drupal/core/modules/link/link.module

<?php

/**
 * @file
 * Defines simple link field types.
 */

/**
 * Implements hook_help().
 */
function link_help($path, $arg) {
  switch ($path) {
    case 'admin/help#link':
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Link module defines a simple link field type for the Field module. Links are external URLs, can have an optional title for each link, and they can be formatted when displayed. See the <a href="@field-help">Field module help page</a> for more information about fields.', array('@field-help' => url('admin/help/field'))) . '</p>';
      return $output;
  }
}

/**
 * Implements hook_field_info().
 */
function link_field_info() {
  $types['link'] = array(
    'label' => t('Link'),
    'description' => t('Stores a URL string, optional varchar title, and optional blob of attributes to assemble a link.'),
    'instance_settings' => array(
      'title' => DRUPAL_OPTIONAL,
    ),
    'default_widget' => 'link_default',
    'default_formatter' => 'link',
  );
  return $types;
}

/**
 * Implements hook_field_instance_settings_form().
 */
function link_field_instance_settings_form($field, $instance) {
  $form['title'] = array(
    '#type' => 'radios',
    '#title' => t('Allow link title'),
    '#default_value' => isset($instance['settings']['title']) ? $instance['settings']['title'] : DRUPAL_OPTIONAL,
    '#options' => array(
      DRUPAL_DISABLED => t('Disabled'),
      DRUPAL_OPTIONAL => t('Optional'),
      DRUPAL_REQUIRED => t('Required'),
    ),
  );
  return $form;
}

/**
 * Implements hook_field_load().
 */
function link_field_load($entity_type, $entities, $field, $instances, $langcode, &$items, $age) {
  foreach ($entities as $id => $entity) {
    foreach ($items[$id] as $delta => &$item) {
      // Unserialize the attributes into an array. The value stored in the
      // field data should either be NULL or a non-empty serialized array.
      if (empty($item['attributes'])) {
        $item['attributes'] = array();
      }
      else {
        $item['attributes'] = unserialize($item['attributes']);
      }
    }
  }
}

/**
 * Implements hook_field_is_empty().
 */
function link_field_is_empty($item, $field) {
  return !isset($item['url']) || $item['url'] === '';
}

/**
 * Implements hook_field_presave().
 */
function link_field_presave($entity_type, $entity, $field, $instance, $langcode, &$items) {
  foreach ($items as $delta => &$item) {
    // Trim any spaces around the URL and title.
    $item['url'] = trim($item['url']);
    $item['title'] = trim($item['title']);

    // Serialize the attributes array.
    $item['attributes'] = !empty($item['attributes']) ? serialize($item['attributes']) : NULL;
  }
}

/**
 * Implements hook_field_widget_info().
 */
function link_field_widget_info() {
  $widgets['link_default'] = array(
    'label' => 'Link',
    'field types' => array('link'),
    'settings' => array(
      'placeholder_title' => '',
      'placeholder_url' => '',
    ),
  );
  return $widgets;
}

/**
 * Implements hook_field_widget_settings_form().
 */
function link_field_widget_settings_form($field, $instance) {
  $widget = $instance['widget'];
  $settings = $widget['settings'];

  $form['placeholder_url'] = array(
    '#type' => 'textfield',
    '#title' => t('Placeholder for URL'),
    '#default_value' => $settings['placeholder_url'],
    '#description' => t('The placeholder is a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format.'),
  );
  $form['placeholder_title'] = array(
    '#type' => 'textfield',
    '#title' => t('Placeholder for link title'),
    '#default_value' => $settings['placeholder_title'],
    '#description' => t('The placeholder is a short hint (a word or short phrase) intended to aid the user with data entry. A hint could be a sample value or a brief description of the expected format.'),
    '#states' => array(
      'invisible' => array(
        ':input[name="instance[settings][title]"]' => array('value' => DRUPAL_DISABLED),
      ),
    ),
  );

  return $form;
}

/**
 * Implements hook_field_widget_form().
 */
function link_field_widget_form(&$form, &$form_state, $field, $instance, $langcode, $items, $delta, $element) {
  $settings = $instance['settings'];
  $widget_settings = $instance['widget']['settings'];

