summaryrefslogtreecommitdiff
path: root/includes/Pager.php
blob: 62c4e551a21c8b6a770b89f2f8f8912e0fedf8fc (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
<?php
/**
 * @defgroup Pager Pager
 *
 * @file
 * @ingroup Pager
 */

/**
 * Basic pager interface.
 * @ingroup Pager
 */
interface Pager {
	function getNavigationBar();
	function getBody();
}

/**
 * IndexPager is an efficient pager which uses a (roughly unique) index in the
 * data set to implement paging, rather than a "LIMIT offset,limit" clause.
 * In MySQL, such a limit/offset clause requires counting through the
 * specified number of offset rows to find the desired data, which can be
 * expensive for large offsets.
 *
 * ReverseChronologicalPager is a child class of the abstract IndexPager, and
 * contains  some formatting and display code which is specific to the use of
 * timestamps as  indexes. Here is a synopsis of its operation:
 *
 *    * The query is specified by the offset, limit and direction (dir)
 *      parameters, in addition to any subclass-specific parameters.
 *    * The offset is the non-inclusive start of the DB query. A row with an
 *      index value equal to the offset will never be shown.
 *    * The query may either be done backwards, where the rows are returned by
 *      the database in the opposite order to which they are displayed to the
 *      user, or forwards. This is specified by the "dir" parameter, dir=prev
 *      means backwards, anything else means forwards. The offset value
 *      specifies the start of the database result set, which may be either
 *      the start or end of the displayed data set. This allows "previous"
 *      links to be implemented without knowledge of the index value at the
 *      start of the previous page.
 *    * An additional row beyond the user-specified limit is always requested.
 *      This allows us to tell whether we should display a "next" link in the
 *      case of forwards mode, or a "previous" link in the case of backwards
 *      mode. Determining whether to display the other link (the one for the
 *      page before the start of the database result set) can be done
 *      heuristically by examining the offset.
 *
 *    * An empty offset indicates that the offset condition should be omitted
 *      from the query. This naturally produces either the first page or the
 *      last page depending on the dir parameter.
 *
 *  Subclassing the pager to implement concrete functionality should be fairly
 *  simple, please see the examples in PageHistory.php and
 *  SpecialIpblocklist.php. You just need to override formatRow(),
 *  getQueryInfo() and getIndexField(). Don't forget to call the parent
 *  constructor if you override it.
 *
 * @ingroup Pager
 */
abstract class IndexPager implements Pager {
	public $mRequest;
	public $mLimitsShown = array( 20, 50, 100, 250, 500 );
	public $mDefaultLimit = 50;
	public $mOffset, $mLimit;
	public $mQueryDone = false;
	public $mDb;
	public $mPastTheEndRow;

	/**
	 * The index to actually be used for ordering.  This is a single string e-
	 * ven if multiple orderings are supported.
	 */
	protected $mIndexField;
	/** For pages that support multiple types of ordering, which one to use. */
	protected $mOrderType;
	/**
	 * $mDefaultDirection gives the direction to use when sorting results:
	 * false for ascending, true for descending.  If $mIsBackwards is set, we
	 * start from the opposite end, but we still sort the page itself according
	 * to $mDefaultDirection.  E.g., if $mDefaultDirection is false but we're
	 * going backwards, we'll display the last page of results, but the last
	 * result will be at the bottom, not the top.
	 *
	 * Like $mIndexField, $mDefaultDirection will be a single value even if the
	 * class supports multiple default directions for different order types.
	 */
	public $mDefaultDirection;
	public $mIsBackwards;

	/**
	 * Result object for the query. Warning: seek before use.
	 */
	public $mResult;

	public function __construct() {
		global $wgRequest, $wgUser;
		$this->mRequest = $wgRequest;

		# NB: the offset is quoted, not validated. It is treated as an
		# arbitrary string to support the widest variety of index types. Be
		# careful outputting it into HTML!
		$this->mOffset = $this->mRequest->getText( 'offset' );

		# Use consistent behavior for the limit options
		$this->mDefaultLimit = intval( $wgUser->getOption( 'rclimit' ) );
		list( $this->mLimit, /* $offset */ ) = $this->mRequest->getLimitOffset();

