LocaleMultilingualFieldsFunctionalTest::testMultilingualNodeForm in core/modules/locale/tests/locale.test

Test if field languages are correctly set through the node form.

LocaleUILanguageNegotiationTest::testUILanguageNegotiation in core/modules/locale/tests/locale.test

Tests for language switching by URL path.

locale_install in core/modules/locale/locale.install

Implements hook_install().

locale_language_from_url in core/includes/locale.inc

Identify language via URL prefix or domain.

locale_language_negotiation_info in core/modules/locale/locale.module

Implements hook_language_negotiation_info().

locale_language_types_info in core/modules/locale/locale.module

Implements hook_language_types_info().