drupal/modules/field/field.module

<?php
// $Id$
/**
 * @file
 * Allows administrators to associate custom fields to field types.
 */

/**
 * @defgroup field Field API
 * @{
 * Attach custom data fields to Drupal objects.
 *
 * The Field API allows custom data fields to be attached to Drupal
 * objects and takes care of storing, loading, editing, and rendering
 * field data.  Any object type (node, user, etc.) can use the Field
 * API to make itself "fieldable" and thus allow fields to be attached
 * to it.  Other modules can provide a user interface for managing custom
 * fields via a web browser as well as a wide and flexible variety of
 * data type, form element, and display format capabilities.
 *
 * - @link field_structs Data structures: Field, Instance, Bundle @endlink.
 *
 * - @link field_types Field Types API @endlink.  Defines field types,
 *   widget types, and display formatters.  Field modules use this API
 *   to provide field types like Text and Node Reference along with the
 *   associated form elements and display formatters.
 *
 * - @link field_crud Field CRUD API @endlink.  Create, updates, and
 *   deletes fields, bundles (a.k.a. "content types"), and instances.
 *   Modules use this API, often in hook_install(), to create
 *   custom data structures.  The Content Construction Kit
 *   user-interface module uses this API for its major functionality.
 *
 * - @link field_attach Field Attach API @endlink.  Connects object
 *   types to the Field API.  Field Attach API functions load, store,
 *   generate Form API structures, display, and perform a vareity of
 *   other functions for field data connected to individual objects.
 *   Fieldable object types like node and user use this API to make
 *   themselves fieldable.
 *
 * - @link field_info Field Info API @endlink.  Exposes information
 *   about all fields, instances, widgets, and related information
 *   defined by or with the Field API.
 *
 * - @link field_storage Field Storage API @endlink.  Provides a
 *   pluggable back-end storage system for actual field data.  The
 *   default implementation, field_sql_storage.module, stores field data
 *   in the local SQL database.
 */

/**
 * Value for $field['cardinality'] property to indicate it can hold an
 * unlimited number of values.
 */
define('FIELD_CARDINALITY_UNLIMITED', -1);

/**
 * TODO
 */
define('FIELD_BEHAVIOR_NONE', 0x0001);
/**
 * TODO
 */
define('FIELD_BEHAVIOR_DEFAULT', 0x0002);
/**
 * TODO
 */
define('FIELD_BEHAVIOR_CUSTOM', 0x0004);

/**
 * Age argument for loading the most recent version of an object's
 * field data with field_attach_load().
 */
define('FIELD_LOAD_CURRENT', 'FIELD_LOAD_CURRENT');
/**
 * Age argument for loading the version of an object's field data
 * specified in the object with field_attach_load().
 */
define('FIELD_LOAD_REVISION', 'FIELD_LOAD_REVISION');

/**
 * Implementation of hook_flush_caches.
 */
function field_flush_caches() {
  return array('cache_field');
}

/**
 * Implementation of hook_help().
 */
function field_help($path, $arg) {
  switch ($path) {
    case 'admin/help#field':
      $output = '<p>' . t('The Field API allows custom data fields to be attached to Drupal objects and takes care of storing, loading, editing, and rendering field data.  Any object type (node, user, etc.) can use the Field API to make itself "fieldable" and thus allow fields to be attached to it.') . '</p>';
      $output .= '<p>' .t('The Field API provides no user interface on its own.  Use the Content Construction Kit (CCK) contrib module to manage custom fields via a web browser.') . '</p>';
      return $output;
  }
}

/**
 * Implementation of hook_init().
 *
 * TODO D7: Determine which functions need to always be "loaded", and
 * put autoloaders for them into field.autoload.inc.  Also figure out
 * how to make this work during installation.
 */
function field_init() {
  module_load_include('inc', 'field', 'field.crud');
  module_load_include('inc', 'field', 'field.autoload');
}

/**
 * Implementation of hook_menu().
 */
function field_menu() {
  $items = array();

  // Callback for AHAH add more buttons.
  $items['field/js_add_more'] = array(
    'page callback' => 'field_add_more_js',
    'access arguments' => array('access content'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

/**
 * Implementation of hook_theme().
 */
function field_theme() {
  $path = drupal_get_path('module', 'field') . '/theme';

  return array(
    'field' => array(
      'template' => 'field',
      'arguments' => array('element' => NULL),
      'path' => $path,
    ),
    // TODO D7 : do we need exclude in core? See [#367215].
    // This is just adding '#post_render' => array('field_wrapper_post_render')
    // at the right places in the render array generated by field_default_view().
    // Can be done in hook_field_attach_post_view if we want.
    'field_exclude' => array(
      'arguments' => array('content' => NULL, 'object' => array(), 'context' => NULL),
    ),
    'field_multiple_value_form' => array(
      'arguments' => array('element' => NULL),
    ),
  );
}