		$this->mIsBackwards = ( $this->mRequest->getVal( 'dir' ) == 'prev' );
		$this->mDb = wfGetDB( DB_SLAVE );

		$index = $this->getIndexField();
		$order = $this->mRequest->getVal( 'order' );
		if( is_array( $index ) && isset( $index[$order] ) ) {
			$this->mOrderType = $order;
			$this->mIndexField = $index[$order];
		} elseif( is_array( $index ) ) {
			# First element is the default
			reset( $index );
			list( $this->mOrderType, $this->mIndexField ) = each( $index );
		} else {
			# $index is not an array
			$this->mOrderType = null;
			$this->mIndexField = $index;
		}

		if( !isset( $this->mDefaultDirection ) ) {
			$dir = $this->getDefaultDirections();
			$this->mDefaultDirection = is_array( $dir )
				? $dir[$this->mOrderType]
				: $dir;
		}
	}

	/**
	 * Do the query, using information from the object context. This function
	 * has been kept minimal to make it overridable if necessary, to allow for
	 * result sets formed from multiple DB queries.
	 */
	function doQuery() {
		# Use the child class name for profiling
		$fname = __METHOD__ . ' (' . get_class( $this ) . ')';
		wfProfileIn( $fname );

		$descending = ( $this->mIsBackwards == $this->mDefaultDirection );
		# Plus an extra row so that we can tell the "next" link should be shown
		$queryLimit = $this->mLimit + 1;

		$this->mResult = $this->reallyDoQuery( $this->mOffset, $queryLimit, $descending );
		$this->extractResultInfo( $this->mOffset, $queryLimit, $this->mResult );
		$this->mQueryDone = true;

		$this->preprocessResults( $this->mResult );
		$this->mResult->rewind(); // Paranoia

		wfProfileOut( $fname );
	}

	/**
	 * Extract some useful data from the result object for use by
	 * the navigation bar, put it into $this
	 */
	function extractResultInfo( $offset, $limit, ResultWrapper $res ) {
		$numRows = $res->numRows();
		if ( $numRows ) {
			$row = $res->fetchRow();
			$firstIndex = $row[$this->mIndexField];

			# Discard the extra result row if there is one
			if ( $numRows > $this->mLimit && $numRows > 1 ) {
				$res->seek( $numRows - 1 );
				$this->mPastTheEndRow = $res->fetchObject();
				$indexField = $this->mIndexField;
				$this->mPastTheEndIndex = $this->mPastTheEndRow->$indexField;
				$res->seek( $numRows - 2 );
				$row = $res->fetchRow();
				$lastIndex = $row[$this->mIndexField];
			} else {
				$this->mPastTheEndRow = null;
				# Setting indexes to an empty string means that they will be
				# omitted if they would otherwise appear in URLs. It just so
				# happens that this  is the right thing to do in the standard
				# UI, in all the relevant cases.
				$this->mPastTheEndIndex = '';
				$res->seek( $numRows - 1 );
				$row = $res->fetchRow();
				$lastIndex = $row[$this->mIndexField];
			}
		} else {
			$firstIndex = '';
			$lastIndex = '';
			$this->mPastTheEndRow = null;
			$this->mPastTheEndIndex = '';
		}

		if ( $this->mIsBackwards ) {
			$this->mIsFirst = ( $numRows < $limit );
			$this->mIsLast = ( $offset == '' );
			$this->mLastShown = $firstIndex;
			$this->mFirstShown = $lastIndex;
		} else {
			$this->mIsFirst = ( $offset == '' );
			$this->mIsLast = ( $numRows < $limit );
			$this->mLastShown = $lastIndex;
			$this->mFirstShown = $firstIndex;
		}
	}

