blocks/moodleblock.class.php

   1 <?php
   2
   3 // This file is part of Moodle - http://moodle.org/
   4 //
   5 // Moodle is free software: you can redistribute it and/or modify
   6 // it under the terms of the GNU General Public License as published by
   7 // the Free Software Foundation, either version 3 of the License, or
   8 // (at your option) any later version.
   9 //
  10 // Moodle is distributed in the hope that it will be useful,
  11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
  12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13 // GNU General Public License for more details.
  14 //
  15 // You should have received a copy of the GNU General Public License
  16 // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  17
  18 /**
  19  * This file contains the parent class for moodle blocks, block_base.
  20  *
  21  * @package    core
  22  * @subpackage block
  23  * @license    http://www.gnu.org/copyleft/gpl.html GNU Public License
  24  */
  25
  26 /// Constants
  27
  28 /**
  29  * 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 $this->content->footer.
  30  */
  31 define('BLOCK_TYPE_LIST',    1);
  32
  33 /**
  34  * Block type of text. Contents of block should be set to standard html text in the content object as items ($this->content->text). Optionally include footer text in $this->content->footer.
  35  */
  36 define('BLOCK_TYPE_TEXT',    2);
  37 /**
  38  * Block type of tree. $this->content->items is a list of tree_item objects and $this->content->footer is a string.
  39  */
  40 define('BLOCK_TYPE_TREE',    3);
  41
  42 /**
  43  * Class for describing a moodle block, all Moodle blocks derive from this class
  44  *
  45  * @author Jon Papaioannou
  46  * @package blocks
  47  */
  48 class block_base {
  49
  50     /**
  51      * Internal var for storing/caching translated strings
  52      * @var string $str
  53      */
  54     var $str;
  55
  56     /**
  57      * The title of the block to be displayed in the block title area.
  58      * @var string $title
  59      */
  60     var $title         = NULL;
  61
  62     /**
  63      * The name of the block to be displayed in the block title area if the title is empty.
  64      * @var string arialabel
  65      */
  66     var $arialabel         = NULL;
  67
  68     /**
  69      * The type of content that this block creates. Currently support options - BLOCK_TYPE_LIST, BLOCK_TYPE_TEXT
  70      * @var int $content_type
  71      */
  72     var $content_type  = BLOCK_TYPE_TEXT;
  73
  74     /**
  75      * An object to contain the information to be displayed in the block.
  76      * @var stdObject $content
  77      */
  78     var $content       = NULL;
  79
  80     /**
  81      * A string generated by {@link _add_edit_controls()} to display block manipulation links when the user is in editing mode.
  82      * @var string $edit_controls
  83      */
  84     var $edit_controls = NULL;
  85
  86     /**
  87      * The initialized instance of this block object.
  88      * @var block $instance
  89      */
  90     var $instance      = NULL;
  91
  92     /**
  93      * The page that this block is appearing on.
  94      * @var moodle_page
  95      */
  96     public $page       = NULL;
  97
  98     /**
  99      * This blocks's context.
 100      * @var stdClass
 101      */
 102     public $context    = NULL;
 103
 104     /**
 105      * An object containing the instance configuration information for the current instance of this block.
 106      * @var stdObject $config
 107      */
 108     var $config        = NULL;
 109
 110     /**
 111      * How often the cronjob should run, 0 if not at all.
 112      * @var int $cron
 113      */
 114
 115     var $cron          = NULL;
 116
 117 /// Class Functions
 118
 119     /**
 120      * Fake constructor to keep PHP5 happy
 121      *
 122      */
 123     function __construct() {
 124         $this->init();
 125     }
 126
 127     /**
 128      * Function that can be overridden to do extra cleanup before
 129      * the database tables are deleted. (Called once per block, not per instance!)
 130      */
 131     function before_delete() {
 132     }
 133
 134     /**
 135      * Returns the block name, as present in the class name,
 136      * the database, the block directory, etc etc.