/**
 * Implementation of hook_modules_installed().
 */
function field_modules_installed($modules) {
  field_cache_clear();
}

/**
 * Implementation of hook_modules_uninstalled().
 */
function field_modules_uninstalled($modules) {
  module_load_include('inc', 'field', 'field.crud');
  foreach ($modules as $module) {
    // TODO D7: field_module_delete is not yet implemented
    // field_module_delete($module);
  }
}

/**
 * Implementation of hook_modules_enabled().
 */
function field_modules_enabled($modules) {
  foreach ($modules as $module) {
    field_associate_fields($module);
  }
  field_cache_clear();
}

/**
 * Implementation of hook_modules_disabled().
 */
function field_modules_disabled($modules) {
  foreach ($modules as $module) {
    db_update('field_config')
      ->fields(array('active' => 0))
      ->condition('module', $module)
      ->execute();
    db_update('field_config_instance')
      ->fields(array('widget_active' => 0))
      ->condition('widget_module', $module)
      ->execute();
    field_cache_clear(TRUE);
  }
}

/**
 * Allows a module to update the database for fields and columns it controls.
 *
 * @param string $module
 *   The name of the module to update on.
 */
function field_associate_fields($module) {
  $module_fields = module_invoke($module, 'field_info');
  if ($module_fields) {
    foreach ($module_fields as $name => $field_info) {
      watchdog('field', 'Updating field type %type with module %module.', array('%type' => $name, '%module' => $module));
      db_update('field_config')
        ->fields(array('module' => $module, 'active' => 1))
        ->condition('type', $name)
        ->execute();
    }
  }
  $module_widgets = module_invoke($module, 'widget_info');
  if ($module_widgets) {
    foreach ($module_widgets as $name => $widget_info) {
      watchdog('field', 'Updating widget type %type with module %module.', array('%type' => $name, '%module' => $module));
      db_update('field_config_instance')
        ->fields(array('widget_module' => $module, 'widget_active' => 1))
        ->condition('widget_type', $name)
        ->execute();
    }
  }
}

/**
 * Helper function to filter out empty values.
 *
 * On order to keep marker rows in the database, the function ensures
 * that the right number of 'all columns NULL' values is kept.
 *
 * @param array $field
 * @param array $items
 * @return array
 *   returns filtered and adjusted item array
 *
 * TODO D7: poorly named...
 */
function field_set_empty($field, $items) {
  // Filter out empty values.
  $filtered = array();
  $function = $field['module'] . '_field_is_empty';
  foreach ((array) $items as $delta => $item) {
    if (!$function($item, $field)) {
      $filtered[] = $item;
    }
  }
  return $filtered;
}

/**
 * Helper function to sort items in a field according to
 * user drag-n-drop reordering.
 */
function _field_sort_items($field, $items) {
  if (($field['cardinality'] > 1 || $field['cardinality'] == FIELD_CARDINALITY_UNLIMITED) && isset($items[0]['_weight'])) {
    usort($items, '_field_sort_items_helper');
    foreach ($items as $delta => $item) {
      if (is_array($items[$delta])) {
        unset($items[$delta]['_weight']);
      }
    }
  }
  return $items;
}

/**
 * Sort function for items order.
 * (copied form element_sort(), which acts on #weight keys)
 */
function _field_sort_items_helper($a, $b) {
  $a_weight = (is_array($a) && isset($a['_weight'])) ? $a['_weight'] : 0;
  $b_weight = (is_array($b) && isset($b['_weight'])) ? $b['_weight'] : 0;
  if ($a_weight == $b_weight) {
    return 0;
  }
  return ($a_weight < $b_weight) ? -1 : 1;
}

/**
 * Same as above, using ['_weight']['#value']
 */
function _field_sort_items_value_helper($a, $b) {
  $a_weight = (is_array($a) && isset($a['_weight']['#value'])) ? $a['_weight']['#value'] : 0;
  $b_weight = (is_array($b) && isset($b['_weight']['#value'])) ? $b['_weight']['#value'] : 0;
  if ($a_weight == $b_weight) {
    return 0;
  }
  return ($a_weight < $b_weight) ? -1 : 1;
}

/**
 * Registry of available build modes.
 * TODO : move into hook_fieldable_info() ?
 */
function field_build_modes($obj_type) {
  static $info;

  if (!isset($info[$obj_type])) {
    // module_invoke_all messes numeric keys.
    // TODO : revisit when we move away from numeric build modes.
    $info[$obj_type] = array();
    foreach (module_implements('field_build_modes') as $module) {
      $info[$obj_type] += module_invoke($module, 'field_build_modes', $obj_type);
    }
  }
  return $info[$obj_type];
}