  $element['url'] = array(
    '#type' => 'url',
    '#title' => t('URL'),
    '#placeholder' => isset($widget_settings['placeholder_url']) ? $widget_settings['placeholder_url'] : '',
    '#default_value' => isset($items[$delta]['url']) ? $items[$delta]['url'] : NULL,
    '#maxlength' => 2048,
    '#required' => $element['#required'],
  );
  $element['title'] = array(
    '#type' => 'textfield',
    '#title' => t('Title'),
    '#placeholder' => isset($widget_settings['placeholder_title']) ? $widget_settings['placeholder_title'] : '',
    '#default_value' => isset($items[$delta]['title']) ? $items[$delta]['title'] : NULL,
    '#maxlength' => 255,
    '#access' => $settings['title'] != DRUPAL_DISABLED,
  );
  // Post-process the title field to make it conditionally required if URL is
  // non-empty. Omit the validation on the field edit form, since the field
  // settings cannot be saved otherwise.
  $is_field_edit_form = ($element['#entity'] === NULL);
  if (!$is_field_edit_form && $settings['title'] == DRUPAL_REQUIRED) {
    $element['#element_validate'][] = 'link_field_widget_validate_title';
  }

  // Exposing the attributes array in the widget is left for alternate and more
  // advanced field widgets.
  $element['attributes'] = array(
    '#type' => 'value',
    '#tree' => TRUE,
    '#value' => !empty($items[$delta]['attributes']) ? $items[$delta]['attributes'] : array(),
    '#attributes' => array('class' => array('link-field-widget-attributes')),
  );

  return $element;
}

/**
 * Form element validation handler for link_field_widget_form().
 *
 * Conditionally requires the link title if a URL value was filled in.
 */
function link_field_widget_validate_title(&$element, &$form_state, $form) {
  if ($element['url']['#value'] !== '' && $element['title']['#value'] === '') {
    $element['title']['#required'] = TRUE;
    form_error($element['title'], t('!name field is required.', array('!name' => $element['title']['#title'])));
  }
}

/**
 * Implements hook_field_prepare_view().
 */
function link_field_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items) {
  foreach ($entities as $id => $entity) {
    foreach ($items[$id] as $delta => &$item) {
      // Split out the link into the parts required for url(): path and options.
      $parsed = drupal_parse_url($item['url']);
      $item['path'] = $parsed['path'];
      $item['options'] = array(
        'query' => $parsed['query'],
        'fragment' => $parsed['fragment'],
        'attributes' => &$item['attributes'],
      );
    }
  }
}

/**
 * Implements hook_field_formatter_info().
 */
function link_field_formatter_info() {
  $formatters['link'] = array(
    'label' => t('Link'),
    'field types' => array('link'),
    'settings' => array(
      'trim_length' => 80,
      'rel' => NULL,
      'target' => NULL,
      'url_only' => FALSE,
      'url_plain' => FALSE,
    ),
  );
  // @todo Merge into 'link' formatter once there is a #type like 'item' that
  //   can render a compound label and content outside of a form context.
  $formatters['link_separate'] = array(
    'label' => t('Separate title and URL'),
    'field types' => array('link'),
    'settings' => array(
      'trim_length' => 80,
      'rel' => NULL,
      'target' => NULL,
    ),
  );
  return $formatters;
}

/**
 * Implements hook_field_formatter_settings_form().
 */
function link_field_formatter_settings_form($field, $instance, $view_mode, $form, &$form_state) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];

  $element['trim_length'] = array(
    '#type' => 'number',
    '#title' => t('Trim link text length'),
    '#field_suffix' => t('characters'),
    '#default_value' => $settings['trim_length'],
    '#min' => 1,
    '#description' => t('Leave blank to allow unlimited link text lengths.'),
  );
  $element['url_only'] = array(
    '#type' => 'checkbox',
    '#title' => t('URL only'),
    '#default_value' => $settings['url_only'],
    '#access' => $display['type'] == 'link',
  );
  $element['url_plain'] = array(
    '#type' => 'checkbox',
    '#title' => t('Show URL as plain text'),
    '#default_value' => $settings['url_plain'],
    '#access' => $display['type'] == 'link',
    '#states' => array(
      'visible' => array(
        ':input[name*="url_only"]' => array('checked' => TRUE),
      ),
    ),
  );
  $element['rel'] = array(
    '#type' => 'checkbox',
    '#title' => t('Add rel="nofollow" to links'),
    '#return_value' => 'nofollow',
    '#default_value' => $settings['nofollow'],
  );
  $element['target'] = array(
    '#type' => 'checkbox',
    '#title' => t('Open link in new window'),
    '#return_value' => '_blank',
    '#default_value' => $settings['target'],
  );

  return $element;
}

/**
 * Implements hook_field_formatter_settings_form().
 */
function link_field_formatter_settings_summary($field, $instance, $view_mode) {
  $display = $instance['display'][$view_mode];
  $settings = $display['settings'];