 137      *
 138      * @return string
 139      */
 140     function name() {
 141         // Returns the block name, as present in the class name,
 142         // the database, the block directory, etc etc.
 143         static $myname;
 144         if ($myname === NULL) {
 145             $myname = strtolower(get_class($this));
 146             $myname = substr($myname, strpos($myname, '_') + 1);
 147         }
 148         return $myname;
 149     }
 150
 151     /**
 152      * Parent class version of this function simply returns NULL
 153      * This should be implemented by the derived class to return
 154      * the content object.
 155      *
 156      * @return stdObject
 157      */
 158     function get_content() {
 159         // This should be implemented by the derived class.
 160         return NULL;
 161     }
 162
 163     /**
 164      * Returns the class $title var value.
 165      *
 166      * Intentionally doesn't check if a title is set.
 167      * This is already done in {@link _self_test()}
 168      *
 169      * @return string $this->title
 170      */
 171     function get_title() {
 172         // Intentionally doesn't check if a title is set. This is already done in _self_test()
 173         return $this->title;
 174     }
 175
 176     /**
 177      * Returns the class $content_type var value.
 178      *
 179      * Intentionally doesn't check if content_type is set.
 180      * This is already done in {@link _self_test()}
 181      *
 182      * @return string $this->content_type
 183      */
 184     function get_content_type() {
 185         // Intentionally doesn't check if a content_type is set. This is already done in _self_test()
 186         return $this->content_type;
 187     }
 188
 189     /**
 190      * Returns true or false, depending on whether this block has any content to display
 191      * and whether the user has permission to view the block
 192      *
 193      * @return boolean
 194      */
 195     function is_empty() {
 196         if ( !has_capability('moodle/block:view', $this->context) ) {
 197             return true;
 198         }
 199
 200         $this->get_content();
 201         return(empty($this->content->text) && empty($this->content->footer));
 202     }
 203
 204     /**
 205      * First sets the current value of $this->content to NULL
 206      * then calls the block's {@link get_content()} function
 207      * to set its value back.
 208      *
 209      * @return stdObject
 210      */
 211     function refresh_content() {
 212         // Nothing special here, depends on content()
 213         $this->content = NULL;
 214         return $this->get_content();
 215     }
 216
 217     /**
 218      * Return a block_contents object representing the full contents of this block.
 219      *
 220      * This internally calls ->get_content(), and then adds the editing controls etc.
 221      *
 222      * You probably should not override this method, but instead override
 223      * {@link html_attributes()}, {@link formatted_contents()} or {@link get_content()},
 224      * {@link hide_header()}, {@link (get_edit_controls)}, etc.
 225      *
 226      * @return block_contents a representation of the block, for rendering.
 227      * @since Moodle 2.0.
 228      */
 229     public function get_content_for_output($output) {
 230         global $CFG;
 231
 232         $bc = new block_contents($this->html_attributes());
 233         $bc->attributes['data-block'] = $this->name();
 234         $bc->blockinstanceid = $this->instance->id;
 235         $bc->blockpositionid = $this->instance->blockpositionid;
 236
 237         if ($this->instance->visible) {
 238             $bc->content = $this->formatted_contents($output);
 239             if (!empty($this->content->footer)) {
 240                 $bc->footer = $this->content->footer;
 241             }
 242         } else {
 243             $bc->add_class('invisible');
 244         }
 245
 246         if (!$this->hide_header()) {
 247             $bc->title = $this->title;
 248         }
 249
 250         if (empty($bc->title)) {
 251             $bc->arialabel = new lang_string('pluginname', get_class($this));
 252             $this->arialabel = $bc->arialabel;
 253         }
 254
 255         if ($this->page->user_is_editing()) {
 256             $bc->controls = $this->page->blocks->edit_controls($this);
 257         } else {
 258             // we must not use is_empty on hidden blocks
 259             if ($this->is_empty() && !$bc->controls) {
 260                 return null;
 261             }
 262         }
 263
 264         if (empty($CFG->allowuserblockhiding)
 265                 || (empty($bc->content) && empty($bc->footer))
 266                 || !$this->instance_can_be_collapsed()) {
 267             $bc->collapsible = block_contents::NOT_HIDEABLE;
 268         } else if (get_user_preferences('block' . $bc->blockinstanceid . 'hidden', false)) {
 269             $bc->collapsible = block_contents::HIDDEN;
 270         } else {
 271             $bc->collapsible = block_contents::VISIBLE;
 272         }
 273
 274         if ($this->instance_can_be_docked() && !$this->hide_header()) {
 275             $bc->dockable = true;
 276         }
 277
 278         $bc->annotation = ''; // TODO MDL-19398 need to work out what to say here.
