround for the qt im module

        :rtype: boolean
        '''
        return self._qt_im_module_workaround

    def set_arrow_keys_reopen_preedit(self, mode, update_gsettings=True):
        '''Sets whether the arrow keys are allowed to reopen a preëdit

        :param mode: Whether arrow keys can reopen a preëdit
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_arrow_keys_reopen_preedit(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._arrow_keys_reopen_preedit:
            return
        self._arrow_keys_reopen_preedit = mode
        if update_gsettings:
            self._gsettings.set_value(
                'arrowkeysreopenpreedit',
                GLib.Variant.new_boolean(mode))

    def toggle_arrow_keys_reopen_preedit(self, update_gsettings=True):
        '''Toggles whether arrow keys are allowed to reopen a preëdit

        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        self.set_arrow_keys_reopen_preedit(
            not self._arrow_keys_reopen_preedit, update_gsettings)

    def get_arrow_keys_reopen_preedit(self):
        '''Returns the current value of the flag whether to
        allow arrow keys to reopen the preëdit

        :rtype: boolean
        '''
        return self._arrow_keys_reopen_preedit

    def set_emoji_prediction_mode(self, mode, update_gsettings=True):
        '''Sets the emoji prediction mode

        :param mode: Whether to switch emoji prediction on or off
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_emoji_prediction_mode(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._emoji_predictions:
            return
        self._emoji_predictions = mode
        self._init_or_update_property_menu(
            self.emoji_prediction_mode_menu, mode)
        if (self._emoji_predictions
            and (not self.emoji_matcher
                 or
                 self.emoji_matcher.get_languages()
                 != self._dictionary_names)):
            self.emoji_matcher = itb_emoji.EmojiMatcher(
                languages=self._dictionary_names)
        self._update_ui()
        if update_gsettings:
            self._gsettings.set_value(
                'emojipredictions',
                GLib.Variant.new_boolean(mode))

    def toggle_emoji_prediction_mode(self, update_gsettings=True):
        '''Toggles whether emoji predictions are shown or not

        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        self.set_emoji_prediction_mode(
            not self._emoji_predictions, update_gsettings)

    def get_emoji_prediction_mode(self):
        '''Returns the current value of the emoji prediction mode

        :rtype: boolean
        '''
        return self._emoji_predictions

    def set_off_the_record_mode(self, mode, update_gsettings=True):
        '''Sets the “Off the record” mode

        :param mode: Whether to prevent saving input to the
                     user database or not
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_off_the_record_mode(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._off_the_record:
            return
        self._off_the_record = mode
        self._init_or_update_property_menu(
            self.off_the_record_mode_menu, mode)
        self._update_ui() # because of the indicator in the auxiliary text
        if update_gsettings:
            self._gsettings.set_value(
                'offtherecord',
                GLib.Variant.new_boolean(mode))

    def toggle_off_the_record_mode(self, update_gsettings=True):
        '''Toggles whether input is saved to the user database or not

        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        self.set_off_the_record_mode(
            not self._off_the_record, update_gsettings)

    def get_off_the_record_mode(self):
        '''Returns the current value of the “off the record” mode

        :rtype: boolean
        '''
        return self._off_the_record

    def set_auto_commit_characters(self, auto_commit_characters,
                                   update_gsettings=True):
        '''Sets the auto commit characters

        :param auto_commit_characters: The characters which trigger a commit
                                       with an extra space
        :type auto_commit_characters: string
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_auto_commit_characters(%s, update_gsettings = %s)\n"
                %(auto_commit_characters, update_gsettings))
        if auto_commit_characters == self._auto_commit_characters:
            return
        self._auto_commit_characters = auto_commit_characters
        if update_gsettings:
            self._gsettings.set_value(
                'autocommitcharacters',
                GLib.Variant.new_string(auto_commit_characters))

    def get_auto_commit_characters(self):
        '''Returns the current auto commit characters

        :rtype: string
        '''
        return self._auto_commit_characters

    def set_tab_enable(self, mode, update_gsettings=True):
        '''Sets the “Tab enable” mode

        :param mode: Whether to show a candidate list only when typing Tab
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_tab_enable(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._tab_enable:
            return
        self._tab_enable = mode
        if update_gsettings:
            self._gsettings.set_value(
                'tabenable',
                GLib.Variant.new_boolean(mode))

    def get_tab_enable(self):
        '''Returns the current value of the “Tab enable” mode

        :rtype: boolean
        '''
        return self._tab_enable

    def set_remember_last_used_preedit_ime(self, mode, update_gsettings=True):
        '''Sets the “Remember last used preëdit ime” mode

