feat(ui): render the language picker as a Vue component

LocalePicker renders the existing picker model with the same markup and
listbox behaviour; ProviderSettingsView shows it while the shell publishes
the active language and its choice handler to the gev-locale store. A host
passing localePicker: false publishes nothing. A choice reaches the shell
after the list is closed on screen, and every opening keeps the active
option in view.

scripts/package-boundaries.json

@@ -27,6 +27,8 @@
       "src/ui/views/panels/RadioPanel.vue",
       "src/ui/views/panels/SdrCard.vue",
       "src/ui/views/panels/RadioTuner.vue",
+      "src/ui/views/panels/LocalePicker.vue",
+      "src/ui/localePicker.js",
       "src/ui/views/panels/PhoneTabBar.vue",
       "src/ui/views/panels/CockpitBriefing.vue",
       "src/ui/views/panels/CockpitContext.vue",
@@ -72,6 +74,7 @@
       "src/ui/stores/radio.js",
       "src/ui/stores/context.js",
       "src/ui/stores/cockpit.js",
+      "src/ui/stores/locale.js",
       "src/ui/stores/location.js",
       "src/ui/stores/streetLevel.js",
       "src/ui/rail/RailChips.vue",
@@ -998,6 +1001,7 @@
       "src/ui/stores/radio.js",
       "src/ui/stores/context.js",
       "src/ui/stores/cockpit.js",
+      "src/ui/stores/locale.js",
       "src/ui/stores/location.js",
       "src/ui/stores/display.js"
     ],
@@ -2975,6 +2979,7 @@
       "src/ui/stores/radio.js",
       "src/ui/stores/context.js",
       "src/ui/stores/cockpit.js",
+      "src/ui/stores/locale.js",
       "src/ui/stores/location.js",
       "src/ui/stores/display.js"
     ],

src/ui/applicationShell.js

@@ -51,11 +51,12 @@ import {
   registerUnsavedWork,
   t,
 } from '../i18n/index.js';
-import { applyLocaleChoice, mountLocalePicker } from './localePicker.js';
+import { applyLocaleChoice } from './localePicker.js';
 import { PanelNavigation } from './panelNavigation.js';
 import { applicationPinia, createUiRuntime } from './vueRuntime.js';
 import { useContextStore } from './stores/context.js';
 import { useDisplayStore } from './stores/display.js';
+import { useLocaleStore } from './stores/locale.js';
 import { useLocationStore } from './stores/location.js';
 import { useCockpitStore } from './stores/cockpit.js';
 
@@ -722,8 +723,9 @@ export class StyleManager extends ShellFacade {
   }
 
   /**
-   * Mounts the language picker (src/ui/localePicker.js). A choice reloads the
-   * page; _confirmLocaleReload asks first when that would lose work.
+   * Publishes the language picker, which ProviderSettingsView renders. A
+   * choice reloads the page; _confirmLocaleReload asks first when that would
+   * lose work.
    * @returns {void}
    */
   _initLocaleSelector() {
@@ -741,14 +743,9 @@ export class StyleManager extends ShellFacade {
         this.cockpitView?.active ? msg('the open cockpit') : null,
       ),
     ];
-    const root = globalThis.document?.getElementById?.('locale-picker');
-    if (!root) return;
-    if (this._localePickerEnabled === false) {
-      root.remove();
-      return;
-    }
-    this._localePicker = mountLocalePicker({
-      root,
+    // A host that does not initialize Core's locale shows no picker.
+    if (this._localePickerEnabled === false) return;
+    useLocaleStore(applicationPinia()).publishPicker({
       current: getLocale(),
       onSelect: (locale) => this._chooseLocale(locale),
     });
@@ -1772,8 +1769,7 @@ export class StyleManager extends ShellFacade {
     this._lifetime.destroy();
     for (const unregister of this._unsavedWorkChecks?.splice(0) ?? [])
       unregister();
-    this._localePicker?.destroy();
-    this._localePicker = null;
+    useLocaleStore(applicationPinia()).publishPicker(null);
     this._recording.destroy();
     this._mobileShell?.destroy();
     this._panelNavigation?.destroy();

src/ui/localePicker.js

@@ -2,7 +2,7 @@
  * Interface language picker: a HUD button in the bottom-right corner that
  * opens a listbox of the shipped languages.
  *
- * The logic is pure and DOM-free; mountLocalePicker() only renders it. The
+ * The logic is pure and DOM-free; the LocalePicker view renders it. The
  * shell decides what a choice does (confirm, reload).
  *
  * The list follows the ARIA listbox pattern: the button opens it, focus moves
@@ -309,12 +309,10 @@ export function createLocalePickerModel({
   };
 }
 
-/* ── DOM ───────────────────────────────────────────────────────────────── */
-
-const SVG_NS = 'http://www.w3.org/2000/svg';
+/* ── Presentation ──────────────────────────────────────────────────────── */
 
 /** Thin-line globe, check mark and caret, drawn in currentColor. */
-const ICONS = Object.freeze({
+export const LOCALE_PICKER_ICONS = Object.freeze({
   globe: {
     stroke: [
       'M12 3a9 9 0 1 0 0 18a9 9 0 1 0 0-18Z',
@@ -329,307 +327,14 @@ const ICONS = Object.freeze({
   caret: { fill: ['M7 10h10l-5 5.5Z'] },
 });
 
