includes/PageHistory.php

   1 <?php
   2 /**
   3  * Page history
   4  *
   5  * Split off from Article.php and Skin.php, 2003-12-22
   6  */
   7
   8 /**
   9  * This class handles printing the history page for an article.  In order to
  10  * be efficient, it uses timestamps rather than offsets for paging, to avoid
  11  * costly LIMIT,offset queries.
  12  *
  13  * Construct it by passing in an Article, and call $h->history() to print the
  14  * history.
  15  *
  16  */
  17 class PageHistory {
  18         const DIR_PREV = 0;
  19         const DIR_NEXT = 1;
  20
  21         var $mArticle, $mTitle, $mSkin;
  22         var $lastdate;
  23         var $linesonpage;
  24         var $mNotificationTimestamp;
  25         var $mLatestId = null;
  26
  27         /**
  28          * Construct a new PageHistory.
  29          *
  30          * @param Article $article
  31          * @returns nothing
  32          */
  33         function __construct($article) {
  34                 global $wgUser;
  35
  36                 $this->mArticle =& $article;
  37                 $this->mTitle =& $article->mTitle;
  38                 $this->mNotificationTimestamp = NULL;
  39                 $this->mSkin = $wgUser->getSkin();
  40                 $this->preCacheMessages();
  41         }
  42
  43         /**
  44          * As we use the same small set of messages in various methods and that
  45          * they are called often, we call them once and save them in $this->message
  46          */
  47         function preCacheMessages() {
  48                 // Precache various messages
  49                 if( !isset( $this->message ) ) {
  50                         foreach( explode(' ', 'cur last rev-delundel' ) as $msg ) {
  51                                 $this->message[$msg] = wfMsgExt( $msg, array( 'escape') );
  52                         }
  53                 }
  54         }
  55
  56         /**
  57          * Print the history page for an article.
  58          *
  59          * @returns nothing
  60          */
  61         function history() {
  62                 global $wgOut, $wgRequest, $wgTitle;
  63
  64                 /*
  65                  * Allow client caching.
  66                  */
  67
  68                 if( $wgOut->checkLastModified( $this->mArticle->getTouched() ) )
  69                         /* Client cache fresh and headers sent, nothing more to do. */
  70                         return;
  71
  72                 wfProfileIn( __METHOD__ );
  73
  74                 /*
  75                  * Setup page variables.
  76                  */
  77                 $wgOut->setPageTitle( wfMsg( 'history-title', $this->mTitle->getPrefixedText() ) );
  78                 $wgOut->setPageTitleActionText( wfMsg( 'history_short' ) );
  79                 $wgOut->setArticleFlag( false );
  80                 $wgOut->setArticleRelated( true );
  81                 $wgOut->setRobotpolicy( 'noindex,nofollow' );
  82                 $wgOut->setSyndicated( true );
  83                 $wgOut->setFeedAppendQuery( 'action=history' );
  84
  85                 $logPage = SpecialPage::getTitleFor( 'Log' );
  86                 $logLink = $this->mSkin->makeKnownLinkObj( $logPage, wfMsgHtml( 'viewpagelogs' ), 'page=' . $this->mTitle->getPrefixedUrl() );
  87                 $wgOut->setSubtitle( $logLink );
  88
  89                 $feedType = $wgRequest->getVal( 'feed' );
  90                 if( $feedType ) {
  91                         wfProfileOut( __METHOD__ );
  92                         return $this->feed( $feedType );
  93                 }
  94
  95                 /*
  96                  * Fail if article doesn't exist.
  97                  */
  98                 if( !$this->mTitle->exists() ) {
  99                         $wgOut->addWikiMsg( 'nohistory' );
 100                         wfProfileOut( __METHOD__ );
 101                         return;
 102                 }
 103
 104                 /*
 105                  * "go=first" means to jump to the last (earliest) history page.
 106                  * This is deprecated, it no longer appears in the user interface
 107                  */
 108                 if ( $wgRequest->getText("go") == 'first' ) {
 109                         $limit = $wgRequest->getInt( 'limit', 50 );
 110                         $wgOut->redirect( $wgTitle->getLocalURL( "action=history&limit={$limit}&dir=prev" ) );
 111                         return;
 112                 }
 113
 114                 wfRunHooks( 'PageHistoryBeforeList', array( &$this->mArticle ) );
 115
 116                 /**
 117                  * Do the list
 118                  */
 119                 $pager = new PageHistoryPager( $this );
 120                 $this->linesonpage = $pager->getNumRows();
 121                 $wgOut->addHTML(
 122                         $pager->getNavigationBar() .
