Pager.php

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<?php
interface Pager {
        function getNavigationBar();
        function getBody();
}

abstract class IndexPager extends ContextSource 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;

        protected $mIndexField;
        protected $mExtraSortFields;
        protected $mOrderType;
        public $mDefaultDirection;
        public $mIsBackwards;

        public $mIsFirst;
        public $mIsLast;

        protected $mLastShown, $mFirstShown, $mPastTheEndIndex, $mDefaultQuery, $mNavigationBar;

        protected $mIncludeOffset = false;

        public $mResult;

        public function __construct( IContextSource $context = null ) {
                if ( $context ) {
                        $this->setContext( $context );
                }

                $this->mRequest = $this->getRequest();

                # 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 = $this->getUser()->getIntOption( 'rclimit' );
                if ( !$this->mLimit ) {
                        // Don't override if a subclass calls $this->setLimit() in its constructor.
                        list( $this->mLimit, /* $offset */ ) = $this->mRequest->getLimitOffset();
                }

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

                $index = $this->getIndexField(); // column to sort on
                $extraSort = $this->getExtraSortFields(); // extra columns to sort on for query planning
                $order = $this->mRequest->getVal( 'order' );
                if( is_array( $index ) && isset( $index[$order] ) ) {
                        $this->mOrderType = $order;
                        $this->mIndexField = $index[$order];
                        $this->mExtraSortFields = isset( $extraSort[$order] )
                                ? (array)$extraSort[$order]
                                : array();
                } elseif( is_array( $index ) ) {
                        # First element is the default
                        reset( $index );
                        list( $this->mOrderType, $this->mIndexField ) = each( $index );
                        $this->mExtraSortFields = isset( $extraSort[$this->mOrderType] )
                                ? (array)$extraSort[$this->mOrderType]
                                : array();
                } else {
                        # $index is not an array
                        $this->mOrderType = null;
                        $this->mIndexField = $index;
                        $this->mExtraSortFields = (array)$extraSort;
                }

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

        public function getDatabase() {
                return $this->mDb;
        }

        public 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;

                if ( $this->mOffset == '' ) {
                        $isFirst = true;
                } else {
                        // If there's an offset, we may or may not be at the first entry.
                        // The only way to tell is to run the query in the opposite
                        // direction see if we get a row.
                        $oldIncludeOffset = $this->mIncludeOffset;
                        $this->mIncludeOffset = !$this->mIncludeOffset;
                        $isFirst = !$this->reallyDoQuery( $this->mOffset, 1, !$descending )->numRows();
                        $this->mIncludeOffset = $oldIncludeOffset;
                }

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

                $this->extractResultInfo( $isFirst, $queryLimit, $this->mResult );
                $this->mQueryDone = true;

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

                wfProfileOut( $fname );
        }

        function getResult() {
                return $this->mResult;
        }

        function setOffset( $offset ) {
                $this->mOffset = $offset;
        }
        function setLimit( $limit ) {
                $limit = (int) $limit;
                // WebRequest::getLimitOffset() puts a cap of 5000, so do same here.
                if ( $limit > 5000 ) {
                        $limit = 5000;
                }
                if ( $limit > 0 ) {
                        $this->mLimit = $limit;
                }
        }

        public function setIncludeOffset( $include ) {
                $this->mIncludeOffset = $include;
        }

        function extractResultInfo( $isFirst, $limit, ResultWrapper $res ) {
                $numRows = $res->numRows();
                if ( $numRows ) {
                        # Remove any table prefix from index field
                        $parts = explode( '.', $this->mIndexField );
                        $indexColumn = end( $parts );

                        $row = $res->fetchRow();
                        $firstIndex = $row[$indexColumn];

                        # Discard the extra result row if there is one
                        if ( $numRows > $this->mLimit && $numRows > 1 ) {
                                $res->seek( $numRows - 1 );
                                $this->mPastTheEndRow = $res->fetchObject();
                                $this->mPastTheEndIndex = $this->mPastTheEndRow->$indexColumn;
                                $res->seek( $numRows - 2 );
                                $row = $res->fetchRow();
                                $lastIndex = $row[$indexColumn];
                        } 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 = $row[$indexColumn];
                        }
                } else {
                        $firstIndex = '';
                        $lastIndex = '';
                        $this->mPastTheEndRow = null;
                        $this->mPastTheEndIndex = '';
                }

