view.inc

<?php
/**
 * @file view.inc
 * Provides the view object type and associated methods.
 */

/**
 * @defgroup views_objects Objects that represent a View or part of a view.
 * @{
 * These objects are the core of Views do the bulk of the direction and
 * storing of data. All database activity is in these objects.
 */

/**
 * An object to contain all of the data to generate a view, plus the member
 * functions to build the view query, execute the query and render the output.
 */
class view extends views_db_object {
  var $db_table = 'views_view';
  var $base_table = 'node';

  // State variables
  var $built = FALSE;
  var $executed = FALSE;

  var $args = array();
  var $build_info = array();

  var $use_ajax = FALSE;

  // Where the results of a query will go.
  var $result = array();

  // pager variables
  var $pager = array(
    'use_pager' => FALSE,
    'items_per_page' => 10,
    'element' => 0,
    'offset' => 0,
    'current_page' => 0,
  );

  // Places to put attached renderings:
  var $attachment_before = '';
  var $attachment_after = '';

  // Exposed widget input
  var $exposed_data = array();
  var $exposed_input = array();

  // Used to store views that were previously running if we recurse.
  var $old_view = array();
  /**
   * Constructor
   */
  function view() {
    parent::init();
    // Make sure all of our sub objects are arrays.
    foreach ($this->db_objects() as $object) {
      $this->$object = array();
    }

    $this->query = new stdClass();
  }

  /**
   * Returns a list of the sub-object types used by this view. These types are
   * stored on the display, and are used in the build process.
   */
  function display_objects() {
    return array('argument', 'field', 'sort', 'filter', 'relationship');
  }

  /**
   * Returns the complete list of dependent objects in a view, for the purpose
   * of initialization and loading/saving to/from the database.
   *
   * Note: In PHP5 this should be static, but PHP4 doesn't support static
   * methods.
   */
  function db_objects() {
    return array('display');
  }

  /**
   * Set the arguments that come to this view. Usually from the URL
   * but possibly from elsewhere.
   */
  function set_arguments($args) {
    $this->args = $args;
  }

  /**
   * Set the page size for ranged or pager queries
   */
  function set_items_per_page($items_per_page) {
    $this->pager['items_per_page'] = $items_per_page;
    if (empty($items_per_page)) {
      $this->pager['use_pager'] = FALSE;
    }
  }

  /**
   * Change/Set the current page for the pager.
   */
  function set_current_page($page) {
    $this->pager['current_page'] = $page;
  }

  /**
   * Whether or not the pager should be used.
   */
  function set_use_pager($use_pager) {
    $this->pager['use_pager'] = $use_pager;
  }

  /**
   * The pager element id to use if use_apger is on
   */
  function set_pager_element($pager_element) {
    $this->pager['element'] = $pager_element;
  }

  /**
   * How many records to skip. This does not function if use_pager is
   * set.
   */
  function set_offset($offset) {
    $this->pager['offset'] = $offset;
  }

  /**
   * Whether or not AJAX should be used. If AJAX is used, paging,
   * tablesorting and exposed filters will be fetched via an AJAX call
   * rather than a page refresh.
   */
  function set_use_ajax($use_ajax) {
    $this->use_ajax = $use_ajax;
  }

  /**
   * Set the exposed filters input to an array. If unset they will be taken
   * from $_GET when the time comes.
   */
  function set_exposed_input($filters) {
    $this->exposed_input = $filters;
  }

  /**
   * Figure out what the exposed input for this view is.
   */
  function get_exposed_input() {
    // Fill our input either from $_GET or from something previously set on the
    // view.
    if (empty($this->exposed_input)) {
      $this->exposed_input = $_GET;
      // unset items that are definitely not our input:
      foreach (array('page', 'q') as $key) {
        if (isset($this->exposed_input[$key])) {
          unset($this->exposed_input[$key]);
        }
      }

      // If we have no input at all, check for remembered input via session.

