[mapserver-users] UTFGrid and Cluster, feature distinction: 0, single or clustered

[Alexandre Dubé]

Alright!  I found a workaround using OpenLayers only.  I also noticed 
that I made a wrong statement earlier.  Let me correct.

   In the grid, both the non-clustered AND clustered features are 
correctly returned.  It's in the 'data' object that only the 
non-clustered features are returned, which is fine by me.

   That being said, we know that the space character is always used to 
represent nothing.  Knowing that, I added an additional information to 
the callback method that normally returns the id of the feature and the 
attributes we had defined in the UTFDATA.  I added the index of the 
character.  If it's 0, the user clicked on nothing.  If it's anything 
else, it's a single feature if the id is set (since it exists in the 
data and was correctly returned) else (when there's no id), it's a cluster.

   I'm fine with using this solution, but if there was a way to 
accomplish that otherwise, i.e. using MapServer settings, please let me 
know.

Regards,

Alexandre


On 14-01-24 09:55 AM, Alexandre Dubé wrote:
> Hi,
>
>   I just noticed that when using Clusters, only the non-clustered 
> features (singles) are returned in the grid, so clicking on a cluster 
> is like clicking on nothing.  That explains the behavior I get.
>
>   I'll continue to look for a solution.
>
> Alexandre
>
>
> On 14-01-24 09:21 AM, Alexandre Dubé wrote:
>> Hello MapServer community,
>>
>>   I'm using the new UTFGrid [1] feature in MapServer in addition with 
>> Clusters [2] in an OpenLayers mapping application.  I'm trying to 
>> implement the following feature: when the user clicks on a single 
>> point, a popup gets shown (this works already) and when he/she clicks 
>> on a clustered feature, then it must show different popup, without 
>> any info about the features inside, nor the extent of the features, 
>> but containing a simple link to invite the user to zoom in more.
>>
>>   So basically, I'm looking for a way for the returned utfgrid data 
>> to know if the clicked element on the map is either: a single 
>> feature, a clustered feature or nothing at all.  I thought I was 
>> close to a solution, but it didn't work as I expected.  I thought of 
>> using the FeatureCount inside the UTFDATA and then use the value 
>> returned to determine the correct type:
>>
>>         UTFDATA '{"c":[Cluster:FeatureCount]}'
>>
>>   But the utf data only returns 2 values: 1 and 2.  It returns 1 when 
>> it's a single feature, else 2 whenever it's a clustered feature 
>> (regardless of the actual real feature count) and it also returns 2 
>> when the user clicks on no feature at all.  I'm not sure if my 
>> approach is a correct one, though...
>>
>>   Does someone have any idea how I could accomplish what I'm trying 
>> to do ?  I'm using a trunk version of MapServer I haven't updated for 
>> a couple months.
>>
>> Many thanks,
>>
>> Alexandre
>>
>> [1] http://mapserver.org/development/rfc/ms-rfc-93.html
>> [2] http://mapserver.org/mapfile/cluster.html
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