 279
 280         return $bc;
 281     }
 282
 283     /**
 284      * Convert the contents of the block to HTML.
 285      *
 286      * This is used by block base classes like block_list to convert the structured
 287      * $this->content->list and $this->content->icons arrays to HTML. So, in most
 288      * blocks, you probaby want to override the {@link get_contents()} method,
 289      * which generates that structured representation of the contents.
 290      *
 291      * @param $output The core_renderer to use when generating the output.
 292      * @return string the HTML that should appearn in the body of the block.
 293      * @since Moodle 2.0.
 294      */
 295     protected function formatted_contents($output) {
 296         $this->get_content();
 297         $this->get_required_javascript();
 298         if (!empty($this->content->text)) {
 299             return $this->content->text;
 300         } else {
 301             return '';
 302         }
 303     }
 304
 305     /**
 306      * Tests if this block has been implemented correctly.
 307      * Also, $errors isn't used right now
 308      *
 309      * @return boolean
 310      */
 311
 312     function _self_test() {
 313         // Tests if this block has been implemented correctly.
 314         // Also, $errors isn't used right now
 315         $errors = array();
 316
 317         $correct = true;
 318         if ($this->get_title() === NULL) {
 319             $errors[] = 'title_not_set';
 320             $correct = false;
 321         }
 322         if (!in_array($this->get_content_type(), array(BLOCK_TYPE_LIST, BLOCK_TYPE_TEXT, BLOCK_TYPE_TREE))) {
 323             $errors[] = 'invalid_content_type';
 324             $correct = false;
 325         }
 326         //following selftest was not working when roles&capabilities were used from block
 327 /*        if ($this->get_content() === NULL) {
 328             $errors[] = 'content_not_set';
 329             $correct = false;
 330         }*/
 331         $formats = $this->applicable_formats();
 332         if (empty($formats) || array_sum($formats) === 0) {
 333             $errors[] = 'no_formats';
 334             $correct = false;
 335         }
 336
 337         $width = $this->preferred_width();
 338         if (!is_int($width) || $width <= 0) {
 339             $errors[] = 'invalid_width';
 340             $correct = false;
 341         }
 342         return $correct;
 343     }
 344
 345     /**
 346      * Subclasses should override this and return true if the
 347      * subclass block has a settings.php file.
 348      *
 349      * @return boolean
 350      */
 351     function has_config() {
 352         return false;
 353     }
 354
 355     /**
 356      * Default behavior: save all variables as $CFG properties
 357      * You don't need to override this if you 're satisfied with the above
 358      *
 359      * @param array $data
 360      * @return boolean
 361      */
 362     function config_save($data) {
 363         foreach ($data as $name => $value) {
 364             set_config($name, $value);
 365         }
 366         return true;
 367     }
 368
 369     /**
 370      * Which page types this block may appear on.
 371      *
 372      * The information returned here is processed by the
 373      * {@link blocks_name_allowed_in_format()} function. Look there if you need
 374      * to know exactly how this works.
 375      *
 376      * Default case: everything except mod and tag.
 377      *
 378      * @return array page-type prefix => true/false.