      // If filters are not overridden, store the 'remember' settings on the
      // default display. If they are, store them on this display. This way,
      // multiple displays in the same view can share the same filters and
      // remember settings.
      $display_id = ($this->display_handler->is_defaulted('filters')) ? 'default' : $this->current_display;

      if (empty($this->exposed_input) && !empty($_SESSION['views'][$this->name][$display_id])) {
        $this->exposed_input = $_SESSION['views'][$this->name][$display_id];
      }
    }

    return $this->exposed_input;
  }

  /**
   * Set the display for this view and initialize the display handler.
   */
  function init_display($reset = FALSE) {
    // The default display is always the first one in the list.
    if (isset($this->current_display)) {
      return TRUE;
    }

    // Instantiate all displays
    foreach (array_keys($this->display) as $id) {
      // Correct for shallow cloning
      // Often we'll have a cloned view so we don't mess up each other's
      // displays, but the clone is pretty shallow and doesn't necessarily
      // clone the displays. We can tell this by looking to see if a handler
      // has already been set; if it has, but $this->current_display is not
      // set, then something is dreadfully wrong.
      if (!empty($this->display[$id]->handler)) {
        $this->display[$id] = drupal_clone($this->display[$id]);
        unset($this->display[$id]->handler);
      }
      $this->display[$id]->handler = views_get_plugin('display', $this->display[$id]->display_plugin);
      if (!empty($this->display[$id]->handler)) {
        // Initialize the new display handler with data.
        $this->display[$id]->handler->init($this, $this->display[$id]);
        // If this is NOT the default display handler, let it know which is
        // since it may well utilize some data from the default.
        // This assumes that the 'default' handler is always first. It always
        // is. Make sure of it.
        if ($id != 'default') {
          $this->display[$id]->handler->default_display = &$this->display['default']->handler;
        }
      }
    }

    $this->current_display = 'default';
    $this->display_handler = &$this->display['default']->handler;

    return TRUE;
  }

  /**
   * Get the first display that is accessible to the user.
   *
   * @param $displays
   *   Either a single display id or an array of display ids.
   */
  function choose_display($displays) {
    if (!is_array($displays)) {
      return $displays;
    }

    $this->init_display();

    foreach ($displays as $display_id) {
      if ($this->display[$display_id]->handler->access()) {
        return $display_id;
      }
    }

    return 'default';
  }

  /**
   * Set the display as current.
   *
   * @param $display_id
   *   The id of the display to mark as current.
   */
  function set_display($display_id = NULL) {
    // If we have not already initialized the display, do so. But be careful.
    if (empty($this->current_display)) {
      $this->init_display();

      // If handlers were not initialized, and no argument was sent, set up
      // to the default display.
      if (empty($display_id)) {
        $display_id = 'default';
      }
    }

    $display_id = $this->choose_display($display_id);

    // If no display id sent in and one wasn't chosen above, we're finished.
    if (empty($display_id)) {
      return FALSE;
    }

    // Ensure the requested display exists.
    if (empty($this->display[$display_id])) {
      $display_id = 'default';
      if (empty($this->display[$display_id])) {
        vpr(t('set_display() called with invalid display id @display.', array('@display' => $display_id)));
        return FALSE;
      }
    }

    // Set the current display.
    $this->current_display = $display_id;

    // Ensure requested display has a working handler.
    if (empty($this->display[$display_id]->handler)) {
      return FALSE;
    }

    // Set a shortcut
    $this->display_handler = &$this->display[$display_id]->handler;

    return TRUE;
  }

  /**
   * Find and initialize the style plugin.
   *
   * Note that arguments may have changed which style plugin we use, so
   * check the view object first, then ask the display handler.
   */
  function init_style() {
    if (isset($this->style_plugin)) {
      return is_object($this->style_plugin);
    }

    if (!isset($this->plugin_name)) {
      $this->plugin_name = $this->display_handler->get_option('style_plugin');
      $this->style_options = $this->display_handler->get_option('style_options');
    }

