[OpenLayers-Dev] Cluster strategy should not process data when layer is currently disabled (visibility=false)

[Eric Lemoine]

Alexandre,

Layers do not have the zoomend event type, so I don't think your patch
is valid. Try with moveend and a check in the listener to handle zoom
change only. Eric

2008/11/13, Alexandre Dube <adube at mapgears.com>:
> Hi Eric, Ivan,
>
>   The following is enough to resolve the bug ( I think ).
>
> ##### patch ? start #####
>
> --- Cluster.js.original    2008-11-13 14:05:25.000000000 -0500
> +++ Cluster.js    2008-11-13 14:06:59.000000000 -0500
> @@ -72,7 +72,7 @@
>                  "beforefeaturesadded": this.cacheFeatures,
>                  scope: this
>              });
> -            this.layer.map.events.on({"zoomend": this.cluster, scope:
> this});
> +            this.layer.events.on({"zoomend": this.cluster, scope: this});
>          }
>          return activated;
>      },
> @@ -93,7 +93,7 @@
>                  "beforefeaturesadded": this.cacheFeatures,
>                  scope: this
>              });
> -            this.layer.map.events.un({"zoomend": this.cluster, scope:
> this});
> +            this.layer.events.un({"zoomend": this.cluster, scope: this});
>          }
>          return deactivated;
>      },
> ##### patch ? end #####
>
>
>
>   Trying that, I found an other bug which occurs with or without this fix.
>
>   If I pan to some place while the layer is not visible, then set it
> back to visible, features won't appear.  I'm not sure if that's because
> my vector layer is not in the layerSwitcher.  I toggle the vector
> layer's visibility with a dummy layer, like this :
>
>
>
> ### code start ###
> olDummy.events.register("visibilitychanged", olDummy, toggleVisibility);
>
> function toggleVisibility()
> {
>     var bVisible = this.getVisibility();
>     olWMS.setVisibility(bVisible);
>     olWFS.setVisibility(bVisible);
> }
> ### code end ###
>
> Ivan, could you test the behavior in your application ?
>
> Best regards,
>
> Alexandre
>
> P.S. Being good at finding bugs is easy and not really rewarding...
> Finding solutions, that's something !  You guys are doing great.  Cheers !
>
> Eric Lemoine wrote:
>> You guys are good to find bugs :-)
>>
>> I think that, instead of listening to the map's zoomend events, the
>> cluster strategy should listen to its layer's moveend events and check
>> in the listener that this is actually a zoom change before doing
>> anything. The moveend listener receives an object with a zoomChanged
>> boolean property. Can one of you try modifying the cluster strategy
>> with that and report back? (don't forget to change the unregistration
>> as well).
>>
>> Thanks.
>>
>> Eric
>>
>> 2008/11/13, Ivan Grcic <ivan.grcic at geofoto.hr>:
>>
>>> Hi Alex,
>>>
>>> i made a little hack to it...inside Strategy.Cluster.js inside cluster
>>> function  I added one more check:
>>> (OpenLayers.Util.indexOf(this.layer.resolutions, resolution) != -1)
>>>
>>> it doesnt do the clustering if current resolution is not contained
>>> inside layers array of resolutions.
>>>
>>> Index: Cluster.js
>>> ===================================================================
>>> --- Cluster.js	(revision 8317)
>>> +++ Cluster.js	(working copy)
>>> @@ -141,7 +141,8 @@
>>>      cluster: function() {
>>>          if(this.features) {
>>>              var resolution = this.layer.map.getResolution();
>>> -            if(resolution != this.resolution || !this.clustersExist()) {
>>> +           if((OpenLayers.Util.indexOf(this.layer.resolutions,
>>> resolution) != -1) && (resolution != this.resolution ||
>>> !this.clustersExist())) {
>>>                  this.resolution = resolution;
>>>                  var clusters = [];
>>>                  var feature, clustered, cluster;
>>>
>>> Greetings,
>>> Ivan
>>> On Thu, Nov 13, 2008 at 3:02 PM, Alexandre Dube <adube at mapgears.com>
>>> wrote:
>>>
>>>> I get the same behavior as Ivan's on my application which has very
>>>> similar
>>>> resolution settings on map an vector layer.
>>>>
>>>> Because a layer's features are not destroyed when it goes out of range
>>>> (inRange) or becomes invisible (visibility), the cluster strategy still
>>>> clusters those existing features. I don't have that many features to
>>>> display
>>>> when the layer becomes inRange, so I never noticed any slowing down.
>>>>
>>>> Alexandre
>>>>
>>>> Ivan Grcic wrote:
>>>>
>>>>> This post evolved from previous discussion named "bbox strategy and
>>>>> zooming"
>>>>>
>>>>> Clustering features with cluster strategy takes some time. If there
>>>>> are many features to cluster, it will take even more time :)
>>>>>
>>>>> So there are some scenarios where clustering shouldnt be recalculated.
>>>>>
>>>>> Example:
>>>>> I want to see my cluster layer only after 5th zoom level. No
>>>>> clustering should be made when i play on zoom level 0-4 with other
>>>>> layers,
>>>>>  because it slows things down, and the cluster layer is still not
>>>>> visible at all (its only clustering features in background)
>>>>>
>>>>> It should only cluster when layer is visible (and the current map
>>>>> resolution is inside array resolution of clustered layer, if we define
>>>>> seperate set of resolution)
>>>>>
>>>>> So if map has:
>>>>> resolutions: [0,1,2,3,4,5,6,7,8,9]
>>>>>
>>>>> and vector layer:
>>>>> resolutions: [5, 6, 7, 8, 9]
>>>>>
>>>>> clustering should occur only on vector layers resolution :5, 6, 7, 8
>>>>> and
>>>>> 9.
>>>>>
>>>>> I hope you see where im pointing now,
>>>>>
>>>>> Best regards,
>>>>>
>>>>>
>>>>>
>>>>>
>>>> --
>>>> Alexandre Dubé
>>>> Mapgears
>>>> www.mapgears.com
>>>>
>>>>
>>>>
>>>
>>> --
>>> Ivan Grcic
>>> _______________________________________________
>>> Dev mailing list
>>> Dev at openlayers.org
>>> http://openlayers.org/mailman/listinfo/dev
>>>
>>>
>
>
> --
> Alexandre Dubé
> Mapgears
> www.mapgears.com
>
>