<?php

/**
 * @file panels.module
 *
 * Core functionality for the Panels engine.
 */

use Drupal\Core\Form\FormStateInterface;
use Drupal\page_manager\PageVariantInterface;
use Drupal\panels\Plugin\DisplayVariant\PanelsDisplayVariant;

define('PANELS_REQUIRED_CTOOLS_API', '2.0-alpha');

define('PANELS_TITLE_FIXED', 0); // Hide title use to be true/false. So false remains old behavior.
define('PANELS_TITLE_NONE', 1); // And true meant no title.
define('PANELS_TITLE_PANE', 2); // And this is the new behavior, where the title field will pick from a pane.

/**
 * Returns the API version of Panels. This didn't exist in 1.
 *
 * @todo -- this should work more like the CTools API version.
 *
 * @return An array with the major and minor versions
 */
function panels_api_version() {
  return array(3, 1);
}

// --------------------------------------------------------------------------
// Page Manager integration

/**
 * Implements hook_ENTITY_TYPE_create().
 *
 * We need to set the storage information on Panels displays being storaged
 * in Page Manager as early as possible, to signal to Panels that features
 * requiring Panels storage (like the IPE) are supported.
 *
 * @see panels_page_variant_presave()
 */
function panels_page_variant_create(PageVariantInterface $page_variant) {
  if ($page_variant->getVariantPluginId() == 'panels_variant') {
    /** @var \Drupal\panels\Plugin\DisplayVariant\PanelsDisplayVariant $panels_display */
    $panels_display = $page_variant->getVariantPlugin();
    // At this point, it very likely that $page_variant->id() is NULL. But
    // setting the storage type to 'page_manager' is enough to trigger Panels
    // to offer the IPE as an option.
    $panels_display->setStorage('page_manager', $page_variant->id());
  }
}

/**
 * Implements hook_ENTITY_TYPE_presave().
 *
 * Now that we have the id for the page variant, we need to set the storage
 * information again.
 *
 * @see panels_page_variant_create()
 */
function panels_page_variant_presave(PageVariantInterface $page_variant) {
  if ($page_variant->getVariantPluginId() == 'panels_variant') {
    /** @var \Drupal\panels\Plugin\DisplayVariant\PanelsDisplayVariant $panels_display */
    $panels_display = $page_variant->getVariantPlugin();
    // Set the storage info now that we have the id.
    $panels_display->setStorage('page_manager', $page_variant->id());
    // It's ConfigEntityBase::preSave() that copies configuration from plugin
    // collections to the config entity, and unfortunately, that runs just
    // before invoking hook_entity_presave(). So, we have to copy the
    // configuration from $panels_display to $page_variant again manually for
    // it to be saved.
    $page_variant->set('variant_settings', $panels_display->getConfiguration());
  }
}

/**
 * Implements hook_form_FORM_ID_alter().
 */
function panels_form_page_manager_add_variant_form_alter(array &$form, FormStateInterface $form_state) {
  $pos = array_search('::submitForm', $form['actions']['submit']['#submit']);
  $handlers_top = array_slice($form['actions']['submit']['#submit'], 0, $pos);
  $handlers_bottom = array_slice($form['actions']['submit']['#submit'], $pos);
  $panels_handler = ['panels_form_page_manager_add_variant_form_submit'];
  $handlers = array_merge($handlers_top, $panels_handler, $handlers_bottom);
  $form['actions']['submit']['#submit'] = $handlers;
}

/**
 * Form submit handler to set page_manager storage for panels display variants.
 */
function panels_form_page_manager_add_variant_form_submit(array &$form, FormStateInterface $form_state) {
  $cached_values = $form_state->getTemporaryValue('wizard');
  /** @var $page_variant \Drupal\page_manager\Entity\PageVariant */
  $page_variant = $cached_values['page_variant'];
  $plugin = $page_variant->getVariantPlugin();
  if ($plugin instanceof PanelsDisplayVariant) {
    $plugin->setStorage('page_manager', $page_variant->id());
  }
}

// --------------------------------------------------------------------------
// Core Drupal hook implementations
/**
 * Implementation of hook_menu
 */
function panels_menu() {
  // Safety: go away if CTools is not at an appropriate version.
  if (!module_invoke('ctools', 'api_version', PANELS_REQUIRED_CTOOLS_API)) {
    return array();
  }
  $items = array();

  // Base AJAX router callback.
  $items['panels/ajax'] = array(
    'access arguments' => array('access content'),
    'page callback' => 'panels_ajax_router',
    'theme callback' => 'ajax_base_page_theme',
    'delivery callback' => 'ajax_deliver',
    'type' => MENU_CALLBACK,
  );

  $admin_base = array(
    'file' => 'includes/callbacks.inc',
    'access arguments' => array('use panels dashboard'),
  );

  $items['admin/structure/panels/settings'] = array(
    'title' => 'Settings',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('panels_admin_settings_page'),
    'type' => MENU_LOCAL_TASK,
  ) + $admin_base;

  $items['admin/structure/panels/settings/general'] = array(
    'title' => 'General',
    'page callback' => 'drupal_get_form',
    'page arguments' => array('panels_admin_settings_page'),
    'access arguments' => array('administer page manager'),
    'type' => MENU_DEFAULT_LOCAL_TASK,
    'weight' => -10,
  ) + $admin_base;

  if (module_exists('page_manager')) {
    $items['admin/structure/panels/settings/panel-page'] = array(
      'title' => 'Panel pages',
      'page callback' => 'panels_admin_panel_context_page',
      'type' => MENU_LOCAL_TASK,
      'weight' => -10,
    ) + $admin_base;
  }

  ctools_include('plugins', 'panels');
  $layouts = panels_get_layouts();
  foreach ($layouts as $name => $data) {
    if (!empty($data['hook menu'])) {
      if (is_array($data['hook menu'])) {
        $items += $data['hook menu'];
      }
      else if (function_exists($data['hook menu'])) {
        $data['hook menu']($items, $data);
      }
    }
  }

  return $items;
}

/**
 * Implements hook_cache_flush().
 * TODO: Implement the cache_panels, if applicable for 8.x
  function panels_cache_flush() {
      return array('cache_panels');
  }
 */


/**
 * Ensure a layout has a minimal set of data.
 */
function panels_layout_process(&$plugin) {
  $plugin += array(
    'category' => t('Miscellaneous'),
    'description' => '',
  );
}