    $this->style_plugin = views_get_plugin('style', $this->plugin_name);

    if (empty($this->style_plugin)) {
      return FALSE;
    }

    // init the new style handler with data.
    $this->style_plugin->init($this, $this->display[$this->current_display], $this->style_options);
    return TRUE;
  }

  /**
   * Acquire and attach all of the handlers.
   */
  function init_handlers() {
    if (empty($this->inited)) {
      foreach (views_object_types() as $key => $info) {
        $this->_init_handler($key, $info);
      }
      $this->inited = TRUE;
    }
  }

  /**
   * Create a list of base tables eligible for this view. Used primarily
   * for the UI. Display must be already initialized.
   */
  function get_base_tables() {
    $base_tables = array(
      $this->base_table => TRUE,
      '#global' => TRUE,
    );

    foreach ($this->display_handler->get_handlers('relationship') as $handler) {
      $base_tables[$handler->definition['base']] = TRUE;
    }
    return $base_tables;
  }

  /**
   * Run the pre_query() on all active handlers.
   */
  function _pre_query() {
    foreach (views_object_types() as $key => $info) {
      $handlers = &$this->$key;
      $position = 0;
      foreach ($handlers as $id => $handler) {
        $handlers[$id]->position = $position;
        $handlers[$id]->pre_query();
        $position++;
      }
    }
  }

  /**
   * Attach all of the handlers for each type.
   *
   * @param $key
   *   One of 'argument', 'field', 'sort', 'filter', 'relationship'
   * @param $info
   *   The $info from views_object_types for this object.
   */
  function _init_handler($key, $info) {
    // Load the requested items from the display onto the object.
    $this->$key = $this->display_handler->get_handlers($key);

    // This reference deals with difficult PHP indirection.
    $handlers = &$this->$key;

    // Run through and test for accessibility.
    foreach ($handlers as $id => $handler) {
      if (!$handler->access()) {
        unset($handlers[$id]);
      }
    }
  }

  /**
   * Render the exposed filter form.
   *
   * This actually does more than that; because it's using FAPI, the form will
   * also assign data to the appropriate handlers for use in building the
   * query.
   */
  function render_exposed_form($block = FALSE) {
    // Deal with any exposed filters we may have, before building.
    $form_state = array(
      'view' => &$this,
      'display' => &$this->display_handler->display,
      'method' => 'get',
      'rerender' => TRUE,
      'no_redirect' => TRUE,
    );

    // Some types of displays (eg. attachments) may wish to use the exposed
    // filters of their parent displays instead of showing an additional
    // exposed filter form for the attachment as well as that for the parent.
    if (!$this->display_handler->displays_exposed() || (!$block && $this->display_handler->get_option('exposed_block'))) {
      unset($form_state['rerender']);
    }

    if (!empty($this->ajax)) {
      $form_state['ajax'] = TRUE;
    }

    $output = drupal_build_form('views_exposed_form', $form_state);
    if (!empty($form_state['js settings'])) {
      $this->js_settings = $form_state['js settings'];
    }

    // Don't render exposed filter form when there's form errors.
    // Applies when filters are in a block ("exposed_block" option).
    if (form_get_errors() && empty($form_state['rerender'])) {
      return NULL;
    }

    return $output;
  }

  /**
   * Build all the arguments.
   */
  function _build_arguments() {
    // Initially, we want to build sorts and fields. This can change, though,
    // if we get a summary view.
    if (empty($this->argument)) {
      return TRUE;
    }

    // build arguments.
    $position = -1;

    // Create a title for use in the breadcrumb trail.
    $title = $this->display_handler->get_option('title');

    $this->build_info['breadcrumb'] = array();
    $breadcrumb_args = array();
    $substitutions = array();

    $status = TRUE;

    // Iterate through each argument and process.
    foreach ($this->argument as $id => $arg) {
      $position++;
      $argument = &$this->argument[$id];

      if ($argument->broken()) {
        continue;
      }

      $argument->set_relationship();

