signal-desktop/ts/services/keyboardLayout.ts

// Copyright 2021 Signal Messenger, LLC
// SPDX-License-Identifier: AGPL-3.0-only

import { strictAssert } from '../util/assert';

type LayoutMapType = { get(code: string): string | undefined };

let layoutMap: LayoutMapType | undefined;

export async function initialize(): Promise<void> {
  strictAssert(layoutMap === undefined, 'keyboardLayout already initialized');

  const experimentalNavigator = window.navigator as unknown as {
    keyboard: { getLayoutMap(): Promise<LayoutMapType> };
  };

  strictAssert(
    typeof experimentalNavigator.keyboard?.getLayoutMap === 'function',
    'No support for getLayoutMap'
  );

  layoutMap = await experimentalNavigator.keyboard.getLayoutMap();
}

export function lookup({
  code,
  key,
}: Pick<KeyboardEvent, 'code' | 'key'>): string | undefined {
  strictAssert(layoutMap !== undefined, 'keyboardLayout not initialized');
  return layoutMap.get(code) ?? key;
}