/**
 * Perform additional processing on a style plugin.
 *
 * Currently this is only being used to apply versioning information to style
 * plugins in order to ensure the legacy renderer passes the right type of
 * parameters to a style plugin in a hybrid environment of both new and old
 * plugins.
 *
 * @see _ctools_process_data()
 *
 * @param array $plugin
 *   The style plugin that is being processed.
 * @param array $info
 *   The style plugin type info array.
 */
function panels_plugin_styles_process(&$plugin, $info) {
  $plugin += array(
    'weight' => 0,
  );

  $compliant_modules = ctools_plugin_api_info('panels', 'styles', 2.0, 2.0);
  $plugin['version'] = empty($compliant_modules[$plugin['module']]) ? 1.0 : $compliant_modules[$plugin['module']]['version'];
}

/**
 * Declare what style types Panels uses.
 */
function panels_ctools_style_base_types() {
  return array(
    'region' => array(
      'title' => t('Panel region'),
      'preview' => 'panels_stylizer_region_preview',
      'theme variables' => array('settings' => NULL, 'class' => NULL, 'content' => NULL),
    ),
    'pane' => array(
      'title' => t('Panel pane'),
      'preview' => 'panels_stylizer_pane_preview',
      'theme variables' => array('settings' => NULL, 'content' => NULL, 'pane' => NULL, 'display' => NULL),
    ),
  );
}

function panels_stylizer_lipsum() {
  return "
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit. Phasellus at velit dolor. Donec egestas tellus sit amet urna rhoncus adipiscing. Proin nec porttitor sem. Maecenas aliquam, purus nec tempus dignissim, nulla arcu aliquam diam, non tincidunt massa ante vel dolor. Aliquam sapien sapien, tincidunt id tristique at, pretium sagittis libero.</p>

    <p>Nulla facilisi. Curabitur lacinia, tellus sed tristique consequat, diam lorem scelerisque felis, at dictum purus augue facilisis lorem. Duis pharetra dignissim rutrum. Curabitur ac elit id dui dapibus tincidunt. Nulla eget sem quam, non eleifend eros. Cras porttitor tempus lectus ac scelerisque. Curabitur vehicula bibendum lorem, vitae ornare ligula venenatis ut.</p>
  ";
}

/**
 * Generate a preview given the current settings.
 */
function panels_stylizer_region_preview($plugin, $settings) {
  ctools_stylizer_add_css($plugin, $settings);
  return theme($plugin['theme'], array('settings' => $settings, 'class' => ctools_stylizer_get_css_class($plugin, $settings), 'content' => panels_stylizer_lipsum()));
}

/**
 * Generate a preview given the current settings.
 */
function panels_stylizer_pane_preview($plugin, $settings) {
  ctools_stylizer_add_css($plugin, $settings);
  $pane = new stdClass();

  $content = new stdClass;
  $content->title = t('Lorem ipsum');
  $content->content = panels_stylizer_lipsum();
  $content->type = 'dummy';
  $content->subtype = 'dummy';

  $content->css_class = ctools_stylizer_get_css_class($plugin, $settings);

  $display = new panels_display();

  if (!empty($plugin['theme'])) {
    return theme($plugin['theme'], array('settings' => $settings, 'content' => $content, 'pane' => $pane, 'display' => $display));
  }
  else {
    return theme('panels_pane', array('content' => $content, 'pane' => $pane, 'display' => $display));
  }
}

// ---------------------------------------------------------------------------
// Panels display editing

/**
 * @defgroup mainapi Functions comprising the main panels API
 * @{
 */

/**
 * Main API entry point to edit a panel display.
 *
 * Sample implementations utiltizing the the complex $destination behavior can be found
 * in panels_page_edit_content() and, in a separate contrib module, OG Blueprints
 * (http://drupal.org/project/og_blueprints), og_blueprints_blueprint_edit().
 *
 * @ingroup mainapi
 *
 * @param object $display instanceof panels_display \n
 *  A fully loaded panels $display object, as returned from panels_load_display().
 *  Merely passing a did is NOT sufficient. \n
 *  Note that 'fully loaded' means the $display must already be loaded with any contexts
 *  the caller wishes to have set for the display.
 * @param mixed $destination \n
 *  The redirect destination that the user should be taken to on form submission or
 *  cancellation. With panels_edit, $destination has complex effects on the return
 *  values of panels_edit() once the form has been submitted. See the explanation of
 *  the return value below to understand the different types of values returned by panels_edit()
 *  at different stages of FAPI. Under most circumstances, simply passing in
 *  drupal_get_destination() is all that's necessary.
 * @param array $content_types \n
 *  An associative array of allowed content types, typically as returned from
 *  panels_common_get_allowed_types(). Note that context partially governs available content types,
 *  so you will want to create any relevant contexts using panels_create_context() or
 *  panels_create_context_empty() to make sure all the appropriate content types are available.
 *
 * @return
 *  Because the functions called by panels_edit() invoke the form API, this function
 *  returns different values depending on the stage of form submission we're at. In Drupal 5,
 *  the phase of form submission is indicated by the contents of $_POST['op']. Here's what you'll
 *  get at different stages:
 *    -# If !$_POST['op']: then we're on on the initial passthrough and the form is being
 *       rendered, so it's the $form itself that's being returned. Because negative margins,
 *       a common CSS technique, bork the display editor's ajax drag-and-drop, it's important
 *       that the $output be printed, not returned. Use this syntax in the caller function: \n
 *          print theme('page', panels_edit($display, $destination, $content_types), FALSE); \n
 *    -# If $_POST['op'] == t('Cancel'): form submission has been cancelled. If empty($destination) == FALSE,
 *       then there is no return value and the panels API takes care of redirecting to $destination.
 *       If empty($destination) == TRUE, then there's still no return value, but the caller function
 *       has to take care of form redirection.
 *    -# If $_POST['op'] == ('Save'): the form has been submitted successfully and has run through
 *        panels_edit_display_submit(). $output depends on the value of $destination:
 *      - If empty($destination) == TRUE: $output contains the modified $display
 *        object, and no redirection will occur. This option is useful if the caller
 *        needs to perform additional operations on or with the modified $display before
 *        the page request is complete. Using hook_form_alter() to add an additional submit
 *        handler is typically the preferred method for something like this, but there
 *        are certain use cases where that is infeasible and $destination = NULL should
 *        be used instead. If this method is employed, the caller will need to handle form
 *        redirection. Note that having $_REQUEST['destination'] set, whether via
 *        drupal_get_destination() or some other method, will NOT interfere with this
 *        functionality; consequently, you can use drupal_get_destination() to safely store
 *        your desired redirect in the caller function, then simply use drupal_goto() once
 *        panels_edit() has done its business.
 *      - If empty($destination) == FALSE: the form will redirect to the URL string
 *        given in $destination and NO value will be returned.
 */
function panels_edit($display, $destination = NULL, $content_types = NULL, $title = FALSE) {
  ctools_include('display-edit', 'panels');
  ctools_include('ajax');
  ctools_include('plugins', 'panels');
  return _panels_edit($display, $destination, $content_types, $title);
}