 123                         $this->beginHistoryList() .
 124                         $pager->getBody() .
 125                         $this->endHistoryList() .
 126                         $pager->getNavigationBar()
 127                 );
 128                 wfProfileOut( __METHOD__ );
 129         }
 130
 131         /**
 132          * Creates begin of history list with a submit button
 133          *
 134          * @return string HTML output
 135          */
 136         function beginHistoryList() {
 137                 global $wgTitle;
 138                 $this->lastdate = '';
 139                 $s = wfMsgExt( 'histlegend', array( 'parse') );
 140                 $s .= '<form action="' . $wgTitle->escapeLocalURL( '-' ) . '" method="get">';
 141                 $prefixedkey = htmlspecialchars($wgTitle->getPrefixedDbKey());
 142
 143                 // The following line is SUPPOSED to have double-quotes around the
 144                 // $prefixedkey variable, because htmlspecialchars() doesn't escape
 145                 // single-quotes.
 146                 //
 147                 // On at least two occasions people have changed it to single-quotes,
 148                 // which creates invalid HTML and incorrect display of the resulting
 149                 // link.
 150                 //
 151                 // Please do not break this a third time. Thank you for your kind
 152                 // consideration and cooperation.
 153                 //
 154                 $s .= "<input type='hidden' name='title' value=\"{$prefixedkey}\" />\n";
 155
 156                 $s .= $this->submitButton();
 157                 $s .= '<ul id="pagehistory">' . "\n";
 158                 return $s;
 159         }
 160
 161         /**
 162          * Creates end of history list with a submit button
 163          *
 164          * @return string HTML output
 165          */
 166         function endHistoryList() {
 167                 $s = '</ul>';
 168                 $s .= $this->submitButton( array( 'id' => 'historysubmit' ) );
 169                 $s .= '</form>';
 170                 return $s;
 171         }
 172
 173         /**
 174          * Creates a submit button
 175          *
 176          * @param array $bits optional CSS ID
 177          * @return string HTML output for the submit button
 178          */
 179         function submitButton( $bits = array() ) {
 180                 # Disable submit button if history has 1 revision only
 181                 if ( $this->linesonpage > 1 ) {
 182                         return Xml::submitButton( wfMsg( 'compareselectedversions' ),
 183                                 $bits + array(
 184                                         'class'     => 'historysubmit',
 185                                         'accesskey' => wfMsg( 'accesskey-compareselectedversions' ),
 186                                         'title'     => wfMsg( 'tooltip-compareselectedversions' ),
 187                                         )
 188                                 );
 189                 } else {
 190                         return '';
 191                 }
 192         }
 193
 194         /**
 195          * Returns a row from the history printout.
 196          *
 197          * @todo document some more, and maybe clean up the code (some params redundant?)
 198          *
 199          * @param Row $row The database row corresponding to the previous line.
 200          * @param mixed $next The database row corresponding to the next line.
 201          * @param int $counter Apparently a counter of what row number we're at, counted from the top row = 1.
 202          * @param $notificationtimestamp
 203          * @param bool $latest Whether this row corresponds to the page's latest revision.
 204          * @param bool $firstInList Whether this row corresponds to the first displayed on this history page.
 205          * @return string HTML output for the row
 206          */
 207         function historyLine( $row, $next, $counter = '', $notificationtimestamp = false, $latest = false, $firstInList = false ) {
 208                 global $wgUser, $wgLang;
 209                 $rev = new Revision( $row );
 210                 $rev->setTitle( $this->mTitle );
 211
 212                 $s = '';
 213                 $curlink = $this->curLink( $rev, $latest );
 214                 $lastlink = $this->lastLink( $rev, $next, $counter );
 215                 $arbitrary = $this->diffButtons( $rev, $firstInList, $counter );
 216                 $link = $this->revLink( $rev );
 217
 218                 $s .= "($curlink) ($lastlink) $arbitrary";
 219
 220                 if( $wgUser->isAllowed( 'deleterevision' ) ) {
 221                         $revdel = SpecialPage::getTitleFor( 'Revisiondelete' );
 222                         if( $firstInList ) {
 223                         // We don't currently handle well changing the top revision's settings
 224                                 $del = $this->message['rev-delundel'];
 225                         } else if( !$rev->userCan( Revision::DELETED_RESTRICTED ) ) {
 226                         // If revision was hidden from sysops
 227                                 $del = $this->message['rev-delundel'];
 228                         } else {
 229                                 $del = $this->mSkin->makeKnownLinkObj( $revdel,
 230                                         $this->message['rev-delundel'],
 231                                         'target=' . urlencode( $this->mTitle->getPrefixedDbkey() ) .