 379      */
 380     function applicable_formats() {
 381         // Default case: the block can be used in courses and site index, but not in activities
 382         return array('all' => true, 'mod' => false, 'tag' => false);
 383     }
 384
 385
 386     /**
 387      * Default return is false - header will be shown
 388      * @return boolean
 389      */
 390     function hide_header() {
 391         return false;
 392     }
 393
 394     /**
 395      * Return any HTML attributes that you want added to the outer <div> that
 396      * of the block when it is output.
 397      *
 398      * Because of the way certain JS events are wired it is a good idea to ensure
 399      * that the default values here still get set.
 400      * I found the easiest way to do this and still set anything you want is to
 401      * override it within your block in the following way
 402      *
 403      * <code php>
 404      * function html_attributes() {
 405      *    $attributes = parent::html_attributes();
 406      *    $attributes['class'] .= ' mynewclass';
 407      *    return $attributes;
 408      * }
 409      * </code>
 410      *
 411      * @return array attribute name => value.
 412      */
 413     function html_attributes() {
 414         $attributes = array(
 415             'id' => 'inst' . $this->instance->id,
 416             'class' => 'block_' . $this->name(). '  block',
 417             'role' => $this->get_aria_role()
 418         );
 419         if ($this->hide_header()) {
 420             $attributes['class'] .= ' no-header';
 421         }
 422         if ($this->instance_can_be_docked() && get_user_preferences('docked_block_instance_'.$this->instance->id, 0)) {
 423             $attributes['class'] .= ' dock_on_load';
 424         }
 425         return $attributes;
 426     }
 427
 428     /**
 429      * Set up a particular instance of this class given data from the block_insances
 430      * table and the current page. (See {@link block_manager::load_blocks()}.)
 431      *
 432      * @param stdClass $instance data from block_insances, block_positions, etc.
 433      * @param moodle_page $the page this block is on.
 434      */
 435     function _load_instance($instance, $page) {
 436         if (!empty($instance->configdata)) {
 437             $this->config = unserialize(base64_decode($instance->configdata));
 438         }
 439         $this->instance = $instance;
 440         $this->context = context_block::instance($instance->id);
 441         $this->page = $page;
 442         $this->specialization();
 443     }
 444
 445     /**
 446      * Allows the block to load any JS it requires into the page.
 447      *
 448      * By default this function simply permits the user to dock the block if it is dockable.
 449      */
 450     function get_required_javascript() {
 451         if ($this->instance_can_be_docked() && !$this->hide_header()) {
 452             user_preference_allow_ajax_update('docked_block_instance_'.$this->instance->id, PARAM_INT);
 453         }
 454     }
 455
 456     /**
 457      * This function is called on your subclass right after an instance is loaded
 458      * Use this function to act on instance data just after it's loaded and before anything else is done
 459      * For instance: if your block will have different title's depending on location (site, course, blog, etc)
 460      */
 461     function specialization() {
 462         // Just to make sure that this method exists.
 463     }
 464
 465     /**
 466      * Is each block of this type going to have instance-specific configuration?
 467      * Normally, this setting is controlled by {@link instance_allow_multiple()}: if multiple
 468      * instances are allowed, then each will surely need its own configuration. However, in some
 469      * cases it may be necessary to provide instance configuration to blocks that do not want to
 470      * allow multiple instances. In that case, make this function return true.
 471      * I stress again that this makes a difference ONLY if {@link instance_allow_multiple()} returns false.
 472      * @return boolean
 473      */
 474     function instance_allow_config() {
 475         return false;
 476     }
 477
 478     /**
 479      * Are you going to allow multiple instances of each block?
 480      * If yes, then it is assumed that the block WILL USE per-instance configuration
 481      * @return boolean
 482      */
 483     function instance_allow_multiple() {
 484         // Are you going to allow multiple instances of each block?
 485         // If yes, then it is assumed that the block WILL USE per-instance configuration
 486         return false;
 487     }
 488
 489     /**
 490      * Default behavior: print the config_instance.html file
 491      * You don't need to override this if you're satisfied with the above
 492      *
 493      * @deprecated since Moodle 2.0.
 494      * @return boolean whether anything was done. Blocks should use edit_form.php.
