[Chameleon] 2 "enhancement bugs"

[Yewondwossen Assefa]

Checking the context (1.0) specs, there seems 2 ways that the Style 
element might be used in a context file. The first is for named styles. 
The second option is to define and SLD. Here is the text from the sepcs 
refering to that :

Each <Style> element may alternatively define the style(s) of the layer 
with a <SLD> element.
The <SLD> element must contain required <Name> and optional <Title> 
elements which identify the particular element of a Styled Layer 
Descriptor to be used for this style. The <SLD> element must then 
contain one of three alternative sources of description of a layer style:

1. an <OnlineResource> element describing a link to the specified SLD 
document.
<OnlineResource
xmlns:xlink="http://www.w3.org/TR/xlink"
xlink:type="simple"
xlink:href=”http://example.org/this/is/an/example/link/to/the/sld">

This reference may be to a separately referenced SLD document or to an 
inline <StyledLayerDescriptor> in the same context document (which may 
define the styles for multiple layers within the Web Map Context)

2. <StyledLayerDescriptor> element containing inline the namedStyle or 
userStyle named in the enclosing <Style> element

3. <FeatureTypeStyle> element containing inline the specific feature 
styling instructions for the enclosing <Style> element


  Here is what can be done to support these :

    * for the online ressource, we need to upgrade the context reader to 
parse the SLD url and save it as a metadata on the layer. Should not be 
too much work to do this.

    * for the inline SLD, It requires more effort since it needed to 
convert SLD to/from mapserver classes. There is though some mapserver 
low level code to do this that can be used as a starting point.

Paul Spencer wrote:

> I'll have to get Assefa or Daniel to comment on this one, but I believe 
> that the style element is intended as a 'NamedStyle' that would be one 
> of the styles explicitly named by the WMS Server in its Capabilities 
> documents.  I am not sure if there is a mechanism to specify an SLD in 
> and/or filter with a layer in a Context document other than by modifying 
> the connection string appropriately.  This would be a misuse of the 
> standard, I think.
> 
> Cheers,
> 
> Paul
> 
> Bart van den Eijnden wrote:
> 
>> Hi list,
>>
>> I have 2 feature requests / "enhancement bugs" which in my opinion 
>> would make a nice addition to Chameleon, but there is also some 
>> overlap with PHP/Mapscript I guess. What would be the best place to 
>> put these, Chameleon bugzilla or Mapserver bugzilla?
>>
>> 1. SLD/Filter in the Web Map Context
>> I see that the Web Map Context standard already has a place (<Style> 
>> element) for including the SLD. This would open up the possibility of 
>> saving a selection created with the ExpressionBuilder widget into the 
>> Web Map Context file.
>>
>> 2. scale dependent LegendTemplate widget
>> The current LegendTemplate implementation does not look at the 
>> MINSCALE and MAXSCALE values to determine if a layer is visible or 
>> not. Would be a nice addition in my opinion to have a LegendTemplate 
>> which looks into these values to determine whether or not to include 
>> the layer.
>>
>> Best regards,
>> Bart
>> _______________________________________________
>> Chameleon mailing list
>> Chameleon@lists.maptools.org
>> http://lists.maptools.org/mailman/listinfo/chameleon
>>
> 


-- 
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Assefa Yewondwossen
Software Analyst

Email: assefa@dmsolutions.ca
http://www.dmsolutions.ca/

Phone: (613) 565-5056 (ext 14)
Fax:   (613) 565-0925
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