/**
 * Clear the cached information; called in several places when field
 * information is changed.
 */
function field_cache_clear($rebuild_schema = FALSE) {
  cache_clear_all('*', 'cache_field', TRUE);

  module_load_include('inc', 'field', 'field.info');
  _field_info_collate_types(TRUE);
  _field_info_collate_fields(TRUE);

  // Refresh the schema to pick up new information.
  // TODO : if db storage gets abstracted out, we'll need to revisit how and when
  // we refresh the schema...
  if ($rebuild_schema) {
    $schema = drupal_get_schema(NULL, TRUE);
  }
}

/**
 * Like filter_xss_admin(), but with a shorter list of allowed tags.
 *
 * Used for items entered by administrators, like field descriptions,
 * allowed values, where some (mainly inline) mark-up may be desired
 * (so check_plain() is not acceptable).
 */
function field_filter_xss($string) {
  return filter_xss($string, _field_filter_xss_allowed_tags());
}

/**
 * List of tags allowed by field_filter_xss().
 */
function _field_filter_xss_allowed_tags() {
  return array('a', 'b', 'big',  'code', 'del', 'em', 'i', 'ins',  'pre', 'q', 'small', 'span', 'strong', 'sub', 'sup', 'tt', 'ol', 'ul', 'li', 'p', 'br', 'img');
}

/**
 * Human-readable list of allowed tags, for display in help texts.
 */
function _field_filter_xss_display_allowed_tags() {
  return '<' . implode('> <', _field_filter_xss_allowed_tags()) . '>';
}

/**
 * Format a field item for display.
 *
 * TODO D7 : do we still need field_format ?
 * - backwards compatibility of templates - check what fallbacks we can propose...
 * - used by Views integration in CCK D6
 * At least needs a little rehaul/update...
 *
 * Used to display a field's values outside the context of the $node, as
 * when fields are displayed in Views, or to display a field in a template
 * using a different formatter than the one set up on the Display Fields tab
 * for the node's context.
 *
 * @param $field
 *   Either a field array or the name of the field.
 * @param $item
 *   The field item(s) to be formatted (such as $node->field_foo[0],
 *   or $node->field_foo if the formatter handles multiple values itself)
 * @param $formatter_name
 *   The name of the formatter to use.
 * @param $node
 *   Optionally, the containing node object for context purposes and
 *   field-instance options.
 *
 * @return
 *   A string containing the contents of the field item(s) sanitized for display.
 *   It will have been passed through the necessary check_plain() or check_markup()
 *   functions as necessary.
 */
function field_format($obj_type, $object, $field, $item, $formatter_name = NULL, $formatter_settings = array()) {
  if (!is_array($field)) {
    $field = field_info_field($field);
  }

  if (field_access('view', $field)) {
    // Basically, we need $field, $instance, $obj_type, $object to be able to display a value...
    list(, , $bundle) = field_attach_extract_ids($obj_type, $object);
    $instance = field_info_instance($field['field_name'], $bundle);

    $display = array(
      'type' => $formatter_name,
      'settings' => $formatter_settings,
    );
    $display = _field_get_formatter($display, $field);
    if ($display['type'] && $display['type'] !== 'hidden') {
      $theme = $formatter['module'] . '_formatter_' . $display['type'];

      $element = array(
        '#theme' => $theme,
        '#field_name' => $field['field_name'],
        '#bundle' => $bundle,
        '#formatter' => $display['type'],
        '#settings' => $display['settings'],
        '#object' => $object,
        '#delta' => isset($item['#delta']) ? $item['#delta'] : NULL,
      );

      if (field_behaviors_formatter('multiple values', $display) == FIELD_BEHAVIOR_DEFAULT) {
        // Single value formatter.

        // hook_field('sanitize') expects an array of items, so we build one.
        $items = array($item);
        $function = $field['module'] . '_field_sanitize';
        if (function_exists($function)) {
          $function($obj_type, $object, $field, $instance, $items);
        }

