[ka-Map-users] Function to clear addObjectGeo

[Brent Pedersen]

hi chris, another utility function you'll use:

kaMap.prototype.removeOverlays = function(canvas){
	len = this.aObjects.length;
  for(i=0;i<len;i++){
	  var item = this.aObjects[i];
		if(item.canvas == canvas){
		  canvas.removeChild(item);
			item.canvas = null;
      item = null;
		  this.aObjects.splice(i--,1);
			len = this.aObjects.length;
		}
	}
}


then call myKaMap.removeOverlays(myCanvas) at the start of drawMarkers.
because otehrwise, you jsut keep adding new markers without getting rid of
the old ones. and it will get rid of them when you're not at the scale you
want.

also as you have it now, you're creating a new canvas every time drawMarkers
is called. probably bad.

i'm not sure about the memory leakage of any of this...
-b




On 3/5/06, Base Bloc <chris at basebloc.com> wrote:
>
>  Hi Guys,
>
>
>
> I'm still plugging away to get some workable functions together to draw
> markers with tool-tips and it's hard work as I'm experienced with PHP but
> not so hot on JavaScript and DOM so am making all the usual mistakes but
> getting there slowly. I now have a system in place that at a curtain scale
> places markers within an extended extent of the visible map tiles using
> HttpRequest. All is working fine and I currently have the system getting
> markers from a database to place markers on the map at the required scale
> (1:300000), then adding more markers as the map is panned.
>
>
>
> The problem I'm encountering now is that although the function is working
> correctly as in it won't add markers+tool-tips until the map is zoomed to
> 1:300000 when the map is zoomed back out above 1:300000 the markers
> previously called all remain on screen and as there are over 7000 points you
> can imagine what this looks like at 1:4000000.
>
>
>
> Is there a simple way to clear all of the markers created by addObjectGeo
> when the map is zoomed out past a curtain scale or better yet add an event
> related to myKaMap.getCurrentScale() so they are only displayed when the
> scale in greater than X?
>
>
>
> Here are the functions I'm using at present:
>
>
>
> //creates separate image for each marker
>
> function create_marker (img_id, var_1, lat, lon)
>
>             {
>
>
>
>     document[img_id] = document.createElement( 'img' );
>
>     document[img_id].src = 'images/kamap.gif';
>
>
>
>                         var bname = navigator.appName;
>
>                         if (bname == "Microsoft Internet Explorer")
>
>                {
>
>
> document[img_id].attachEvent("onmouseover",tool_tip)
>
>
> document[img_id].attachEvent("onmouseout",tool_tip_out)
>
>                         document[img_id].attachEvent("onclick",page_link)
>
>                }
>
>                         else
>
>                {
>
>
> document[img_id].addEventListener("mouseover",tool_tip,false)
>
>
> document[img_id].addEventListener("mouseout",tool_tip_out,false)
>
>
> document[img_id].addEventListener("click",page_link,false)
>
>                }
>
>
>
>                                     //Sends content and format options to
> tool-tip
>
>                                     function tool_tip(){
>
>
>
>                                                 var test_var = var_1;
>
>                                                 var text = "My name is "
> +test_var+ ", and I'm am now understanding JavaScripts";
>
>                                                 overlib(text, STICKY,
> MOUSEOFF, CAPTION, 'info')
>
>                                                 }
>
>
>
>     myKaMap.addObjectGeo( myCanvas, lat, lon, document[img_id] );
>
>
>
>             }
>
>
>
>             function drawMarkers(){
>
>   Big_Extents = myKaMap.getGeoExpandedExtents();
>
>   myCanvas = myKaMap.createDrawingCanvas( 5000 );
>
>
>
>   //draw Markers within Big_Extents using kaXMLOverlay or just
> addObjectGeo()
>
>
>
>             var scale = myKaMap.getCurrentScale();
>
>
>
>             if (scale <= 200000)
>
>             {
>
>
>
>             //this is where the HttpRequest would normally go, but I have
> placed a couple of sample markers to make the script more clear
>
>             create_marker('C02573', 'Box', 511275, 1363860);
>
>             create_marker('C02574', 'Pipe', 515736, 1364260);
>
>
>
>             }
>
>
>
> }
>
>
>
> var scale = myKaMap.getCurrentScale();
>
>
>
>
>
>             myKaMap.registerForEvent( KAMAP_SCALE_CHANGED, null,
> drawMarkers );
>
>             myKaMap.registerForEvent( KAMAP_EXTENTS_CHANGED, null,
> maybeRedraw );
>
>             myKaMap.registerForEvent( KAMAP_MAP_INITIALIZED, null,
> drawMarkers );
>
>
>
> }
>
>
>
> Sorry there are a few calls to functions there which I have not added
> above, I didn't want to do a 500 line cut and paste, once I have it working
> properly I will post the full code and related functions.
>
>
>
> Any suggestions on a fix to this problem would be appreciated.
>
>
>
> Thanks,
>
>
>
> Chris
>
>
>
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Christopher Brown
>
> Head of Internet Development
>
> Base Bloc Cambodia
>
> #33, 123, Phnom Penh, Cambodia.
>
> P.O. Box 2086
>
> www.basebloc.com
>
> Tel (+885) 12 315 302
>
>
>
> _______________________________________________
> ka-Map-users mailing list
> ka-Map-users at lists.maptools.org
> http://lists.maptools.org/mailman/listinfo/ka-map-users
>
>
>
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