-function icon(documentRef, name, className) {
-  const svg = documentRef.createElementNS(SVG_NS, 'svg');
-  svg.setAttribute('viewBox', '0 0 24 24');
-  svg.setAttribute('aria-hidden', 'true');
-  svg.setAttribute('focusable', 'false');
-  svg.setAttribute('class', className);
-  const { stroke = [], fill = [] } = ICONS[name];
-  for (const d of stroke) {
-    const path = documentRef.createElementNS(SVG_NS, 'path');
-    path.setAttribute('d', d);
-    path.setAttribute('fill', 'none');
-    path.setAttribute('stroke', 'currentColor');
-    path.setAttribute('stroke-width', '1.4');
-    path.setAttribute('stroke-linecap', 'round');
-    path.setAttribute('stroke-linejoin', 'round');
-    svg.append(path);
-  }
-  for (const d of fill) {
-    const path = documentRef.createElementNS(SVG_NS, 'path');
-    path.setAttribute('d', d);
-    path.setAttribute('fill', 'currentColor');
-    svg.append(path);
-  }
-  return svg;
-}
-
-function element(documentRef, tag, className) {
-  const node = documentRef.createElement(tag);
-  if (className) node.className = className;
-  return node;
-}
-
 /**
- * Render the picker into `root` and wire it.
- * @param {object} input
- * @param {HTMLElement} input.root Empty #locale-picker container.
- * @param {string} input.current Active interface language.
- * @param {(locale: string) => void} input.onSelect Called after the list
- *   closes, for a language other than the current one.
- * @param {readonly string[]} [input.locales]
- * @param {Record<string, string>} [input.nativeNames]
- * @param {number} [input.searchThreshold]
- * @returns {{open: Function, close: Function, isOpen: () => boolean, destroy: Function}}
+ * The code shown beside a language's name. Chinese variants are named by
+ * script rather than region, in English.
+ * @param {string} code
+ * @returns {{text: string, lang: string|undefined}}
  */
-export function mountLocalePicker({
-  root,
-  current,
-  onSelect,
-  locales = LOCALES,
-  nativeNames = LOCALE_NAMES,
-  searchThreshold = LOCALE_SEARCH_THRESHOLD,
-}) {
-  const documentRef = root.ownerDocument;
-  const windowRef = documentRef.defaultView;
-  const model = createLocalePickerModel({
-    locales,
-    current,
-    nativeNames,
-    localName: createLocalNameReader(current),
-    searchThreshold,
-  });
-  const id = root.id || 'locale-picker';
-  const ids = {
-    popup: `${id}-popup`,
-    heading: `${id}-heading`,
-    listbox: `${id}-listbox`,
-    option: (code) => `${id}-option-${code}`,
-  };
-
-  root.textContent = '';
-  root.classList.add('locale-picker');
-
-  const button = element(documentRef, 'button', 'locale-picker-button');
-  button.type = 'button';
-  button.setAttribute('aria-haspopup', 'listbox');
-  button.setAttribute('aria-expanded', 'false');
-  button.setAttribute('aria-controls', ids.popup);
-  button.setAttribute(
-    'aria-label',
-    t('Language: {language}', {
-      language: nativeNames[current] || current,
-    }),
-  );
-  button.title = t('Change the interface language');
-  const code = element(documentRef, 'span', 'locale-picker-code');
-  code.setAttribute('translate', 'no');
-  code.setAttribute('aria-hidden', 'true');
-  code.textContent = current.toUpperCase();
-  button.append(
-    icon(documentRef, 'globe', 'locale-picker-globe'),
-    code,
-    icon(documentRef, 'caret', 'locale-picker-caret'),
-  );
-
-  const popup = element(documentRef, 'div', 'locale-picker-popup');
-  popup.id = ids.popup;
-  popup.hidden = true;
-  const heading = element(documentRef, 'div', 'locale-picker-heading');
-  heading.id = ids.heading;
-  heading.textContent = t('Interface language');
-  popup.append(heading);
-
-  const listbox = element(documentRef, 'ul', 'locale-picker-list ui-scroll');
-  listbox.id = ids.listbox;
-  listbox.setAttribute('role', 'listbox');
-  listbox.setAttribute('aria-labelledby', ids.heading);
-  listbox.tabIndex = -1;
-
-  let search = null;
-  if (model.searchable) {
-    search = element(documentRef, 'input', 'locale-picker-search');
-    search.type = 'search';
-    search.autocomplete = 'off';
-    search.spellcheck = false;
-    search.setAttribute('role', 'combobox');
-    search.setAttribute('aria-autocomplete', 'list');
-    search.setAttribute('aria-expanded', 'true');
-    search.setAttribute('aria-controls', ids.listbox);
-    search.setAttribute('aria-label', t('Search languages'));
-    search.placeholder = t('Search languages');
-    popup.append(search);
-  }
-  popup.append(listbox);
-  const empty = element(documentRef, 'p', 'locale-picker-empty');
-  empty.setAttribute('role', 'status');
-  empty.textContent = t('No matching languages');
-  empty.hidden = true;
-  popup.append(empty);
-  root.append(button, popup);
-
-  const optionNodes = new Map();
-  for (const option of model.options) {
-    const item = element(documentRef, 'li', 'locale-picker-option');
-    item.id = ids.option(option.code);
-    item.setAttribute('role', 'option');
-    item.setAttribute('aria-selected', String(option.selected));
-    item.lang = option.code;
-    item.dataset.locale = option.code;
-    const name = element(documentRef, 'span', 'locale-picker-native');
-    name.textContent = option.nativeName;
-    // Chinese variants are distinguished by script rather than region.
-    const meta = element(documentRef, 'span', 'locale-picker-meta');
-    const codeLabel = element(documentRef, 'span', 'locale-picker-option-code');
-    codeLabel.setAttribute('translate', 'no');
-    codeLabel.textContent =