/**
 * API entry point for selecting a layout for a given display.
 *
 * Layout selection is nothing more than a list of radio items encompassing the available
 * layouts for this display, as defined by .inc files in the panels/layouts subdirectory.
 * The only real complexity occurs when a user attempts to change the layout of a display
 * that has some content in it.
 *
 * @param object $display instanceof panels_display \n
 *  A fully loaded panels $display object, as returned from panels_load_display().
 *  Merely passing a did is NOT sufficient.
 * @param string $finish
 *  A string that will be used for the text of the form submission button. If no value is provided,
 *  then the form submission button will default to t('Save').
 * @param mixed $destination
 *  Basic usage is a string containing the URL that the form should redirect to upon submission.
 *  For a discussion of advanced usages, see panels_edit().
 * @param mixed $allowed_layouts
 *  Allowed layouts has three different behaviors that depend on which of three value types
 *  are passed in by the caller:
 *    #- if $allowed_layouts instanceof panels_allowed_layouts (includes subclasses): the most
 *       complex use of the API. The caller is passing in a loaded panels_allowed_layouts object
 *       that the client module previously created and stored somewhere using a custom storage
 *       mechanism.
 *    #- if is_string($allowed_layouts): the string will be used in a call to variable_get() which
 *       will call the $allowed_layouts . '_allowed_layouts' var. If the data was stored properly
 *       in the system var, the $allowed_layouts object will be unserialized and recreated.
 *       @see panels_common_set_allowed_layouts()
 *    #- if is_null($allowed_layouts): the default behavior, which also provides backwards
 *       compatibility for implementations of the Panels2 API written before beta4. In this case,
 *       a dummy panels_allowed_layouts object is created which does not restrict any layouts.
 *       Subsequent behavior is indistinguishable from pre-beta4 behavior.
 *
 * @return
 *  Can return nothing, or a modified $display object, or a redirection string; return values for the
 *  panels_edit* family of functions are quite complex. See panels_edit() for detailed discussion.
 * @see panels_edit()
 */
function panels_edit_layout($display, $finish, $destination = NULL, $allowed_layouts = NULL) {
  ctools_include('display-layout', 'panels');
  ctools_include('plugins', 'panels');
  return _panels_edit_layout($display, $finish, $destination, $allowed_layouts);
}

// ---------------------------------------------------------------------------
// Panels database functions

/**
 * Forms the basis of a panel display
 *
 */
class panels_display {
  var $args = array();
  var $content = array();
  var $panels = array();
  var $incoming_content = NULL;
  var $css_id = NULL;
  var $context = array();
  var $did = 'new';
  var $renderer = 'standard';

  function add_pane(&$pane, $location = NULL) {
    // If no location specified, use what's set in the pane.
    if (empty($location)) {
      $location = $pane->panel;
    }
    else {
      $pane->panel = $location;
    }

    // Generate a permanent uuid for this pane, and use
    // it as a temporary pid.
    $pane->uuid = ctools_uuid_generate();
    $pane->pid = 'new-' . $pane->uuid;

    // Add the pane to the approprate spots.
    $this->content[$pane->pid] = &$pane;
    $this->panels[$location][] = $pane->pid;
  }

  function duplicate_pane($pid, $location = FALSE) {
    $pane = $this->clone_pane($pid);
    $this->add_pane($pane, $location);
  }

  function clone_pane($pid) {
    $pane = clone $this->content[$pid];
    $pane->uuid = ctools_uuid_generate();
    return $pane;
  }

  /**
   * Get the title from a display.
   *
   * The display must have already been rendered, or the setting to set the
   * display's title from a pane's title will not have worked.
   *
   * @return
   *   The title to use. If NULL, this means to let any default title that may be in use
   *   pass through. i.e, do not actually set the title.
   */
  function get_title() {
    switch ($this->hide_title) {
      case PANELS_TITLE_NONE:
        return '';

      case PANELS_TITLE_PANE:
        return isset($this->stored_pane_title) ? $this->stored_pane_title : '';

      case PANELS_TITLE_FIXED:
      case FALSE; // For old exported panels that are not in the database.
        if (!empty($this->title)) {
          return filter_xss_admin(ctools_context_keyword_substitute($this->title, array(), $this->context));
        }
        return NULL;
    }
  }

  /**
   * Render this panels display.
   *
   * After checking to ensure the designated layout plugin is valid, a
   * display renderer object is spawned and runs its rendering logic.
   *
   * @param mixed $renderer
   *    An instantiated display renderer object, or the name of a display
   *    renderer plugin+class to be fetched. Defaults to NULL. When NULL, the
   *    predesignated display renderer will be used.
   */
  function render($renderer = NULL) {
    $layout = panels_get_layout($this->layout);
    if (!$layout) {
      return NULL;
    }

    // If we were not given a renderer object, load it.
    if (!is_object($renderer)) {
      // If the renderer was not specified, default to $this->renderer
      // which is either standard or was already set for us.
      $renderer = panels_get_renderer_handler(!empty($renderer) ? $renderer : $this->renderer, $this);
      if (!$renderer) {
        return NULL;
      }
    }

    $output = '';
    // Let modules act just prior to render.
    foreach (module_implements('panels_pre_render') as $module) {
      $function = $module . '_panels_pre_render';
      $output .= $function($this, $renderer);
    }

    $output .= $renderer->render();

    // Let modules act just after render.
    foreach (module_implements('panels_post_render') as $module) {
      $function = $module . '_panels_post_render';
      $output .= $function($this, $renderer);
    }
    return $output;
  }
}

/**
 * }@ End of 'defgroup mainapi', although other functions are specifically added later
 */

/**
 * Creates a new display, setting the ID to our magic new id.
 */
function panels_new_display() {
  ctools_include('export');
  $display = ctools_export_new_object('panels_display', FALSE);
  $display->did = 'new';
  return $display;
}