      $arg = isset($this->args[$position]) ? $this->args[$position] : NULL;
      $argument->position = $position;

      if (isset($arg) || $argument->has_default_argument()) {
        if (!isset($arg)) {
          $arg = $argument->get_default_argument();
          // make sure default args get put back.
          if (isset($arg)) {
            $this->args[$position] = $arg;
          }
        }

        // Set the argument, which will also validate that the argument can be set.
        if (!$argument->set_argument($arg)) {
          $status = $argument->validate_fail($arg);
          break;
        }

        if ($argument->is_wildcard()) {
          $arg_title = $argument->wildcard_title();
        }
        else {
          $arg_title = $argument->get_title();
          $argument->query();
        }

        // Add this argument's substitution
        $substitutions['%' . ($position + 1)] = $arg_title;

        // Since we're really generating the breadcrumb for the item above us,
        // check the default action of this argument.
        if ($this->display_handler->uses_breadcrumb() && $argument->uses_breadcrumb()) {
          $path = $this->get_url($breadcrumb_args);
          if (strpos($path, '%') === FALSE) {
            $breadcrumb = !empty($argument->options['breadcrumb'])? $argument->options['breadcrumb'] : $title;
            $this->build_info['breadcrumb'][$path] = str_replace(array_keys($substitutions), $substitutions, $breadcrumb);
          }
        }

        // Allow the argument to muck with this breadcrumb.
        $argument->set_breadcrumb($this->build_info['breadcrumb']);

        // Test to see if we should use this argument's title
        if (!empty($argument->options['title'])) {
          $title = $argument->options['title'];
        }

        $breadcrumb_args[] = $arg;
      }
      else {
        // determine default condition and handle.
        $status = $argument->default_action();
        break;
      }

      // Be safe with references and loops:
      unset($argument);
    }

    // set the title in the build info.
    if (!empty($title)) {
      $this->build_info['title'] = str_replace(array_keys($substitutions), $substitutions, $title);
    }

    // Store the arguments for later use.
    $this->build_info['substitutions'] = $substitutions;

    return $status;
  }

  /**
   * Do some common building initialization.
   */
  function init_query() {
    // Create and initialize the query object.
    $views_data = views_fetch_data($this->base_table);
    $this->base_field = $views_data['table']['base']['field'];
    if (!empty($views_data['table']['base']['database'])) {
      $this->base_database = $views_data['table']['base']['database'];
    }
    views_include('query');
    $this->query = new views_query($this->base_table, $this->base_field);
  }

  /**
   * Build the query for the view.
   */
  function build($display_id = NULL) {
    if (!empty($this->built)) {
      return;
    }

    if (empty($this->current_display) || $display_id) {
      if (!$this->set_display($display_id)) {
        return FALSE;
      }
    }

    // Let modules modify the view just prior to building it.
    foreach (module_implements('views_pre_build') as $module) {
      $function = $module . '_views_pre_build';
      $function($this);
    }

    // Attempt to load from cache.
    // @todo Load a build_info from cache.

    $start = views_microtime();
    // If that fails, let's build!
    $this->build_info = array(
      'query' => '',
      'count_query' => '',
      'query_args' => array(),
    );

    $this->init_query();

    // Call a module hook and see if it wants to present us with a
    // pre-built query or instruct us not to build the query for
    // some reason.
    // @todo: Implement this. Use the same mechanism Panels uses.