-      CHINESE_LABELS[option.code] || option.code.toUpperCase();
-    if (CHINESE_LABELS[option.code]) codeLabel.lang = 'en';
-    meta.append(codeLabel);
-    const text = element(documentRef, 'span', 'locale-picker-text');
-    text.append(name, meta);
-    item.append(text);
-    if (option.selected)
-      item.append(icon(documentRef, 'check', 'locale-picker-check'));
-    optionNodes.set(option.code, item);
-  }
-
-  const focusTarget = () => search || listbox;
-
-  const render = () => {
-    const visible = new Set(model.visible.map((option) => option.code));
-    listbox.replaceChildren(
-      ...model.visible.map((option) => optionNodes.get(option.code)),
-    );
-    for (const [localeCode, item] of optionNodes) {
-      item.classList.toggle(
-        'is-active',
-        visible.has(localeCode) && model.activeOption?.code === localeCode,
-      );
-    }
-    empty.hidden = model.visible.length > 0;
-    const activeNode = model.activeOption
-      ? optionNodes.get(model.activeOption.code)
-      : null;
-    if (activeNode) {
-      focusTarget().setAttribute('aria-activedescendant', activeNode.id);
-      activeNode.scrollIntoView?.({ block: 'nearest' });
-    } else {
-      focusTarget().removeAttribute('aria-activedescendant');
-    }
-  };
-
-  let swallowSpaceKeyup = false;
-
-  const close = ({ restoreFocus = false } = {}) => {
-    if (!model.open) return;
-    model.closeList();
-    popup.hidden = true;
-    root.classList.remove('is-open');
-    button.setAttribute('aria-expanded', 'false');
-    windowRef?.removeEventListener('keydown', onWindowKeyDown, true);
-    documentRef.removeEventListener('pointerdown', onDocumentPointerDown, true);
-    if (restoreFocus) button.focus({ preventScroll: true });
-  };
-
-  const choose = (localeCode) => {
-    close({ restoreFocus: true });
-    if (localeCode !== current) onSelect(localeCode);
-  };
-
-  const open = () => {
-    if (model.open) return;
-    model.openList();
-    if (search) search.value = '';
-    popup.hidden = false;
-    root.classList.add('is-open');
-    button.setAttribute('aria-expanded', 'true');
-    render();
-    // Window capture runs before the document-level shortcut handlers
-    // (cockpit, hotkeys, push-to-talk), so keys typed in the list stay here.
-    windowRef?.addEventListener('keydown', onWindowKeyDown, true);
-    documentRef.addEventListener('pointerdown', onDocumentPointerDown, true);
-    focusTarget().focus({ preventScroll: true });
-  };
-
-  function onWindowKeyDown(event) {
-    if (!model.open || event.isComposing) return;
-    const inside = root.contains(event.target);
-    if (!inside && event.key !== 'Escape') return;
-    const result = model.keydown(event);
-    if (!result.handled) return;
-    event.preventDefault();
-    event.stopImmediatePropagation();
-    if (result.close) close({ restoreFocus: true });
-    else if (result.choose) {
-      if (event.key === ' ') swallowSpaceKeyup = true;
-      choose(result.choose);
-    } else render();
-  }
-
-  function onDocumentPointerDown(event) {
-    if (!root.contains(event.target)) close();
-  }
-
-  const onButtonClick = () => {
-    if (model.open) close({ restoreFocus: true });
-    else open();
-  };
-
-  const onButtonKeyDown = (event) => {
-    if (event.key !== 'ArrowDown' && event.key !== 'ArrowUp') return;
-    event.preventDefault();
-    event.stopPropagation();
-    open();
-  };
-
-  // Space chose an option and moved focus here; its keyup must not click.
-  const onButtonKeyUp = (event) => {
-    if (event.key !== ' ' || !swallowSpaceKeyup) return;
-    swallowSpaceKeyup = false;
-    event.preventDefault();
-  };
-
-  const optionFromEvent = (event) =>
-    event.target?.closest?.('[role="option"]')?.dataset.locale || null;
-
-  const onListClick = (event) => {
-    const localeCode = optionFromEvent(event);
-    if (localeCode) choose(localeCode);
-  };
-
-  const onListPointerMove = (event) => {
-    const localeCode = optionFromEvent(event);
-    if (!localeCode || model.activeOption?.code === localeCode) return;
-    model.setActive(
-      model.visible.findIndex((option) => option.code === localeCode),
-    );
-    render();
-  };
-
-  const onSearchInput = () => {
-    model.setQuery(search.value);
-    render();
-  };
-
-  const onFocusOut = (event) => {
-    const next = event.relatedTarget;
-    if (model.open && next && !root.contains(next)) close();
-  };
-
-  button.addEventListener('click', onButtonClick);
-  button.addEventListener('keydown', onButtonKeyDown);
-  button.addEventListener('keyup', onButtonKeyUp);
-  listbox.addEventListener('click', onListClick);
-  listbox.addEventListener('pointermove', onListPointerMove);
-  search?.addEventListener('input', onSearchInput);
-  root.addEventListener('focusout', onFocusOut);
-
-  return {
-    open,
-    close,
-    isOpen: () => model.open,
-    destroy() {
-      close();
-      button.removeEventListener('click', onButtonClick);
-      button.removeEventListener('keydown', onButtonKeyDown);
-      button.removeEventListener('keyup', onButtonKeyUp);
-      listbox.removeEventListener('click', onListClick);
-      listbox.removeEventListener('pointermove', onListPointerMove);
-      search?.removeEventListener('input', onSearchInput);
-      root.removeEventListener('focusout', onFocusOut);
-      root.textContent = '';
-    },
-  };
+export function localeOptionCode(code) {
+  return CHINESE_LABELS[code]
+    ? { text: CHINESE_LABELS[code], lang: 'en' }
+    : { text: code.toUpperCase(), lang: undefined };
 }