/**
 * Create a new pane.
 *
 * @todo -- use schema API for some of this?
 */
function panels_new_pane($type, $subtype, $set_defaults = FALSE) {
  ctools_include('export');
  $pane = ctools_export_new_object('panels_pane', FALSE);
  $pane->pid = 'new';
  $pane->type = $type;
  $pane->subtype = $subtype;
  if ($set_defaults) {
    ctools_include('content');
    $content_type = ctools_get_content_type($type);
    $content_subtype = ctools_content_get_subtype($content_type, $subtype);
    $pane->configuration = ctools_content_get_defaults($content_type, $content_subtype);
  }

  return $pane;
}

/**
 * Load and fill the requested $display object(s).
 *
 * Helper function primarily for for panels_load_display().
 *
 * @param array $dids
 *  An indexed array of dids to be loaded from the database.
 *
 * @return $displays
 *  An array of displays, keyed by their display dids.
 *
 * @todo schema API can drasticly simplify this code.
 */
function panels_load_displays($dids) {
  $displays = array();
  if (empty($dids) || !is_array($dids)) {
    return $displays;
  }

  $result = db_query("SELECT * FROM {panels_display} WHERE did IN (:dids)", array(':dids' => $dids));

  ctools_include('export');
  foreach ($result as $obj) {
    $displays[$obj->did] = ctools_export_unpack_object('panels_display', $obj);
    // Modify the hide_title field to go from a bool to an int if necessary.
  }

  $result = db_query("SELECT * FROM {panels_pane} WHERE did IN (:dids) ORDER BY did, panel, position", array(':dids' => $dids));
  foreach ($result as $obj) {
    $pane = ctools_export_unpack_object('panels_pane', $obj);

    $displays[$pane->did]->panels[$pane->panel][] = $pane->pid;
    $displays[$pane->did]->content[$pane->pid] = $pane;
  }

  return $displays;
}

/**
 * Load a single display.
 *
 * @ingroup mainapi
 *
 * @param int $did
 *  The display id (did) of the display to be loaded.
 *
 * @return object $display instanceof panels_display \n
 *  Returns a partially-loaded panels_display object. $display objects returned from
 *  from this function have only the following data:
 *    - $display->did (the display id)
 *    - $display->name (the 'name' of the display, where applicable - it often isn't)
 *    - $display->layout (a string with the system name of the display's layout)
 *    - $display->panel_settings (custom layout style settings contained in an associative array; NULL if none)
 *    - $display->layout_settings (panel size and configuration settings for Flexible layouts; NULL if none)
 *    - $display->css_id (the special css_id that has been assigned to this display, if any; NULL if none)
 *    - $display->content (an array of pane objects, keyed by pane id (pid))
 *    - $display->panels (an associative array of panel regions, each an indexed array of pids in the order they appear in that region)
 *    - $display->cache (any relevant data from panels_simple_cache)
 *    - $display->args
 *    - $display->incoming_content
 *
 * While all of these members are defined, $display->context is NEVER defined in the returned $display;
 * it must be set using one of the ctools_context_create() functions.
 */
function panels_load_display($did) {
  $displays = panels_load_displays(array($did));
  if (!empty($displays)) {
    return array_shift($displays);
  }
}

/**
 * Save a display object.
 *
 * @ingroup mainapi
 *
 * Note that a new $display only receives a real did once it is run through
 * this function, and likewise for the pid of any new pane.
 *
 * Until then, a new display uses a string placeholder, 'new', in place of
 * a real did, and a new pane (whether on a new $display or not) appends a
 * universally-unique identifier (which is stored permanently in the 'uuid'
 * field). This format is also used in place of the real pid for exports.
 *
 * @param object $display instanceof panels_display \n
 *  The display object to be saved. Passed by reference so the caller need not use
 *  the return value for any reason except convenience.
 *
 * @return object $display instanceof panels_display \n
 */
function panels_save_display(&$display) {
  $update = (isset($display->did) && is_numeric($display->did)) ? array('did') : array();
  if (empty($display->uuid) || !ctools_uuid_is_valid($display->uuid)) {
    $display->uuid = ctools_uuid_generate();
  }
  drupal_write_record('panels_display', $display, $update);

  $pids = array();
  if ($update) {
    // Get a list of all panes currently in the database for this display so we can know if there
    // are panes that need to be deleted. (i.e, aren't currently in our list of panes).
    $result = db_query("SELECT pid FROM {panels_pane} WHERE did = :did", array(':did' => $display->did));
    foreach ($result as $pane) {
      $pids[$pane->pid] = $pane->pid;
    }
  }

  // update all the panes
  ctools_include('plugins', 'panels');
  ctools_include('content');

  foreach ($display->panels as $id => $panes) {
    $position = 0;
    $new_panes = array();
    foreach ((array) $panes as $pid) {
      if (!isset($display->content[$pid])) {
        continue;
      }
      $pane = $display->content[$pid];
      $type = ctools_get_content_type($pane->type);

      $pane->position = $position++;
      $pane->did = $display->did;

      $old_pid = $pane->pid;

      if (empty($pane->uuid) || !ctools_uuid_is_valid($pane->uuid)) {
        $pane->uuid = ctools_uuid_generate();
      }

      drupal_write_record('panels_pane', $pane, is_numeric($pid) ? array('pid') : array());

      // Allow other modules to take action after a pane is saved.
      if ($pane->pid == $old_pid) {
        module_invoke_all('panels_pane_update', $pane);
      }
      else {
        module_invoke_all('panels_pane_insert', $pane);
      }

      if ($pane->pid != $old_pid) {
        // Remove the old new-* entry from the displays content.
        unset($display->content[$pid]);

        // and put it back so our pids and positions can be used.
        $display->content[$pane->pid] = $pane;

        // If the title pane was one of our panes that just got its ID changed,
        // we need to change it in the database, too.
        if (isset($display->title_pane) && $display->title_pane == $old_pid) {
          $display->title_pane = $pane->pid;
          // Do a simple update query to write it so we don't have to rewrite
          // the whole record. We can't just save writing the whole record here
          // because it was needed to get the did. Chicken, egg, more chicken.
          db_update('panels_display')
            ->fields(array(
              'title_pane' => $pane->pid
            ))
            ->condition('did', $display->did)
            ->execute();
        }
      }

      // re-add this to the list of content for this panel.
      $new_panes[] = $pane->pid;

      // Remove this from the list of panes scheduled for deletion.
      if (isset($pids[$pane->pid])) {
        unset($pids[$pane->pid]);
      }
    }