        $element['#item'] = $items[0];
      }
      else {
        // Multiple values formatter.
        $items = $item;
        $function = $field['module'] . '_field_sanitize';
        if (function_exists($function)) {
          $function($obj_type, $object, $field, $instance, $items);
        }

        foreach ($items as $delta => $item) {
          $element[$delta] = array(
            '#item' => $item,
            '#weight' => $delta,
          );
        }
      }

      return theme($theme, $element);
    }
  }
}

/**
 * Render a single field, fully themed with label and multiple values.
 *
 * To be used by third-party code (Views, Panels...) that needs to output
 * an isolated field. Do *not* use inside node templates, use the
 * $FIELD_NAME_rendered variables instead.
 *
 * By default, the field is displayed using the settings defined for the
 * 'full' or 'teaser' contexts (depending on the value of the $teaser param).
 * Set $node->build_mode to a different value to use a different context.
 *
 * Different settings can be specified by adjusting $field['display'].
 *
 * @param $field
 *   The field definition.
 * @param $object
 *   The object containing the field to display. Must at least contain the id key,
 *   revision key (if applicable), bundle key, and the field data.
 * @param $teaser
 *   Similar to hook_nodeapi('view')
 * @return
 *   The themed output for the field.
 */
function field_view_field($obj_type, $object, $field, $instance, $teaser = FALSE) {
  $output = '';
  if (isset($object->$field['field_name'])) {
    $items = $object->$field['field_name'];

    // Use 'full'/'teaser' if not specified otherwise.
    $object->build_mode = isset($object->build_mode) ? $object->build_mode : NODE_BUILD_NORMAL;

    // One-field equivalent to _field_invoke('sanitize').
    $function = $field['module'] . '_field_sanitize';
    if (drupal_function_exists($function)) {
      $function($obj_type, $object, $field, $instance, $items);
      $object->$field['field_name'] = $items;
    }

    $view = field_default_view($obj_type, $object, $field, $instance, $items, $teaser);
    // TODO : what about hook_field_attach_view ?

    // field_default_view() adds a wrapper to handle variables and 'excluded'
    // fields for node templates. We bypass it and render the actual field.
    $output = drupal_render($view[$field['field_name']]['field']);
  }
  return $output;
}

/**
 * Determine whether the user has access to a given field.
 *
 * @param $op
 *   The operation to be performed. Possible values:
 *   - "edit"
 *   - "view"
 * @param $field
 *   The field on which the operation is to be performed.
 * @param $account
 *   (optional) The account to check, if not given use currently logged in user.
 * @return
 *   TRUE if the operation is allowed;
 *   FALSE if the operation is denied.
 */
function field_access($op, $field, $account = NULL) {
  global $user;

  if (is_null($account)) {
    $account = $user;
  }

  $field_access = module_invoke_all('field_access', $op, $field, $account);
  foreach ($field_access as $value) {
    if ($value === FALSE) {
      return FALSE;
    }
  }
  return TRUE;
}

/**
 * Theme preprocess function for field.tpl.php.
 *
 * The $variables array contains the following arguments:
 * - $object
 * - $field
 * - $items
 * - $teaser
 * - $page
 *
 * @see field.tpl.php
 */
function template_preprocess_field(&$variables) {
  $element = $variables['element'];
  list(, , $bundle) = field_attach_extract_ids($element['#object_type'], $element['#object']);
  $instance = field_info_instance($element['#field_name'], $bundle);
  $field = field_info_field($element['#field_name']);

  $variables['object'] = $element['#object'];
  $variables['field'] = $field;
  $variables['instance'] = $instance;
  $variables['items'] = array();

  if ($element['#single']) {
    // Single value formatter.
    foreach (element_children($element['items']) as $delta) {
      $variables['items'][$delta] = $element['items'][$delta]['#item'];
      $variables['items'][$delta]['view'] = drupal_render_children($element['items'], array($delta));
    }
  }
  else {
    // Multiple values formatter.
    // We display the 'all items' output as $items[0], as if it was the
    // output of a single valued field.
    // Raw values are still exposed for all items.
    foreach (element_children($element['items']) as $delta) {
      $variables['items'][$delta] = $element['items'][$delta]['#item'];
    }
    $variables['items'][0]['view'] = drupal_render_children($element, array('items'));
  }

  $variables['teaser'] = $element['#teaser'];
  $variables['page'] = (bool)menu_get_object();

  $field_empty = TRUE;

  foreach ($variables['items'] as $delta => $item) {
    if (!isset($item['view']) || (empty($item['view']) && (string)$item['view'] !== '0')) {
      $variables['items'][$delta]['empty'] = TRUE;
    }
    else {
      $field_empty = FALSE;
      $variables['items'][$delta]['empty'] = FALSE;
    }
  }

  $additions = array(
    'field_type' => $field['type'],
    'field_name' => $field['field_name'],
    'field_type_css' => strtr($field['type'], '_', '-'),
    'field_name_css' => strtr($field['field_name'], '_', '-'),
    'label' => check_plain(t($instance['label'])),
    'label_display' => $element['#label_display'],
    'field_empty' => $field_empty,
    'template_files' => array(
      'field',
      'field-' . $element['#field_name'],
      'field-' . $bundle,
      'field-' . $element['#field_name'] . '-' . $bundle,
    ),
  );
  $variables = array_merge($variables, $additions);
}

/**
 * @} End of "defgroup field"
 */