[OpenLayers-Users] understanding and implementing Strategy.BBOX correctly

[Puneet Kishor]

I don't quite understand Strategy.BBOX so I would welcome some help. My code is like so

    var vec = new OpenLayers.Layer.Vector(
        "Vector layer", {
            strategies: [new OpenLayers.Strategy.BBOX()],
            protocol: new OpenLayers.Protocol.HTTP({
                url: "http://path/to/data.json",
                params: {
                    "polygon": map.getExtent()
                        .transform(
                            proj.google,
                            proj.latlng
                        )
                        .toGeometry()
                        .toString()
                },
                format: new OpenLayers.Format.GeoJSON()
            }),
            
            styleMap: new OpenLayers.StyleMap({
                "default": style,
                "select": new OpenLayers.Style({
                    strokeColor: "red",
                    strokeWidth: 2,
                    graphicZIndex: 2
                })
            })
        }
    );
    
    map.addLayer(vec);    
    vec.setVisibility(true);
    
Now, the above works well if the map is loaded centered on a view whose `getExtent()` results in data. However, if the map is loaded centered on a view whose extent has no data, then no data are retrieved even when the map is then panned into the right extent. My understanding is that whenever extent changes, a new call is made, so it wouldn't matter if the initial extent didn't have any data. Once I panned/zoomed into the right extent, data would be retrieved and the layer rendered. However, that is not happening. What is the error of my ways, and how do I correct it?

Many thanks,


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Puneet Kishor