[Chameleon] dataurl question

[Paul Spencer]

Debbie,

you raise a good issue relating to legends and how MapServer handles (or 
doesn't) handle them.

I just checked with Assefa and there is no support in MapServer for 
DataURL via metadata.  By this, I mean that setting a metadata item for 
wms_dataurl will not result in the dataurl appearing in either the WMS 
capabilities.  What is a bit confusing is that it is handled in Context 
documents (or at least it should be).  By this, I mean that when you 
load a context file, mapserver will create a wms_dataurl metadata (if 
necessary), and when you save a context, it should read the wms_dataurl 
metadata and include it in the context.  It is not clear to me if this 
is not working for you, or if you are trying to get it to work with the 
WMS server (which it won't yet).

As an aside, you mentioned that this is a work around :)  The SLD 
support being added into MapServer WMS will include GetLegendGraphic 
requests as well.  How this will be implemented is not yet clear to me, 
but I am expecting that legend graphic url information will be 
propogated to the WMS capabilities document will include a 
GetLegendGraphic request.  This may be driven by metadata, or 
automatically generated, or a combination of the two.

I would also like to see WMS client support for this in MapServer, so 
that if you are working with WMS layers in a mapfile (as is the case 
with CWC2), you could use the standard MapServer legend functionality 
and it would trigger a call to get the graphic associated with a WMS 
layer (as defined from capabilities or context), this would have to be 
driven by metadata.  There is already a preliminary implementation of 
this for legend icon information coming from contexts, I believe the 
metadata entry ends up being four space separated values as in: "<mime 
type> <width> <height> <url>"

Supporting legend graphics doesn't seem to be too difficult, but there 
are many issues surrounding it because of the interconnection between 
the various specs, including WMC, WMS, and SLD (getting a legend graphic 
should take into account any applied SLD).  There is also an issue with 
classes on layers, I don't know how that is handled (but I think there 
is a way).

Cheers,

Paul


Debbie Pagurek wrote:

> Hi all,
> I'm using a CWC installation, and am trying to work around the ongoing
> legend issue.  I notice that when you add a wms layer to CWC, and you
> click on the layer link, it opens up a box that shows "dataURL".  I
> would like to try to use this for my legend url, by putting a mapserver
> mode=legend url in there, as in:
> http://wms1.agr.gc.ca/cgi-bin/soil/ns/pockwock?mode=legend&layer=kind_dom
> 
> Question is, where do I put this data url in the mapfile so that it
> will appear in the CWC dataURL part?  I tried to put it in the metadata
> section of the layer under "wms_dataurl" but that doesn't seem to work?
> 
> Can anyone help?
> Debbie Pagurek
> 
> Debbie Pagurek, M.Sc.
> GIS and Remote Sensing Analyst / Télédétection, SIG
> Research Branch / D.G. Recherche
> Agriculture and Agri-Food Canada / Agriculture et Agroalimentaire
> Canada
> Telephone / Téléphone: 613-759-1543
> Facsimile / Télécopieur: 613-759-1937
> 960 Carling Avenue
> Ottawa, Ontario
> K1A 0C6
> pagurekd@agr.gc.ca
> 
> _______________________________________________
> 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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