[OpenLayers-Users] IE strategies

[Andreas Hocevar]

Yves Moisan wrote:
> Here's my vector layer : 
>
> pts_gps = new OpenLayers.Layer.Vector("GeoJSON", {
>      strategies: [new OpenLayers.Strategy.BBOX(),new
> OpenLayers.Strategy.Cluster()],
>      protocol: new OpenLayers.Protocol.HTTP({
>      url: "http://myserver:8080/PGTEST4326/all.json",
>     format: new OpenLayers.Format.GeoJSON(),
>     params:{maxfeatures: 100}
>      }),
>     format: new OpenLayers.Format.GeoJSON(),
>     styleMap: new OpenLayers.StyleMap({
>                "default": style,
>         "select": {
>         fillColor: "#8aeeef",
>          strokeColor: "#32a8a9"
>          }
>     })
> });
>   

This looks perfectly sane.

> To illustrate what I was saying in the previous email, here's a bunch of
> screenshots : 
>
> maxFeatures=  1000 :
> http://www.flickr.com/photos/30818159@N05/3180683492/
>
> maxFeatures=  1000, zoomed in :
> http://www.flickr.com/photos/30818159@N05/3179845579/
>
> maxFeatures=  5 : http://www.flickr.com/photos/30818159@N05/3180683598/
>
> maxFeatures=  5, zoomed in :
> http://www.flickr.com/photos/30818159@N05/3179845687/
>
> The first level of zoom is the same for both maxFeature values.  Zooming
> in mean I hit the + sign on the OL control once.  You can see (well
> almost) that when I zoom in with maxFeature = 5, i get *3* clusters each
> worth 1 feature.  It is clear from the zoomed in example with
> maxFeatures = 1000 that there *are* more than 3 features at that zoom
> level so I was expecting to see 5 features spread into N <= 5 clusters
> so something is wrong there.  If I zoom into the top right portion of my
> zoomed out window, I see no feature.  The same rubberband zoom with
> maxFeatures = 1000 gives me some features ??
>
> I saw a thread explaining the issue but I don't remember where.  I will
> investigate further and report if I find an explanation.
>   

You are probably referring to
http://n2.nabble.com/bbox-strategy-and-zooming-td1836240.html#a20489423

New features will only be fetched if you zoom out, not if you zoom in. I
had forgotten about this thread in my previous reply, sorry for the
confusion.

You can make the BBOX strategy aggressive by instantiating your BBOX
strategy like this:

new OpenLayers.Strategy.BBOX(invalidBounds: function(){return true;});

This will cause features to be fetched also if you zoom in.

Regards,
Andreas.

-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.