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

        function getSqlComment() {
                return get_class( $this );
        }

        public function reallyDoQuery( $offset, $limit, $descending ) {
                list( $tables, $fields, $conds, $fname, $options, $join_conds ) = $this->buildQueryInfo( $offset, $limit, $descending );
                return $this->mDb->select( $tables, $fields, $conds, $fname, $options, $join_conds );
        }

        protected function buildQueryInfo( $offset, $limit, $descending ) {
                $fname = __METHOD__ . ' (' . $this->getSqlComment() . ')';
                $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();
                $sortColumns = array_merge( array( $this->mIndexField ), $this->mExtraSortFields );
                if ( $descending ) {
                        $options['ORDER BY'] = $sortColumns;
                        $operator = $this->mIncludeOffset ? '>=' : '>';
                } else {
                        $orderBy = array();
                        foreach ( $sortColumns as $col ) {
                                $orderBy[] = $col . ' DESC';
                        }
                        $options['ORDER BY'] = $orderBy;
                        $operator = $this->mIncludeOffset ? '<=' : '<';
                }
                if ( $offset != '' ) {
                        $conds[] = $this->mIndexField . $operator . $this->mDb->addQuotes( $offset );
                }
                $options['LIMIT'] = intval( $limit );
                return array( $tables, $fields, $conds, $fname, $options, $join_conds );
        }

        protected function preprocessResults( $result ) {}

        public function getBody() {
                if ( !$this->mQueryDone ) {
                        $this->doQuery();
                }

                if ( $this->mResult->numRows() ) {
                        # Do any special query batches before display
                        $this->doBatchLookups();
                }

                # 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;
        }

        function makeLink( $text, array $query = null, $type = null ) {
                if ( $query === null ) {
                        return $text;
                }

                $attrs = array();
                if( in_array( $type, array( 'first', 'prev', 'next', 'last' ) ) ) {
                        # HTML5 rel attributes
                        $attrs['rel'] = $type;
                }

                if( $type ) {
                        $attrs['class'] = "mw-{$type}link";
                }

                return Linker::linkKnown(
                        $this->getTitle(),
                        $text,
                        $attrs,
                        $query + $this->getDefaultQuery()
                );
        }

        protected function doBatchLookups() {}

        protected function getStartBody() {
                return '';
        }

        protected function getEndBody() {
                return '';
        }

        protected function getEmptyBody() {
                return '';
        }

        function getDefaultQuery() {
                if ( !isset( $this->mDefaultQuery ) ) {
                        $this->mDefaultQuery = $this->getRequest()->getQueryValues();
                        unset( $this->mDefaultQuery['title'] );
                        unset( $this->mDefaultQuery['dir'] );
                        unset( $this->mDefaultQuery['offset'] );
                        unset( $this->mDefaultQuery['limit'] );
                        unset( $this->mDefaultQuery['order'] );
                        unset( $this->mDefaultQuery['month'] );
                        unset( $this->mDefaultQuery['year'] );
                }
                return $this->mDefaultQuery;
        }

        function getNumRows() {
                if ( !$this->mQueryDone ) {
                        $this->doQuery();
                }
                return $this->mResult->numRows();
        }

        function getPagingQueries() {
                if ( !$this->mQueryDone ) {
                        $this->doQuery();
                }

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

        function isNavigationBarShown() {
                if ( !$this->mQueryDone ) {
                        $this->doQuery();
                }
                // Hide navigation by default if there is nothing to page
                return !($this->mIsFirst && $this->mIsLast);
        }

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

        abstract function formatRow( $row );

        abstract function getQueryInfo();

        abstract function getIndexField();

        protected function getExtraSortFields() { return array(); }

        protected function getDefaultDirections() { return false; }
}

abstract class AlphabeticPager extends IndexPager {

        function getNavigationBar() {
                if ( !$this->isNavigationBarShown() ) {
                        return '';
                }

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

                $linkTexts = array(
                        'prev' => $this->msg( 'prevn' )->numParams( $this->mLimit )->escaped(),
                        'next' => $this->msg( 'nextn' )->numParams( $this->mLimit )->escaped(),
                        'first' => $this->msg( 'page_first' )->escaped(),
                        'last' => $this->msg( 'page_last' )->escaped()
                );

                $lang = $this->getLanguage();

                $pagingLinks = $this->getPagingLinks( $linkTexts );
                $limitLinks = $this->getLimitLinks();
                $limits = $lang->pipeList( $limitLinks );

                $this->mNavigationBar = $this->msg( 'parentheses' )->rawParams(
                        $lang->pipeList( array( $pagingLinks['first'],
                        $pagingLinks['last'] ) ) )->escaped() . " " .
                        $this->msg( 'viewprevnext' )->rawParams( $pagingLinks['prev'],
                                $pagingLinks['next'], $limits )->escaped();

                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 .= $this->msg( 'pipe-separator' )->escaped();
                        }