src/ui/localePickerView.test.mjs

@@ -0,0 +1,351 @@
+// src/ui/localePickerView.test.mjs — the language picker renders the
+// model in localePicker.js and wires the listbox pattern, over happy-dom.
+import '../testSupport/registerDom.mjs';
+import test from 'node:test';
+import assert from 'node:assert/strict';
+import { createApp, h, nextTick } from 'vue';
+import { createPinia } from 'pinia';
+import { useLocaleStore } from './stores/locale.js';
+import ProviderSettingsView from './views/ProviderSettingsView.vue';
+import LocalePicker from './views/panels/LocalePicker.vue';
+
+const NAMES = {
+  en: 'English',
+  de: 'Deutsch',
+  es: 'Español',
+  fr: 'Français',
+  'zh-CN': '简体中文',
+};
+
+function fixture(t, { searchThreshold = 8 } = {}) {
+  document.body.replaceChildren();
+  const outside = document.body.appendChild(document.createElement('button'));
+  const host = document.body.appendChild(document.createElement('div'));
+  const chosen = [];
+  // Whether the list was closed on screen when each choice arrived.
+  const closedAtChoice = [];
+  let picker = null;
+  const app = createApp({
+    render: () =>
+      h(LocalePicker, {
+        ref: (instance) => {
+          picker = instance;
+        },
+        current: 'en',
+        locales: Object.keys(NAMES),
+        nativeNames: NAMES,
+        searchThreshold,
+        onSelect: (locale) => {
+          chosen.push(locale);
+          closedAtChoice.push(
+            document.getElementById('locale-picker-popup').hidden,
+          );
+        },
+      }),
+  });
+  app.mount(host);
+  let mounted = true;
+  const unmount = () => {
+    if (mounted) app.unmount();
+    mounted = false;
+  };
+  t.after(unmount);
+  const $ = (selector) => document.querySelector(selector);
+  const key = (target, init) =>
+    target.dispatchEvent(
+      new KeyboardEvent('keydown', {
+        bubbles: true,
+        cancelable: true,
+        ...init,
+      }),
+    );
+  const settle = async () => {
+    await nextTick();
+    await nextTick();
+  };
+  return {
+    $,
+    outside,
+    chosen,
+    closedAtChoice,
+    key,
+    settle,
+    unmount,
+    picker: () => picker,
+  };
+}
+
+const optionCodes = () =>
+  [...document.querySelectorAll('.locale-picker-option')].map(
+    (option) => option.dataset.locale,
+  );
+
+test('closed, the button names the active language and the list is hidden', (t) => {
+  const { $ } = fixture(t);
+  const button = $('.locale-picker-button');
+  assert.equal(button.getAttribute('aria-label'), 'Language: English');
+  assert.equal(button.getAttribute('aria-expanded'), 'false');
+  assert.equal(button.getAttribute('aria-controls'), 'locale-picker-popup');
+  assert.equal($('.locale-picker-code').textContent, 'EN');
+  assert.equal($('#locale-picker-popup').hidden, true);
+  assert.equal($('#locale-picker').classList.contains('is-open'), false);
+  // The current language first, then the rest by their own names.
+  assert.deepEqual(optionCodes(), ['en', 'de', 'es', 'fr', 'zh-CN']);
+  assert.equal($('[data-locale="en"]').getAttribute('aria-selected'), 'true');
+  assert.ok($('[data-locale="en"] .locale-picker-check'));
+  assert.equal($('[data-locale="de"] .locale-picker-check'), null);
+  const chinese = $('[data-locale="zh-CN"] .locale-picker-option-code');
+  assert.equal(chinese.textContent, 'Chinese (Simplified)');
+  assert.equal(chinese.lang, 'en');
+  assert.equal($('[data-locale="de"] .locale-picker-option-code').lang, '');
+  assert.equal($('.locale-picker-search'), null);
+});
+
+test('opening focuses the list on the current language; keys move and choose', async (t) => {
+  const { $, chosen, key, settle } = fixture(t);
+  const button = $('.locale-picker-button');
+  button.click();
+  await settle();
+  const list = $('#locale-picker-listbox');
+  assert.equal($('#locale-picker-popup').hidden, false);
+  assert.equal(button.getAttribute('aria-expanded'), 'true');
+  assert.equal($('#locale-picker').classList.contains('is-open'), true);
+  assert.equal(document.activeElement?.id, 'locale-picker-listbox');
+  assert.equal(
+    list.getAttribute('aria-activedescendant'),
+    'locale-picker-option-en',
+  );
+  key(list, { key: 'ArrowDown' });
+  await settle();
+  assert.equal(
+    list.getAttribute('aria-activedescendant'),
+    'locale-picker-option-de',
+  );
+  assert.equal($('[data-locale="de"]').classList.contains('is-active'), true);
+  assert.equal($('[data-locale="en"]').classList.contains('is-active'), false);
+  key(list, { key: 'Enter' });
+  await settle();
+  assert.deepEqual(chosen, ['de']);
+  assert.equal($('#locale-picker-popup').hidden, true);
+  assert.equal(document.activeElement === button, true);
+});
+
+test('choosing the active language closes without a choice; Escape and outside presses close', async (t) => {
+  const { $, chosen, key, outside, settle } = fixture(t);
+  const button = $('.locale-picker-button');
+  button.click();
+  await settle();
+  $('[data-locale="en"]').click();
+  await settle();
+  assert.deepEqual(chosen, []);
+  assert.equal($('#locale-picker-popup').hidden, true);
+
+  button.click();
+  await settle();
+  key(document.body, { key: 'Escape' });
+  await settle();
+  assert.equal($('#locale-picker-popup').hidden, true);
+  assert.equal(document.activeElement === button, true);
+
+  button.click();
+  await settle();
+  outside.dispatchEvent(new PointerEvent('pointerdown', { bubbles: true }));
+  await settle();
+  assert.equal($('#locale-picker-popup').hidden, true);
+});
+
+test('while open, keys typed in the list stay out of the page shortcuts', async (t) => {
+  const { $, key, settle } = fixture(t);
+  let reached = 0;
+  const shortcut = () => reached++;
+  document.addEventListener('keydown', shortcut);
+  t.after(() => document.removeEventListener('keydown', shortcut));
+  $('.locale-picker-button').click();
+  await settle();
+  key($('#locale-picker-listbox'), { key: 'f' });
+  await settle();
+  assert.equal(reached, 0);
+  assert.equal(
+    $('#locale-picker-listbox').getAttribute('aria-activedescendant'),
+    'locale-picker-option-fr',
+  );
+  $('.locale-picker-button').click();
+  await settle();
+  key(document.body, { key: 'f' });