	/**
	 * Do a query with specified parameters, rather than using the object
	 * context
	 *
	 * @param string $offset Index offset, inclusive
	 * @param integer $limit Exact query limit
	 * @param boolean $descending Query direction, false for ascending, true for descending
	 * @return ResultWrapper
	 */
	function reallyDoQuery( $offset, $limit, $descending ) {
		$fname = __METHOD__ . ' (' . get_class( $this ) . ')';
		$info = $this->getQueryInfo();
		$tables = $info['tables'];
		$fields = $info['fields'];
		$conds = isset( $info['conds'] ) ? $info['conds'] : array();
		$options = isset( $info['options'] ) ? $info['options'] : array();
		$join_conds = isset( $info['join_conds'] ) ? $info['join_conds'] : array();
		if ( $descending ) {
			$options['ORDER BY'] = $this->mIndexField;
			$operator = '>';
		} else {
			$options['ORDER BY'] = $this->mIndexField . ' DESC';
			$operator = '<';
		}
		if ( $offset != '' ) {
			$conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset );
		}
		$options['LIMIT'] = intval( $limit );
		$res = $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
		return new ResultWrapper( $this->mDb, $res );
	}

	/**
	 * Pre-process results; useful for performing batch existence checks, etc.
	 *
	 * @param ResultWrapper $result Result wrapper
	 */
	protected function preprocessResults( $result ) {}

	/**
	 * Get the formatted result list. Calls getStartBody(), formatRow() and
	 * getEndBody(), concatenates the results and returns them.
	 */
	function getBody() {
		if ( !$this->mQueryDone ) {
			$this->doQuery();
		}
		# Don't use any extra rows returned by the query
		$numRows = min( $this->mResult->numRows(), $this->mLimit );

		$s = $this->getStartBody();
		if ( $numRows ) {
			if ( $this->mIsBackwards ) {
				for ( $i = $numRows - 1; $i >= 0; $i-- ) {
					$this->mResult->seek( $i );
					$row = $this->mResult->fetchObject();
					$s .= $this->formatRow( $row );
				}
			} else {
				$this->mResult->seek( 0 );
				for ( $i = 0; $i < $numRows; $i++ ) {
					$row = $this->mResult->fetchObject();
					$s .= $this->formatRow( $row );
				}
			}
		} else {
			$s .= $this->getEmptyBody();
		}
		$s .= $this->getEndBody();
		return $s;
	}

	/**
	 * Make a self-link
	 */
	function makeLink($text, $query = null, $type=null) {
		if ( $query === null ) {
			return $text;
		}
		if( $type == 'prev' || $type == 'next' ) {
			$attrs = "rel=\"$type\"";
		} elseif( $type == 'first' ) {
			$attrs = "rel=\"start\"";
		} else {
			# HTML 4 has no rel="end" . . .
			$attrs = '';
		}
		return $this->getSkin()->makeKnownLinkObj( $this->getTitle(), $text,
				wfArrayToCGI( $query, $this->getDefaultQuery() ), '', '',
				$attrs );
	}

	/**
	 * Hook into getBody(), allows text to be inserted at the start. This
	 * will be called even if there are no rows in the result set.
	 */
	function getStartBody() {
		return '';
	}

	/**
	 * Hook into getBody() for the end of the list
	 */
	function getEndBody() {
		return '';
	}

	/**
	 * Hook into getBody(), for the bit between the start and the
	 * end when there are no rows
	 */
	function getEmptyBody() {
		return '';
	}

	/**
	 * Title used for self-links. Override this if you want to be able to
	 * use a title other than $wgTitle
	 */
	function getTitle() {
		return $GLOBALS['wgTitle'];
	}

	/**
	 * Get the current skin. This can be overridden if necessary.
	 */
	function getSkin() {
		if ( !isset( $this->mSkin ) ) {
			global $wgUser;
			$this->mSkin = $wgUser->getSkin();
		}
		return $this->mSkin;
	}

	/**
	 * Get an array of query parameters that should be put into self-links.
	 * By default, all parameters passed in the URL are used, except for a
	 * short blacklist.
	 */
	function getDefaultQuery() {
		if ( !isset( $this->mDefaultQuery ) ) {
			$this->mDefaultQuery = $_GET;
			unset( $this->mDefaultQuery['title'] );
			unset( $this->mDefaultQuery['dir'] );
			unset( $this->mDefaultQuery['offset'] );
			unset( $this->mDefaultQuery['limit'] );
			unset( $this->mDefaultQuery['order'] );
		}
		return $this->mDefaultQuery;
	}

	/**
	 * Get the number of rows in the result set
	 */
	function getNumRows() {
		if ( !$this->mQueryDone ) {
			$this->doQuery();
		}
		return $this->mResult->numRows();
	}