    // Run through our handlers and ensure they have necessary information.
    $this->init_handlers();

    // Let the handlers interact with each other if they really want.
    $this->_pre_query();

    if ($this->display_handler->uses_exposed()) {
      $this->exposed_widgets = $this->render_exposed_form();
      if (form_set_error() || !empty($this->build_info['abort'])) {
        $this->built = TRUE;
        // Don't execute the query, but rendering will still be executed to display the empty text.
        $this->executed = TRUE;
        return empty($this->build_info['fail']);
      }
    }

    // Build all the relationships first thing.
    $this->_build('relationship');

    // Build all the filters.
    $this->_build('filter');

    $this->build_sort = TRUE;

    // Arguments can, in fact, cause this whole thing to abort.
    if (!$this->_build_arguments()) {
      $this->build_time = views_microtime() - $start;
      $this->attach_displays();
      return $this->built;
    }

    // Initialize the style; arguments may have changed which style we use,
    // so waiting as long as possible is important. But we need to know
    // about the style when we go to build fields.
    if (!$this->init_style()) {
      $this->build_info['fail'] = TRUE;
      return FALSE;
    }

    if ($this->style_plugin->uses_fields()) {
      $this->_build('field');
    }

    // Build our sort criteria if we were instructed to do so.
    if (!empty($this->build_sort)) {
      // Allow the style handler to deal with sorting.
      if ($this->style_plugin->build_sort()) {
        $this->_build('sort');
      }
      // allow the plugin to build second sorts as well.
      $this->style_plugin->build_sort_post();
    }

    // Allow display handler to affect the query:
    $this->display_handler->query();

    // Allow style handler to affect the query:
    $this->style_plugin->query();

    if (variable_get('views_sql_signature', FALSE)) {
      $this->query->add_field(NULL, "'" . $this->name . ':' . $this->current_display . "'", 'view_name');
    }

    // Let modules modify the query just prior to finalizing it.
    foreach (module_implements('views_query_alter') as $module) {
      $function = $module . '_views_query_alter';
      $function($this, $this->query);
    }

    $this->build_info['query'] = $this->query->query();
    $this->build_info['count_query'] = $this->query->query(TRUE);
    $this->build_info['query_args'] = $this->query->get_where_args();
    $this->built = TRUE;
    $this->build_time = views_microtime() - $start;

    // Attach displays
    $this->attach_displays();

    // Let modules modify the view just after building it.
    foreach (module_implements('views_post_build') as $module) {
      $function = $module . '_views_post_build';
      $function($this);
    }

    return TRUE;
  }

  /**
   * Internal method to build an individual set of handlers.
   */
  function _build($key) {
    $handlers = &$this->$key;
    foreach ($handlers as $id => $data) {
      if (!empty($handlers[$id]) && is_object($handlers[$id])) {
        // Give this handler access to the exposed filter input.
        if (!empty($this->exposed_data)) {
          $rc = $handlers[$id]->accept_exposed_input($this->exposed_data);
          $handlers[$id]->store_exposed_input($this->exposed_data, $rc);
          if (!$rc) {
            continue;
          }
        }
        $handlers[$id]->set_relationship();
        $handlers[$id]->query();
      }
    }
  }

  /**
   * Execute the view's query.
   */
  function execute($display_id = NULL) {
    if (empty($this->built)) {
      if (!$this->build($display_id)) {
        return FALSE;
      }
    }

    if (!empty($this->executed)) {
      return TRUE;
    }

    // Let modules modify the view just prior to executing it.
    foreach (module_implements('views_pre_execute') as $module) {
      $function = $module . '_views_pre_execute';
      $function($this);
    }

    $query = db_rewrite_sql($this->build_info['query'], $this->base_table, $this->base_field, array('view' => &$this));
    $count_query = db_rewrite_sql($this->build_info['count_query'], $this->base_table, $this->base_field, array('view' => &$this));

    $args = $this->build_info['query_args'];

    vpr($query);


    // Check for already-cached results.
    if (!empty($this->live_preview)) {
      $cache = FALSE;
    }
    else {
      $cache = $this->display_handler->get_cache_plugin();
    }
    if ($cache && $cache->cache_get('results')) {
      vpr('Used cached results');
    }
    else {
      $items = array();
      if ($query) {
        $replacements = module_invoke_all('views_query_substitutions', $this);
        $query = str_replace(array_keys($replacements), $replacements, $query);
        $count_query = 'SELECT COUNT(*) FROM (' . str_replace(array_keys($replacements), $replacements, $count_query) . ') count_alias';

        if (is_array($args)) {
          foreach ($args as $id => $arg) {
            $args[$id] = str_replace(array_keys($replacements), $replacements, $arg);
          }
        }

