Add support for WMS layer source in 1.3.0 version

[AlexGacon]

Hi,

I need to setup a GeoWebCache on the service available at https://data.geopf.fr/wms-r/wms?SERVICE=WMS&version=1.3.0.

When I configure the service in GeoWebCache, the tile requests fail because the GetMap request expects a CRS parameter instead of a SRS parameter.

It would be great to have the good parameter sent to the service.

[jusabatier]

Currently, you could use vendorParameter until it's patched :

    <wmsLayer>
      <name>ign:plan</name>
      <metaInformation>
        <title>Plan IGN</title>
        <description>Représentation graphique des bases de données IGN. Source : IGN</description>
      </metaInformation>
      <mimeFormats>
        <string>image/png</string>
        <string>image/jpeg</string>
      </mimeFormats>
      <gridSubsets>
        <gridSubset>
          <gridSetName>EPSG:3857</gridSetName>
        </gridSubset>
      </gridSubsets>
      <wmsUrl><string>https://data.geopf.fr/wms-r</string></wmsUrl>
      <wmsVersion>1.3.0</wmsVersion>
      <wmsLayers>GEOGRAPHICALGRIDSYSTEMS.PLANIGNV2</wmsLayers>
      <vendorParameters>CRS=EPSG:3857</vendorParameters>
    </wmsLayer>

But it'll work only if you deserve a single CRS.

[AlexGacon]

This is not enough : WMS 1.3.0 uses the parameter "CRS" to define the target CRS whereas GWC always send a SRS paramete. For a strict WMS 1.3.0 service, it does not work.

[aaime]

Such service seems broken then? The specification says that un-recognized parameters should be ignored (to allow for vendor parameters). Quoting from section 6.8.1:

A WMS shall be prepared to encounter additional request parameters that are not part of this International
Standard.

I cannot find better wording, but the executable test suite checks for parameters outside the spec, and makes sure they are ignored:

https://github.com/opengeospatial/ets-wms13/blob/548fb428cbe43e72d452a5202031fa6605cfdcdf/src/main/scripts/ctl/basic_elements.xml#L86

At the same time, I concur it's not enough to add CRS, WMS 1.3 uses an axis order that depends on the CRS being sent, so the BBOX parameter encoding should be rewritten accordingly.

[AlexGacon]

@aaime the problem is not that the service fails because of the presence of the SRS parameter but it fails because GWC does not provide a CRS parameter.