	/**
	 * Get a URL query array for the prev, next, first and last links.
	 */
	function getPagingQueries() {
		if ( !$this->mQueryDone ) {
			$this->doQuery();
		}

		# Don't announce the limit everywhere if it's the default
		$urlLimit = $this->mLimit == $this->mDefaultLimit ? '' : $this->mLimit;

		if ( $this->mIsFirst ) {
			$prev = false;
			$first = false;
		} else {
			$prev = array( 'dir' => 'prev', 'offset' => $this->mFirstShown, 'limit' => $urlLimit );
			$first = array( 'limit' => $urlLimit );
		}
		if ( $this->mIsLast ) {
			$next = false;
			$last = false;
		} else {
			$next = array( 'offset' => $this->mLastShown, 'limit' => $urlLimit );
			$last = array( 'dir' => 'prev', 'limit' => $urlLimit );
		}
		return array( 'prev' => $prev, 'next' => $next, 'first' => $first, 'last' => $last );
	}

	/**
	 * Get paging links. If a link is disabled, the item from $disabledTexts
	 * will be used. If there is no such item, the unlinked text from
	 * $linkTexts will be used. Both $linkTexts and $disabledTexts are arrays
	 * of HTML.
	 */
	function getPagingLinks( $linkTexts, $disabledTexts = array() ) {
		$queries = $this->getPagingQueries();
		$links = array();
		foreach ( $queries as $type => $query ) {
			if ( $query !== false ) {
				$links[$type] = $this->makeLink( $linkTexts[$type], $queries[$type], $type );
			} elseif ( isset( $disabledTexts[$type] ) ) {
				$links[$type] = $disabledTexts[$type];
			} else {
				$links[$type] = $linkTexts[$type];
			}
		}
		return $links;
	}

	function getLimitLinks() {
		global $wgLang;
		$links = array();
		if ( $this->mIsBackwards ) {
			$offset = $this->mPastTheEndIndex;
		} else {
			$offset = $this->mOffset;
		}
		foreach ( $this->mLimitsShown as $limit ) {
			$links[] = $this->makeLink( $wgLang->formatNum( $limit ),
				array( 'offset' => $offset, 'limit' => $limit ) );
		}
		return $links;
	}

	/**
	 * Abstract formatting function. This should return an HTML string
	 * representing the result row $row. Rows will be concatenated and
	 * returned by getBody()
	 */
	abstract function formatRow( $row );

	/**
	 * This function should be overridden to provide all parameters
	 * needed for the main paged query. It returns an associative
	 * array with the following elements:
	 *    tables => Table(s) for passing to Database::select()
	 *    fields => Field(s) for passing to Database::select(), may be *
	 *    conds => WHERE conditions
	 *    options => option array
	 */
	abstract function getQueryInfo();

	/**
	 * This function should be overridden to return the name of the index fi-
	 * eld.  If the pager supports multiple orders, it may return an array of
	 * 'querykey' => 'indexfield' pairs, so that a request with &count=querykey
	 * will use indexfield to sort.  In this case, the first returned key is
	 * the default.
	 *
	 * Needless to say, it's really not a good idea to use a non-unique index
	 * for this!  That won't page right.
	 */
	abstract function getIndexField();

	/**
	 * Return the default sorting direction: false for ascending, true for de-
	 * scending.  You can also have an associative array of ordertype => dir,
	 * if multiple order types are supported.  In this case getIndexField()
	 * must return an array, and the keys of that must exactly match the keys
	 * of this.
	 *
	 * For backward compatibility, this method's return value will be ignored
	 * if $this->mDefaultDirection is already set when the constructor is
	 * called, for instance if it's statically initialized.  In that case the
	 * value of that variable (which must be a boolean) will be used.
	 *
	 * Note that despite its name, this does not return the value of the
	 * $this->mDefaultDirection member variable.  That's the default for this
	 * particular instantiation, which is a single value.  This is the set of
	 * all defaults for the class.
	 */
	protected function getDefaultDirections() { return false; }
}


