[OpenLayers-Users] how to update bounds in a vector feature after modifications ?

[Andreas Hocevar]

See answers inline.

On Nov 18, 2011, at 10:55 , JS Ubei wrote:

> Hi dear list,
> 
> I have a vector feature "boxFeature" like :
> 
> ########
> var pointList = [
> new OpenLayers.Geometry.Point(-180, -90),
> new OpenLayers.Geometry.Point(180, -90),
> new OpenLayers.Geometry.Point(180, 90),
> new OpenLayers.Geometry.Point(-180, 90),
> new OpenLayers.Geometry.Point(-180, -90)
> ];
> var linearRing = new OpenLayers.Geometry.LinearRing(pointList);
> boxFeature = new OpenLayers.Feature.Vector(new OpenLayers.Geometry.Polygon([linearRing]));
> ########
> 
> 
> After object creation, if I ask feature bounds I have :
> 
> -180,-90,180,90
> 
> 
> Ok.
> 
> After I modify my feature like :
> 
> ########
> 
> boxFeature.geometry.components[0].components[0].x = 0;
> boxFeature.geometry.components[0].components[0].y = 0;

You have to use the API to modify coordinates. Instead of the above two lines, just do:

boxFeature.geometry.components[0].components[0].move(180, 90);

Or if you want to set the coordinates directly, you have to call clearBounds() on the geometry you changed, i.e.

boxFeature.geometry.components[0].components[0].x = 0;
boxFeature.geometry.components[0].components[0].y = 0;
boxFeature.geometry.components[0].components[0].clearBounds();

> [etc.]
> 
> myLayer.drawFeature(boxFeature);
> 
> ########
> 
> 
> And when I ask for feature bounds I have the old values :
> -180,-90,180,90

Now you will still have the same bounds, because these are still the bounds of the polygon.

"POLYGON((0 0,180 -90,180 90,-180 90,0 0))"

But if you now do

boxFeature.geometry.components[0].components[1].move(-180,90);

your polygon will be

"POLYGON((0 0,0 0,180 90,-180 90,0 0))"

and the bounds will be

-180,0,180,90

Andreas.

> 
> 
> I've try to use some functions like :
> 
> #######
> boxFeature.geometry.clearBounds();
> boxFeature.geometry.bounds = new OpenLayers.Bounds(0, 0, 180, 90);            
> boxFeature.geometry.calculateBounds();
> #######
> 
> But unfortunatly I always get the old bounds -180,-90,180,90
>  ...
> 
> Someone can help me ?
> 
> Thanks and best regards,
> 
> Nono
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-- 
Andreas Hocevar
OpenGeo - http://opengeo.org/
Expert service straight from the developers.