    $display->panels[$id] = $new_panes;
  }
  if (!empty($pids)) {
    // Allow other modules to take action before a panes are deleted.
    module_invoke_all('panels_pane_delete', $pids);
    db_delete('panels_pane')->condition('pid', $pids)->execute();
  }

  // Clear any cached content for this display.
  panels_clear_cached_content($display);

  // Allow other modules to take action when a display is saved.
  module_invoke_all('panels_display_save', $display);

  // Log the change to watchdog, using the same style as node.module
  $watchdog_args = array('%did' => $display->did);
  if (!empty($display->title)) {
    $watchdog_args['%title'] = $display->title;
    watchdog('content', 'Panels: saved display "%title" with display id %did', $watchdog_args, WATCHDOG_NOTICE);
  }
  else {
    watchdog('content', 'Panels: saved display with id %did', $watchdog_args, WATCHDOG_NOTICE);
  }

  // to be nice, even tho we have a reference.
  return $display;
}

/**
 * Delete a display.
 */
function panels_delete_display($display) {
  if (is_object($display)) {
    $did = $display->did;
  }
  else {
    $did = $display;
  }
  module_invoke_all('panels_delete_display', $did);
  db_delete('panels_display')->condition('did', $did)->execute();
  db_delete('panels_pane')->condition('did', $did)->execute();
}

/**
 * Exports the provided display into portable code.
 *
 * This function is primarily intended as a mechanism for cloning displays.
 * It generates an exact replica (in code) of the provided $display, with
 * the exception that it replaces all ids (dids and pids) with place-holder
 * values (consisting of the display or pane's uuid, with a 'new-' prefix).
 *
 * Only once panels_save_display() is called on the code version of $display
 * will the exported display be written to the database and permanently saved.
 *
 * @see panels_page_export() or _panels_page_fetch_display() for sample implementations.
 *
 * @ingroup mainapi
 *
 * @param object $display instanceof panels_display \n
 *  This export function does no loading of additional data about the provided
 *  display. Consequently, the caller should make sure that all the desired data
 *  has been loaded into the $display before calling this function.
 * @param string $prefix
 *  A string prefix that is prepended to each line of exported code. This is primarily
 *  used for prepending a double space when exporting so that the code indents and lines up nicely.
 *
 * @return string $output
 *  The passed-in $display expressed as code, ready to be imported. Import by running
 *  eval($output) in the caller function; doing so will create a new $display variable
 *  with all the exported values. Note that if you have already defined a $display variable in
 *  the same scope as where you eval(), your existing $display variable WILL be overwritten.
 */
function panels_export_display($display, $prefix = '') {
  ctools_include('export');
  if (empty($display->uuid) || !ctools_uuid_is_valid($display->uuid)) {
    $display->uuid = ctools_uuid_generate();
  }
  $display->did = 'new-' . $display->uuid;
  $output = ctools_export_object('panels_display', $display, $prefix);

  // Initialize empty properties.
  $output .= $prefix . '$display->content = array()' . ";\n";
  $output .= $prefix . '$display->panels = array()' . ";\n";
  $panels = array();

  $title_pid = 0;
  if (!empty($display->content)) {
    $region_counters = array();
    foreach ($display->content as $pane) {

      if (!isset($pane->uuid) || !ctools_uuid_is_valid($pane->uuid)) {
        $pane->uuid = ctools_uuid_generate();
      }
      $pid = 'new-' . $pane->uuid;

      if ($pane->pid == $display->title_pane) {
        $title_pid = $pid;
      }
      $pane->pid = $pid;
      $output .= ctools_export_object('panels_pane', $pane, $prefix . '  ');
      $output .= "$prefix  " . '$display->content[\'' . $pane->pid . '\'] = $pane' . ";\n";
      if (!isset($region_counters[$pane->panel])) {
        $region_counters[$pane->panel] = 0;
      }
      $output .= "$prefix  " . '$display->panels[\'' . $pane->panel . '\'][' . $region_counters[$pane->panel]++ .'] = \'' . $pane->pid . "';\n";
    }
  }
  $output .= $prefix . '$display->hide_title = ';
  switch ($display->hide_title) {
    case PANELS_TITLE_FIXED:
      $output .= 'PANELS_TITLE_FIXED';
      break;
    case PANELS_TITLE_NONE:
      $output .= 'PANELS_TITLE_NONE';
      break;
    case PANELS_TITLE_PANE:
      $output .= 'PANELS_TITLE_PANE';
      break;
  }
  $output .= ";\n";

  $output .= $prefix . '$display->title_pane =' . " '$title_pid';\n";
  return $output;
}

/**
 * Render a display by loading the content into an appropriate
 * array and then passing through to panels_render_layout.
 *
 * if $incoming_content is NULL, default content will be applied. Use
 * an empty string to indicate no content.
 * @ingroup hook_invocations
 */
function panels_render_display(&$display, $renderer = NULL) {
  ctools_include('plugins', 'panels');
  ctools_include('context');

  if (!empty($display->context)) {
    if ($form_context = ctools_context_get_form($display->context)) {
      $form_context->form['#theme'] = 'panels_render_display_form';
      if (empty($form_context->form['#theme_wrappers']) || !in_array('form', $form_context->form['#theme_wrappers'])) {
        $form_context['#theme_wrappers'][] = 'form';
      }
      $form_context->form['#display'] = &$display;
      return $form_context->form;
    }
  }
  return $display->render($renderer);
}

/**
 * Theme function to render our panel as a form.
 *
 * When rendering a display as a form, the entire display needs to be
 * inside the <form> tag so that the form can be spread across the
 * panes. This sets up the form system to be the main caller and we
 * then operate as a theme function of the form.
 */
function theme_panels_render_display_form($vars) {
  return $vars['element']['#display']->render();
}

// @layout
function panels_print_layout_icon($id, $layout, $title = NULL) {
  ctools_add_css('panels_admin', 'panels');
  $file = $layout['path'] . '/' . $layout['icon'];
  return theme('panels_layout_icon', array('id' => $id, 'image' => theme('image', array('path' => $file, 'alt' => strip_tags($layout['title']), 'title' => strip_tags($layout['description']))), 'title' => $title));
}

/**
 * Theme the layout icon image
 * @layout
 * @todo move to theme.inc
 */
function theme_panels_layout_icon($vars) {
  $id = $vars['id'];
  $image = $vars['image'];
  $title = $vars['title'];

  $output = '<div class="layout-icon">';
  $output .= $image;
  if ($title) {
    $output .= '<div class="caption">' . $title . '</div>';
  }
  $output .= '</div>';
  return $output;
}