/**
 * IndexPager with an alphabetic list and a formatted navigation bar
 * @ingroup Pager
 */
abstract class AlphabeticPager extends IndexPager {
	/**
	 * Shamelessly stolen bits from ReverseChronologicalPager,
	 * didn't want to do class magic as may be still revamped
	 */
	function getNavigationBar() {
		global $wgLang;

		if( isset( $this->mNavigationBar ) ) {
			return $this->mNavigationBar;
		}

		$opts = array( 'parsemag', 'escapenoentities' );
		$linkTexts = array(
			'prev' => wfMsgExt( 'prevn', $opts, $wgLang->formatNum( $this->mLimit ) ),
			'next' => wfMsgExt( 'nextn', $opts, $wgLang->formatNum($this->mLimit ) ),
			'first' => wfMsgExt( 'page_first', $opts ),
			'last' => wfMsgExt( 'page_last', $opts )
		);

		$pagingLinks = $this->getPagingLinks( $linkTexts );
		$limitLinks = $this->getLimitLinks();
		$limits = implode( ' | ', $limitLinks );

		$this->mNavigationBar =
			"({$pagingLinks['first']} | {$pagingLinks['last']}) " .
			wfMsgHtml( 'viewprevnext', $pagingLinks['prev'],
			$pagingLinks['next'], $limits );

		if( !is_array( $this->getIndexField() ) ) {
			# Early return to avoid undue nesting
			return $this->mNavigationBar;
		}

		$extra = '';
		$first = true;
		$msgs = $this->getOrderTypeMessages();
		foreach( array_keys( $msgs ) as $order ) {
			if( $first ) {
				$first = false;
			} else {
				$extra .= ' | ';
			}

			if( $order == $this->mOrderType ) {
				$extra .= wfMsgHTML( $msgs[$order] );
			} else {
				$extra .= $this->makeLink(
					wfMsgHTML( $msgs[$order] ),
					array( 'order' => $order )
				);
			}
		}

		if( $extra !== '' ) {
			$this->mNavigationBar .= " ($extra)";
		}

		return $this->mNavigationBar;
	}

	/**
	 * If this supports multiple order type messages, give the message key for
	 * enabling each one in getNavigationBar.  The return type is an associa-
	 * tive array whose keys must exactly match the keys of the array returned
	 * by getIndexField(), and whose values are message keys.
	 * @return array
	 */
	protected function getOrderTypeMessages() {
		return null;
	}
}

/**
 * IndexPager with a formatted navigation bar
 * @ingroup Pager
 */
abstract class ReverseChronologicalPager extends IndexPager {
	public $mDefaultDirection = true;

	function __construct() {
		parent::__construct();
	}

	function getNavigationBar() {
		global $wgLang;

		if ( isset( $this->mNavigationBar ) ) {
			return $this->mNavigationBar;
		}
		$nicenumber = $wgLang->formatNum( $this->mLimit );
		$linkTexts = array(
			'prev' => wfMsgExt( 'pager-newer-n', array( 'parsemag' ), $nicenumber ),
			'next' => wfMsgExt( 'pager-older-n', array( 'parsemag' ), $nicenumber ),
			'first' => wfMsgHtml( 'histlast' ),
			'last' => wfMsgHtml( 'histfirst' )
		);

		$pagingLinks = $this->getPagingLinks( $linkTexts );
		$limitLinks = $this->getLimitLinks();
		$limits = implode( ' | ', $limitLinks );

		$this->mNavigationBar = "({$pagingLinks['first']} | {$pagingLinks['last']}) " .
			wfMsgHtml("viewprevnext", $pagingLinks['prev'], $pagingLinks['next'], $limits);
		return $this->mNavigationBar;
	}
}

/**
 * Table-based display with a user-selectable sort order
 * @ingroup Pager
 */
abstract class TablePager extends IndexPager {
	var $mSort;
	var $mCurrentRow;

	function __construct() {
		global $wgRequest;
		$this->mSort = $wgRequest->getText( 'sort' );
		if ( !array_key_exists( $this->mSort, $this->getFieldNames() ) ) {
			$this->mSort = $this->getDefaultSort();
		}
		if ( $wgRequest->getBool( 'asc' ) ) {
			$this->mDefaultDirection = false;
		} elseif ( $wgRequest->getBool( 'desc' ) ) {
			$this->mDefaultDirection = true;
		} /* Else leave it at whatever the class default is */

		parent::__construct();
	}

	function getStartBody() {
		global $wgStylePath;
		$tableClass = htmlspecialchars( $this->getTableClass() );
		$sortClass = htmlspecialchars( $this->getSortHeaderClass() );