 232                                         '&oldid=' . urlencode( $rev->getId() ) );
 233                                 // Bolden oversighted content
 234                                 if( $rev->isDeleted( Revision::DELETED_RESTRICTED ) )
 235                                         $del = "<strong>$del</strong>";
 236                         }
 237                         $s .= " <tt>(<small>$del</small>)</tt> ";
 238                 }
 239
 240                 $s .= " $link";
 241                 $s .= " <span class='history-user'>" . $this->mSkin->revUserTools( $rev, true ) . "</span>";
 242
 243                 if( $row->rev_minor_edit ) {
 244                         $s .= ' ' . Xml::element( 'span', array( 'class' => 'minor' ), wfMsg( 'minoreditletter') );
 245                 }
 246
 247                 if ( !is_null( $size = $rev->getSize() ) && $rev->userCan( Revision::DELETED_TEXT ) ) {
 248                         if ( $size == 0 )
 249                                 $stxt = wfMsgHtml( 'historyempty' );
 250                         else
 251                                 $stxt = wfMsgExt( 'historysize', array( 'parsemag' ), $wgLang->formatNum( $size ) );
 252                         $s .= " <span class=\"history-size\">$stxt</span>";
 253                 }
 254
 255                 $s .= $this->mSkin->revComment( $rev, false, true );
 256
 257                 if ($notificationtimestamp && ($row->rev_timestamp >= $notificationtimestamp)) {
 258                         $s .= ' <span class="updatedmarker">' .  wfMsgHtml( 'updatedmarker' ) . '</span>';
 259                 }
 260                 #add blurb about text having been deleted
 261                 if( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
 262                         $s .= ' <tt>' . wfMsgHtml( 'deletedrev' ) . '</tt>';
 263                 }
 264
 265                 $tools = array();
 266
 267                 if ( !is_null( $next ) && is_object( $next ) ) {
 268                         if( !$this->mTitle->getUserPermissionsErrors( 'rollback', $wgUser )
 269                         && !$this->mTitle->getUserPermissionsErrors( 'edit', $wgUser )
 270                         && $latest ) {
 271                                 $tools[] = '<span class="mw-rollback-link">'
 272                                         . $this->mSkin->buildRollbackLink( $rev )
 273                                         . '</span>';
 274                         }
 275
 276                         if( $this->mTitle->quickUserCan( 'edit' ) ) {
 277                                 $undolink = $this->mSkin->makeKnownLinkObj(
 278                                         $this->mTitle,
 279                                         wfMsgHtml( 'editundo' ),
 280                                         'action=edit&undoafter=' . $next->rev_id . '&undo=' . $rev->getId()
 281                                 );
 282                                 $tools[] = "<span class=\"mw-history-undo\">{$undolink}</span>";
 283                         }
 284                 }
 285
 286                 if( $tools ) {
 287                         $s .= ' (' . implode( ' | ', $tools ) . ')';
 288                 }
 289
 290                 wfRunHooks( 'PageHistoryLineEnding', array( &$row , &$s ) );
 291
 292                 return "<li>$s</li>\n";
 293         }
 294
 295         /**
 296         * Create a link to view this revision of the page
 297         * @param Revision $rev
 298         * @returns string
 299         */
 300         function revLink( $rev ) {
 301                 global $wgLang;
 302                 $date = $wgLang->timeanddate( wfTimestamp(TS_MW, $rev->getTimestamp()), true );
 303                 if( $rev->userCan( Revision::DELETED_TEXT ) ) {
 304                         $link = $this->mSkin->makeKnownLinkObj(
 305                                 $this->mTitle, $date, "oldid=" . $rev->getId() );
 306                 } else {
 307                         $link = $date;
 308                 }
 309                 if( $rev->isDeleted( Revision::DELETED_TEXT ) ) {
 310                         return '<span class="history-deleted">' . $link . '</span>';
 311                 }
 312                 return $link;
 313         }
 314
 315         /**
 316         * Create a diff-to-current link for this revision for this page
 317         * @param Revision $rev
 318         * @param Bool $latest, this is the latest revision of the page?
