blocks/moodleblock.class.php

   1 <?php
   2 // This file is part of Moodle - http://moodle.org/
   3 //
   4 // Moodle is free software: you can redistribute it and/or modify
   5 // it under the terms of the GNU General Public License as published by
   6 // the Free Software Foundation, either version 3 of the License, or
   7 // (at your option) any later version.
   8 //
   9 // Moodle is distributed in the hope that it will be useful,
  10 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 // GNU General Public License for more details.
  13 //
  14 // You should have received a copy of the GNU General Public License
  15 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16
  17 /**
  18  * This file contains the parent class for moodle blocks, block_base.
  19  *
  20  * @package    core_block
  21  * @license    http://www.gnu.org/copyleft/gpl.html GNU Public License
  22  */
  23
  24 /// Constants
  25
  26 /**
  27  * Block type of list. Contents of block should be set as an associative array in the content object as items ($this->content->items). Optionally include footer text in $this->content->footer.
  28  */
  29 define('BLOCK_TYPE_LIST',    1);
  30
  31 /**
  32  * Block type of text. Contents of block should be set to standard html text in the content object as items ($this->content->text). Optionally include footer text in $this->content->footer.
  33  */
  34 define('BLOCK_TYPE_TEXT',    2);
  35 /**
  36  * Block type of tree. $this->content->items is a list of tree_item objects and $this->content->footer is a string.
  37  */
  38 define('BLOCK_TYPE_TREE',    3);
  39
  40 /**
  41  * Class for describing a moodle block, all Moodle blocks derive from this class
  42  *
  43  * @author Jon Papaioannou
  44  * @package core_block
  45  */
  46 class block_base {
  47
  48     /**
  49      * Internal var for storing/caching translated strings
  50      * @var string $str
  51      */
  52     var $str;
  53
  54     /**
  55      * The title of the block to be displayed in the block title area.
  56      * @var string $title
  57      */
  58     var $title         = NULL;
  59
  60     /**
  61      * The name of the block to be displayed in the block title area if the title is empty.
  62      * @var string arialabel
  63      */
  64     var $arialabel         = NULL;
  65
  66     /**
  67      * The type of content that this block creates. Currently support options - BLOCK_TYPE_LIST, BLOCK_TYPE_TEXT
  68      * @var int $content_type
  69      */
  70     var $content_type  = BLOCK_TYPE_TEXT;
  71
  72     /**
  73      * An object to contain the information to be displayed in the block.
  74      * @var stdObject $content
  75      */
  76     var $content       = NULL;
  77
  78     /**
  79      * The initialized instance of this block object.
  80      * @var block $instance
  81      */
  82     var $instance      = NULL;
  83
  84     /**
  85      * The page that this block is appearing on.
  86      * @var moodle_page
  87      */
  88     public $page       = NULL;
  89
  90     /**
  91      * This blocks's context.
  92      * @var stdClass
  93      */
  94     public $context    = NULL;
  95
  96     /**
  97      * An object containing the instance configuration information for the current instance of this block.
  98      * @var stdObject $config
  99      */
 100     var $config        = NULL;
 101
 102     /**
 103      * How often the cronjob should run, 0 if not at all.
 104      * @var int $cron
 105      */
 106
 107     var $cron          = NULL;
 108
 109 /// Class Functions
 110
 111     /**
 112      * Fake constructor to keep PHP5 happy
 113      *
 114      */
 115     function __construct() {
 116         $this->init();
 117     }
 118
 119     /**
 120      * Function that can be overridden to do extra cleanup before
 121      * the database tables are deleted. (Called once per block, not per instance!)
 122      */
 123     function before_delete() {
 124     }
 125
 126     /**
 127      * Returns the block name, as present in the class name,
 128      * the database, the block directory, etc etc.
 129      *
 130      * @return string
 131      */
 132     function name() {
 133         // Returns the block name, as present in the class name,
 134         // the database, the block directory, etc etc.
 135         static $myname;
 136         if ($myname === NULL) {
 137             $myname = strtolower(get_class($this));
 138             $myname = substr($myname, strpos($myname, '_') + 1);
 139         }
 140         return $myname;
 141     }
 142
 143     /**
 144      * Parent class version of this function simply returns NULL
 145      * This should be implemented by the derived class to return
 146      * the content object.
 147      *
 148      * @return stdObject
 149      */
 150     function get_content() {
 151         // This should be implemented by the derived class.