		$s = "<table border='1' class=\"$tableClass\"><thead><tr>\n";
		$fields = $this->getFieldNames();

		# Make table header
		foreach ( $fields as $field => $name ) {
			if ( strval( $name ) == '' ) {
				$s .= "<th>&nbsp;</th>\n";
			} elseif ( $this->isFieldSortable( $field ) ) {
				$query = array( 'sort' => $field, 'limit' => $this->mLimit );
				if ( $field == $this->mSort ) {
					# This is the sorted column
					# Prepare a link that goes in the other sort order
					if ( $this->mDefaultDirection ) {
						# Descending
						$image = 'Arr_u.png';
						$query['asc'] = '1';
						$query['desc'] = '';
						$alt = htmlspecialchars( wfMsg( 'descending_abbrev' ) );
					} else {
						# Ascending
						$image = 'Arr_d.png';
						$query['asc'] = '';
						$query['desc'] = '1';
						$alt = htmlspecialchars( wfMsg( 'ascending_abbrev' ) );
					}
					$image = htmlspecialchars( "$wgStylePath/common/images/$image" );
					$link = $this->makeLink(
						"<img width=\"12\" height=\"12\" alt=\"$alt\" src=\"$image\" />" .
						htmlspecialchars( $name ), $query );
					$s .= "<th class=\"$sortClass\">$link</th>\n";
				} else {
					$s .= '<th>' . $this->makeLink( htmlspecialchars( $name ), $query ) . "</th>\n";
				}
			} else {
				$s .= '<th>' . htmlspecialchars( $name ) . "</th>\n";
			}
		}
		$s .= "</tr></thead><tbody>\n";
		return $s;
	}

	function getEndBody() {
		return "</tbody></table>\n";
	}

	function getEmptyBody() {
		$colspan = count( $this->getFieldNames() );
		$msgEmpty = wfMsgHtml( 'table_pager_empty' );
		return "<tr><td colspan=\"$colspan\">$msgEmpty</td></tr>\n";
	}

	function formatRow( $row ) {
		$s = "<tr>\n";
		$fieldNames = $this->getFieldNames();
		$this->mCurrentRow = $row;  # In case formatValue needs to know
		foreach ( $fieldNames as $field => $name ) {
			$value = isset( $row->$field ) ? $row->$field : null;
			$formatted = strval( $this->formatValue( $field, $value ) );
			if ( $formatted == '' ) {
				$formatted = '&nbsp;';
			}
			$class = 'TablePager_col_' . htmlspecialchars( $field );
			$s .= "<td class=\"$class\">$formatted</td>\n";
		}
		$s .= "</tr>\n";
		return $s;
	}

	function getIndexField() {
		return $this->mSort;
	}

	function getTableClass() {
		return 'TablePager';
	}

	function getNavClass() {
		return 'TablePager_nav';
	}

	function getSortHeaderClass() {
		return 'TablePager_sort';
	}

	/**
	 * A navigation bar with images
	 */
	function getNavigationBar() {
		global $wgStylePath, $wgContLang;
		$path = "$wgStylePath/common/images";
		$labels = array(
			'first' => 'table_pager_first',
			'prev' => 'table_pager_prev',
			'next' => 'table_pager_next',
			'last' => 'table_pager_last',
		);
		$images = array(
			'first' => $wgContLang->isRTL() ? 'arrow_last_25.png' : 'arrow_first_25.png',
			'prev' =>  $wgContLang->isRTL() ? 'arrow_right_25.png' : 'arrow_left_25.png',
			'next' =>  $wgContLang->isRTL() ? 'arrow_left_25.png' : 'arrow_right_25.png',
			'last' =>  $wgContLang->isRTL() ? 'arrow_first_25.png' : 'arrow_last_25.png',
		);
		$disabledImages = array(
			'first' => $wgContLang->isRTL() ? 'arrow_disabled_last_25.png' : 'arrow_disabled_first_25.png',
			'prev' =>  $wgContLang->isRTL() ? 'arrow_disabled_right_25.png' : 'arrow_disabled_left_25.png',
			'next' =>  $wgContLang->isRTL() ? 'arrow_disabled_left_25.png' : 'arrow_disabled_right_25.png',
			'last' =>  $wgContLang->isRTL() ? 'arrow_disabled_first_25.png' : 'arrow_disabled_last_25.png',
		);