 319         * @returns string
 320         */
 321         function curLink( $rev, $latest ) {
 322                 $cur = $this->message['cur'];
 323                 if( $latest || !$rev->userCan( Revision::DELETED_TEXT ) ) {
 324                         return $cur;
 325                 } else {
 326                         return $this->mSkin->makeKnownLinkObj(
 327                                 $this->mTitle, $cur,
 328                                 'diff=' . $this->getLatestID() .
 329                                 "&oldid=" . $rev->getId() );
 330                 }
 331         }
 332
 333         /**
 334         * Create a diff-to-previous link for this revision for this page.
 335         * @param Revision $prevRev, the previous revision
 336         * @param mixed $next, the newer revision
 337         * @param int $counter, what row on the history list this is
 338         * @returns string
 339         */
 340         function lastLink( $prevRev, $next, $counter ) {
 341                 $last = $this->message['last'];
 342                 # $next may either be a Row, null, or "unkown"
 343                 $nextRev = is_object($next) ? new Revision( $next ) : $next;
 344                 if( is_null($next) ) {
 345                         # Probably no next row
 346                         return $last;
 347                 } elseif( $next === 'unknown' ) {
 348                         # Next row probably exists but is unknown, use an oldid=prev link
 349                         return $this->mSkin->makeKnownLinkObj(
 350                                 $this->mTitle,
 351                                 $last,
 352                                 "diff=" . $prevRev->getId() . "&oldid=prev" );
 353                 } elseif( !$prevRev->userCan(Revision::DELETED_TEXT) || !$nextRev->userCan(Revision::DELETED_TEXT) ) {
 354                         return $last;
 355                 } else {
 356                         return $this->mSkin->makeKnownLinkObj(
 357                                 $this->mTitle,
 358                                 $last,
 359                                 "diff=" . $prevRev->getId() . "&oldid={$next->rev_id}"
 360                                 /*,
 361                                 '',
 362                                 '',
 363                                 "tabindex={$counter}"*/ );
 364                 }
 365         }
 366
 367         /**
 368          * Create radio buttons for page history
 369          *
 370          * @param object $rev Revision
 371          * @param bool $firstInList Is this version the first one?
 372          * @param int $counter A counter of what row number we're at, counted from the top row = 1.
 373          * @return string HTML output for the radio buttons
 374          */
 375         function diffButtons( $rev, $firstInList, $counter ) {
 376                 if( $this->linesonpage > 1) {
 377                         $radio = array(
 378                                 'type'  => 'radio',
 379                                 'value' => $rev->getId(),
 380                         );
 381
 382                         if( !$rev->userCan( Revision::DELETED_TEXT ) ) {
 383                                 $radio['disabled'] = 'disabled';
 384                         }
 385
 386                         /** @todo: move title texts to javascript */
 387                         if ( $firstInList ) {
 388                                 $first = Xml::element( 'input', array_merge(
 389                                         $radio,
 390                                         array(
 391                                                 'style' => 'visibility:hidden',
 392                                                 'name'  => 'oldid' ) ) );
 393                                 $checkmark = array( 'checked' => 'checked' );
 394                         } else {
 395                                 if( $counter == 2 ) {
 396                                         $checkmark = array( 'checked' => 'checked' );
 397                                 } else {
 398                                         $checkmark = array();
 399                                 }
 400                                 $first = Xml::element( 'input', array_merge(
 401                                         $radio,
 402                                         $checkmark,
 403                                         array( 'name'  => 'oldid' ) ) );
 404                                 $checkmark = array();
 405                         }
 406                         $second = Xml::element( 'input', array_merge(
 407                                 $radio,
 408                                 $checkmark,
 409                                 array( 'name'  => 'diff' ) ) );
 410                         return $first . $second;
 411                 } else {
 412                         return '';
 413                 }
 414         }
 415
 416         /** @todo document */
 417         function getLatestId() {
 418                 if( is_null( $this->mLatestId ) ) {
 419                         $id = $this->mTitle->getArticleID();
 420                         $db = wfGetDB( DB_SLAVE );
 421                         $this->mLatestId = $db->selectField( 'page',
 422                                 "page_latest",
 423                                 array( 'page_id' => $id ),
 424                                 __METHOD__ );
 425                 }
 426                 return $this->mLatestId;
 427         }
 428
 429         /**
 430          * Fetch an array of revisions, specified by a given limit, offset and
 431          * direction. This is now only used by the feeds. It was previously
 432          * used by the main UI but that's now handled by the pager.
