Add option to force the use of the US keyboard layout

ibus-typing-booster >= 2.27.0 also offers simple engines emulating the
behaviour of the ibus-m17n engines, see:

#570

ibus-m17n has an option `☑️ Use US keyboard layout` which some users of
ibus-m17n might miss if they try to use the Typing Booster engines
emulating ibus-m17n.

To make the switch to Typing Booster easier for such users, I am adding
the same option to Typing Booster here.

engine/hunspell_table.py

@@ -219,6 +219,9 @@ def __init__(
             'ibuseventsleepseconds']['user']
         LOGGER.info('self._ibus_event_sleep_seconds=%s', self._ibus_event_sleep_seconds)
 
+        self._ibus_us_keymap = IBus.Keymap('us')
+        self._use_us_layout: bool = self._settings_dict['useuslayout']['user']
+
         self._emoji_predictions: bool = self._settings_dict[
             'emojipredictions']['user']
 
@@ -748,6 +751,9 @@ def _init_settings_dict(self) -> Dict[str, Any]:
             'ibuseventsleepseconds': {
                 'set': self.set_ibus_event_sleep_seconds,
                 'get': self.get_ibus_event_sleep_seconds},
+            'useuslayout': {
+                'set': self.set_use_us_layout,
+                'get': self.get_use_us_layout},
             'errorsound': {
                 'set': self.set_error_sound,
                 'get': self.get_error_sound},
@@ -5251,6 +5257,32 @@ def get_ibus_event_sleep_seconds(self) -> float:
         '''Returns the current value ibus event sleep seconds '''
         return self._ibus_event_sleep_seconds
 
+    def set_use_us_layout(
+            self, mode: bool, update_gsettings: bool = True) -> None:
+        '''Sets whether the use of the US keyboard is forced
+
+        :param mode: True if the use of the US keyboard is forced, False if 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.
+        '''
+        if self._debug_level > 1:
+            LOGGER.debug(
+                '(%s, update_gsettings = %s)', mode, update_gsettings)
+        if mode == self._use_us_layout:
+            return
+        self._use_us_layout = mode
+        if update_gsettings:
+            self._gsettings.set_value(
+                'useuslayout',
+                GLib.Variant.new_boolean(mode))
+
+    def get_use_us_layout(self) -> bool:
+        '''Returns whether the use of the US keyboard layout is forced'''
+        return self._use_us_layout
+
     def set_error_sound(
             self, error_sound: bool, update_gsettings: bool = True) -> None:
         '''Sets whether a sound is played on error or not
@@ -6968,6 +7000,21 @@ def do_process_key_event( # pylint: disable=arguments-differ
         key = itb_util.KeyEvent(keyval, keycode, state)
         if self._debug_level > 1:
             LOGGER.debug('KeyEvent object: %s', key)
+        if self._use_us_layout and key.name != 'Multi_key':
+            # Do not translate the Multi_key: If the non-US layout as
+            # a Multi_key, trying to translate it to US layout just
+            # takes it away. Skipping the translation keeps the
+            # Multi_key around which is more useful, it can still be
+            # used for Compose then.
+            key = itb_util.KeyEvent(
+                IBus.Keymap.lookup_keysym(
+                    self._ibus_us_keymap,
+                    keycode,
+                    state),
+                keycode, state)
+            if self._debug_level > 1:
+                LOGGER.debug('Forcing US layout...')
+                LOGGER.debug('KeyEvent object: %s', key)
 
         disabled = False
         if not self._input_mode:

org.freedesktop.ibus.engine.typing-booster.gschema.xml

@@ -399,6 +399,9 @@
         have been typed.
       </description>
     </key>
+    <key name="useuslayout" type="b">
+      <default>false</default>
+    </key>
     <key name="errorsound" type="b">
       <default>false</default>
     </key>

setup/main.py

@@ -789,6 +789,22 @@ def __init__( # pylint: disable=too-many-statements
             self._ascii_digits_checkbutton,
             0, _options_grid_row, 2, 1)
 
+        self._use_us_layout_checkbutton = Gtk.CheckButton(
+            # Translators: Whether the use of the US keyboard layout is
+            # forced while Typing Booster is active
+            label=_('Use US keyboard layout'))
+        self._use_us_layout_checkbutton.set_tooltip_text(
+            _('Whether the use of the US keyboard layout is forced '
+              'while Typing Booster is active.'))
+        self._use_us_layout_checkbutton.connect(
+            'clicked', self._on_use_us_layout_checkbutton)
+        self._use_us_layout_checkbutton.set_active(
+            self._settings_dict['useuslayout']['user'])
+        _options_grid_row += 1
+        self._options_grid.attach(
+            self._use_us_layout_checkbutton,
+            0, _options_grid_row, 2, 1)
+
         self._emoji_trigger_characters_label = Gtk.Label()
         self._emoji_trigger_characters_label.set_text(
             # Translators: The characters in this list trigger an
@@ -2304,6 +2320,7 @@ def _init_settings_dict(self) -> Dict[str, Any]:
             'preeditstyleonlywhenlookup':
             self.set_preedit_style_only_when_lookup,
             'mincharcomplete': self.set_min_char_complete,
+            'useuslayout': self.set_use_us_layout,
             'errorsound': self.set_error_sound,
             'errorsoundfile': self.set_error_sound_file,
             'soundbackend': self.set_sound_backend,
@@ -3187,6 +3204,15 @@ def _on_ascii_digits_checkbutton(
         self.set_ascii_digits(
             widget.get_active(), update_gsettings=True)
 
+    def _on_use_us_layout_checkbutton(
+            self, widget: Gtk.CheckButton) -> None:
+        '''
+        The checkbutton whether to force the use of the US
+        keyboard layout has been clicked.
+        '''
+        self.set_use_us_layout(
+            widget.get_active(), update_gsettings=True)
+
     def _on_emoji_trigger_characters_entry(
             self, widget: Gtk.Entry, _property_spec: Any) -> None:
         '''
@@ -6099,6 +6125,30 @@ def set_min_char_complete(
                 self._min_char_complete_adjustment.set_value(
                     int(min_char_complete))
 
+    def set_use_us_layout(
+            self,
+            mode: bool,
+            update_gsettings: bool = True) -> None:
+        '''Sets whether the use of the US keyboard is forced
+
+        :param mode: True if the use of the US keyboard is forced, False if 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.
+        '''
+        LOGGER.info(
+            '(%s, update_gsettings = %s)', mode, update_gsettings)
+        mode = bool(mode)
+        self._settings_dict['useuslayout']['user'] = mode
+        if update_gsettings:
+            self._gsettings.set_value(
+                'useuslayout',
+                GLib.Variant.new_boolean(mode))
+        else:
+            self._use_us_layout_checkbutton.set_active(mode)
+
     def set_error_sound(
             self,
             error_sound: bool,