 495      */
 496     function instance_config_print() {
 497         global $CFG, $DB, $OUTPUT;
 498         // Default behavior: print the config_instance.html file
 499         // You don't need to override this if you're satisfied with the above
 500         if (!$this->instance_allow_multiple() && !$this->instance_allow_config()) {
 501             return false;
 502         }
 503
 504         if (is_file($CFG->dirroot .'/blocks/'. $this->name() .'/config_instance.html')) {
 505             echo $OUTPUT->box_start('generalbox boxaligncenter blockconfiginstance');
 506             include($CFG->dirroot .'/blocks/'. $this->name() .'/config_instance.html');
 507             echo $OUTPUT->box_end();
 508         } else {
 509             notice(get_string('blockconfigbad'), str_replace('blockaction=', 'dummy=', qualified_me()));
 510         }
 511
 512         return true;
 513     }
 514
 515     /**
 516      * Serialize and store config data
 517      */
 518     function instance_config_save($data, $nolongerused = false) {
 519         global $DB;
 520         $DB->set_field('block_instances', 'configdata', base64_encode(serialize($data)),
 521                 array('id' => $this->instance->id));
 522     }
 523
 524     /**
 525      * Replace the instance's configuration data with those currently in $this->config;
 526      */
 527     function instance_config_commit($nolongerused = false) {
 528         global $DB;
 529         $this->instance_config_save($this->config);
 530     }
 531
 532     /**
 533      * Do any additional initialization you may need at the time a new block instance is created
 534      * @return boolean
 535      */
 536     function instance_create() {
 537         return true;
 538     }
 539
 540     /**
 541      * Delete everything related to this instance if you have been using persistent storage other than the configdata field.
 542      * @return boolean
 543      */
 544     function instance_delete() {
 545         return true;
 546     }
 547
 548     /**
 549      * Allows the block class to have a say in the user's ability to edit (i.e., configure) blocks of this type.
 550      * The framework has first say in whether this will be allowed (e.g., no editing allowed unless in edit mode)
 551      * but if the framework does allow it, the block can still decide to refuse.
 552      * @return boolean
 553      */
 554     function user_can_edit() {
 555         global $USER;
 556
 557         if (has_capability('moodle/block:edit', $this->context)) {
 558             return true;
 559         }
 560
 561         // The blocks in My Moodle are a special case.  We want them to inherit from the user context.
 562         if (!empty($USER->id)
 563             && $this->instance->parentcontextid == $this->page->context->id   // Block belongs to this page
 564             && $this->page->context->contextlevel == CONTEXT_USER             // Page belongs to a user
 565             && $this->page->context->instanceid == $USER->id) {               // Page belongs to this user
 566             return has_capability('moodle/my:manageblocks', $this->page->context);
 567         }
 568
 569         return false;
 570     }
 571
 572     /**
 573      * Allows the block class to have a say in the user's ability to create new instances of this block.
 574      * The framework has first say in whether this will be allowed (e.g., no adding allowed unless in edit mode)
 575      * but if the framework does allow it, the block can still decide to refuse.
 576      * This function has access to the complete page object, the creation related to which is being determined.
 577      *
 578      * @param moodle_page $page
 579      * @return boolean
 580      */
 581     function user_can_addto($page) {
 582         global $USER;
 583
 584         // The blocks in My Moodle are a special case and use a different capability.
 585         if (!empty($USER->id)
 586             && $page->context->contextlevel == CONTEXT_USER // Page belongs to a user
 587             && $page->context->instanceid == $USER->id // Page belongs to this user
 588             && $page->pagetype == 'my-index') { // Ensure we are on the My Moodle page
 589             $capability = 'block/' . $this->name() . ':myaddinstance';
 590             return $this->has_add_block_capability($page, $capability)
 591                     && has_capability('moodle/my:manageblocks', $page->context);
 592         }
 593
 594         $capability = 'block/' . $this->name() . ':addinstance';
 595         if ($this->has_add_block_capability($page, $capability)
 596                 && has_capability('moodle/block:edit', $page->context)) {
 597             return true;
 598         }
 599
 600         return false;
 601     }
 602
 603     /**
 604      * Returns true if the user can add a block to a page.