 152         return NULL;
 153     }
 154
 155     /**
 156      * Returns the class $title var value.
 157      *
 158      * Intentionally doesn't check if a title is set.
 159      * This is already done in {@link _self_test()}
 160      *
 161      * @return string $this->title
 162      */
 163     function get_title() {
 164         // Intentionally doesn't check if a title is set. This is already done in _self_test()
 165         return $this->title;
 166     }
 167
 168     /**
 169      * Returns the class $content_type var value.
 170      *
 171      * Intentionally doesn't check if content_type is set.
 172      * This is already done in {@link _self_test()}
 173      *
 174      * @return string $this->content_type
 175      */
 176     function get_content_type() {
 177         // Intentionally doesn't check if a content_type is set. This is already done in _self_test()
 178         return $this->content_type;
 179     }
 180
 181     /**
 182      * Returns true or false, depending on whether this block has any content to display
 183      * and whether the user has permission to view the block
 184      *
 185      * @return boolean
 186      */
 187     function is_empty() {
 188         if ( !has_capability('moodle/block:view', $this->context) ) {
 189             return true;
 190         }
 191
 192         $this->get_content();
 193         return(empty($this->content->text) && empty($this->content->footer));
 194     }
 195
 196     /**
 197      * First sets the current value of $this->content to NULL
 198      * then calls the block's {@link get_content()} function
 199      * to set its value back.
 200      *
 201      * @return stdObject
 202      */
 203     function refresh_content() {
 204         // Nothing special here, depends on content()
 205         $this->content = NULL;
 206         return $this->get_content();
 207     }
 208
 209     /**
 210      * Return a block_contents object representing the full contents of this block.
 211      *
 212      * This internally calls ->get_content(), and then adds the editing controls etc.
 213      *
 214      * You probably should not override this method, but instead override
 215      * {@link html_attributes()}, {@link formatted_contents()} or {@link get_content()},
 216      * {@link hide_header()}, {@link (get_edit_controls)}, etc.
 217      *
 218      * @return block_contents a representation of the block, for rendering.
 219      * @since Moodle 2.0.
 220      */
 221     public function get_content_for_output($output) {
 222         global $CFG;
 223
 224         $bc = new block_contents($this->html_attributes());
 225         $bc->attributes['data-block'] = $this->name();
 226         $bc->blockinstanceid = $this->instance->id;
 227         $bc->blockpositionid = $this->instance->blockpositionid;
 228
 229         if ($this->instance->visible) {
 230             $bc->content = $this->formatted_contents($output);
 231             if (!empty($this->content->footer)) {
 232                 $bc->footer = $this->content->footer;
 233             }
 234         } else {
 235             $bc->add_class('invisibleblock');
 236         }
 237
 238         if (!$this->hide_header()) {
 239             $bc->title = $this->title;
 240         }
 241
 242         if (empty($bc->title)) {
 243             $bc->arialabel = new lang_string('pluginname', get_class($this));
 244             $this->arialabel = $bc->arialabel;
 245         }
 246
 247         if ($this->page->user_is_editing()) {
 248             $bc->controls = $this->page->blocks->edit_controls($this);
 249         } else {
 250             // we must not use is_empty on hidden blocks
 251             if ($this->is_empty() && !$bc->controls) {
 252                 return null;
 253             }
 254         }
 255
 256         if (empty($CFG->allowuserblockhiding)
 257                 || (empty($bc->content) && empty($bc->footer))
 258                 || !$this->instance_can_be_collapsed()) {
 259             $bc->collapsible = block_contents::NOT_HIDEABLE;
 260         } else if (get_user_preferences('block' . $bc->blockinstanceid . 'hidden', false)) {
 261             $bc->collapsible = block_contents::HIDDEN;
 262         } else {
 263             $bc->collapsible = block_contents::VISIBLE;
 264         }
 265
 266         if ($this->instance_can_be_docked() && !$this->hide_header()) {
 267             $bc->dockable = true;
 268         }
 269
 270         $bc->annotation = ''; // TODO MDL-19398 need to work out what to say here.
 271
 272         return $bc;
 273     }
 274
 275
 276     /**
 277      * Return an object containing all the block content to be returned by external functions.
 278      *
 279      * If your block is returning formatted content or provide files for download, you should override this method to use the
 280      * external_format_text, external_format_string functions for formatting or external_util::get_area_files for files.
 281      *
 282      * @param  core_renderer $output the rendered used for output
 283      * @return stdClass      object containing the block title, central content, footer and linked files (if any).