        :param mode: Whether to remember the input method used last for
                     the preëdit
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_remember_last_used_preedit_ime(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._remember_last_used_preedit_ime:
            return
        self._remember_last_used_preedit_ime = mode
        if update_gsettings:
            self._gsettings.set_value(
                'rememberlastusedpreeditime',
                GLib.Variant.new_boolean(mode))

    def get_remember_last_used_preedit_ime(self):
        '''Returns the current value of the
        “Remember last used preëdit ime” mode

        :rtype: boolean
        '''
        return self._remember_last_used_preedit_ime

    def set_page_size(self, page_size, update_gsettings=True):
        '''Sets the page size of the lookup table

        :param page_size: The page size of the lookup table
        :type mode: integer >= 1 and <= 9
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_page_size(%s, update_gsettings = %s)\n"
                %(page_size, update_gsettings))
        if page_size == self._page_size:
            return
        if page_size >= 1 and page_size <= 9:
            self._page_size = page_size
            self._lookup_table.set_page_size(self._page_size)
            self.reset()
            if update_gsettings:
                self._gsettings.set_value(
                    'pagesize',
                    GLib.Variant.new_int32(page_size))

    def get_page_size(self):
        '''Returns the current page size of the lookup table

        :rtype: integer
        '''
        return self._page_size

    def set_lookup_table_orientation(self, orientation, update_gsettings=True):
        '''Sets the page size of the lookup table

        :param orientation: The orientation of the lookup table
        :type mode: integer >= 0 and <= 2
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_lookup_table_orientation(%s, update_gsettings = %s)\n"
                %(orientation, update_gsettings))
        if orientation == self._lookup_table_orientation:
            return
        if orientation >= 0 and orientation <= 2:
            self._lookup_table_orientation = orientation
            self._lookup_table.set_orientation(self._lookup_table_orientation)
            self.reset()
            if update_gsettings:
                self._gsettings.set_value(
                    'lookuptableorientation',
                    GLib.Variant.new_int32(orientation))

    def get_lookup_table_orientation(self):
        '''Returns the current orientation of the lookup table

        :rtype: integer
        '''
        return self._lookup_table_orientation

    def set_min_char_complete(self, min_char_complete, update_gsettings=True):
        '''Sets the minimum number of characters to try completion

        :param min_char_complete: The minimum number of characters
                                  to type before completion is tried.
        :type mode: integer >= 1 and <= 9
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_min_char_complete(%s, update_gsettings = %s)\n"
                %(min_char_complete, update_gsettings))
        if min_char_complete == self._min_char_complete:
            return
        if min_char_complete >= 1 and min_char_complete <= 9:
            self._min_char_complete = min_char_complete
            self.reset()
            if update_gsettings:
                self._gsettings.set_value(
                    'mincharcomplete',
                    GLib.Variant.new_int32(min_char_complete))

    def get_min_char_complete(self):
        '''Returns the current minimum number of characters to try completion

        :rtype: integer
        '''
        return self._min_char_complete

    def set_show_number_of_candidates(self, mode, update_gsettings=True):
        '''Sets the “Show number of candidates” mode

        :param mode: Whether to show the number of candidates
                     in the auxiliary text
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_show_number_of_candidates(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._show_number_of_candidates:
            return
        self._show_number_of_candidates = mode
        self.reset()
        if update_gsettings:
            self._gsettings.set_value(
                'shownumberofcandidates',
                GLib.Variant.new_boolean(mode))

    def get_show_number_of_candidates(self):
        '''Returns the current value of the “Show number of candidates” mode

        :rtype: boolean
        '''
        return self._show_number_of_candidates

    def set_show_status_info_in_auxiliary_text(self, mode, update_gsettings=True):
        '''Sets the “Show status info in auxiliary text” mode

        :param mode: Whether to show status information in the
                     auxiliary text.
                     Currently the status information which can be
                     displayed there is whether emoji mode and
                     off-the-record mode are on or off
                     and which input method is currently used for
                     the preëdit text.
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_show_status_info_in_auxiliary_text"
                + "(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._show_status_info_in_auxiliary_text:
            return
        self._show_status_info_in_auxiliary_text = mode
        self.reset()
        if update_gsettings:
            self._gsettings.set_value(
                'showstatusinfoinaux',
                GLib.Variant.new_boolean(mode))

    def get_show_status_info_in_auxiliary_text(self):
        '''Returns the current value of the
        “Show status in auxiliary text” mode

        :rtype: boolean
        '''
        return self._show_status_info_in_auxiliary_text

    def set_use_digits_as_select_keys(self, mode, update_gsettings=True):
        '''Sets the “Use digits as select keys” mode