/**
 * Theme the layout link image
 * @layout
 *
 * @todo Why isn't this a template at this point?
 * @todo Why does this take 4 arguments but only makes use of two?
 */
function theme_panels_layout_link($vars) {
  $title = $vars['title'];
  $image = $vars['image'];
  $class = $vars['class'];

  $output = '<div class="' . implode(' ', $class) . '">';
  $output .= $vars['image'];
  $output .= '<div>' . $vars['title'] . '</div>';
  $output .= '</div>';
  return $output;
}

/**
 * Print the layout link. Sends out to a theme function.
 * @layout
 */
function panels_print_layout_link($id, $layout, $link, $options = array(), $current_layout = FALSE) {
  if (isset($options['query']['q'])) {
    unset($options['query']['q']);
  }

  // Setup classes for layout link, including current-layout information
  $class = array('layout-link');
  if ($current_layout == $id) {
    $options['attributes']['class'][] = 'current-layout-link';
    $class[] = 'current-layout';
  }

  ctools_add_css('panels_admin', 'panels');
  $file = $layout['path'] . '/' . $layout['icon'];
  $image = l(theme('image', array('path' => $file)), $link, array('html' => true) + $options);
  $title = l($layout['title'], $link, $options);
  return theme('panels_layout_link', array('title' => $title, 'image' => $image, 'class' => $class));
}


/**
 * Gateway to the PanelsLegacyState class/object, which does all legacy state
 * checks and provides information about the cause of legacy states as needed.
 *
 * @return PanelsLegacyState $legacy
 */
function panels_get_legacy_state() {
  static $legacy = NULL;
  if (!isset($legacy)) {
    ctools_include('legacy', 'panels');
    $legacy = new PanelsLegacyState();
  }
  return $legacy;
}

/**
 * Get the display that is currently being rendered as a page.
 *
 * Unlike in previous versions of this, this only returns the display,
 * not the page itself, because there are a number of different ways
 * to get to this point. It is hoped that the page data isn't needed
 * at this point. If it turns out there is, we will do something else to
 * get that functionality.
 */
function panels_get_current_page_display($change = NULL) {
  static $display = NULL;
  if ($change) {
    $display = $change;
  }

  return $display;
}

/**
 * Clean up the panel pane variables for the template.
 */
function template_preprocess_panels_pane(&$vars) {
  $content = &$vars['content'];

  $vars['contextual_links'] = array();
  $vars['classes_array'] = array();
  $vars['admin_links'] = '';

  if (module_exists('contextual') && user_access('access contextual links')) {
    $links = array();
    // These are specified by the content.
    if (!empty($content->admin_links)) {
      $links += $content->admin_links;
    }

    // Take any that may have been in the render array we were given and
    // move them up so they appear outside the pane properly.
    if (is_array($content->content) && isset($content->content['#contextual_links'])) {
      $element = array(
        '#type' => 'contextual_links',
        '#contextual_links' => $content->content['#contextual_links'],
      );
      unset($content->content['#contextual_links']);

      // Add content to $element array
      if (is_array($content->content)) {
        $element['#element'] = $content->content;
      }

      $element = contextual_pre_render_links($element);
      if(!empty($element['#links'])) {
        $links += $element['#links'];
      }
    }

    if ($links) {
      $build = array(
        '#prefix' => '<div class="contextual-links-wrapper">',
        '#suffix' => '</div>',
        '#theme' => 'links__contextual',
        '#links' => $links,
        '#attributes' => array('class' => array('contextual-links')),
        '#attached' => array(
          'library' => array(array('contextual', 'contextual-links')),
        ),
      );
      $vars['classes_array'][] = 'contextual-links-region';
      $vars['admin_links'] = drupal_render($build);
    }
  }

  // basic classes
  $vars['classes_array'][] = 'panel-pane';
  $vars['id'] = '';

  // Add some usable classes based on type/subtype
  ctools_include('cleanstring');
  $type_class = $content->type ? 'pane-'. ctools_cleanstring($content->type, array('lower case' => TRUE)) : '';
  $subtype_class = $content->subtype ? 'pane-'. ctools_cleanstring($content->subtype, array('lower case' => TRUE)) : '';

  // Sometimes type and subtype are the same. Avoid redundant classes.
  $vars['classes_array'][] = $type_class;
  if ($type_class != $subtype_class) {
    $vars['classes_array'][] = $subtype_class;
  }

  // Add id and custom class if sent in.
  if (!empty($content->content)) {
    if (!empty($content->css_id)) {
      $vars['id'] = ' id="' . $content->css_id . '"';
    }
    if (!empty($content->css_class)) {
      $vars['classes_array'][] = $content->css_class;
    }
  }

  // Set up some placeholders for constructing template file names.
  $base = 'panels_pane';
  $delimiter = '__';

  // Add template file suggestion for content type and sub-type.
  $vars['theme_hook_suggestions'][] = $base . $delimiter . $content->type;
  $vars['theme_hook_suggestions'][] = $base . $delimiter . strtr(ctools_cleanstring($content->type, array('lower case' => TRUE)), '-', '_') . $delimiter . strtr(ctools_cleanstring($content->subtype, array('lower case' => TRUE)), '-', '_');

  $vars['pane_prefix'] = !empty($content->pane_prefix) ? $content->pane_prefix : '';
  $vars['pane_suffix'] = !empty($content->pane_suffix) ? $content->pane_suffix : '';

  $vars['title'] = !empty($content->title) ? $content->title : '';
  $vars['title_attributes_array']['class'][] = 'pane-title';

  $vars['feeds'] = !empty($content->feeds) ? implode(' ', $content->feeds) : '';

  $vars['links'] = !empty($content->links) ? theme('links', array('links' => $content->links)) : '';
  $vars['more'] = '';
  if (!empty($content->more)) {
    if (empty($content->more['title'])) {
      $content->more['title'] = t('more');
    }
    $vars['more'] = l($content->more['title'], $content->more['href'], $content->more);
  }

  $vars['content'] = !empty($content->content) ? $content->content : '';