 433          */
 434         function fetchRevisions($limit, $offset, $direction) {
 435                 $dbr = wfGetDB( DB_SLAVE );
 436
 437                 if ($direction == PageHistory::DIR_PREV)
 438                         list($dirs, $oper) = array("ASC", ">=");
 439                 else /* $direction == PageHistory::DIR_NEXT */
 440                         list($dirs, $oper) = array("DESC", "<=");
 441
 442                 if ($offset)
 443                         $offsets = array("rev_timestamp $oper '$offset'");
 444                 else
 445                         $offsets = array();
 446
 447                 $page_id = $this->mTitle->getArticleID();
 448
 449                 $res = $dbr->select(
 450                         'revision',
 451                         Revision::selectFields(),
 452                         array_merge(array("rev_page=$page_id"), $offsets),
 453                         __METHOD__,
 454                         array('ORDER BY' => "rev_timestamp $dirs",
 455                                 'USE INDEX' => 'page_timestamp', 'LIMIT' => $limit)
 456                         );
 457
 458                 $result = array();
 459                 while (($obj = $dbr->fetchObject($res)) != NULL)
 460                         $result[] = $obj;
 461
 462                 return $result;
 463         }
 464
 465         /** @todo document */
 466         function getNotificationTimestamp() {
 467                 global $wgUser, $wgShowUpdatedMarker;
 468
 469                 if ($this->mNotificationTimestamp !== NULL)
 470                         return $this->mNotificationTimestamp;
 471
 472                 if ($wgUser->isAnon() || !$wgShowUpdatedMarker)
 473                         return $this->mNotificationTimestamp = false;
 474
 475                 $dbr = wfGetDB(DB_SLAVE);
 476
 477                 $this->mNotificationTimestamp = $dbr->selectField(
 478                         'watchlist',
 479                         'wl_notificationtimestamp',
 480                         array(  'wl_namespace' => $this->mTitle->getNamespace(),
 481                                 'wl_title' => $this->mTitle->getDBkey(),
 482                                 'wl_user' => $wgUser->getID()
 483                         ),
 484                         __METHOD__ );
 485
 486                 // Don't use the special value reserved for telling whether the field is filled
 487                 if ( is_null( $this->mNotificationTimestamp ) ) {
 488                         $this->mNotificationTimestamp = false;
 489                 }
 490
 491                 return $this->mNotificationTimestamp;
 492         }
 493
 494         /**
 495          * Output a subscription feed listing recent edits to this page.
 496          * @param string $type
 497          */
 498         function feed( $type ) {
 499                 require_once 'SpecialRecentchanges.php';
 500
 501                 global $wgFeed, $wgFeedClasses;
 502
 503                 if ( !$wgFeed ) {
 504                         global $wgOut;
 505                         $wgOut->addWikiMsg( 'feed-unavailable' );
 506                         return;
 507                 }
 508
 509                 if( !isset( $wgFeedClasses[$type] ) ) {
 510                         global $wgOut;
 511                         $wgOut->addWikiMsg( 'feed-invalid' );
 512                         return;
 513                 }
 514
 515                 $feed = new $wgFeedClasses[$type](
 516                         $this->mTitle->getPrefixedText() . ' - ' .
 517                                 wfMsgForContent( 'history-feed-title' ),
 518                         wfMsgForContent( 'history-feed-description' ),
 519                         $this->mTitle->getFullUrl( 'action=history' ) );
 520
 521                 $items = $this->fetchRevisions(10, 0, PageHistory::DIR_NEXT);
 522                 $feed->outHeader();
 523                 if( $items ) {
 524                         foreach( $items as $row ) {
 525                                 $feed->outItem( $this->feedItem( $row ) );
 526                         }
 527                 } else {
 528                         $feed->outItem( $this->feedEmpty() );
 529                 }
 530                 $feed->outFooter();
 531         }
 532
 533         function feedEmpty() {
 534                 global $wgOut;
 535                 return new FeedItem(
 536                         wfMsgForContent( 'nohistory' ),
 537                         $wgOut->parse( wfMsgForContent( 'history-feed-empty' ) ),
 538                         $this->mTitle->getFullUrl(),
 539                         wfTimestamp( TS_MW ),
 540                         '',
 541                         $this->mTitle->getTalkPage()->getFullUrl() );
 542         }
 543
 544         /**
 545          * Generate a FeedItem object from a given revision table row
 546          * Borrows Recent Changes' feed generation functions for formatting;
 547          * includes a diff to the previous revision (if any).