        :param mode: Whether to use digits as select keys
        :type mode: boolean
        :param update_gsettings: Whether to write the change to Gsettings.
                                 Set this to False if this method is
                                 called because the Gsettings key changed
                                 to avoid endless loops when the Gsettings
                                 key is changed twice in a short time.
        :type update_gsettings: boolean
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "set_use_digits_as_select_keys(%s, update_gsettings = %s)\n"
                %(mode, update_gsettings))
        if mode == self._use_digits_as_select_keys:
            return
        self._use_digits_as_select_keys = mode
        self.reset()
        if update_gsettings:
            self._gsettings.set_value(
                'usedigitsasselectkeys',
                GLib.Variant.new_boolean(mode))

    def get_use_digits_as_select_keys(self):
        '''Returns the current value of the “Use digits as select keys” mode

        :rtype: boolean
        '''
        return self._use_digits_as_select_keys

    def do_candidate_clicked(self, index, button, state):
        '''Called when a candidate in the lookup table
        is clicked with the mouse
        '''
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                'do_candidate_clicked() index = %s button = %s state = %s\n'
                %(index, button, state))
        if not self._set_lookup_table_cursor_pos_in_current_page(index):
            return
        self._lookup_table.set_cursor_visible(True)
        if button == 1 and (state & IBus.ModifierType.CONTROL_MASK):
            self.remove_candidate_from_user_database(index)
            self._update_ui()
            return
        if button == 1:
            phrase = self.get_string_from_lookup_table_cursor_pos()
            if phrase:
                self._commit_string(phrase + ' ')
            return
        if (button == 3
            and (state & IBus.ModifierType.MOD1_MASK)
            and (state & IBus.ModifierType.CONTROL_MASK)):
            self._start_setup()
            return
        if button == 3 and (state & IBus.ModifierType.CONTROL_MASK):
            self.toggle_emoji_prediction_mode()
            return
        if button == 3 and (state & IBus.ModifierType.MOD1_MASK):
            self.toggle_off_the_record_mode()
            return
        if button == 3:
            self._lookup_related_candidates()
            return

    def _return_false(self, keyval, keycode, state):
        '''A replacement for “return False” in do_process_key_event()

        do_process_key_event should return “True” if a key event has
        been handled completely. It should return “False” if the key
        event should be passed to the application.

        But just doing “return False” doesn’t work well when trying to
        do the unit tests. The MockEngine class in the unit tests
        cannot get that return value. Therefore, it cannot do the
        necessary updates to the self._mock_committed_text etc. which
        prevents proper testing of the effects of such keys passed to
        the application. Instead of “return False”, one can also use
        self.forward_key_event(keyval, keycode, keystate) to pass the
        key to the application. And this works fine with the unit
        tests because a forward_key_event function is implemented in
        MockEngine as well which then gets the key and can test its
        effects.

        Unfortunately, “forward_key_event()” does not work in Qt5
        applications because the ibus module in Qt5 does not implement
        “forward_key_event()”. Therefore, always using
        “forward_key_event()” instead of “return False” in
        “do_process_key_event()” would break ibus-typing-booster
        completely for all Qt5 applictions.

        To work around this problem and make unit testing possible
        without breaking Qt5 applications, we use this helper function
        which uses “forward_key_event()” when unit testing and “return
        False” during normal usage.

        '''
        if self._unit_test:
            self.forward_key_event(keyval, keycode, state)
            return True
        else:
            return False

    def _forward_key_event_left(self):
        '''Forward an arrow left event to the application.'''
        # Why is the keycode for IBus.KEY_Left 105?  Without using the
        # right keycode, this does not work correctly, i.e.
        # self.forward_key_event(IBus.KEY_Left, 0, 0) does *not* work!
        self.forward_key_event(IBus.KEY_Left, 105, 0)
        return

    def do_process_key_event(self, keyval, keycode, state):
        '''Process Key Events
        Key Events include Key Press and Key Release,
        modifier means Key Pressed
        '''
        if (self._has_input_purpose
            and self._input_purpose
            in [IBus.InputPurpose.PASSWORD, IBus.InputPurpose.PIN]):
            return self._return_false(keyval, keycode, state)

        key = KeyEvent(keyval, keycode, state)
        if DEBUG_LEVEL > 1:
            sys.stderr.write(
                "process_key_event() "
                "KeyEvent object: %s" % key)

        result = self._process_key_event(key)
        return result

    def _process_key_event(self, key):
        '''Internal method to process key event

        Returns True if the key event has been completely handled by
        ibus-typing-booster and should not be passed through anymore.
        Returns False if the key event has not been handled completely
        and is passed through.

