[Google Maps API v2] Snap a polyline to a road with GoogleMaps

[Khai Pham]

II want an user to draw a route with polylines on GoogleMaps. I've
found a way to snap a polyline ( example in the link, code in below ).
The code works with the directions service to draw a polyline on a
road, the only problem is this only works with G_TRAVELMODE_DRIVING
but I want to use G_TRAVELMODE_WALKING and when you use WALKING you
have to supply the map and a div in the constructor of the directions
object. When I do that it automatically removes the last line and only
displays the current line. I've tried several things like supplying
the map as null, or leaving out the map in the constructor.. I've also
tried to give a second map in the constructor, get the polylines from
the directions service and display them on the right map. But nothing
works! I'd appreciate it if someone could help me!

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

if (GBrowserIsCompatible()) {

  var map = new GMap2(document.getElementById("map"));
  map.setCenter(new GLatLng(53.7877, -2.9832),13)
  map.addControl(new GLargeMapControl());
  map.addControl(new GMapTypeControl());
  var dirn = new GDirections();

  var firstpoint = true;
  var gmarkers = [];
  var gpolys = [];
  var dist = 0;


  GEvent.addListener(map, "click", function(overlay,point) {
    // == When the user clicks on a the map, get directiobns from that
point to itself ==
    if (!overlay) {
      if (firstpoint) {
 
dirn.loadFromWaypoints([point.toUrlValue(6),point.toUrlValue(6)],
{getPolyline:true});
      } else {
 
dirn.loadFromWaypoints([gmarkers[gmarkers.length-1].getPoint(),point.toUrlValue(6)],
{getPolyline:true});
      }
    }
  });

  // == when the load event completes, plot the point on the street ==
  GEvent.addListener(dirn,"load", function() {
    // snap to last vertex in the polyline
    var n = dirn.getPolyline().getVertexCount();
    var p=dirn.getPolyline().getVertex(n-1);
    var marker=new GMarker(p);
    map.addOverlay(marker);
    // store the details
    gmarkers.push(marker);
    if (!firstpoint) {
      map.addOverlay(dirn.getPolyline());
      gpolys.push(dirn.getPolyline());
      dist += dirn.getPolyline().Distance();
      document.getElementById("distance").innerHTML="Path length: "+
(dist/1000).toFixed(2)+" km. "+(dist/1609.344).toFixed(2)+" miles.";
    }
    firstpoint = false;
  });

  GEvent.addListener(dirn,"error", function() {
    GLog.write("Failed: "+dirn.getStatus().code);
  });

}
else {
  alert("Sorry, the Google Maps API is not compatible with this
browser");
}

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