		$linkTexts = array();
		$disabledTexts = array();
		foreach ( $labels as $type => $label ) {
			$msgLabel = wfMsgHtml( $label );
			$linkTexts[$type] = "<img src=\"$path/{$images[$type]}\" alt=\"$msgLabel\"/><br/>$msgLabel";
			$disabledTexts[$type] = "<img src=\"$path/{$disabledImages[$type]}\" alt=\"$msgLabel\"/><br/>$msgLabel";
		}
		$links = $this->getPagingLinks( $linkTexts, $disabledTexts );

		$navClass = htmlspecialchars( $this->getNavClass() );
		$s = "<table class=\"$navClass\" align=\"center\" cellpadding=\"3\"><tr>\n";
		$cellAttrs = 'valign="top" align="center" width="' . 100 / count( $links ) . '%"';
		foreach ( $labels as $type => $label ) {
			$s .= "<td $cellAttrs>{$links[$type]}</td>\n";
		}
		$s .= "</tr></table>\n";
		return $s;
	}

	/**
	 * Get a <select> element which has options for each of the allowed limits
	 */
	function getLimitSelect() {
		global $wgLang;
		$s = "<select name=\"limit\">";
		foreach ( $this->mLimitsShown as $limit ) {
			$selected = $limit == $this->mLimit ? 'selected="selected"' : '';
			$formattedLimit = $wgLang->formatNum( $limit );
			$s .= "<option value=\"$limit\" $selected>$formattedLimit</option>\n";
		}
		$s .= "</select>";
		return $s;
	}

	/**
	 * Get <input type="hidden"> elements for use in a method="get" form.
	 * Resubmits all defined elements of the $_GET array, except for a
	 * blacklist, passed in the $blacklist parameter.
	 */
	function getHiddenFields( $blacklist = array() ) {
		$blacklist = (array)$blacklist;
		$query = $_GET;
		foreach ( $blacklist as $name ) {
			unset( $query[$name] );
		}
		$s = '';
		foreach ( $query as $name => $value ) {
			$encName = htmlspecialchars( $name );
			$encValue = htmlspecialchars( $value );
			$s .= "<input type=\"hidden\" name=\"$encName\" value=\"$encValue\"/>\n";
		}
		return $s;
	}

	/**
	 * Get a form containing a limit selection dropdown
	 */
	function getLimitForm() {
		# Make the select with some explanatory text
		$url = $this->getTitle()->escapeLocalURL();
		$msgSubmit = wfMsgHtml( 'table_pager_limit_submit' );
		return
			"<form method=\"get\" action=\"$url\">" .
			wfMsgHtml( 'table_pager_limit', $this->getLimitSelect() ) .
			"\n<input type=\"submit\" value=\"$msgSubmit\"/>\n" .
			$this->getHiddenFields( 'limit' ) .
			"</form>\n";
	}

	/**
	 * Return true if the named field should be sortable by the UI, false
	 * otherwise
	 *
	 * @param string $field
	 */
	abstract function isFieldSortable( $field );

	/**
	 * Format a table cell. The return value should be HTML, but use an empty
	 * string not &nbsp; for empty cells. Do not include the <td> and </td>.
	 *
	 * The current result row is available as $this->mCurrentRow, in case you
	 * need more context.
	 *
	 * @param string $name The database field name
	 * @param string $value The value retrieved from the database
	 */
	abstract function formatValue( $name, $value );

	/**
	 * The database field name used as a default sort order
	 */
	abstract function getDefaultSort();

	/**
	 * An array mapping database field names to a textual description of the
	 * field name, for use in the table header. The description should be plain
	 * text, it will be HTML-escaped later.
	 */
	abstract function getFieldNames();
}