        '''
        # Ignore key release events
        if key.state & IBus.ModifierType.RELEASE_MASK:
            return self._return_false(key.val, key.code, key.state)

        if self.is_empty():
            if DEBUG_LEVEL > 1:
                sys.stderr.write(
                    "_process_key_event() self.is_empty(): "
                    "KeyEvent object: %s\n" % key)
            # This is the first character typed since the last commit
            # there is nothing in the preëdit yet.
            if key.val < 32:
                # If the first character of a new word is a control
                # character, return False to pass the character through as is,
                # it makes no sense trying to complete something
                # starting with a control character:
                return self._return_false(key.val, key.code, key.state)
            if key.val == IBus.KEY_space and not key.mod5:
                # if the first character is a space, just pass it through
                # it makes not sense trying to complete (“not key.mod5” is
                # checked here because AltGr+Space is the key binding to
                # insert a literal space into the preëdit):
                return self._return_false(key.val, key.code, key.state)
            if key.val in (IBus.KEY_BackSpace,
                           IBus.KEY_Left, IBus.KEY_KP_Left,
                           IBus.KEY_Delete,
                           IBus.KEY_Right, IBus.KEY_KP_Right):
                return self._reopen_preedit_or_return_false(key)
            if key.val >= 32 and not key.control:
                if (self._use_digits_as_select_keys
                    and not self._tab_enable
                    and key.msymbol
                    in ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')):
                    # If digits are used as keys to select candidates
                    # it is not possibly to type them while the preëdit
                    # is non-empty and candidates are displayed.
                    # In that case we have to make it possible to
                    # type digits here where the preëdit is still empty.
                    # If digits are not used to select candidates, they
                    # can be treated just like any other input keys.
                    #
                    # When self._tab_enable is on, the candidate list
                    # is only shown when explicitely requested by Tab.
                    # Therefore, in that case digits can be typed
                    # normally as well until the candidate list is
                    # opened.  Putting a digit into the candidate list
                    # is better in that case, one may be able to get a
                    # reasonable completion that way.
                    if self.get_current_imes()[0] == 'NoIme':
                        # If a digit has been typed and no transliteration
                        # is used, we can pass it through
                        return self._return_false(key.val, key.code, key.state)
                    # If a digit has been typed and we use
                    # transliteration, we may want to convert it to
                    # native digits. For example, with mr-inscript we
                    # want “3” to be converted to “३”. So we try
                    # to transliterate and commit the result:
                    transliterated_digit = self._transliterators[
                        self.get_current_imes()[0]
                    ].transliterate([key.msymbol])
                    self._commit_string(
                        transliterated_digit,
                        input_phrase=transliterated_digit)
                    return True

        if key.val == IBus.KEY_Escape:
            if self.is_empty():
                return self._return_false(key.val, key.code, key.state)
            if self.get_lookup_table().cursor_visible:
                # A candidate is selected in the lookup table.
                # Deselect it and show the first page of the candidate
                # list:
                self.get_lookup_table().set_cursor_visible(False)
                self.get_lookup_table().set_cursor_pos(0)
                self._update_lookup_table_and_aux()
                return True
            if self._lookup_table_shows_related_candidates:
                # Force an update to the original lookup table:
                self._update_ui()
                return True
            if self._tab_enable and self.is_lookup_table_enabled_by_tab:
                # If lookup table was enabled by typing Tab, close it again
                # but keep the preëdit:
                self.is_lookup_table_enabled_by_tab = False
                self.get_lookup_table().clear()
                self.get_lookup_table().set_cursor_visible(False)
                self._update_lookup_table_and_aux()
                self._candidates = []
                return True
            self.reset()
            self._update_ui()
            return True

        if (key.val == IBus.KEY_Tab
            and self._tab_enable
            and not self.is_lookup_table_enabled_by_tab
            and not self.is_empty()):
            self.is_lookup_table_enabled_by_tab = True
            # update the ui here to see the effect immediately
            # do not wait for the next keypress:
            self._update_ui()
            return True

        if key.val in (IBus.KEY_Down, IBus.KEY_KP_Down) and key.control:
            imes = self.get_current_imes()
            if len(imes) > 1:
                # remove the first ime from the list and append it to the end.
                self.set_current_imes(
                    imes[1:] + imes[:1],
                    update_gsettings=self._remember_last_used_preedit_ime)
                return True

        if key.val in (IBus.KEY_Up, IBus.KEY_KP_Up) and key.control:
            imes = self.get_current_imes()
            if len(imes) > 1:
                # remove the last ime in the list and add it in front:
                self.set_current_imes(
                    imes[-1:] + imes[:-1],
                    update_gsettings=self._remember_last_used_preedit_ime)
                return True

        if (key.val in (IBus.KEY_Down, IBus.KEY_KP_Down, IBus.KEY_Tab)
            and self.get_lookup_table().get_number_of_candidates()):
            dummy = self._arrow_down()
            self._update_lookup_table_and_aux()
            return True