 548          *
 549          * @param $row
 550          * @return FeedItem
 551          */
 552         function feedItem( $row ) {
 553                 $rev = new Revision( $row );
 554                 $rev->setTitle( $this->mTitle );
 555                 $text = rcFormatDiffRow( $this->mTitle,
 556                         $this->mTitle->getPreviousRevisionID( $rev->getId() ),
 557                         $rev->getId(),
 558                         $rev->getTimestamp(),
 559                         $rev->getComment() );
 560
 561                 if( $rev->getComment() == '' ) {
 562                         global $wgContLang;
 563                         $title = wfMsgForContent( 'history-feed-item-nocomment',
 564                                 $rev->getUserText(),
 565                                 $wgContLang->timeanddate( $rev->getTimestamp() ) );
 566                 } else {
 567                         $title = $rev->getUserText() . ": " . $this->stripComment( $rev->getComment() );
 568                 }
 569
 570                 return new FeedItem(
 571                         $title,
 572                         $text,
 573                         $this->mTitle->getFullUrl( 'diff=' . $rev->getId() . '&oldid=prev' ),
 574                         $rev->getTimestamp(),
 575                         $rev->getUserText(),
 576                         $this->mTitle->getTalkPage()->getFullUrl() );
 577         }
 578
 579         /**
 580          * Quickie hack... strip out wikilinks to more legible form from the comment.
 581          */
 582         function stripComment( $text ) {
 583                 return preg_replace( '/\[\[([^]]*\|)?([^]]+)\]\]/', '\2', $text );
 584         }
 585 }
 586
 587
 588 /**
 589  * @addtogroup Pager
 590  */
 591 class PageHistoryPager extends ReverseChronologicalPager {
 592         public $mLastRow = false, $mPageHistory;
 593
 594         function __construct( $pageHistory ) {
 595                 parent::__construct();
 596                 $this->mPageHistory = $pageHistory;
 597         }
 598
 599         function getQueryInfo() {
 600                 return array(
 601                         'tables' => 'revision',
 602                         'fields' => Revision::selectFields(),
 603                         'conds' => array('rev_page' => $this->mPageHistory->mTitle->getArticleID() ),
 604                         'options' => array( 'USE INDEX' => 'page_timestamp' )
 605                 );
 606         }
 607
 608         function getIndexField() {
 609                 return 'rev_timestamp';
 610         }
 611
 612         function formatRow( $row ) {
 613                 if ( $this->mLastRow ) {
 614                         $latest = $this->mCounter == 1 && $this->mIsFirst;
 615                         $firstInList = $this->mCounter == 1;
 616                         $s = $this->mPageHistory->historyLine( $this->mLastRow, $row, $this->mCounter++,
 617                                 $this->mPageHistory->getNotificationTimestamp(), $latest, $firstInList );
 618                 } else {
 619                         $s = '';
 620                 }
 621                 $this->mLastRow = $row;
 622                 return $s;
 623         }
 624
 625         function getStartBody() {
 626                 $this->mLastRow = false;
 627                 $this->mCounter = 1;
 628                 return '';
 629         }
 630
 631         function getEndBody() {
 632                 if ( $this->mLastRow ) {
 633                         $latest = $this->mCounter == 1 && $this->mIsFirst;
 634                         $firstInList = $this->mCounter == 1;
 635                         if ( $this->mIsBackwards ) {
 636                                 # Next row is unknown, but for UI reasons, probably exists if an offset has been specified
 637                                 if ( $this->mOffset == '' ) {
 638                                         $next = null;
 639                                 } else {
 640                                         $next = 'unknown';
 641                                 }
 642                         } else {
 643                                 # The next row is the past-the-end row
 644                                 $next = $this->mPastTheEndRow;
 645                         }
 646                         $s = $this->mPageHistory->historyLine( $this->mLastRow, $next, $this->mCounter++,
 647                                 $this->mPageHistory->getNotificationTimestamp(), $latest, $firstInList );
 648                 } else {
 649                         $s = '';
 650                 }
 651                 return $s;
 652         }
 653 }