+  assert.equal(reached, 1);
+});
+
+test('above the threshold a search field filters the list and owns the active option', async (t) => {
+  const { $, chosen, key, settle } = fixture(t, { searchThreshold: 3 });
+  $('.locale-picker-button').click();
+  await settle();
+  const search = $('.locale-picker-search');
+  assert.equal(document.activeElement === search, true);
+  assert.equal(
+    search.getAttribute('aria-activedescendant'),
+    'locale-picker-option-en',
+  );
+  assert.equal(
+    $('#locale-picker-listbox').hasAttribute('aria-activedescendant'),
+    false,
+  );
+  search.value = 'espa';
+  search.dispatchEvent(new Event('input', { bubbles: true }));
+  await settle();
+  assert.deepEqual(optionCodes(), ['es']);
+  assert.equal($('.locale-picker-empty').hidden, true);
+  search.value = 'zzz';
+  search.dispatchEvent(new Event('input', { bubbles: true }));
+  await settle();
+  assert.deepEqual(optionCodes(), []);
+  assert.equal($('.locale-picker-empty').hidden, false);
+  assert.equal(search.hasAttribute('aria-activedescendant'), false);
+  search.value = 'fran';
+  search.dispatchEvent(new Event('input', { bubbles: true }));
+  await settle();
+  key(search, { key: 'Enter' });
+  await settle();
+  assert.deepEqual(chosen, ['fr']);
+  // Reopening starts from an empty search with every language.
+  $('.locale-picker-button').click();
+  await settle();
+  assert.equal($('.locale-picker-search').value, '');
+  assert.equal(optionCodes().length, 5);
+});
+
+test('focus leaving the picker closes it', async (t) => {
+  const { $, outside, picker, settle } = fixture(t);
+  $('.locale-picker-button').click();
+  await settle();
+  $('#locale-picker').dispatchEvent(
+    new FocusEvent('focusout', { bubbles: true, relatedTarget: outside }),
+  );
+  await settle();
+  assert.equal($('#locale-picker-popup').hidden, true);
+  assert.equal(picker().isOpen(), false);
+});
+
+test('a choice arrives after the list is closed on screen', async (t) => {
+  const { $, chosen, closedAtChoice, settle } = fixture(t);
+  $('.locale-picker-button').click();
+  await settle();
+  $('[data-locale="fr"]').click();
+  await settle();
+  assert.deepEqual(chosen, ['fr']);
+  assert.deepEqual(closedAtChoice, [true]);
+});
+
+test('every opening scrolls the active option into view', async (t) => {
+  const { $, settle } = fixture(t);
+  const scrolled = [];
+  const original = HTMLElement.prototype.scrollIntoView;
+  HTMLElement.prototype.scrollIntoView = function () {
+    scrolled.push(this.dataset.locale);
+  };
+  t.after(() => {
+    HTMLElement.prototype.scrollIntoView = original;
+  });
+  const button = $('.locale-picker-button');
+  button.click();
+  await settle();
+  button.click();
+  await settle();
+  button.click();
+  await settle();
+  assert.deepEqual(scrolled, ['en', 'en']);
+});
+
+test('closing or unmounting an open picker releases its page listeners', async (t) => {
+  const { $, settle, unmount } = fixture(t);
+  const added = [];
+  const removed = [];
+  const spy = (target, list) => {
+    const add = target.addEventListener;
+    const remove = target.removeEventListener;
+    target.addEventListener = function (type, fn, capture) {
+      added.push(type);
+      return add.call(this, type, fn, capture);
+    };
+    target.removeEventListener = function (type, fn, capture) {
+      list.push(type);
+      return remove.call(this, type, fn, capture);
+    };
+    t.after(() => {
+      target.addEventListener = add;
+      target.removeEventListener = remove;
+    });
+  };
+  spy(globalThis, removed);
+  spy(document, removed);
+  $('.locale-picker-button').click();
+  await settle();
+  assert.deepEqual(added.sort(), ['keydown', 'pointerdown']);
+  $('.locale-picker-button').click();
+  await settle();
+  assert.deepEqual(removed.sort(), ['keydown', 'pointerdown']);
+  removed.length = 0;
+  $('.locale-picker-button').click();
+  await settle();
+  unmount();
+  assert.deepEqual(removed.sort(), ['keydown', 'pointerdown']);
+});
+
+test('arrow keys on the button open the list; the Space that chose an option does not click it', async (t) => {
+  const { $, chosen, key, settle } = fixture(t);
+  const button = $('.locale-picker-button');
+  key(button, { key: 'ArrowDown' });
+  await settle();
+  assert.equal($('#locale-picker-popup').hidden, false);
+  const list = $('#locale-picker-listbox');
+  key(list, { key: 'ArrowDown' });
+  key(list, { key: ' ' });
+  await settle();
+  assert.deepEqual(chosen, ['de']);
+  assert.equal(document.activeElement === button, true);
+  const keyup = new KeyboardEvent('keyup', {
+    key: ' ',
+    bubbles: true,
+    cancelable: true,
+  });
+  button.dispatchEvent(keyup);
+  assert.equal(keyup.defaultPrevented, true);
+  const nextKeyup = new KeyboardEvent('keyup', {
+    key: ' ',
+    bubbles: true,
+    cancelable: true,
+  });
+  button.dispatchEvent(nextKeyup);
+  assert.equal(nextKeyup.defaultPrevented, false);
+});
+
+test('pointing at an option makes it the active one', async (t) => {
+  const { $, settle } = fixture(t);
+  $('.locale-picker-button').click();
+  await settle();
+  $('[data-locale="es"] .locale-picker-native').dispatchEvent(
+    new PointerEvent('pointermove', { bubbles: true }),
+  );
+  await settle();
+  assert.equal(
+    $('#locale-picker-listbox').getAttribute('aria-activedescendant'),
+    'locale-picker-option-es',
+  );
+});
+
+test('the provider settings corner shows the picker only while the shell publishes one', async (t) => {
+  document.body.replaceChildren();
+  const host = document.body.appendChild(document.createElement('div'));
+  const pinia = createPinia();
+  const app = createApp(ProviderSettingsView).use(pinia);
+  app.mount(host);
+  t.after(() => app.unmount());
+  const store = useLocaleStore(pinia);
+  assert.equal(document.getElementById('locale-picker'), null);
+  store.publishPicker({ current: 'de', onSelect() {} });
+  await nextTick();
+  const code = document.querySelector('#corner-actions .locale-picker-code');
+  assert.equal(code?.textContent, 'DE');
+  store.publishPicker(null);
+  await nextTick();
+  assert.equal(document.getElementById('locale-picker'), null);
+});