        if (((key.val in (IBus.KEY_Up, IBus.KEY_KP_Up))
             or
             (key.val in (IBus.KEY_Tab, IBus.KEY_ISO_Left_Tab) and key.shift))
            and self.get_lookup_table().get_number_of_candidates()):
            dummy = self._arrow_up()
            self._update_lookup_table_and_aux()
            return True

        if (key.val in (IBus.KEY_Page_Down, IBus.KEY_KP_Page_Down)
            and self.get_lookup_table().get_number_of_candidates()):
            dummy = self._page_down()
            self._update_lookup_table_and_aux()
            return True

        if (key.val in (IBus.KEY_Page_Up, IBus.KEY_KP_Page_Up)
            and self.get_lookup_table().get_number_of_candidates()):
            dummy = self._page_up()
            self._update_lookup_table_and_aux()
            return True

        # Select a candidate to commit or remove:
        if (self.get_lookup_table().get_number_of_candidates()
            and not key.mod1 and not key.mod5):
            # key.mod1 (= Alt) and key.mod5 (= AltGr) should not be set
            # here because:
            #
            # - in case of the digits these are used for input, not to select
            #   (e.g. mr-inscript2 transliterates AltGr-4 to “₹”)
            #
            # - in case of the F1-F9 keys I want to reserve the Alt and AltGr
            #   modifiers for possible future extensions.
            index = -1
            if self._use_digits_as_select_keys:
                if key.val >= IBus.KEY_1 and key.val <= IBus.KEY_9:
                    index = key.val - IBus.KEY_1
                if key.val >= IBus.KEY_KP_1 and key.val <= IBus.KEY_KP_9:
                    index = key.val - IBus.KEY_KP_1
            if key.val >= IBus.KEY_F1 and key.val <= IBus.KEY_F9:
                index = key.val - IBus.KEY_F1
            if index >= 0 and index < self._page_size:
                if key.control:
                    # Remove the candidate from the user database
                    res = self.remove_candidate_from_user_database(
                        index)
                    self._update_ui()
                    return res
                else:
                    # Commit a candidate:
                    phrase = (
                        self.get_string_from_lookup_table_current_page(
                            index))
                    if phrase:
                        self._commit_string(phrase + ' ')
                    return True

        if key.val == IBus.KEY_F6 and key.mod5: # AltGr+F6
            self.toggle_emoji_prediction_mode()
            return True

        if key.val == IBus.KEY_F9 and key.mod5: # AltGr+F9
            self.toggle_off_the_record_mode()
            return True

        if (key.val == IBus.KEY_F12 and key.mod5 # AltGr+F12
            and not self.is_empty()):
            self._lookup_related_candidates()
            return True

        if key.val == IBus.KEY_F10 and key.mod5: # AltGr+F10
            self._start_setup()
            return True

