Form constructor for the book settings form.
book_admin_settings_validate()
function book_admin_settings() {
$types = node_type_get_names();
$form['book_allowed_types'] = array(
'#type' => 'checkboxes',
'#title' => t('Content types allowed in book outlines'),
'#default_value' => variable_get('book_allowed_types', array(
'book',
)),
'#options' => $types,
'#description' => t('Users with the %outline-perm permission can add all content types.', array(
'%outline-perm' => t('Administer book outlines'),
)),
'#required' => TRUE,
);
$form['book_child_type'] = array(
'#type' => 'radios',
'#title' => t('Content type for child pages'),
'#default_value' => variable_get('book_child_type', 'book'),
'#options' => $types,
'#required' => TRUE,
);
$form['array_filter'] = array(
'#type' => 'value',
'#value' => TRUE,
);
$form['#validate'][] = 'book_admin_settings_validate';
return system_settings_form($form);
}