[OpenLayers-Users] Using cookies to remember the map state

Fri Feb 26 10:06:46 EST 2010

Hi all,

I recently ported the following Google Maps API tutorial (using cookies to
remember the map state when the user leaves the page and comes back) to
OpenLayers.

http://econym.org.uk/gmap/cookies.htm http://econym.org.uk/gmap/cookies.htm 

Here's the code..

<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <link rel="stylesheet"
href="http://openlayers.org/dev/theme/default/style.css" type="text/css" />
    <link rel="stylesheet"
href="http://openlayers.org/dev/examples/style.css" type="text/css" />
    <script src="http://openlayers.org/dev/OpenLayers.js"></script>
    <script type="text/javascript">
        var lon = 5;
        var lat = 40;
        var zoom = 5;
        var map, layer;

		// === Some cookie parameters ===
      var cookiename = "mapinfo";  // name for this cookie
      var expiredays = 7;          // number of days before cookie expiry

      // === Look for the cookie ===
      if (document.cookie.length>0) {
        cookieStart = document.cookie.indexOf(cookiename + "=");
        if (cookieStart!=-1) {
          cookieStart += cookiename.length+1; 
          cookieEnd=document.cookie.indexOf(";",cookieStart);
          if (cookieEnd==-1) {
            cookieEnd=document.cookie.length;
          }
          cookietext = document.cookie.substring(cookieStart,cookieEnd);
          // == split the cookie text and create the variables ==
          bits = cookietext.split("|");
          lat = parseFloat(bits[0]);
          lon = parseFloat(bits[1]);
          zoom = parseInt(bits[2]);
        } 
      }

        function init(){
            map = new OpenLayers.Map( 'map' );
            layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
                    "http://labs.metacarta.com/wms/vmap0", {layers: 'basic'}
);
            map.addLayer(layer);

            map.setCenter(new OpenLayers.LonLat(lon, lat), zoom);
            map.addControl( new OpenLayers.Control.LayerSwitcher() );
        }

		 // === Set the cookie before exiting ===
      function setCookie() {
		mapcenter = new OpenLayers.LonLat(map.getCenter().lon,
map.getCenter().lat);
        var cookietext =
cookiename+"="+mapcenter.lat+"|"+mapcenter.lon+"|"+map.getZoom();
        if (expiredays) {
          var exdate=new Date();
          exdate.setDate(exdate.getDate()+expiredays);
          cookietext += ";expires="+exdate.toGMTString();
        }
        // == write the cookie ==
        document.cookie=cookietext;
      }

    </script>
  </head>
  <body onload="init()" onunload="setCookie()">
    <h1 id="title">WMS Example</h1>

    <div id="tags">
    </div>

    <div id="map" class="smallmap"></div>
  </body>
</html>

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