        # These keys may trigger a commit:
        if (key.msymbol not in ('G- ',)
            and (key.val in (IBus.KEY_space, IBus.KEY_Tab,
                             IBus.KEY_Return, IBus.KEY_KP_Enter,
                             IBus.KEY_Right, IBus.KEY_KP_Right,
                             IBus.KEY_Delete,
                             IBus.KEY_Left, IBus.KEY_KP_Left,
                             IBus.KEY_BackSpace,
                             IBus.KEY_Down, IBus.KEY_KP_Down,
                             IBus.KEY_Up, IBus.KEY_KP_Up,
                             IBus.KEY_Page_Down, IBus.KEY_KP_Page_Down,
                             IBus.KEY_Page_Up, IBus.KEY_KP_Page_Up)
                 or (len(key.msymbol) == 3
                     and key.msymbol[:2] in ('A-', 'C-', 'G-')
                     and not self._has_transliteration([key.msymbol])))):
                # See:
                # https://bugzilla.redhat.com/show_bug.cgi?id=1351748
                # If the user types a modifier key combination, it
                # might have a transliteration in some input methods.
                # For example, AltGr-4 (key.msymbol = 'G-4')
                # transliterates to ₹ when the “hi-inscript2” input
                # method is used.  But trying to handle all modifier
                # key combinations as input is not nice because it
                # prevents the use of such key combinations for other
                # purposes.  C-c is usually used for for copying, C-v
                # for pasting for example. If the user has typed a
                # modifier key combination, check whether any of the
                # current input methods actually transliterates it to
                # something. If none of the current input methods uses
                # it, the key combination can be passed through to be
                # used for its original purpose.  If the preëdit is
                # non empty, commit the preëdit first before passing
                # the modifier key combination through. (Passing
                # something like C-a through without committing the
                # preëdit would be quite confusing, C-a usually goes
                # to the beginning of the current line, leaving the
                # preëdit open while moving would be strange).
                #
                # Up, Down, Page_Up, and Page_Down may trigger a
                # commit if no lookup table is shown because the
                # option to show a lookup table only on request by
                # typing tab is used and no lookup table is shown at
                # the moment.
                #
                # 'G- ' (AltGr-Space) is prevented from triggering
                # a commit here, because it is used to enter spaces
                # into the preëdit, if possible.
            if self.is_empty():
                return self._return_false(key.val, key.code, key.state)
            if (key.val in (IBus.KEY_Right, IBus.KEY_KP_Right)
                and (self._typed_string_cursor
                     < len(self._typed_string))):
                if key.control:
                    # Move cursor to the end of the typed string
                    self._typed_string_cursor = len(self._typed_string)
                else:
                    self._typed_string_cursor += 1
                self._update_preedit()
                self._update_lookup_table_and_aux()
                return True
            if (key.val in (IBus.KEY_Left, IBus.KEY_KP_Left)
                and self._typed_string_cursor > 0):
                if key.control:
                    # Move cursor to the beginning of the typed string
                    self._typed_string_cursor = 0
                else:
                    self._typed_string_cursor -= 1
                self._update_preedit()
                self._update_lookup_table_and_aux()
                return True
            if (key.val in (IBus.KEY_BackSpace,)
                and self._typed_string_cursor > 0):
                self.is_lookup_table_enabled_by_tab = False
                if key.control:
                    self._remove_string_before_cursor()
                else:
                    self._remove_character_before_cursor()
                self._update_ui()
                return  True
            if (key.val in (IBus.KEY_Delete,)
                and self._typed_string_cursor < len(self._typed_string)):
                self.is_lookup_table_enabled_by_tab = False
                if key.control:
                    self._remove_string_after_cursor()
                else:
                    self._remove_character_after_cursor()
                self._update_ui()
                return True
            # This key does not only a cursor movement in the preëdit,
            # it really triggers a commit.
            if DEBUG_LEVEL > 1:
                sys.stderr.write('_process_key_event() commit triggered.\n')
            # We need to transliterate
            # the preëdit again here, because adding the commit key to
            # the input might influence the transliteration. For example
            # When using hi-itrans, “. ” translates to “। ”
            # (See: https://bugzilla.redhat.com/show_bug.cgi?id=1353672)
            preedit_ime = self._current_imes[0]
            input_phrase = self._transliterators[
                preedit_ime].transliterate(
                    self._typed_string + [key.msymbol])
            # If the transliteration now ends with the commit key, cut
            # it off because the commit key is passed to the
            # application later anyway and we do not want to pass it
            # twice:
            if len(key.msymbol) and input_phrase.endswith(key.msymbol):
                input_phrase = input_phrase[:-len(key.msymbol)]
            if (self.get_lookup_table().get_number_of_candidates()
                and self.get_lookup_table().cursor_visible):
                # something is selected in the lookup table, commit
                # the selected phrase
                phrase = self.get_string_from_lookup_table_cursor_pos()
                commit_string = phrase
            elif (key.val in (IBus.KEY_Return, IBus.KEY_KP_Enter)
                  and (self._typed_string_cursor
                       < len(self._typed_string))):
                # “Return” or “Enter” is used to commit the preëdit
                # while the cursor is not at the end of the preëdit.
                # That means the part of the preëdit to the left of
                # the cursor should be commited first, then the
                # “Return” or enter should be forwarded to the
                # application, then the part of the preëdit to the
                # right of the cursor should be committed.
                input_phrase_left = (
                    self._transliterators[preedit_ime].transliterate(
                        self._typed_string[:self._typed_string_cursor]))
                input_phrase_right = (
                    self._transliterators[preedit_ime].transliterate(
                        self._typed_string[self._typed_string_cursor:]))
                if input_phrase_left:
                    self._commit_string(
                        input_phrase_left, input_phrase=input_phrase_left)
                # The sleep is needed because this is racy, without the
                # sleep it works unreliably.
                time.sleep(self._ibus_event_sleep_seconds)
                self.forward_key_event(key.val, key.code, key.state)
                self._commit_string(
                    input_phrase_right, input_phrase=input_phrase_right)
                for dummy_char in input_phrase_right:
                    self._forward_key_event_left()
                return True
            else:
                # nothing is selected in the lookup table, commit the
                # input_phrase
                commit_string = input_phrase
            if not commit_string:
                # This should not happen, we returned already above when
                # self.is_empty(), if we get here there should
                # have been something in the preëdit or the lookup table:
                if DEBUG_LEVEL > 0:
                    sys.stderr.write(
                        '_process_key_event() '
                        + 'commit string unexpectedly empty.\n')
                return self._return_false(key.val, key.code, key.state)
            self._commit_string(commit_string, input_phrase=input_phrase)
            if (key.val
                in (IBus.KEY_Left, IBus.KEY_KP_Left, IBus.KEY_BackSpace)):
                # After committing, the cursor is at the right side of
                # the committed string. When the string has been
                # committed because of arrow-left or
                # control-arrow-left, the cursor has to be moved to
                # the left side of the string. This should be done in
                # a way which works even when surrounding text is not
                # supported. We can do it by forwarding as many
                # arrow-left events to the application as the
                # committed string has characters.
                for dummy_char in commit_string:
                    self._forward_key_event_left()
                # The sleep is needed because this is racy, without the
                # sleep it works unreliably.
                time.sleep(self._ibus_event_sleep_seconds)
                if self._reopen_preedit_or_return_false(key):
                    return True
            if key.val in (IBus.KEY_Right, IBus.KEY_KP_Right, IBus.KEY_Delete):
                if self._reopen_preedit_or_return_false(key):
                    return True
            # Forward the key event which triggered the commit here
            # and return True instead of trying to pass that key event
            # to the application by returning False. Doing it by
            # returning false works correctly in GTK applications
            # and Qt applications when using the ibus module of Qt.
            # But not when using XIM, i.e. not when using Qt with the XIM
            # module and not in X11 applications like xterm.
            #
            # When “return False” is used, the key event which
            # triggered the commit here arrives *before* the committed
            # string when XIM is used. I.e. when typing “word ” the
            # space which triggered the commit gets to application
            # first and the applications receives “ word”. No amount
            # of sleep before the “return False” can fix this. See:
            # https://bugzilla.redhat.com/show_bug.cgi?id=1291238
            if self._qt_im_module_workaround:
                return self._return_false(key.val, key.code, key.state)
            else:
                self.forward_key_event(key.val, key.code, key.state)
                return True

