webform_term_select.module

<?php

/**
 * Implements hook_form_taxonomy_form_term_alter().
 * Adds the form fields this module needs to flag a term as visible to our select
 * options callback function. We also verify the absence of "confirm_delete" on 
 * the form state to prevent our fields from displaying on the delete confirmation page. 
 */
function webform_term_select_form_taxonomy_form_term_alter(&$form, &$form_state, $form_id) {
    $term = $form_state['term'];

    if (!isset($form_state['confirm_delete'])) {
        $form['webform_term_select'] = array(
            '#type' => 'fieldset',
            '#title' => t('Webform Term Select'),
            '#collapsible' => TRUE,
            '#weight' => 0,
        );
        $form['webform_term_select']['show'] = array(
            '#type' =>'checkbox', 
            '#title' => t('Show this term on the Webform pre-built lists'),
            '#default_value' => isset($term->wts_visible) ? $term->wts_visible : '0',
        );
        array_unshift($form['#submit'], "webform_term_select_taxonomy_form_submit");
    }
}

/**
 * Additional submit handler for the taxonomy_form_term form.
 * Fills in the $term->wts_visible flag according to the value in our "show" form field 
 * whenever a term is created or updated.
 */
function webform_term_select_taxonomy_form_submit($form, &$form_state) {
    if ($form_state['triggering_element']['#value'] != t('Delete')) {
        $form_state['term']->wts_visible = $form_state['values']['show'];
    }
}

/**
 * Implements hook_form_taxonomy_overview_terms_alter().
 * Edits the term links in admin/structure/taxonomy/<vocabulary_machine_name> 
 * to display whether or not a term has been flagged into Webforms
 */
function webform_term_select_form_taxonomy_overview_terms_alter(&$form, &$form_state, $form_id) {
    $query = 'tid:';
    foreach ($form as $key => $value) { 
        if(substr($key, 0, strlen($query)) === $query) {
            if($value['#term']['wts_visible'] === '1') {
                $form[$key]['view'] = array(
                    '#markup' => l(
                        $form[$key]['view']['#title'], 
                        $form[$key]['view']['#href']) . ' <small>'. t('Shown in Webforms').'</small>',
                );
            }
        }
    }
}


/**
 * Implements hook_webform_select_options_info().
 * Fetches each vocabulary and adds a pre-built option list entry for each one.
 */
function webform_term_select_webform_select_options_info() {
  $items = array();

  $vocabularies = taxonomy_get_vocabularies();

  foreach ($vocabularies as $voc) {
    $items['vid_' . $voc->vid] = array(
      'title' => t('Flagged terms from') .' '. $voc->name,
      'options callback' => 'webform_term_select_vocabulary_terms',
      'options arguments' => array('vid' => $voc->vid),
    );
  }

  return $items;
}

/**
 * Pre-built option list callback to populate the select options. 
 * This particular callback filters "wts_visible" flagged fields 
 * into the select options array.
 */
function webform_term_select_vocabulary_terms($component, $flat, $arguments) {
  $terms = array();
  $tree = taxonomy_get_tree($arguments['vid']);

  foreach ($tree as $term) {
      if($term->wts_visible === "1") {
          $terms['tid_' . $term->tid] = $term->name;
      }
  }

  return $terms;
}