 284      * @since  Moodle 3.6
 285      */
 286     public function get_content_for_external($output) {
 287         $bc = new stdClass;
 288         $bc->title = null;
 289         $bc->content = null;
 290         $bc->contentformat = FORMAT_HTML;
 291         $bc->footer = null;
 292         $bc->files = [];
 293
 294         if ($this->instance->visible) {
 295             $bc->content = $this->formatted_contents($output);
 296             if (!empty($this->content->footer)) {
 297                 $bc->footer = $this->content->footer;
 298             }
 299         }
 300
 301         if (!$this->hide_header()) {
 302             $bc->title = $this->title;
 303         }
 304
 305         return $bc;
 306     }
 307
 308     /**
 309      * Convert the contents of the block to HTML.
 310      *
 311      * This is used by block base classes like block_list to convert the structured
 312      * $this->content->list and $this->content->icons arrays to HTML. So, in most
 313      * blocks, you probaby want to override the {@link get_contents()} method,
 314      * which generates that structured representation of the contents.
 315      *
 316      * @param $output The core_renderer to use when generating the output.
 317      * @return string the HTML that should appearn in the body of the block.
 318      * @since Moodle 2.0.
 319      */
 320     protected function formatted_contents($output) {
 321         $this->get_content();
 322         $this->get_required_javascript();
 323         if (!empty($this->content->text)) {
 324             return $this->content->text;
 325         } else {
 326             return '';
 327         }
 328     }
 329
 330     /**
 331      * Tests if this block has been implemented correctly.
 332      * Also, $errors isn't used right now
 333      *
 334      * @return boolean
 335      */
 336
 337     function _self_test() {
 338         // Tests if this block has been implemented correctly.
 339         // Also, $errors isn't used right now
 340         $errors = array();
 341
 342         $correct = true;
 343         if ($this->get_title() === NULL) {
 344             $errors[] = 'title_not_set';
 345             $correct = false;
 346         }
 347         if (!in_array($this->get_content_type(), array(BLOCK_TYPE_LIST, BLOCK_TYPE_TEXT, BLOCK_TYPE_TREE))) {
 348             $errors[] = 'invalid_content_type';
 349             $correct = false;
 350         }
 351         //following selftest was not working when roles&capabilities were used from block
 352 /*        if ($this->get_content() === NULL) {
 353             $errors[] = 'content_not_set';
 354             $correct = false;
 355         }*/
 356         $formats = $this->applicable_formats();
 357         if (empty($formats) || array_sum($formats) === 0) {
 358             $errors[] = 'no_formats';
 359             $correct = false;
 360         }
 361
 362         return $correct;
 363     }
 364
 365     /**
 366      * Subclasses should override this and return true if the
 367      * subclass block has a settings.php file.
 368      *
 369      * @return boolean
 370      */
 371     function has_config() {
 372         return false;
 373     }
 374
 375     /**
 376      * Default behavior: save all variables as $CFG properties
 377      * You don't need to override this if you 're satisfied with the above
 378      *
 379      * @deprecated since Moodle 2.9 MDL-49385 - Please use Admin Settings functionality to save block configuration.
 380      */
 381     function config_save($data) {
 382         throw new coding_exception('config_save() can not be used any more, use Admin Settings functionality to save block configuration.');
 383     }
 384
 385     /**
 386      * Which page types this block may appear on.
 387      *
 388      * The information returned here is processed by the
 389      * {@link blocks_name_allowed_in_format()} function. Look there if you need
 390      * to know exactly how this works.
 391      *
 392      * Default case: everything except mod and tag.
 393      *
 394      * @return array page-type prefix => true/false.
 395      */
 396     function applicable_formats() {
 397         // Default case: the block can be used in courses and site index, but not in activities
 398         return array('all' => true, 'mod' => false, 'tag' => false);
 399     }
 400
 401
 402     /**
 403      * Default return is false - header will be shown
 404      * @return boolean
 405      */
 406     function hide_header() {
 407         return false;
 408     }
 409
 410     /**
 411      * Return any HTML attributes that you want added to the outer <div> that
 412      * of the block when it is output.
 413      *
 414      * Because of the way certain JS events are wired it is a good idea to ensure
 415      * that the default values here still get set.
 416      * I found the easiest way to do this and still set anything you want is to
 417      * override it within your block in the following way
 418      *
 419      * <code php>
 420      * function html_attributes() {
 421      *    $attributes = parent::html_attributes();
 422      *    $attributes['class'] .= ' mynewclass';
 423      *    return $attributes;
 424      * }
 425      * </code>
 426      *
 427      * @return array attribute name => value.