}

/**
 * Route Panels' AJAX calls to the correct object.
 *
 * Panels' AJAX is controlled mostly by renderer objects. This menu callback
 * accepts the incoming request, figures out which object should handle the
 * request, and attempts to route it. If no object can be found, the default
 * Panels editor object is used.
 *
 * Calls are routed via the ajax_* method space. For example, if visiting
 * panels/ajax/add-pane then $renderer::ajax_add_pane() will be called.
 * This means commands can be added without having to create new callbacks.
 *
 * The first argument *must always* be the cache key so that a cache object
 * can be passed through. Other arguments will be passed through untouched
 * so that the method can do whatever it needs to do.
 */
function panels_ajax_router() {
  $args = func_get_args();
  if (count($args) < 3) {
    return MENU_NOT_FOUND;
  }

  ctools_include('display-edit', 'panels');
  ctools_include('plugins', 'panels');
  ctools_include('ajax');
  ctools_include('modal');
  ctools_include('context');
  ctools_include('content');

  $plugin_name = array_shift($args);
  $method = array_shift($args);
  $cache_key = array_shift($args);

  $plugin = panels_get_display_renderer($plugin_name);
  if (!$plugin) {
    // This is the default renderer for handling AJAX commands.
    $plugin = panels_get_display_renderer('editor');
  }

  $cache = panels_edit_cache_get($cache_key);
  if (empty($cache)) {
    return MENU_ACCESS_DENIED;
  }

  $renderer = panels_get_renderer_handler($plugin, $cache->display);
  if (!$renderer) {
    return MENU_ACCESS_DENIED;
  }

  $method = 'ajax_' . str_replace('-', '_', $method);
  if (!method_exists($renderer, $method)) {
    return MENU_NOT_FOUND;
  }

  $renderer->cache = &$cache;
  ctools_include('cleanstring');
  $renderer->clean_key = ctools_cleanstring($cache_key);

  $output = call_user_func_array(array($renderer, $method), $args);

  if (empty($output) && !empty($renderer->commands)) {
    return array(
      '#type' => 'ajax',
      '#commands' => $renderer->commands,
    );
  }
  else {
    return $output;
  }
}

// --------------------------------------------------------------------------
// Panels caching functions and callbacks
//
// When editing displays and the like, Panels has a caching system that relies
// on a callback to determine where to get the actual cache.

// @todo This system needs to be ported to Drupal 8

/**
 * Get an object from cache.
function panels_cache_get($obj, $did, $skip_cache = FALSE) {
  ctools_include('object-cache');
  // we often store contexts in cache, so let's just make sure we can load
  // them.
  ctools_include('context');
  return ctools_object_cache_get($obj, 'panels_display:' . $did, $skip_cache);
}
 */

/**
 * Save the edited object into the cache.
function panels_cache_set($obj, $did, $cache) {
  ctools_include('object-cache');
  return ctools_object_cache_set($obj, 'panels_display:' . $did, $cache);
}
 */

/**
 * Clear a object from the cache; used if the editing is aborted.
function panels_cache_clear($obj, $did) {
  ctools_include('object-cache');
  return ctools_object_cache_clear($obj, 'panels_display:' . $did);
}
 */

/**
 * Create the default cache for editing panel displays.
 *
 * If an application is using the Panels display editor without having
 * specified a cache key, this method can be used to create the default
 * cache.
function panels_edit_cache_get_default(&$display, $content_types = NULL, $title = FALSE) {
  if (empty($content_types)) {
    $content_types = ctools_content_get_available_types();
  }

  $display->cache_key = $display->did;
  panels_cache_clear('display', $display->did);

  $cache = new stdClass();
  $cache->display = &$display;
  $cache->content_types = $content_types;
  $cache->display_title = $title;

  panels_edit_cache_set($cache);
  return $cache;
}
 */

/**
 * Method to allow modules to provide their own caching mechanism for the
 * display editor.

function panels_edit_cache_get($cache_key) {
  if (strpos($cache_key, ':') !== FALSE) {
    list($module, $argument) = explode(':', $cache_key, 2);
    return module_invoke($module, 'panels_cache_get', $argument);
  }

  // Fall back to our normal method:
  return panels_cache_get('display', $cache_key);
}
 */

/**
 * Method to allow modules to provide their own caching mechanism for the
 * display editor.
function panels_edit_cache_set($cache) {
  $cache_key = $cache->display->cache_key;
  if (strpos($cache_key, ':') !== FALSE) {
    list($module, $argument) = explode(':', $cache_key, 2);
    return module_invoke($module, 'panels_cache_set', $argument, $cache);
  }

  // Fall back to our normal method:
  return panels_cache_set('display', $cache_key, $cache);
}
 */

/**
 * Method to allow modules to provide their own mechanism to write the
 * cache used in the display editor.

function panels_edit_cache_save($cache) {
  $cache_key = $cache->display->cache_key;
  if (strpos($cache_key, ':') !== FALSE) {
    list($module, $argument) = explode(':', $cache_key, 2);
    if (function_exists($module . '_panels_cache_save')) {
      return module_invoke($module, 'panels_cache_save', $argument, $cache);
    }
  }

  // Fall back to our normal method:
  return panels_save_display($cache->display);
}
 */
/**
 * Method to allow modules to provide their own mechanism to clear the
 * cache used in the display editor.

function panels_edit_cache_clear($cache) {
  $cache_key = $cache->display->cache_key;
  if (strpos($cache_key, ':') !== FALSE) {
    list($module, $argument) = explode(':', $cache_key, 2);
    if (function_exists($module . '_panels_cache_clear')) {
      return module_invoke($module, 'panels_cache_clear', $argument, $cache);
    }
  }

  // Fall back to our normal method:
  return panels_cache_clear('display', $cache_key);
}
 */
/**
 * Method to allow modules to provide a mechanism to break locks.

function panels_edit_cache_break_lock($cache) {
  if (empty($cache->locked)) {
    return;
  }

  $cache_key = $cache->display->cache_key;
  if (strpos($cache_key, ':') !== FALSE) {
    list($module, $argument) = explode(':', $cache_key, 2);
    if (function_exists($module . '_panels_cache_break_lock')) {
      return module_invoke($module, 'panels_cache_break_lock', $argument, $cache);
    }
  }

  // Normal panel display editing has no locks, so we do nothing if there is
  // no fallback.
  return;
}
 */
// --------------------------------------------------------------------------
// Callbacks on behalf of the panel_context plugin.
//
// The panel_context plugin lets Panels be used in page manager. These
// callbacks allow the display editing system to use the page manager
// cache rather than the default display cache. They are routed by the cache
// key via panels_edit_cache_* functions.