src/ui/localeSwitchReload.test.mjs

@@ -4,6 +4,8 @@
 import { test } from 'node:test';
 import assert from 'node:assert/strict';
 import { StyleManager } from './applicationShell.js';
+import { useLocaleStore } from './stores/locale.js';
+import { applicationPinia } from './vueRuntime.js';
 import {
   describeUnsavedWork,
   msg,
@@ -12,7 +14,8 @@ import {
 } from '../i18n/index.js';
 
 /** Wire the shell's language choice with the given shell state. No picker
- * markup here: the picker's own behaviour is covered by localePicker.test. */
+ * markup here: the picker's own behaviour is covered by localePicker.test
+ * and localePickerView.test. */
 function renderSwitch({ calDirty = false, cockpit = false } = {}) {
   const previous = {
     document: globalThis.document,
@@ -137,20 +140,25 @@ test('the language already active neither asks nor reloads', () => {
   }
 });
 
-test('a host without Core locales removes the picker instead of mounting it', () => {
-  const previous = globalThis.document;
-  let removed = 0;
-  const root = { remove: () => removed++ };
-  globalThis.document = {
-    getElementById: (id) => (id === 'locale-picker' ? root : null),
+test('a host without Core locales shows no picker; otherwise the shell publishes one', () => {
+  const store = useLocaleStore(applicationPinia());
+  store.publishPicker(null);
+  const disabled = { services: {}, _localePickerEnabled: false };
+  const enabled = {
+    services: {},
+    _chooseLocale: (locale) => chosen.push(locale),
   };
-  const shell = { services: {}, _localePickerEnabled: false };
+  const chosen = [];
   try {
-    StyleManager.prototype._initLocaleSelector.call(shell);
-    assert.equal(removed, 1);
-    assert.equal(shell._localePicker, undefined);
+    StyleManager.prototype._initLocaleSelector.call(disabled);
+    assert.equal(store.picker, null);
+    StyleManager.prototype._initLocaleSelector.call(enabled);
+    assert.equal(store.picker.current, 'en');
+    store.picker.onSelect('fr');
+    assert.deepEqual(chosen, ['fr']);
   } finally {
-    for (const unregister of shell._unsavedWorkChecks) unregister();
-    globalThis.document = previous;
+    store.publishPicker(null);
+    for (const shell of [disabled, enabled])
+      for (const unregister of shell._unsavedWorkChecks ?? []) unregister();
   }
 });

src/ui/stores/locale.js

@@ -0,0 +1,19 @@
+import { defineStore } from 'pinia';
+import { markRaw, shallowRef } from 'vue';
+
+/**
+ * The interface language picker as its view renders it. The shell publishes
+ * the active language and what a choice does once it decides to show the
+ * picker; a host that does not initialize Core's locale never does.
+ */
+export const useLocaleStore = defineStore('gev-locale', () => {
+  /** `{current, onSelect}`, or null while no picker is shown. */
+  const picker = shallowRef(null);
+
+  /** @param {?{current: string, onSelect: (locale: string) => void}} next */
+  function publishPicker(next) {
+    picker.value = next && markRaw(next);
+  }
+
+  return { picker, publishPicker };
+});