        if key.unicode:
            # If the suggestions are only enabled by Tab key, i.e. the
            # lookup table is not shown until Tab has been typed, hide
            # the lookup table again when characters are added to the
            # preëdit:
            self.is_lookup_table_enabled_by_tab = False
            if self.is_empty():
                # first key typed, we will try to complete something now
                # get the context if possible
                self.get_context()
            if (key.msymbol in ('G- ',)
                and not self._has_transliteration([key.msymbol])):
                self._insert_string_at_cursor([' '])
            else:
                self._insert_string_at_cursor([key.msymbol])
            # If the character typed could end a sentence, we can
            # *maybe* commit immediately.  However, if transliteration
            # is used, we may need to handle a punctuation or symbol
            # character. For example, “.c” is transliterated to “ċ” in
            # the “t-latn-pre” transliteration method, therefore we
            # cannot commit when encountering a “.”, we have to wait
            # what comes next.
            input_phrase = (
                self._transliterated_strings[
                    self.get_current_imes()[0]])
            # pylint: disable=too-many-boolean-expressions
            if (len(key.msymbol) == 1
                and key.msymbol != ' '
                and key.msymbol in self._auto_commit_characters
                and input_phrase
                and input_phrase[-1] == key.msymbol
                and itb_util.contains_letter(input_phrase)
            ):
                if DEBUG_LEVEL > 1:
                    sys.stderr.write(
                        'auto committing because of key.msymbol = %s'
                        %key.msymbol)
                self._commit_string(
                    input_phrase + ' ', input_phrase=input_phrase)
            self._update_ui()
            return True

        # What kind of key was this??
        #
        # The unicode character for this key is apparently the empty
        # string.  And apparently it was not handled as a select key
        # or other special key either.  So whatever this was, we
        # cannot handle it, just pass it through to the application by
        # returning “False”.
        return self._return_false(key.val, key.code, key.state)

    def do_focus_in(self):
        '''Called when a window gets focus while this input engine is enabled

        '''
        self.register_properties(self.main_prop_list)
        self.clear_context()
        self._commit_happened_after_focus_in = False
        self._update_ui()

    def do_focus_out(self):
        '''Called when a window looses focus while this input engine is
        enabled

        '''
        if self._has_input_purpose:
            self._input_purpose = 0
        self.clear_context()
        self.reset()
        return

    def do_set_content_type(self, purpose, dummy_hints):
        '''Called when the input purpose changes

        The input purpose is one of these

        IBus.InputPurpose.FREE_FORM
        IBus.InputPurpose.ALPHA
        IBus.InputPurpose.DIGITS
        IBus.InputPurpose.NUMBER
        IBus.InputPurpose.PHONE
        IBus.InputPurpose.URL
        IBus.InputPurpose.EMAIL
        IBus.InputPurpose.NAME
        IBus.InputPurpose.PASSWORD
        IBus.InputPurpose.PIN