 428      */
 429     function html_attributes() {
 430         $attributes = array(
 431             'id' => 'inst' . $this->instance->id,
 432             'class' => 'block_' . $this->name() . ' block',
 433             'role' => $this->get_aria_role()
 434         );
 435         if ($this->hide_header()) {
 436             $attributes['class'] .= ' no-header';
 437         }
 438         if ($this->instance_can_be_docked() && get_user_preferences('docked_block_instance_' . $this->instance->id, 0)) {
 439             $attributes['class'] .= ' dock_on_load';
 440         }
 441         return $attributes;
 442     }
 443
 444     /**
 445      * Set up a particular instance of this class given data from the block_insances
 446      * table and the current page. (See {@link block_manager::load_blocks()}.)
 447      *
 448      * @param stdClass $instance data from block_insances, block_positions, etc.
 449      * @param moodle_page $the page this block is on.
 450      */
 451     function _load_instance($instance, $page) {
 452         if (!empty($instance->configdata)) {
 453             $this->config = unserialize(base64_decode($instance->configdata));
 454         }
 455         $this->instance = $instance;
 456         $this->context = context_block::instance($instance->id);
 457         $this->page = $page;
 458         $this->specialization();
 459     }
 460
 461     /**
 462      * Allows the block to load any JS it requires into the page.
 463      *
 464      * By default this function simply permits the user to dock the block if it is dockable.
 465      */
 466     function get_required_javascript() {
 467         if ($this->instance_can_be_docked() && !$this->hide_header()) {
 468             user_preference_allow_ajax_update('docked_block_instance_'.$this->instance->id, PARAM_INT);
 469         }
 470     }
 471
 472     /**
 473      * This function is called on your subclass right after an instance is loaded
 474      * Use this function to act on instance data just after it's loaded and before anything else is done
 475      * For instance: if your block will have different title's depending on location (site, course, blog, etc)
 476      */
 477     function specialization() {
 478         // Just to make sure that this method exists.
 479     }
 480
 481     /**
 482      * Is each block of this type going to have instance-specific configuration?
 483      * Normally, this setting is controlled by {@link instance_allow_multiple()}: if multiple
 484      * instances are allowed, then each will surely need its own configuration. However, in some
 485      * cases it may be necessary to provide instance configuration to blocks that do not want to
 486      * allow multiple instances. In that case, make this function return true.
 487      * I stress again that this makes a difference ONLY if {@link instance_allow_multiple()} returns false.
 488      * @return boolean
 489      */
 490     function instance_allow_config() {
 491         return false;
 492     }
 493
 494     /**
 495      * Are you going to allow multiple instances of each block?
 496      * If yes, then it is assumed that the block WILL USE per-instance configuration
 497      * @return boolean
 498      */
 499     function instance_allow_multiple() {
 500         // Are you going to allow multiple instances of each block?
 501         // If yes, then it is assumed that the block WILL USE per-instance configuration
 502         return false;
 503     }
 504
 505     /**
 506      * Serialize and store config data
 507      */
 508     function instance_config_save($data, $nolongerused = false) {
 509         global $DB;
 510         $DB->update_record('block_instances', ['id' => $this->instance->id,
 511                 'configdata' => base64_encode(serialize($data)), 'timemodified' => time()]);
 512     }
 513
 514     /**
 515      * Replace the instance's configuration data with those currently in $this->config;
 516      */
 517     function instance_config_commit($nolongerused = false) {
 518         global $DB;
 519         $this->instance_config_save($this->config);
 520     }
 521
 522     /**
 523      * Do any additional initialization you may need at the time a new block instance is created
 524      * @return boolean
 525      */
 526     function instance_create() {
 527         return true;
 528     }
 529
 530     /**
 531      * Copy any block-specific data when copying to a new block instance.
 532      * @param int $fromid the id number of the block instance to copy from
 533      * @return boolean
 534      */
 535     public function instance_copy($fromid) {
 536         return true;
 537     }
 538
 539     /**
 540      * Delete everything related to this instance if you have been using persistent storage other than the configdata field.
 541      * @return boolean
 542      */
 543     function instance_delete() {
 544         return true;
 545     }
 546
 547     /**
 548      * Allows the block class to have a say in the user's ability to edit (i.e., configure) blocks of this type.