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

                if( $extra !== '' ) {
                        $extra = ' ' . $this->msg( 'parentheses' )->rawParams( $extra )->escaped();
                        $this->mNavigationBar .= $extra;
                }

                return $this->mNavigationBar;
        }

        protected function getOrderTypeMessages() {
                return null;
        }
}

abstract class ReverseChronologicalPager extends IndexPager {
        public $mDefaultDirection = true;
        public $mYear;
        public $mMonth;

        function getNavigationBar() {
                if ( !$this->isNavigationBarShown() ) {
                        return '';
                }

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

                $linkTexts = array(
                        'prev' => $this->msg( 'pager-newer-n' )->numParams( $this->mLimit )->escaped(),
                        'next' => $this->msg( 'pager-older-n' )->numParams( $this->mLimit )->escaped(),
                        'first' => $this->msg( 'histlast' )->escaped(),
                        'last' => $this->msg( 'histfirst' )->escaped()
                );

                $pagingLinks = $this->getPagingLinks( $linkTexts );
                $limitLinks = $this->getLimitLinks();
                $limits = $this->getLanguage()->pipeList( $limitLinks );
                $firstLastLinks = $this->msg( 'parentheses' )->rawParams( "{$pagingLinks['first']}" .
                        $this->msg( 'pipe-separator' )->escaped() .
                        "{$pagingLinks['last']}" )->escaped();

                $this->mNavigationBar = $firstLastLinks . ' ' .
                        $this->msg( 'viewprevnext' )->rawParams(
                                $pagingLinks['prev'], $pagingLinks['next'], $limits )->escaped();

                return $this->mNavigationBar;
        }

        function getDateCond( $year, $month ) {
                $year = intval( $year );
                $month = intval( $month );

                // Basic validity checks
                $this->mYear = $year > 0 ? $year : false;
                $this->mMonth = ( $month > 0 && $month < 13 ) ? $month : false;

                // Given an optional year and month, we need to generate a timestamp
                // to use as "WHERE rev_timestamp <= result"
                // Examples: year = 2006 equals < 20070101 (+000000)
                // year=2005, month=1    equals < 20050201
                // year=2005, month=12   equals < 20060101
                if ( !$this->mYear && !$this->mMonth ) {
                        return;
                }

                if ( $this->mYear ) {
                        $year = $this->mYear;
                } else {
                        // If no year given, assume the current one
                        $year = gmdate( 'Y' );
                        // If this month hasn't happened yet this year, go back to last year's month
                        if( $this->mMonth > gmdate( 'n' ) ) {
                                $year--;
                        }
                }

                if ( $this->mMonth ) {
                        $month = $this->mMonth + 1;
                        // For December, we want January 1 of the next year
                        if ( $month > 12 ) {
                                $month = 1;
                                $year++;
                        }
                } else {
                        // No month implies we want up to the end of the year in question
                        $month = 1;
                        $year++;
                }

                // Y2K38 bug
                if ( $year > 2032 ) {
                        $year = 2032;
                }

                $ymd = (int)sprintf( "%04d%02d01", $year, $month );

                if ( $ymd > 20320101 ) {
                        $ymd = 20320101;
                }

                $this->mOffset = $this->mDb->timestamp( "${ymd}000000" );
        }
}

abstract class TablePager extends IndexPager {
        var $mSort;
        var $mCurrentRow;

        public function __construct( IContextSource $context = null ) {
                if ( $context ) {
                        $this->setContext( $context );
                }

                $this->mSort = $this->getRequest()->getText( 'sort' );
                if ( !array_key_exists( $this->mSort, $this->getFieldNames() ) ) {
                        $this->mSort = $this->getDefaultSort();
                }
                if ( $this->getRequest()->getBool( 'asc' ) ) {
                        $this->mDefaultDirection = false;
                } elseif ( $this->getRequest()->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 style='border:1px;' class=\"mw-datatable $tableClass\"><thead><tr>\n";
                $fields = $this->getFieldNames();

                # Make table header
                foreach ( $fields as $field => $name ) {
                        if ( strval( $name ) == '' ) {
                                $s .= "<th>&#160;</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_d.png';
                                                $query['asc'] = '1';
                                                $query['desc'] = '';
                                                $alt = $this->msg( 'descending_abbrev' )->escaped();
                                        } else {
                                                # Ascending
                                                $image = 'Arr_u.png';
                                                $query['asc'] = '';
                                                $query['desc'] = '1';
                                                $alt = $this->msg( 'ascending_abbrev' )->escaped();
                                        }
                                        $image = htmlspecialchars( "$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 = $this->msg( 'table_pager_empty' )->escaped();
                return "<tr><td colspan=\"$colspan\">$msgEmpty</td></tr>\n";
        }

        function formatRow( $row ) {
                $this->mCurrentRow = $row; // In case formatValue etc need to know
                $s = Xml::openElement( 'tr', $this->getRowAttrs( $row ) );
                $fieldNames = $this->getFieldNames();

                foreach ( $fieldNames as $field => $name ) {
                        $value = isset( $row->$field ) ? $row->$field : null;
                        $formatted = strval( $this->formatValue( $field, $value ) );