        '''
        purpose_names = {
            IBus.InputPurpose.FREE_FORM: 'FREE_FORM',
            IBus.InputPurpose.ALPHA: 'ALPHA',
            IBus.InputPurpose.DIGITS: 'DIGITS',
            IBus.InputPurpose.NUMBER: 'NUMBER',
            IBus.InputPurpose.PHONE: 'PHONE',
            IBus.InputPurpose.URL: 'URL',
            IBus.InputPurpose.EMAIL: 'EMAIL',
            IBus.InputPurpose.NAME: 'NAME',
            IBus.InputPurpose.PASSWORD: 'PASSWORD',
            IBus.InputPurpose.PIN: 'PIN',
        }
        sys.stderr.write(
            'do_set_content_type(%s) self._has_input_purpose = %s\n'
            %(purpose, self._has_input_purpose))
        if purpose in purpose_names:
            sys.stderr.write('purpose_name = %s\n' %purpose_names[purpose])
        else:
            sys.stderr.write('unknown purpose_name\n')
        if self._has_input_purpose:
            self._input_purpose = purpose

    def do_enable(self):
        '''Called when this input engine is enabled'''
        # Tell the input-context that the engine will utilize
        # surrounding-text:
        self.get_surrounding_text()
        self.do_focus_in()

    def do_disable(self):
        '''Called when this input engine is disabled'''
        self.reset()

    def do_page_up(self):
        '''Called when the page up button in the lookup table is clicked with
        the mouse

        '''
        if self._page_up():
            self._update_lookup_table_and_aux()
            return True
        return True

    def do_page_down(self):
        '''Called when the page down button in the lookup table is clicked with
        the mouse

        '''
        if self._page_down():
            self._update_lookup_table_and_aux()
            return True
        return False

    def do_cursor_up(self):
        '''Called when the mouse wheel is rolled up in the candidate area of
        the lookup table

        '''
        res = self._arrow_up()
        self._update_lookup_table_and_aux()
        return res

    def do_cursor_down(self):
        '''Called when the mouse wheel is rolled down in the candidate area of
        the lookup table

        '''
        res = self._arrow_down()
        self._update_lookup_table_and_aux()
        return res

    def on_gsettings_value_changed(self, settings, key):
        '''
        Called when a value in the settings has been changed.

        :param settings: The settings object
        :type settings: Gio.Settings object
        :param key: The key of the setting which has changed
        :type key: String
        '''
        value = itb_util.variant_to_value(self._gsettings.get_value(key))
        sys.stderr.write('Settings changed: key=%s value=%s\n' %(key, value))
        if key == 'qtimmoduleworkaround':
            self.set_qt_im_module_workaround(value, update_gsettings=False)
            return
        if key == 'arrowkeysreopenpreedit':
            self.set_arrow_keys_reopen_preedit(value, update_gsettings=False)
            return
        if key == 'emojipredictions':
            self.set_emoji_prediction_mode(value, update_gsettings=False)
            return
        if key == 'offtherecord':
            self.set_off_the_record_mode(value, update_gsettings=False)
            return
        if key == 'autocommitcharacters':
            self.set_auto_commit_characters(value, update_gsettings=False)
            return
        if key == 'tabenable':
            self.set_tab_enable(value, update_gsettings=False)
            return
        if key == 'rememberlastusedpreeditime':
            self.set_remember_last_used_preedit_ime(
                value, update_gsettings=False)
            return
        if key == 'pagesize':
            self.set_page_size(value, update_gsettings=False)
            return
        if key == 'lookuptableorientation':
            self.set_lookup_table_orientation(value, update_gsettings=False)
            return
        if key == 'mincharcomplete':
            self.set_min_char_complete(value, update_gsettings=False)
            return
        if key == 'shownumberofcandidates':
            self.set_show_number_of_candidates(value, update_gsettings=False)
            return
        if key == 'showstatusinfoinaux':
            self.set_show_status_info_in_auxiliary_text(
                value, update_gsettings=False)
            return
        if key == 'usedigitsasselectkeys':
            self.set_use_digits_as_select_keys(value, update_gsettings=False)
            return
        if key == 'inputmethod':
            self.set_current_imes(
                [x.strip() for x in value.split(',')], update_gsettings=False)
            return
        if key == 'dictionary':
            self.set_dictionary_names(
                [x.strip() for x in value.split(',')], update_gsettings=False)
            return
        if key == 'dictionaryinstalltimestamp':
            # A dictionary has been updated or installed,
            # (re)load all dictionaries:
            print('Reloading dictionaries ...')
            self.db.hunspell_obj.init_dictionaries()
            self.reset()
            return
        sys.stderr.write('Unknown key\n')
        return