        // Allow for a view to query an external database.
        if (isset($this->base_database)) {
          db_set_active($this->base_database);
          $external = TRUE;
        }

        $start = views_microtime();
        if (!empty($this->pager['items_per_page'])) {
          // We no longer use pager_query() here because pager_query() does not
          // support an offset. This is fine as we don't actually need pager
          // query; we've already been doing most of what it does, and we
          // just need to do a little more playing with globals.
          if (!empty($this->pager['use_pager']) || !empty($this->get_total_rows)) {
            $this->total_rows = db_result(db_query($count_query, $args)) - $this->pager['offset'];
          }

          if (!empty($this->pager['use_pager'])) {
            // dump information about what we already know into the globals
            global $pager_page_array, $pager_total, $pager_total_items;
            // total rows in query
            $pager_total_items[$this->pager['element']] = $this->total_rows;
            // total pages
            $pager_total[$this->pager['element']] = ceil($pager_total_items[$this->pager['element']] / $this->pager['items_per_page']);

            // What page was requested:
            $pager_page_array = isset($_GET['page']) ? explode(',', $_GET['page']) : array();

            // If the requested page was within range. $this->pager['current_page']
            // defaults to 0 so we don't need to set it in an out-of-range condition.
            if (!empty($pager_page_array[$this->pager['element']])) {
              $page = intval($pager_page_array[$this->pager['element']]);
              if ($page > 0 && $page < $pager_total[$this->pager['element']]) {
                $this->pager['current_page'] = $page;
              }
            }
            $pager_page_array[$this->pager['element']] = $this->pager['current_page'];
          }

          $offset = $this->pager['current_page'] * $this->pager['items_per_page'] + $this->pager['offset'];
          $result = db_query_range($query, $args, $offset, $this->pager['items_per_page']);

        }
        else {
          $result = db_query($query, $args);
        }

        $this->result = array();
        while ($item = db_fetch_object($result)) {
          $this->result[] = $item;
        }

        // If we already know how many items we have even if we did not run the
        // count query, go ahead and set that value:
        if (empty($this->pager['items_per_page'])) {
          $this->total_rows = count($this->result);
        }

        if (!empty($external)) {
          db_set_active();
        }
        $this->execute_time = views_microtime() - $start;
      }
      if ($cache) {
        $cache->cache_set('results');
      }
    }

    // Let modules modify the view just after executing it.
    foreach (module_implements('views_post_execute') as $module) {
      $function = $module . '_views_post_execute';
      $function($this);
    }

    $this->executed = TRUE;
  }

  /**
   * Render this view for display.
   */
  function render($display_id = NULL) {
    $this->execute($display_id);

    // Check to see if the build failed.
    if (!empty($this->build_info['fail'])) {
      return;
    }

    init_theme();

    $start = views_microtime();
    if (!empty($this->live_preview) && variable_get('views_show_additional_queries', FALSE)) {
      $this->start_query_capture();
    }

    // Check for already-cached output.
    if (!empty($this->live_preview)) {
      $cache = FALSE;
    }
    else {
      $cache = $this->display_handler->get_cache_plugin();
    }
    if ($cache && $cache->cache_get('output')) {
      vpr('Used cached output');
    }
    else {
      if ($cache) {
        $cache->cache_start();
      }

      // Initialize the style plugin.
      $this->init_style();

      $this->style_plugin->pre_render($this->result);

      // Let modules modify the view just prior to rendering it.
      foreach (module_implements('views_pre_render') as $module) {
        $function = $module . '_views_pre_render';
        $function($this);
      }