src/ui/styles/locale-picker.css

@@ -1,7 +1,7 @@
 /* ============================================================
    Bottom-right corner row: the POWER UP chip (provider-settings.css)
    and, in the very corner, the interface language picker
-   (src/ui/localePicker.js). Logical properties throughout, so a
+   (src/ui/views/panels/LocalePicker.vue). Logical properties throughout, so a
    right-to-left page mirrors the row and the list.
    ============================================================ */
 

src/ui/views/ProviderSettingsView.vue

@@ -1,16 +1,24 @@
+<script setup>
+import { storeToRefs } from 'pinia';
+import { useLocaleStore } from '../stores/locale.js';
+import LocalePicker from './panels/LocalePicker.vue';
+
+const { picker } = storeToRefs(useLocaleStore());
+</script>
+
 <template>
   <!-- POWER UP — in-app key setup. Dev-server only: src/keySetup.js removes
        both the chip and this dialog outright when /api/setup/status is not
        there to answer (prod builds, LAN visitors). Rows are rendered from
        that payload, so the key registry lives in src/keySetupCore.mjs alone. -->
   <!-- Bottom-right HUD row: the POWER UP chip (while keys are missing) and
-       the language picker that src/ui/localePicker.js renders into #locale-picker. -->
+       the language picker, once the shell publishes it. -->
   <div id="corner-actions">
     <button id="key-setup-chip" type="button" hidden aria-haspopup="dialog" aria-controls="key-setup">
       <span class="material-symbols-outlined" aria-hidden="true">bolt</span>
       <span data-key-setup-chip-label data-i18n>POWER UP</span>
     </button>
-    <div id="locale-picker"></div>
+    <LocalePicker v-if="picker" :key="picker.current" :current="picker.current" :on-select="picker.onSelect" />
   </div>
   <aside id="key-setup" role="dialog" aria-labelledby="key-setup-title" aria-describedby="key-setup-description" hidden>
     <div class="key-setup-scanline" aria-hidden="true"></div>