/**
 * Get display edit cache on behalf of panel context.
 *
 * The key is the second half of the key in this form:
 * panel_context:TASK_NAME::HANDLER_NAME::args::url;
 */
function panel_context_panels_cache_get($key) {
  ctools_include('common', 'panels');
  ctools_include('context');
  ctools_include('context-task-handler');
  // this loads the panel context inc even if we don't use the plugin.
  $plugin = page_manager_get_task_handler('panel_context');

  list($task_name, $handler_name, $args, $q) = explode('::', $key, 4);
  $page = page_manager_get_page_cache($task_name);
  if (isset($page->display_cache[$handler_name])) {
    return $page->display_cache[$handler_name];
  }

  if ($handler_name) {
    $handler = &$page->handlers[$handler_name];
  }
  else {
    $handler = &$page->new_handler;
  }
  $cache = new stdClass();

  $task = page_manager_get_task($page->task_id);
  //ctools_context_handler_get_all_contexts($page->task, $page->subtask, $handler);
  $arguments = array();
  if ($args) {
    $arguments = explode('\\', $args);
    $contexts = ctools_context_handler_get_task_contexts($task, $page->subtask, $arguments);
    $contexts = ctools_context_handler_get_handler_contexts($contexts, $handler);
  }
  else {
    $contexts = ctools_context_handler_get_all_contexts($page->task, $page->subtask, $handler);
  }

  $cache->display = &panels_panel_context_get_display($handler);
  $cache->display->context = $contexts;
  $cache->display->cache_key = 'panel_context:' . $key;
  $cache->content_types = panels_common_get_allowed_types('panels_page', $cache->display->context);
  $cache->display_title = TRUE;
  $cache->locked = $page->locked;

  return $cache;
}

/**
 * Get the Page Manager cache for the panel_context plugin.
 */
function _panel_context_panels_cache_get_page_cache($key, $cache) {
  list($task_name, $handler_name, $args, $q) = explode('::', $key, 4);
  $page = page_manager_get_page_cache($task_name);
  $page->display_cache[$handler_name] = $cache;
  if ($handler_name) {
    $page->handlers[$handler_name]->conf['display'] = $cache->display;
    $page->handler_info[$handler_name]['changed'] |= PAGE_MANAGER_CHANGED_CACHED;
  }
  else {
    $page->new_handler->conf['display'] = $cache->display;
  }

  return $page;
}

/**
 * Store a display edit in progress in the page cache.
 */
function panel_context_panels_cache_set($key, $cache) {
  $page = _panel_context_panels_cache_get_page_cache($key, $cache);
  page_manager_set_page_cache($page);
}

/**
 * Save all changes made to a display using the Page Manager page cache.
 */
function panel_context_panels_cache_clear($key, $cache) {
  $page = _panel_context_panels_cache_get_page_cache($key, $cache);
  page_manager_clear_page_cache($page->task_name);
}

/**
 * Save all changes made to a display using the Page Manager page cache.
 */
function panel_context_panels_cache_save($key, $cache) {
  $page = _panel_context_panels_cache_get_page_cache($key, $cache);
  page_manager_save_page_cache($page);
}

/**
 * Break the lock on a page manager page.
 */
function panel_context_panels_cache_break_lock($key, $cache) {
  $page = _panel_context_panels_cache_get_page_cache($key, $cache);
  ctools_object_cache_clear_all('page_manager_page', $page->task_name);
}

// --------------------------------------------------------------------------
// Callbacks on behalf of the panels page wizards
//
// The page wizards are a pluggable set of 'wizards' to make it easy to create
// specific types of pages based upon whatever someone felt like putting
// together. Since they will very often have content editing, we provide
// a generic mechanism to allow them to store their editing cache in the
// wizard cache.
//
// For them to use this mechanism, they just need to use:
//   $cache = panels_edit_cache_get('panels_page_wizard:' . $plugin['name']);

/**
 * Get display edit cache for the panels mini export UI
 *
 * The key is the second half of the key in this form:
 * panels_page_wizard:TASK_NAME:HANDLER_NAME;
 */
function panels_page_wizard_panels_cache_get($key) {
  ctools_include('page-wizard');
  ctools_include('context');
  $wizard_cache = page_manager_get_wizard_cache($key);
  if (isset($wizard_cache->display_cache)) {
    return $wizard_cache->display_cache;
  }

  ctools_include('common', 'panels');
  $cache = new stdClass();
  $cache->display = $wizard_cache->display;
  $cache->display->context = !empty($wizard_cache->context) ? $wizard_cache->context : array();
  $cache->display->cache_key = 'panels_page_wizard:' . $key;
  $cache->content_types = panels_common_get_allowed_types('panels_page', $cache->display->context);
  $cache->display_title = TRUE;

  return $cache;
}

/**
 * Store a display edit in progress in the page cache.
 */
function panels_page_wizard_panels_cache_set($key, $cache) {
  ctools_include('page-wizard');
  $wizard_cache = page_manager_get_wizard_cache($key);
  $wizard_cache->display_cache = $cache;
  page_manager_set_wizard_cache($wizard_cache);
}

// --------------------------------------------------------------------------
// General utility functions

/**
 * Perform a drupal_goto on a destination that may be an array like url().
 */
function panels_goto($destination) {
  if (!is_array($destination)) {
    return drupal_goto($destination);
  }
  else {
    // Prevent notices by adding defaults
    $destination += array(
      'query' => NULL,
      'fragment' => NULL,
      'http_response_code' => NULL,
    );

    return drupal_goto($destination['path'], $destination['query'], $destination['fragment'], $destination['http_response_code']);
  }
}


/**
 * For external use: Given a layout ID and a $content array, return the
 * panel display.
 *
 * The content array is filled in based upon the content available in the
 * layout. If it's a two column with a content array defined like
 * @code
 *   array(
 *    'left' => t('Left side'),
 *    'right' => t('Right side')
 *  ),
 * @endcode
 *
 * Then the $content array should be
 * @code
 * array(
 *   'left' => $output_left,
 *   'right' => $output_right,
 * )
 * @endcode
 *
 * The output within each panel region can be either a single rendered
 * HTML string or an array of rendered HTML strings as though they were
 * panes. They will simply be concatenated together without separators.
 */
function panels_print_layout($layout, $content, $meta = 'standard') {
  ctools_include('plugins', 'panels');

  // Create a temporary display for this.
  $display = panels_new_display();
  $display->layout = is_array($layout) ? $layout['name'] : $layout;
  $display->content = $content;

  // Get our simple renderer
  $renderer = panels_get_renderer_handler('simple', $display);
  $renderer->meta_location = $meta;

  return $renderer->render();
}

/**
 * Filter callback for array_filter to remove builders from a list of layouts.
 */
function _panels_builder_filter($layout) {
  return empty($layout['builder']);
}