 549      * The framework has first say in whether this will be allowed (e.g., no editing allowed unless in edit mode)
 550      * but if the framework does allow it, the block can still decide to refuse.
 551      * @return boolean
 552      */
 553     function user_can_edit() {
 554         global $USER;
 555
 556         if (has_capability('moodle/block:edit', $this->context)) {
 557             return true;
 558         }
 559
 560         // The blocks in My Moodle are a special case.  We want them to inherit from the user context.
 561         if (!empty($USER->id)
 562             && $this->instance->parentcontextid == $this->page->context->id   // Block belongs to this page
 563             && $this->page->context->contextlevel == CONTEXT_USER             // Page belongs to a user
 564             && $this->page->context->instanceid == $USER->id) {               // Page belongs to this user
 565             return has_capability('moodle/my:manageblocks', $this->page->context);
 566         }
 567
 568         return false;
 569     }
 570
 571     /**
 572      * Allows the block class to have a say in the user's ability to create new instances of this block.
 573      * The framework has first say in whether this will be allowed (e.g., no adding allowed unless in edit mode)
 574      * but if the framework does allow it, the block can still decide to refuse.
 575      * This function has access to the complete page object, the creation related to which is being determined.
 576      *
 577      * @param moodle_page $page
 578      * @return boolean
 579      */
 580     function user_can_addto($page) {
 581         global $USER;
 582
 583         // The blocks in My Moodle are a special case and use a different capability.
 584         if (!empty($USER->id)
 585             && $page->context->contextlevel == CONTEXT_USER // Page belongs to a user
 586             && $page->context->instanceid == $USER->id // Page belongs to this user
 587             && $page->pagetype == 'my-index') { // Ensure we are on the My Moodle page
 588
 589             // If the block cannot be displayed on /my it is ok if the myaddinstance capability is not defined.
 590             $formats = $this->applicable_formats();
 591             // Is 'my' explicitly forbidden?
 592             // If 'all' has not been allowed, has 'my' been explicitly allowed?
 593             if ((isset($formats['my']) && $formats['my'] == false)
 594                 || (empty($formats['all']) && empty($formats['my']))) {
 595
 596                 // Block cannot be added to /my regardless of capabilities.
 597                 return false;
 598             } else {
 599                 $capability = 'block/' . $this->name() . ':myaddinstance';
 600                 return $this->has_add_block_capability($page, $capability)
 601                        && has_capability('moodle/my:manageblocks', $page->context);
 602             }
 603         }
 604
 605         $capability = 'block/' . $this->name() . ':addinstance';
 606         if ($this->has_add_block_capability($page, $capability)
 607                 && has_capability('moodle/block:edit', $page->context)) {
 608             return true;
 609         }
 610
 611         return false;
 612     }
 613
 614     /**
 615      * Returns true if the user can add a block to a page.
 616      *
 617      * @param moodle_page $page
 618      * @param string $capability the capability to check
 619      * @return boolean true if user can add a block, false otherwise.
 620      */
 621     private function has_add_block_capability($page, $capability) {
 622         // Check if the capability exists.
 623         if (!get_capability_info($capability)) {
 624             // Debug warning that the capability does not exist, but no more than once per page.
 625             static $warned = array();
 626             if (!isset($warned[$this->name()])) {
 627                 debugging('The block ' .$this->name() . ' does not define the standard capability ' .
 628                         $capability , DEBUG_DEVELOPER);
 629                 $warned[$this->name()] = 1;
 630             }
 631             // If the capability does not exist, the block can always be added.
 632             return true;
 633         } else {
 634             return has_capability($capability, $page->context);
 635         }
 636     }
 637
 638     static function get_extra_capabilities() {
 639         return array('moodle/block:view', 'moodle/block:edit');
 640     }
 641
 642     /**
 643      * Can be overridden by the block to prevent the block from being dockable.
 644      *
 645      * @return bool
 646      */
 647     public function instance_can_be_docked() {
 648         global $CFG;
 649         return (!empty($CFG->allowblockstodock) && $this->page->theme->enable_dock);
 650     }
 651
 652     /**
 653      * If overridden and set to false by the block it will not be hidable when
 654      * editing is turned on.
 655      *
 656      * @return bool
 657      */
 658     public function instance_can_be_hidden() {
 659         return true;
 660     }
 661
 662     /**
 663      * If overridden and set to false by the block it will not be collapsible.