  $summary = array();

  if (!empty($settings['trim_length'])) {
    $summary[] = t('Link text trimmed to @limit characters', array('@limit' => $settings['trim_length']));
  }
  else {
    $summary[] = t('Link text not trimmed');
  }
  if (!empty($settings['url_only'])) {
    if (!empty($settings['url_plain'])) {
      $summary[] = t('Show URL only as plain-text');
    }
    else {
      $summary[] = t('Show URL only');
    }
  }
  if (!empty($settings['rel'])) {
    $summary[] = t('Add rel="@rel"', array('@rel' => $settings['rel']));
  }
  if (!empty($settings['target'])) {
    $summary[] = t('Open link in new window');
  }

  return implode('<br />', $summary);
}

/**
 * Implements hook_field_formatter_prepare_view().
 */
function link_field_formatter_prepare_view($entity_type, $entities, $field, $instances, $langcode, &$items, $displays) {
  foreach ($entities as $id => $entity) {
    $settings = $displays[$id]['settings'];

    foreach ($items[$id] as $delta => &$item) {
      // Add optional 'rel' attribute to link options.
      if (!empty($settings['rel'])) {
        $item['options']['attributes']['rel'] = $settings['rel'];
      }
      // Add optional 'target' attribute to link options.
      if (!empty($settings['target'])) {
        $item['options']['attributes']['target'] = $settings['target'];
      }
    }
  }
}

/**
 * Implements hook_field_formatter_view().
 */
function link_field_formatter_view($entity_type, $entity, $field, $instance, $langcode, $items, $display) {
  $element = array();
  $settings = $display['settings'];

  foreach ($items as $delta => $item) {
    // By default use the full URL as the link title.
    $link_title = $item['url'];

    // If the title field value is available, use it for the link title.
    if (empty($settings['url_only']) && !empty($item['title'])) {
      // Unsanitizied token replacement here because $options['html'] is FALSE
      // by default in theme_link().
      $link_title = token_replace($item['title'], array($entity_type => $entity), array('sanitize' => FALSE, 'clear' => TRUE));
    }

    // Trim the link title to the desired length.
    if (!empty($settings['trim_length'])) {
      $link_title = truncate_utf8($link_title, $settings['trim_length'], FALSE, TRUE);
    }

    if ($display['type'] == 'link') {
      if (!empty($settings['url_only']) && !empty($settings['url_plain'])) {
        $element[$delta] = array(
          '#type' => 'markup',
          '#markup' => check_plain($link_title),
        );
      }
      else {
        $element[$delta] = array(
          '#type' => 'link',
          '#title' => $link_title,
          '#href' => $item['path'],
          '#options' => $item['options'],
        );
      }
    }
    elseif ($display['type'] == 'link_separate') {
      // The link_separate formatter has two titles; the link title (as in the
      // field values) and the URL itself. If there is no title value,
      // $link_title defaults to the URL, so it needs to be unset.
      // The URL title may need to be trimmed as well.
      if (empty($item['title'])) {
        $link_title = NULL;
      }
      $url_title = $item['url'];
      if (!empty($settings['trim_length'])) {
        $url_title = truncate_utf8($item['url'], $settings['trim_length'], FALSE, TRUE);
      }
      $element[$delta] = array(
        '#theme' => 'link_formatter_link_separate',
        '#title' => $link_title,
        '#url_title' => $url_title,
        '#href' => $item['path'],
        '#options' => $item['options'],
      );
    }
  }
  return $element;
}

/**
 * Implements hook_theme().
 */
function link_theme() {
  return array(
    'link_formatter_link_separate' => array(
      'variables' => array('title' => NULL, 'url_title' => NULL, 'href' => NULL, 'options' => array()),
    ),
  );
}

/**
 * Formats a link as separate title and URL elements.
 */
function theme_link_formatter_link_separate($vars) {
  $output = '';
  $output .= '<div class="link-item">';
  if (!empty($vars['title'])) {
    $output .= '<div class="link-title">' . check_plain($vars['title']) . '</div>';
  }
  $output .= '<div class="link-url">' . l($vars['url_title'], $vars['href'], $vars['options']) . '</div>';
  $output .= '</div>';
  return $output;
}