 605      *
 606      * @param moodle_page $page
 607      * @param string $capability the capability to check
 608      * @return boolean true if user can add a block, false otherwise.
 609      */
 610     private function has_add_block_capability($page, $capability) {
 611         // Check if the capability exists.
 612         if (!get_capability_info($capability)) {
 613             // Debug warning that the capability does not exist, but no more than once per page.
 614             static $warned = array();
 615             if (!isset($warned[$this->name()])) {
 616                 debugging('The block ' .$this->name() . ' does not define the standard capability ' .
 617                         $capability , DEBUG_DEVELOPER);
 618                 $warned[$this->name()] = 1;
 619             }
 620             // If the capability does not exist, the block can always be added.
 621             return true;
 622         } else {
 623             return has_capability($capability, $page->context);
 624         }
 625     }
 626
 627     static function get_extra_capabilities() {
 628         return array('moodle/block:view', 'moodle/block:edit');
 629     }
 630
 631     // Methods deprecated in Moodle 2.0 ========================================
 632
 633     /**
 634      * Default case: the block wants to be 180 pixels wide
 635      * @deprecated since Moodle 2.0.
 636      * @return int
 637      */
 638     function preferred_width() {
 639         return 180;
 640     }
 641
 642     /** @deprecated since Moodle 2.0. */
 643     function _print_block() {
 644         throw new coding_exception('_print_block is no longer used. It was a private ' .
 645                 'method of the block class, only for use by the blocks system. You ' .
 646                 'should not have been calling it anyway.');
 647     }
 648
 649     /** @deprecated since Moodle 2.0. */
 650     function _print_shadow() {
 651         throw new coding_exception('_print_shadow is no longer used. It was a private ' .
 652                 'method of the block class, only for use by the blocks system. You ' .
 653                 'should not have been calling it anyway.');
 654     }
 655
 656     /** @deprecated since Moodle 2.0. */
 657     function _title_html() {
 658         throw new coding_exception('_title_html is no longer used. It was a private ' .
 659                 'method of the block class, only for use by the blocks system. You ' .
 660                 'should not have been calling it anyway.');
 661     }
 662
 663     /** @deprecated since Moodle 2.0. */
 664     function _add_edit_controls() {
 665         throw new coding_exception('_add_edit_controls is no longer used. It was a private ' .
 666                 'method of the block class, only for use by the blocks system. You ' .
 667                 'should not have been calling it anyway.');
 668     }
 669
 670     /** @deprecated since Moodle 2.0. */
 671     function config_print() {
 672         throw new coding_exception('config_print() can no longer be used. Blocks should use a settings.php file.');
 673     }
 674
 675     /**
 676      * Can be overridden by the block to prevent the block from being dockable.
 677      *
 678      * @return bool
 679      */
 680     public function instance_can_be_docked() {
 681         global $CFG;
 682         return (!empty($CFG->allowblockstodock) && $this->page->theme->enable_dock);
 683     }
 684
 685     /**
 686      * If overridden and set to false by the block it will not be hidable when
 687      * editing is turned on.
 688      *
 689      * @return bool
 690      */
 691     public function instance_can_be_hidden() {
 692         return true;
 693     }
 694
 695     /**
 696      * If overridden and set to false by the block it will not be collapsible.
 697      *
 698      * @return bool
 699      */
 700     public function instance_can_be_collapsed() {
 701         return true;
 702     }
 703
 704     /** @callback callback functions for comments api */
 705     public static function comment_template($options) {
 706         $ret = <<<EOD
 707 <div class="comment-userpicture">___picture___</div>
 708 <div class="comment-content">
 709     ___name___ - <span>___time___</span>
 710     <div>___content___</div>
 711 </div>
 712 EOD;
 713         return $ret;
 714     }
 715     public static function comment_permissions($options) {
 716         return array('view'=>true, 'post'=>true);
 717     }
 718     public static function comment_url($options) {
 719         return null;
 720     }
 721     public static function comment_display($comments, $options) {
 722         return $comments;
 723     }
 724     public static function comment_add(&$comments, $options) {
 725         return true;
 726     }
 727
 728     /**
 729      * Returns the aria role attribute that best describes this block.
