[mapguide-users] Getting all object Enveloppe

[David Hequet]

Arg, i was so close of my goal

I think i have to take a look on your idea because of MGSelection seems to
have a limit.

here is my code:

For i = 0 To aMgLayerCollection.GetCount() - 1
    aLayer = aMgLayerCollection.GetItem(i)
    aProvider = Me._getLayerSourceType(, aLayer)
    If aProvider <> "Autodesk.Raster" And aProvider <> "DWF" Then

        aLayerClassName = aLayer.GetFeatureClassName()
        If aClassArray.IndexOf(aLayerClassName) = -1 Then
            Me._log(aLayerClassName)
            aLayerFeatureId = aLayer.GetFeatureSourceId()
            aLayerResId = New MgResourceIdentifier(aLayerFeatureId)
            aFeatureReader = Me._featureService.SelectFeatures(aLayerResId,
aLayerClassName, aMGQueryOptions)
            aMGSelection.AddFeatures(aLayer, aFeatureReader, 0)
            aClassArray.Add(aLayerClassName)
        End If
    End If
Next i
aMgEnveloppe = aMGSelection.GetExtents(Me._featureService)
I got an error:
Une exception non classifiée s'est produite.Une exception non classifiée
s'est produite.
Une exception s'est produite dans la méthode
MgServerSelectFeatures.SelectFeatures à  la ligne 217 dans le fichier
c:\build_tux_area\mgdev\server\src\services\feature\ServerSelectFeatures.cpp
In english "non classified error"
When i use this method
aMgEnveloppe = aMGSelection.GetExtents(Me._featureService)

it didn't happen every time: 
on a map with ~30 features dispatched on 4 layers it's ok
on a map with ~1200 features on 2 layers it crash (if i try too much the
mgserver service crash).

i didn't see a getExtent method on the featurereader, i think i have to
check enveloppe for each feature in the reader?


Kenneth, GEOGRAF A/S wrote:
> 
> You don't have to use the selection part.
> You can extract the object directly from the feature reader.
> Once you have the object, you can also get the extent (aka bbox).
> If you then construct an envelope object, you can add the features 
> envelope to original envelope.
> 
> Something like:
> 
> create a new MgFeatureQueryOptions with an empty filter
> create a new Envelope
> For Each Layer
> {
>    Use a featureReader with the MgFeatureQueryOptions
>    Add the feature's envelope to the outer Envelope
> }
> Get zoom extents from the Envelope
> 
> 
> Other than this, I don't think you can optimize it anymore, as you need 
> to execute the query on each layer.
> 
> I think there is a "Get Extents" on the feature source, but I can't find 
> it. And I don't think it works on filtered datasources.
> 
> Perhaps you can execute the query with some SQL optimizations like 
> "Select Envelope(geometry) from datasource".
> 
> Hope it helps.
> 
> Regards, Kenneth, GEOGRAF A/S
> 
> 
> 
> David Hequet wrote:
>> Hello,
>>
>> I'm trying to make a fonction that can return me the enveloppe of the
>> entire
>> visible map (no way with original map extent).
>>
>> Explain: I have a map "template" with a lot of layers, i have a function
>> that change all the layer filter (basic filter, no spatial) to see
>> different
>> map based on that template. Doing that make the "zoom to original extent"
>> useless, because data are not on the same area.
>> I wan't to set the new map extent in the MapDefinition. 
>> My ask is about getting the new extent.
>>
>> I thought to do it like that:
>>
>> create a new MgSelection
>> create a new MgFeatureQueryOptions with an empty filter
>> For Each Layer
>> {
>>    Use a featureReader with the MgFeatureQueryOptions
>>    Add the selected feature to the MgSelection
>> }
>> Getting the MgSelection enveloppe
>>
>> It will work, but i don't think it's very optimized with a lot of
>> Layer/Feature (and it will used at each map load, filter modification..)
>>
>> Did someone have a better way?
>>
>> Thank you!
>>
>> Ps: sorry for my poor english, ask i you want precision.
>>   
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> 
> 

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