src/ui/views/panels/LocalePicker.vue

@@ -0,0 +1,200 @@
+<script setup>
+import {
+  computed,
+  nextTick,
+  onBeforeUnmount,
+  shallowRef,
+  useTemplateRef,
+} from 'vue';
+import { t } from '../../../i18n/index.js';
+import { LOCALES, LOCALE_NAMES } from '../../../i18n/locale.js';
+import {
+  LOCALE_PICKER_ICONS,
+  LOCALE_SEARCH_THRESHOLD,
+  createLocalNameReader,
+  createLocalePickerModel,
+  localeOptionCode,
+} from '../../localePicker.js';
+import { vClassToggle } from '../../rail/classToggle.js';
+
+// The interface language picker. The model in localePicker.js holds the
+// list, search, active option and keyboard rules; this renders it and wires
+// the listbox pattern. The shell decides what a choice does.
+const props = defineProps({
+  current: { type: String, required: true },
+  onSelect: { type: Function, required: true },
+  locales: { type: Array, default: () => LOCALES },
+  nativeNames: { type: Object, default: () => LOCALE_NAMES },
+  searchThreshold: { type: Number, default: LOCALE_SEARCH_THRESHOLD },
+});
+
+const model = createLocalePickerModel({
+  locales: props.locales,
+  current: props.current,
+  nativeNames: props.nativeNames,
+  localName: createLocalNameReader(props.current),
+  searchThreshold: props.searchThreshold,
+});
+const id = 'locale-picker';
+const ids = {
+  popup: `${id}-popup`,
+  heading: `${id}-heading`,
+  listbox: `${id}-listbox`,
+  option: (code) => `${id}-option-${code}`,
+};
+
+// The model is plain state; each change bumps this so the template rereads it.
+const revision = shallowRef(0);
+const view = computed(() => {
+  void revision.value;
+  return {
+    open: model.open,
+    visible: model.visible,
+    active: model.activeOption?.code ?? null,
+  };
+});
+// Each render keeps the active option in view, as the list opens too.
+const render = () => {
+  revision.value += 1;
+  nextTick(() => {
+    const code = model.open ? model.activeOption?.code : null;
+    if (!code) return;
+    root.value
+      ?.querySelector(`#${CSS.escape(ids.option(code))}`)
+      ?.scrollIntoView?.({ block: 'nearest' });
+  });
+};
+
+const root = useTemplateRef('root');
+const button = useTemplateRef('button');
+const listbox = useTemplateRef('listbox');
+const search = useTemplateRef('search');
+const focusTarget = () => search.value || listbox.value;
+const activeDescendant = computed(() =>
+  view.value.active ? ids.option(view.value.active) : undefined,
+);
+const buttonLabel = t('Language: {language}', {
+  language: props.nativeNames[props.current] || props.current,
+});
+
+let swallowSpaceKeyup = false;
+
+function close({ restoreFocus = false } = {}) {
+  if (!model.open) return;
+  model.closeList();
+  render();
+  globalThis.removeEventListener('keydown', onWindowKeyDown, true);
+  document.removeEventListener('pointerdown', onDocumentPointerDown, true);
+  if (restoreFocus) button.value?.focus({ preventScroll: true });
+}
+
+// The shell may ask before switching; the list is closed on screen first.
+async function choose(code) {
+  close({ restoreFocus: true });
+  if (code === props.current) return;
+  await nextTick();
+  props.onSelect(code);
+}
+
+async function open() {
+  if (model.open) return;
+  model.openList();
+  if (search.value) search.value.value = '';
+  render();
+  // Window capture runs before the document-level shortcut handlers
+  // (cockpit, hotkeys, push-to-talk), so keys typed in the list stay here.
+  globalThis.addEventListener('keydown', onWindowKeyDown, true);
+  document.addEventListener('pointerdown', onDocumentPointerDown, true);
+  // The popup shows when Vue renders it; focus it after.
+  await nextTick();
+  if (model.open) focusTarget()?.focus({ preventScroll: true });
+}
+
+function onWindowKeyDown(event) {
+  if (!model.open || event.isComposing) return;
+  const inside = root.value?.contains(event.target);
+  if (!inside && event.key !== 'Escape') return;
+  const result = model.keydown(event);
+  if (!result.handled) return;
+  event.preventDefault();
+  event.stopImmediatePropagation();
+  if (result.close) close({ restoreFocus: true });
+  else if (result.choose) {
+    if (event.key === ' ') swallowSpaceKeyup = true;
+    choose(result.choose);
+  } else render();
+}
+
+function onDocumentPointerDown(event) {
+  if (!root.value?.contains(event.target)) close();
+}
+
+function onButtonClick() {
+  if (model.open) close({ restoreFocus: true });
+  else open();
+}
+
+function onButtonKeyDown(event) {
+  if (event.key !== 'ArrowDown' && event.key !== 'ArrowUp') return;
+  event.preventDefault();
+  event.stopPropagation();
+  open();
+}
+
+// Space chose an option and moved focus here; its keyup must not click.
+function onButtonKeyUp(event) {
+  if (event.key !== ' ' || !swallowSpaceKeyup) return;
+  swallowSpaceKeyup = false;
+  event.preventDefault();
+}
+
+const optionFromEvent = (event) =>
+  event.target?.closest?.('[role="option"]')?.dataset.locale || null;
+
+function onListClick(event) {
+  const code = optionFromEvent(event);
+  if (code) choose(code);
+}
+
+function onListPointerMove(event) {
+  const code = optionFromEvent(event);
+  if (!code || model.activeOption?.code === code) return;
+  model.setActive(model.visible.findIndex((option) => option.code === code));
+  render();
+}
+
+function onSearchInput(event) {
+  model.setQuery(event.target.value);
+  render();
+}
+
+function onFocusOut(event) {
+  const next = event.relatedTarget;
+  if (model.open && next && !root.value?.contains(next)) close();
+}
+
+onBeforeUnmount(() => close());
+
+defineExpose({ open, close, isOpen: () => model.open });
+</script>
+
+<template>
+  <div id="locale-picker" ref="root" class="locale-picker" v-class-toggle="{ 'is-open': view.open }" @focusout="onFocusOut">
+    <button ref="button" class="locale-picker-button" type="button" aria-haspopup="listbox" :aria-expanded="String(view.open)" :aria-controls="ids.popup" :aria-label="buttonLabel" :title="t('Change the interface language')" @click="onButtonClick" @keydown="onButtonKeyDown" @keyup="onButtonKeyUp">
+      <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false" class="locale-picker-globe"><path v-for="d in LOCALE_PICKER_ICONS.globe.stroke" :key="d" :d="d" fill="none" stroke="currentColor" stroke-width="1.4" stroke-linecap="round" stroke-linejoin="round" /></svg>
+      <span class="locale-picker-code" translate="no" aria-hidden="true">{{ current.toUpperCase() }}</span>
+      <svg viewBox="0 0 24 24" aria-hidden="true" focusable="false" class="locale-picker-caret"><path v-for="d in LOCALE_PICKER_ICONS.caret.fill" :key="d" :d="d" fill="currentColor" /></svg>
+    </button>
+    <div :id="ids.popup" class="locale-picker-popup" :hidden="!view.open">
+      <div :id="ids.heading" class="locale-picker-heading">{{ t('Interface language') }}</div>
+      <input v-if="model.searchable" ref="search" class="locale-picker-search" type="search" autocomplete="off" spellcheck="false" role="combobox" aria-autocomplete="list" aria-expanded="true" :aria-controls="ids.listbox" :aria-label="t('Search languages')" :placeholder="t('Search languages')" :aria-activedescendant="activeDescendant" @input="onSearchInput" />
+      <ul ref="listbox" :id="ids.listbox" class="locale-picker-list ui-scroll" role="listbox" :aria-labelledby="ids.heading" tabindex="-1" :aria-activedescendant="model.searchable ? undefined : activeDescendant" @click="onListClick" @pointermove="onListPointerMove">
+        <li v-for="option in view.visible" :key="option.code" :id="ids.option(option.code)" class="locale-picker-option" v-class-toggle="{ 'is-active': view.active === option.code }" role="option" :aria-selected="String(option.selected)" :lang="option.code" :data-locale="option.code">
+          <span class="locale-picker-text"><span class="locale-picker-native">{{ option.nativeName }}</span><span class="locale-picker-meta"><span class="locale-picker-option-code" translate="no" :lang="localeOptionCode(option.code).lang">{{ localeOptionCode(option.code).text }}</span></span></span>
+          <svg v-if="option.selected" viewBox="0 0 24 24" aria-hidden="true" focusable="false" class="locale-picker-check"><path v-for="d in LOCALE_PICKER_ICONS.check.stroke" :key="d" :d="d" fill="none" stroke="currentColor" stroke-width="1.4" stroke-linecap="round" stroke-linejoin="round" /></svg>
+        </li>
+      </ul>
+      <p class="locale-picker-empty" role="status" :hidden="view.visible.length > 0">{{ t('No matching languages') }}</p>
+    </div>
+  </div>
+</template>