On Wed, Nov 18, 2009 at 12:56:34PM -0800, Dragan Podvezanec wrote:
>
> Hi all.
>
> I have 10 WMS layers (polygons) which do not overlap. I'm trying to panZoom
> to the center of the polygon which user clicked. I registered
> "featureselected" events on all WMS layers, like this:
>
> for(var i in map.layers[layer]) {
> mapa.events.layers[layer] = new
> OpenLayers.Control.GetFeature({
> protocol:
> OpenLayers.Protocol.WFS.fromWMSLayer(map.layers[layer],{
> geometryName:
> 'geometry',
> srsName: "EPSG:900913"
> }),
> hover: false
> });
>
>
> mapa.events.layers[layer][i].events.register("featureselected", this,
> function(e) {
>
> var objekt = e.feature;
> var bbox =
> (objekt.geometry.bounds);
> var newcenter =
> (bbox.getCenterLonLat());
> mapa.panTo(newcenter);
> }
>
> And this works. Map gets centered to the object that I have clicked. But as
> I see, there are 10 post request to Geoserver, featureselected is triggered
> on every WMS layer. Is this not an overhead? Why is event featureselected
> triggered, even I have clicked outside a layer?
The featureselected event *isn't* triggered -- that event just
centers the map. The event that requests the datai s the GetFeature control.
The GetFeature Control has no way of knowing that there is a feature under
your cursor without asking the server. What you have downloaded is just
images -- OL knows nothing about the geometries.
As such, it has to ask the server for each of the layers whether there is an
intersecting feature.
> 1. Is this normal behavior?
> 2. What would happen if I have 100 layers?
Probably what you would expect.
> 3. Should I use different approach? (To make invisible WFS layers on top of
> WMS layers, and then register featureselected to WFS layers?)
You could, assuming 'invisible' layers actually get select events (I don't
know if they do.)
> --
> View this message in context:
> http://n2.nabble.com/WFS-fromWMSLayer-selection-question-tp4028249p4028249.html
> Sent from the OpenLayers Users mailing list archive at Nabble.com.
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--
Christopher Schmidt
MetaCarta
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