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