 730      *
 731      * Region is the default, but this should be overridden by a block is there is a region child, or even better
 732      * a landmark child.
 733      *
 734      * Options are as follows:
 735      *    - landmark
 736      *      - application
 737      *      - banner
 738      *      - complementary
 739      *      - contentinfo
 740      *      - form
 741      *      - main
 742      *      - navigation
 743      *      - search
 744      *
 745      * @return string
 746      */
 747     public function get_aria_role() {
 748         return 'complementary';
 749     }
 750 }
 751
 752 /**
 753  * Specialized class for displaying a block with a list of icons/text labels
 754  *
 755  * The get_content method should set $this->content->items and (optionally)
 756  * $this->content->icons, instead of $this->content->text.
 757  *
 758  * @author Jon Papaioannou
 759  * @package blocks
 760  */
 761
 762 class block_list extends block_base {
 763     var $content_type  = BLOCK_TYPE_LIST;
 764
 765     function is_empty() {
 766         if ( !has_capability('moodle/block:view', $this->context) ) {
 767             return true;
 768         }
 769
 770         $this->get_content();
 771         return (empty($this->content->items) && empty($this->content->footer));
 772     }
 773
 774     protected function formatted_contents($output) {
 775         $this->get_content();
 776         $this->get_required_javascript();
 777         if (!empty($this->content->items)) {
 778             return $output->list_block_contents($this->content->icons, $this->content->items);
 779         } else {
 780             return '';
 781         }
 782     }
 783
 784     function html_attributes() {
 785         $attributes = parent::html_attributes();
 786         $attributes['class'] .= ' list_block';
 787         return $attributes;
 788     }
 789
 790 }
 791
 792 /**
 793  * Specialized class for displaying a tree menu.
 794  *
 795  * The {@link get_content()} method involves setting the content of
 796  * <code>$this->content->items</code> with an array of {@link tree_item}
 797  * objects (these are the top-level nodes). The {@link tree_item::children}
 798  * property may contain more tree_item objects, and so on. The tree_item class
 799  * itself is abstract and not intended for use, use one of it's subclasses.
 800  *
 801  * Unlike {@link block_list}, the icons are specified as part of the items,
 802  * not in a separate array.
 803  *
 804  * @author Alan Trick
 805  * @package blocks
 806  * @internal this extends block_list so we get is_empty() for free
 807  */
 808 class block_tree extends block_list {
 809
 810     /**
 811      * @var int specifies the manner in which contents should be added to this
 812      * block type. In this case <code>$this->content->items</code> is used with
 813      * {@link tree_item}s.
 814      */
 815     public $content_type = BLOCK_TYPE_TREE;
 816
 817     /**
 818      * Make the formatted HTML ouput.
 819      *
 820      * Also adds the required javascript call to the page output.
 821      *
 822      * @param core_renderer $output
 823      * @return string HTML
 824      */
 825     protected function formatted_contents($output) {
 826         // based of code in admin_tree
 827         global $PAGE; // TODO change this when there is a proper way for blocks to get stuff into head.
 828         static $eventattached;
 829         if ($eventattached===null) {
 830             $eventattached = true;
 831         }
 832         if (!$this->content) {
 833             $this->content = new stdClass;
 834             $this->content->items = array();
 835         }
 836         $this->get_required_javascript();
 837         $this->get_content();
 838         $content = $output->tree_block_contents($this->content->items,array('class'=>'block_tree list'));
 839         if (isset($this->id) && !is_numeric($this->id)) {
 840             $content = $output->box($content, 'block_tree_box', $this->id);
 841         }
 842         return $content;
 843     }
 844 }