File: autoscroll.php

<?php
/**
* PageNavigator_AutoScroll is a class for creating page views that
* scroll automatically while the user navigates through the PageNavigator.
* The view starts out with the minimum number of pages. When the user 
* gets closer to the right edge, the view adjusts itself so that 
* the current page is in the center of the view. The closer he gets to 
* the right edge, the more pages he sees on the screen. The maximum amount
* of pages is settable via object's methods.
* This is used by Google.com, Yandex.ru and many other search engines.
*
* @author   Stanislav Okhvat <stanis@ngs.ru>
* @version  $Id: PageNavigator_AutoScroll.php,v 1.00 2002/02/20 11:40:00 stasokhvat Exp $
* @package  PageNavigator_AutoScroll
* @access   public
*/
class PageNavigator_AutoScroll extends PageNavigator
{
    /**
    * Minimum number of pages to show within set of pages
    *
    * @var      integer
    * @access   private
    */
	var $min_pages_per_set = 10;

    /**
    * Maximum pages to show within set of pages
    *
    * @var      integer
    * @access   private
    */
	var $max_pages_per_set = 20;

    /**
    * How many pages to show to either side of the active page.
    * Default is to center within the set (-1).
    *
    * @var      integer
    * @access   private
    */
	var $show_side_pages;

    /**
    * Constructor. Initializes the PageNavigator_AutoScroll object with the 
	* most important properties.
    *
    * @param    integer    current page number
    * @param    integer    number of records per one page
    * @param    integer    total records. May be initialized later.
    * @param    integer    minimum number of pages displayed per one set.
    * @param    integer    maximum number of pages displayed per one set.
    * @param    integer    number of pages to show to the right of 
    *					   the current page. The default is -1, i.e. center the
    *					   current page in the view. Setting this property will
    *					   override the default behaviour.
    * @return   void
    * @access   public
    */
	function PageNavigator_AutoScroll($current_page=0, $records_per_page=15, $total_records=0, $min_pages_per_set=10, $max_pages_per_set=20, $show_side_pages=-1, $query_vars='')
	{
		PageNavigator::PageNavigator($current_page, $records_per_page, $total_records, $query_vars);

		$this->min_pages_per_set = $min_pages_per_set;
		$this->max_pages_per_set = $max_pages_per_set;

		$this->setSidePageNum($show_side_pages);

	} // end func

	/* SidePageNum */
	function setSidePageNum($show_side_pages)
	{
		if ($show_side_pages == -1 || $show_side_pages > ceil($this->max_pages_per_set / 2))
		{
			// auto-center active page within set. Calculate.
			$show_side_pages = ceil($this->max_pages_per_set / 2);
		}

		$this->show_side_pages = $show_side_pages;
	}
	function getSidePageNum()
	{
		return $this->show_side_pages;
	}

	function preCalculateParameters()
	{
		// 1. Calculate total pages
		$this->totalpages = $this->getTotalPages();
		
		// 2. If we are on the first page, the first record is 1 and the last is min_pages_per_set (assuming it does not exceed pages returned)
		if ($this->current_page == 1)
		{
			$this->startpage = 1;
			
			$this->endpage = 
				($this->min_pages_per_set > $this->totalpages ? $this->totalpages : $this->min_pages_per_set);
		}
		else
		{
			// 3. End page if we are not on first page
			$endpage = $this->current_page + $this->show_side_pages;
			if ($endpage < $this->min_pages_per_set)
			{
				$endpage = $this->min_pages_per_set;
			}
			$this->endpage = ($endpage >= $this->totalpages ? $this->totalpages : $endpage);

			// 4. Start page if we are not on first page
			$startpage = $this->endpage - $this->max_pages_per_set + 1;
			$this->startpage = ($startpage <= 0 ? 1 : $startpage);
		}
		return true;
	}

	function render()
	{
		// do not allow to proceed if not initialized correctly
		if ($this->total_records == 0)
		{
			return false;
		}
		
		// HEADER
		$output = $this->formatHeader();
		
		// GET INITIAL VARS
		$this->preCalculateParameters(); // calculate totalpages, startpage, endpage

		// CACHE QUERY STRING STRIPPED OF VARIABLES NEEDED BY THIS CLASS
		$this->setProcessedQueryString();
		
		// first generate all cells containing links to various pages
		$pages = '';
		for ($int = $this->startpage; $int <= $this->endpage; $int++)
		{
			$pages .= ( ($int == $this->current_page) ?
					$this->formatActivePage($int) :
					$this->formatPage($int) );

		}
		
		//  LINK TO PREVIOUS PAGE
		if ($this->current_page > 1)
		{
			$prevpage = $this->formatMovePrevious($this->current_page - 1);
		}
		else
		{
			$prevpage = $this->empty_cell;
		}

		//  LINK TO NEXT PAGE
		if ($this->current_page < $this->totalpages)
		{
			$nextpage = $this->formatMoveNext($this->current_page + 1);
		}
		else
		{
			$nextpage = $this->empty_cell;
		}
		
		// RENDER PAGE NAVIGATION VIEW
		$output .= $prevpage.$pages.$nextpage;
		
		// ADD TABLE FOOTER
		$output .= $this->formatFooter();
		
		return $output;
	} // end func render

} // end class PageNavigator_AutoScroll
?>