                        if ( $formatted == '' ) {
                                $formatted = '&#160;';
                        }

                        $s .= Xml::tags( 'td', $this->getCellAttrs( $field, $value ), $formatted );
                }

                $s .= "</tr>\n";

                return $s;
        }

        function getRowClass( $row ) {
                return '';
        }

        function getRowAttrs( $row ) {
                $class = $this->getRowClass( $row );
                if ( $class === '' ) {
                        // Return an empty array to avoid clutter in HTML like class=""
                        return array();
                } else {
                        return array( 'class' => $this->getRowClass( $row ) );
                }
        }

        function getCellAttrs( $field, $value ) {
                return array( 'class' => 'TablePager_col_' . $field );
        }

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

        function getTableClass() {
                return 'TablePager';
        }

        function getNavClass() {
                return 'TablePager_nav';
        }

        function getSortHeaderClass() {
                return 'TablePager_sort';
        }

        public function getNavigationBar() {
                global $wgStylePath;

                if ( !$this->isNavigationBarShown() ) {
                        return '';
                }

                $path = "$wgStylePath/common/images";
                $labels = array(
                        'first' => 'table_pager_first',
                        'prev' => 'table_pager_prev',
                        'next' => 'table_pager_next',
                        'last' => 'table_pager_last',
                );
                $images = array(
                        'first' => 'arrow_first_25.png',
                        'prev' => 'arrow_left_25.png',
                        'next' => 'arrow_right_25.png',
                        'last' => 'arrow_last_25.png',
                );
                $disabledImages = array(
                        'first' => 'arrow_disabled_first_25.png',
                        'prev' => 'arrow_disabled_left_25.png',
                        'next' => 'arrow_disabled_right_25.png',
                        'last' => 'arrow_disabled_last_25.png',
                );
                if( $this->getLanguage()->isRTL() ) {
                        $keys = array_keys( $labels );
                        $images = array_combine( $keys, array_reverse( $images ) );
                        $disabledImages = array_combine( $keys, array_reverse( $disabledImages ) );
                }

                $linkTexts = array();
                $disabledTexts = array();
                foreach ( $labels as $type => $label ) {
                        $msgLabel = $this->msg( $label )->escaped();
                        $linkTexts[$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\"><tr>\n";
                $width = 100 / count( $links ) . '%';
                foreach ( $labels as $type => $label ) {
                        $s .= "<td style='width:$width;'>{$links[$type]}</td>\n";
                }
                $s .= "</tr></table>\n";
                return $s;
        }

        public function getLimitSelect() {
                # Add the current limit from the query string
                # to avoid that the limit is lost after clicking Go next time
                if ( !in_array( $this->mLimit, $this->mLimitsShown ) ) {
                        $this->mLimitsShown[] = $this->mLimit;
                        sort( $this->mLimitsShown );
                }
                $s = Html::openElement( 'select', array( 'name' => 'limit' ) ) . "\n";
                foreach ( $this->mLimitsShown as $key => $value ) {
                        # The pair is either $index => $limit, in which case the $value
                        # will be numeric, or $limit => $text, in which case the $value
                        # will be a string.
                        if( is_int( $value ) ) {
                                $limit = $value;
                                $text = $this->getLanguage()->formatNum( $limit );
                        } else {
                                $limit = $key;
                                $text = $value;
                        }
                        $s .= Xml::option( $text, $limit, $limit == $this->mLimit ) . "\n";
                }
                $s .= Html::closeElement( 'select' );
                return $s;
        }

        function getHiddenFields( $blacklist = array() ) {
                $blacklist = (array)$blacklist;
                $query = $this->getRequest()->getQueryValues();
                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;
        }

        function getLimitForm() {
                global $wgScript;

                return Xml::openElement(
                        'form',
                        array(
                                'method' => 'get',
                                'action' => $wgScript
                        ) ) . "\n" . $this->getLimitDropdown() . "</form>\n";
        }

        function getLimitDropdown() {
                # Make the select with some explanatory text
                $msgSubmit = $this->msg( 'table_pager_limit_submit' )->escaped();

                return $this->msg( 'table_pager_limit' )
                        ->rawParams( $this->getLimitSelect() )->escaped() .
                        "\n<input type=\"submit\" value=\"$msgSubmit\"/>\n" .
                        $this->getHiddenFields( array( 'limit' ) );
        }

        abstract function isFieldSortable( $field );

        abstract function formatValue( $name, $value );

        abstract function getDefaultSort();

        abstract function getFieldNames();
}