[Chameleon] adding several layers from the same external WMS

[Paul Spencer]

Yes, we have discussed this performance enhancement internally because 
of issues another client was having with performance.  The intention, I 
believe, is to implement the combining 'automagically' in mapserver wms 
client code, it would detect that more than one layer is coming from the 
same wms server in the same projection etc and would combine the 
requests if possible (i.e. if the layers are together).  I don't know if 
there is a bug in mapserver bugzilla on this or not, but I suspect there 
is ... in fact it is bug 116, and it has been marked P1 for version 4.1 
which means that it should get implemented in time for the next release 
sometime before March (hopefully).

I have cc'd Bart on this bug.

Re the combining of layers in a context, I know this works because I 
have been using it recently.  However, it does cause some funny side 
effects, like layer transparency doesn't seem to work correctly.

I would recommend that you create a bug in chameleon on maptools 
regarding the interaction with the upload/download context and I will 
try to take a look at it before the release.

Cheers,

Paul

Huub Fleuren wrote:

> 
> one of the Geodan mapswing components (the java  mApplet) uses a 
> combine=true setting for this purpose.
> the applet 'combines' a request to the server if the layers are al from 
> the same server url into a sigle GET request to the Geodan mapserver
> 
> in the chameleon/mapserv setup this would have to be done by the 
> mapserver after reading the map file
> 
> Huub
> 
> bartvde@xs4all.nl wrote:
> 
>> Hi list,
>>
>> in Chameleon there is the possibility to add layers from a treeview to 
>> the
>> map.
>>
>> In this case if a user adds e.g. 5 layers from the same external WMS, 5
>> LAYERS are created in the session MAP file, all with a connection type
>> WMS.
>>
>> This means 5 requests to the external WMS per Chameleon MAP refresh. In
>> theory, this could be solved by asking just one image to the WMS server
>> (layers=A,B,C,D,E). Ofcourse, this has the assumption that the five 
>> layers
>> from the external WMS are in sequence on top of each other, and not some
>> other layer in between.
>>
>> I have also noticed that when using the layers=A,B,C,D,E type of syntax,
>> the Web Map Context (save, upload) does not function any more.
>>
>> Any thoughts on this, could this be a potential performance enhancement
>> for Chameleon, and would this require changes in PHP/Mapscript or in the
>> Chameleon PHP code?
>>
>> Best regards,
>> Bart
>> _______________________________________________
>> Chameleon mailing list
>> Chameleon@lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/chameleon
>>
>>
>>  
>>
> 

-- 
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|Paul Spencer                           spencer@dmsolutions.ca    |
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|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|
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