 664      *
 665      * @return bool
 666      */
 667     public function instance_can_be_collapsed() {
 668         return true;
 669     }
 670
 671     /** @callback callback functions for comments api */
 672     public static function comment_template($options) {
 673         $ret = <<<EOD
 674 <div class="comment-userpicture">___picture___</div>
 675 <div class="comment-content">
 676     ___name___ - <span>___time___</span>
 677     <div>___content___</div>
 678 </div>
 679 EOD;
 680         return $ret;
 681     }
 682     public static function comment_permissions($options) {
 683         return array('view'=>true, 'post'=>true);
 684     }
 685     public static function comment_url($options) {
 686         return null;
 687     }
 688     public static function comment_display($comments, $options) {
 689         return $comments;
 690     }
 691     public static function comment_add(&$comments, $options) {
 692         return true;
 693     }
 694
 695     /**
 696      * Returns the aria role attribute that best describes this block.
 697      *
 698      * Region is the default, but this should be overridden by a block is there is a region child, or even better
 699      * a landmark child.
 700      *
 701      * Options are as follows:
 702      *    - landmark
 703      *      - application
 704      *      - banner
 705      *      - complementary
 706      *      - contentinfo
 707      *      - form
 708      *      - main
 709      *      - navigation
 710      *      - search
 711      *
 712      * @return string
 713      */
 714     public function get_aria_role() {
 715         return 'complementary';
 716     }
 717 }
 718
 719 /**
 720  * Specialized class for displaying a block with a list of icons/text labels
 721  *
 722  * The get_content method should set $this->content->items and (optionally)
 723  * $this->content->icons, instead of $this->content->text.
 724  *
 725  * @author Jon Papaioannou
 726  * @package core_block
 727  */
 728
 729 class block_list extends block_base {
 730     var $content_type  = BLOCK_TYPE_LIST;
 731
 732     function is_empty() {
 733         if ( !has_capability('moodle/block:view', $this->context) ) {
 734             return true;
 735         }
 736
 737         $this->get_content();
 738         return (empty($this->content->items) && empty($this->content->footer));
 739     }
 740
 741     protected function formatted_contents($output) {
 742         $this->get_content();
 743         $this->get_required_javascript();
 744         if (!empty($this->content->items)) {
 745             return $output->list_block_contents($this->content->icons, $this->content->items);
 746         } else {
 747             return '';
 748         }
 749     }
 750
 751     function html_attributes() {
 752         $attributes = parent::html_attributes();
 753         $attributes['class'] .= ' list_block';
 754         return $attributes;
 755     }
 756
 757 }
 758
 759 /**
 760  * Specialized class for displaying a tree menu.
 761  *
 762  * The {@link get_content()} method involves setting the content of
 763  * <code>$this->content->items</code> with an array of {@link tree_item}
 764  * objects (these are the top-level nodes). The {@link tree_item::children}
 765  * property may contain more tree_item objects, and so on. The tree_item class
 766  * itself is abstract and not intended for use, use one of it's subclasses.
 767  *
 768  * Unlike {@link block_list}, the icons are specified as part of the items,
 769  * not in a separate array.
 770  *
 771  * @author Alan Trick
 772  * @package core_block
 773  * @internal this extends block_list so we get is_empty() for free
 774  */
 775 class block_tree extends block_list {
 776
 777     /**
 778      * @var int specifies the manner in which contents should be added to this
 779      * block type. In this case <code>$this->content->items</code> is used with
 780      * {@link tree_item}s.
 781      */
 782     public $content_type = BLOCK_TYPE_TREE;
 783
 784     /**
 785      * Make the formatted HTML ouput.
 786      *
 787      * Also adds the required javascript call to the page output.
 788      *
 789      * @param core_renderer $output
 790      * @return string HTML
 791      */
 792     protected function formatted_contents($output) {
 793         // based of code in admin_tree
 794         global $PAGE; // TODO change this when there is a proper way for blocks to get stuff into head.
 795         static $eventattached;
 796         if ($eventattached===null) {
 797             $eventattached = true;
 798         }
 799         if (!$this->content) {
 800             $this->content = new stdClass;
 801             $this->content->items = array();
 802         }
 803         $this->get_required_javascript();
 804         $this->get_content();
 805         $content = $output->tree_block_contents($this->content->items,array('class'=>'block_tree list'));
 806         if (isset($this->id) && !is_numeric($this->id)) {
 807             $content = $output->box($content, 'block_tree_box', $this->id);
 808         }
 809         return $content;
 810     }
 811 }