keyboard: Handle extended keyboards through TERMINAL input purpose

Drop the channeling of this specific signal from the InputMethod, and
update the OSK Keyboard object to using the purpose hint to find out
whether a extended keymap is necessary.

Part-of: <https://gitlab.gnome.org/GNOME/gnome-shell/-/merge_requests/3162>

js/misc/inputMethod.js

@@ -21,7 +21,6 @@ const HAVE_REQUIRE_SURROUNDING_TEXT = GObject.signal_lookup('require-surrounding
 export const InputMethod = GObject.registerClass({
     Signals: {
         'surrounding-text-set': {},
-        'terminal-mode-changed': {},
     },
 }, class InputMethod extends Clutter.InputMethod {
     _init() {
@@ -34,7 +33,6 @@ export const InputMethod = GObject.registerClass({
         this._preeditAnchor = 0;
         this._preeditVisible = false;
         this._hidePanelId = 0;
-        this.terminalMode = false;
         this._ibus = IBus.Bus.new_async();
         this._ibus.connect('connected', this._onConnected.bind(this));
         this._ibus.connect('disconnected', this._clear.bind(this));
@@ -229,7 +227,6 @@ export const InputMethod = GObject.registerClass({
         this._surroundingTextCursor = null;
         this._surroundingTextAnchor = null;
         this._preeditStr = null;
-        this._setTerminalMode(false);
     }
 
     vfunc_set_cursor_location(rect) {
@@ -302,21 +299,11 @@ export const InputMethod = GObject.registerClass({
                  IBus.InputPurpose.TERMINAL)
             ibusPurpose = IBus.InputPurpose.TERMINAL;
 
-        this._setTerminalMode(
-            purpose === Clutter.InputContentPurpose.TERMINAL);
-
         this._purpose = ibusPurpose;
         if (this._context)
             this._context.set_content_type(this._purpose, this._hints);
     }
 
-    _setTerminalMode(terminalMode) {
-        if (this.terminalMode !== terminalMode) {
-            this.terminalMode = terminalMode;
-            this.emit('terminal-mode-changed');
-        }
-    }
-
     vfunc_filter_key_event(event) {
         if (!this._context)
             return false;

js/ui/keyboard.js

@@ -1413,10 +1413,6 @@ export const Keyboard = GObject.registerClass({
 
         this._updateKeys();
 
-        Main.inputMethod.connectObject(
-            'terminal-mode-changed', this._onTerminalModeChanged.bind(this),
-            this);
-
         this._keyboardController.connectObject(
             'active-group', this._onGroupChanged.bind(this),
             'groups-changed', this._onKeyboardGroupsChanged.bind(this),
@@ -1493,7 +1489,12 @@ export const Keyboard = GObject.registerClass({
     }
 
     _ensureKeys() {
-        const group = this._keyboardController.getCurrentGroup();
+        let group;
+        if (this._purpose === Clutter.InputContentPurpose.TERMINAL)
+            group = 'us-extended';
+        else
+            group = this._keyboardController.getCurrentGroup();
+
         if (!this._groups[group])
             this._groups[group] = this._createLayersForGroup(group);
     }
@@ -1617,7 +1618,7 @@ export const Keyboard = GObject.registerClass({
         if (enabled &&
             (!Main.inputMethod.currentFocus ||
              Main.inputMethod.hasPreedit() ||
-             Main.inputMethod.terminalMode)) {
+             this._purpose === Clutter.InputContentPurpose.TERMINAL)) {
             this._keyboardController.keyvalPress(Clutter.KEY_BackSpace);
             this._backspacePressed = true;
             return;
@@ -1803,10 +1804,6 @@ export const Keyboard = GObject.registerClass({
         this._updateKeys();
     }
 
-    _onTerminalModeChanged() {
-        this._updateKeys();
-    }
-
     _onKeyboardGroupsChanged() {
         let nonGroupActors = [this._emojiSelection, this._keypad];
         this._aspectContainer.get_children().filter(c => !nonGroupActors.includes(c)).forEach(c => {
@@ -2220,9 +2217,6 @@ class KeyboardController extends Signals.EventEmitter {
     }
 
     getCurrentGroup() {
-        if (Main.inputMethod.terminalMode)
-            return 'us-extended';
-
         // Special case for Korean, if Hangul mode is disabled, use the 'us' keymap
         if (this._currentSource.id === 'hangul') {
             const inputSourceManager = InputSourceManager.getInputSourceManager();