Enable default language during drupal profile installation

myprofile.install

<?php
/**
 * @file
 * Install, update and uninstall functions for the myprofile installation profile.
 */

/**
 * Implements hook_install().
 *
 * Performs actions to set up the site for this profile.
 *
 * @see system_install()
 */
function myprofile_install() {
  // Allow visitors to register.
  variable_set('user_register', USER_REGISTER_VISITORS);

  // Give access to the published content to everyone.
  user_role_grant_permissions(DRUPAL_ANONYMOUS_RID, array('access content'));
  user_role_grant_permissions(DRUPAL_AUTHENTICATED_RID, array('access content'));
}

/**
 * Implements hook_install_tasks().
 */
function myprofile_install_tasks(&$install_state) {
  $tasks = array();

  $tasks['myprofile_install_theme'] = array(
    'display_name' => st('myprofile install theme'),
    'display' => TRUE,
    'type' => 'normal',
    'run' => INSTALL_TASK_RUN_IF_NOT_COMPLETED,
    'function' => '_myprofile_install_theme',
  );

  $tasks['myprofile_install_locale'] = array(
    'display_name' => st('myprofile install locale'),
    'display' => TRUE,
    'type' => 'batch',
    'run' => INSTALL_TASK_RUN_IF_NOT_COMPLETED,
    'function' => '_myprofile_install_locale',
  );

  return $tasks;
}

/**
 * Install task callback.
 */
function _myprofile_install_theme() {
  // Use the same name as the profile for the default theme.
  $theme_name = basename(__DIR__);

  // Set default theme.
  theme_enable(array($theme_name));
  theme_disable(array('bartik', 'garland', 'seven', 'stark'));
  variable_set('theme_default', $theme_name);
  variable_set('admin_theme', 'rubik');
  variable_set('node_admin_theme', FALSE);

  // Disable all blocks by default except system-main. Use context to enable them.
  db_update('block')
    ->fields(array('region' => -1))
    ->condition(
      db_or()
        ->condition('delta', 'main', '!=')
        ->condition('module', 'system', '!=')
    )
    ->execute();
}

/**
 * Install task callback.
 */
function _myprofile_install_locale(&$install_state) {
  include_once DRUPAL_ROOT . '/includes/locale.inc';
  $install_locale = $install_state['parameters']['locale'];
  $enabled_langs = locale_language_list();

  // Disable previously default English language.
  if (array_key_exists('en', $enabled_langs)) {
    db_update('languages')
      ->fields(array(
        'enabled' => '0',
      ))
      ->condition('language', 'en')
      ->execute();
  }
  // Enable language FR on if no language has been selected.
  if ($install_locale == 'en' && !array_key_exists('fr', $enabled_langs)) {
    locale_add_language('fr', 'French', 'Français', LANGUAGE_LTR, '', 'fr', TRUE, TRUE);
  }

  // Build batch with l10n_update module.
  // Second pass will only update translations of freshly installed modules.
  // We force each step to refresh its cache, as modules may have been
  // installed since last call.
  $history = l10n_update_get_history(TRUE);
  module_load_include('check.inc', 'l10n_update');
  // This variable forces l10n_update to rebuild its projects list.
  variable_set('l10n_update_rebuild_projects', 1);
  $available = l10n_update_available_releases(TRUE);
  $updates = l10n_update_build_updates($history, $available);

  module_load_include('batch.inc', 'l10n_update');
  $updates = _l10n_update_prepare_updates($updates, NULL, array());
  // Overwrite previous translations, as the downloaded ones are the most
  // recent, and valid.
  $batch = l10n_update_batch_multiple($updates, LOCALE_IMPORT_OVERWRITE);

  return $batch;
}