      // Let the theme play too, because pre render is a very themey thing.
      $function = $GLOBALS['theme'] . '_views_pre_render';
      if (function_exists($function)) {
        $function($this, $this->display_handler->output, $cache);
      }

      // Give field handlers the opportunity to perform additional queries
      // using the entire resultset prior to rendering.
      if ($this->style_plugin->uses_fields()) {
        foreach ($this->field as $id => $handler) {
          if (!empty($this->field[$id])) {
            $this->field[$id]->pre_render($this->result);
          }
        }
      }
      $this->display_handler->output = $this->display_handler->render();
      if ($cache) {
        $cache->cache_set('output');
      }
    }

    if ($cache) {
      $cache->post_render($this->display_handler->output);
    }

    // Let modules modify the view output after it is rendered.
    foreach (module_implements('views_post_render') as $module) {
      $function = $module . '_views_post_render';
      $function($this, $this->display_handler->output, $cache);
    }

    // Let the theme play too, because post render is a very themey thing.
    $function = $GLOBALS['theme'] . '_views_post_render';
    if (function_exists($function)) {
      $function($this, $this->display_handler->output, $cache);
    }

    if (!empty($this->live_preview) && variable_get('views_show_additional_queries', FALSE)) {
      $this->end_query_capture();
    }
    $this->render_time = views_microtime() - $start;

    return $this->display_handler->output;
  }

  /**
   * Render a specific field via the field ID and the row #.
   */
  function render_field($field, $row) {
    if (isset($this->field[$field]) && isset($this->result[$row])) {
      return $this->field[$field]->advanced_render($this->result[$row]);
    }
  }

  /**
   * Execute the given display, with the given arguments.
   * To be called externally by whatever mechanism invokes the view,
   * such as a page callback, hook_block, etc.
   *
   * This function should NOT be used by anything external as this
   * returns data in the format specified by the display. It can also
   * have other side effects that are only intended for the 'proper'
   * use of the display, such as setting page titles and breadcrumbs.
   *
   * If you simply want to view the display, use view::preview() instead.
   */
  function execute_display($display_id = NULL, $args = array()) {
    if (empty($this->current_display) || $this->current_display != $this->choose_display($display_id)) {
      if (!$this->set_display($display_id)) {
        return FALSE;
      }
    }

    $this->pre_execute($args);

    // Execute the view
    $output = $this->display_handler->execute();

    $this->post_execute();
    return $output;
  }

  /**
   * Preview the given display, with the given arguments.
   *
   * To be called externally, probably by an AJAX handler of some flavor.
   * Can also be called when views are embedded, as this guarantees
   * normalized output.
   */
  function preview($display_id = NULL, $args = array()) {
    if (empty($this->current_display) || ((!empty($display_id)) && $this->current_display != $display_id)) {
      if (!$this->set_display($display_id)) {
        return FALSE;
      }
    }

    $this->preview = TRUE;
    $this->pre_execute($args);
    // Preview the view.
    $output = $this->display_handler->preview();

    $this->post_execute();
    return $output;
  }

  /**
   * Run attachments and let the display do what it needs to do prior
   * to running.
   */
  function pre_execute($args = array()) {
    $this->old_view[] = views_get_current_view();
    views_set_current_view($this);
    $display_id = $this->current_display;

    // Let modules modify the view just prior to executing it.
    foreach (module_implements('views_pre_view') as $module) {
      $function = $module . '_views_pre_view';
      $function($this, $display_id, $args);
    }

    // Prepare the view with the information we have, but only if we were
    // passed arguments, as they may have been set previously.
    if ($args) {
      $this->set_arguments($args);
    }

//    $this->attach_displays();

    // Allow the display handler to set up for execution
    $this->display_handler->pre_execute();
  }

  /**
   * Unset the current view, mostly.
   */
  function post_execute() {
    // unset current view so we can be properly destructed later on.
    // Return the previous value in case we're an attachment.

    if ($this->old_view) {
      $old_view = array_pop($this->old_view);