[OpenLayers-Dev] Cluster strategy getResolution bug ?

[Tim Schaub]

Hey-

Alexandre Dube wrote:
> Hi Eric,
> 
>   Ok, I understand what you mean.  But I already set specific scales to 
> the vector layer that are supposed to give the same resolutions I need.  
> I mean :
> 
>   Base layer (map) has scales in its options: [ 100000, 50000, 25000, 
> 10000, 5000, 2500, 1000, 500, 250, 100]
>   Vector layer has scales in its options: [10000, 5000, 2500, 1000, 500, 
> 250, 100]
> 
>   So I expect the vector layer to have the good corresponding 
> resolutions, but it hasn't.  Maybe that is the issue.  Any thoughts ?

Only the resolutions in your base layer are respected.  Individual 
resolution values on all overlay layers are ignored.  When your map 
changes resolution, layer.calculateInRange is called for each overlay 
layer.  If this returns false, the layer is not displayed.

The layer.calculateInRange method checks layer.minResolution and 
layer.maxResolution.  If map.getResolution returns a value that is 
between the min/max for the layer (inclusive), calculateInRange returns 
true.  (The exception to this is when layer.alwaysInRange is true.)

If you are encountering a situation where calculateInRange does not 
return the appropriate value, or if you think the precision in the scale 
to resolution conversion is not consistent, please start a new thread 
(this has nothing to do with vector layers or the cluster strategy).

Tim

> 
> Alexandre
> 
> Eric Lemoine wrote:
>> Hi Alexandre
>>
>> If you want your vector layer to be visible only for a subset of the
>> base layer's resolutions you should set maxResolution and/or
>> minResolution in your vector layer options.
>>
>> If you pass an array of resolutions to the vector layer, you can end
>> up with vectorlayer.resolutions[i]  != baselayer.resolutions[i], where
>> i is any index of the vector layer's resolutions array.
>>
>> And I think you are hitting the above case, which is making the
>> cluster strategy doesn't behave as you expect it to.
>>
>> So I don't see anything wrong with the cluster strategy relying on
>> this.layer.getResolution.
>>
>> I'd really like to hear what others think about that.
>>
>> Cheers,
>>
>> Eric
>>
>> 2008/11/7, Alexandre Dube <adube at mapgears.com>:
>>   
>>> Hi devs,
>>>
>>>   I got a problem using the cluster strategy.  At first, it didn't
>>> seemed to work at all.  I always got the same number of feature with or
>>> without the cluster strategy applied.  After a few search, I found out
>>> the problem was at line 143 : *var* resolution =
>>> *this*.layer.getResolution();
>>>
>>>   I just replaced the line for : *var* resolution =
>>> *this*.layer.map.getResolution(); and it worked.
>>>
>>>   The reason is :
>>>
>>>   My base layer has 10 fixed scales ( which gives 10 resolutions), from
>>> 0 to 9.  My vector layer has only 7, which represents resolutions 3 to 9
>>> of the base layer's scales, but the vector layer itself has his own
>>> scales array from 0 to 6.  So, the line 143 which called resolution 3
>>> from the base layer calls resolution 3 from the vector layer, which is
>>> wrong !
>>>
>>>   Anyone else noticed this ?
>>>
>>> --
>>> Alexandre Dubé
>>> Mapgears
>>> www.mapgears.com
>>>
>>> _______________________________________________
>>> Dev mailing list
>>> Dev at openlayers.org
>>> http://openlayers.org/mailman/listinfo/dev
>>>
>>>     
> 
> 


-- 
Tim Schaub
OpenGeo - http://opengeo.org
Expert service straight from the developers.