[Qgis-developer] SLD export not compliant due to unit attribute in the root element

Mon Jul 25 01:04:16 PDT 2016

Hi Andrea,

I'm the author of the commits that add a 'units' attribute to 
StyleLayerDescriptor element.
https://github.com/qgis/QGIS/commit/b54b1598a6ba145a51aa266cde9282ae4d0378ad
https://github.com/qgis/QGIS/commit/f7ce8b94344e7a7dd12fac2a90bd84df30b7e82f

If you look at the code of these 2 commits, I didn't change anything 
about QGIS SLD interpretation. In the QGIS core, a 'units' attribute is 
used to defined the SLD default units for distance.
But I didn't add this 'units' attribute for QGIS and QGIS Server SLD 
interpretation, I add these 'units' for GeoServer.

I didn't used uomScale because of SLD has to be used for any DPI screen. 
So if a QGIS user made style in pixels, he has made the choice to have 
different rendering in different DPI screen. But if the user made style 
in mm on the screen, the stroke or line has to have the same size in 
different DPI screen.

Can QGIS extend SLD by added it's own schema for defining units attribute ?

Can we used a VendorOption, to specify mm on the screen like in GeoServer ?
http://docs.geoserver.org/latest/en/user/styling/sld-extensions/label-obstacles.html

About uom in Symbolizer, I think QGIS has to add it like GeoServer 
http://docs.geoserver.org/latest/en/user/styling/sld-extensions/uom.html#example

Regards,

René-Luc

Le 23/07/2016 à 14:53, Andrea Aime a écrit :
> Hi,
> I'm looking into improving the SLD export, and stumbled into a schema 
> violation
> that, if fixed, may cause other regression.
> In particular, the root element StyledLayerDescriptor contains a 
> "units" attribute that
> is not part of the SLD/SE specification, and thus makes validation fail:
>
> <?xml version="1.0" encoding="UTF-8"?>
> <StyledLayerDescriptor xmlns="http://www.opengis.net/sld" 
> xmlns:ogc="http://www.opengis.net/ogc" 
> xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" version="1.1.0" 
> xmlns:xlink="http://www.w3.org/1999/xlink" *units="mm" 
> *xsi:schemaLocation="http://www.opengis.net/sld 
> http://schemas.opengis.net/sld/1.1.0/StyledLayerDescriptor.xsd" 
> xmlns:se="http://www.opengis.net/se">
>    ...
> </StyledLayerDescriptor>
>
> It's in particular the units="mm" element. Checking the git history I 
> found it has been introduced by this commit:
>
> ---------------------
>
> b54b159 - rldhont <rldhont at gmail.com <mailto:rldhont at gmail.com>> 
> 23-ott-2015
> [BUGFIX] Set default units to mm in exportSld
>
> The default units in QgsMapRenderer is Millimeters. The default units 
> in SLD
>  is Pixel but exportSld does not convert all millimeters in pixels.
>
> We notes this bug by comparing default QGS Server rendering and 
> rendering with
>  the SLD generated by QGIS.
>
> To resolve it, we just have to add units to the document element.
>
> ---------------------
>
> The above comments seems to suggest something is actually using that 
> attribute, but I'm not sure what.
>
> Mind, GeoServer can parse the file the same, but if users try to 
> validate it (there is a validation button in the style editor), they 
> will get the following error:
>
> "ine 2: cvc-complex-type.3.2.2: Attribute 'units' is not allowed to 
> appear in element 'StyledLayerDescriptor'."
>
> Also, the attribute per se does nothing in a compliant client, since 
> SLD 1.1 lacks the very concept of "on screen unit", the uom allowed
> are pixel (on screen), meter (on ground), feet (on ground).
> A SLD export trying to be compliant should convert mm to pixels 
> assuming some DPI conversion factor (which means,
> making many changes around... bummer). I see there is already a 
> uomScale in the conversion properties, but I see it's not
> used for point symbol sizes (as the commit message says.. I actually 
> don't see it being used anywhere).
>
> Would it be ok to remove that attribute and use uomScale to properly 
> adapt sizes from mm to px instead?
>
> Cheers
> Andrea
>
> -- 
> ==
> GeoServer Professional Services from the experts! Visit
> http://goo.gl/it488V for more information.
> ==
>
> Ing. Andrea Aime
> @geowolf
> Technical Lead
>
> GeoSolutions S.A.S.
> Via di Montramito 3/A
> 55054 Massarosa (LU)
> phone: +39 0584 962313
> fax: +39 0584 1660272
> mob: +39  339 8844549
>
> http://www.geo-solutions.it
> http://twitter.com/geosolutions_it
>
> *AVVERTENZE AI SENSI DEL D.Lgs. 196/2003*
>
> Le informazioni contenute in questo messaggio di posta elettronica e/o 
> nel/i file/s allegato/i sono da considerarsi strettamente riservate. 
> Il loro utilizzo è consentito esclusivamente al destinatario del 
> messaggio, per le finalità indicate nel messaggio stesso. Qualora 
> riceviate questo messaggio senza esserne il destinatario, Vi preghiamo 
> cortesemente di darcene notizia via e-mail e di procedere alla 
> distruzione del messaggio stesso, cancellandolo dal Vostro sistema. 
> Conservare il messaggio stesso, divulgarlo anche in parte, 
> distribuirlo ad altri soggetti, copiarlo, od utilizzarlo per finalità 
> diverse, costituisce comportamento contrario ai principi dettati dal 
> D.Lgs. 196/2003.
>
> The information in this message and/or attachments, is intended solely 
> for the attention and use of the named addressee(s) and may be 
> confidential or proprietary in nature or covered by the provisions of 
> privacy act (Legislative Decree June, 30 2003, no.196 - Italy's New 
> Data Protection Code).Any use not in accord with its purpose, any 
> disclosure, reproduction, copying, distribution, or either 
> dissemination, either whole or partial, is strictly forbidden except 
> previous formal approval of the named addressee(s). If you are not the 
> intended recipient, please contact immediately the sender by 
> telephone, fax or e-mail and delete the information in this message 
> that has been received in error. The sender does not give any warranty 
> or accept liability as the content, accuracy or completeness of sent 
> messages and accepts no responsibility  for changes made after they 
> were sent or for other risks which arise as a result of e-mail 
> transmission, viruses, etc.
>
>
> -------------------------------------------------------
>
>
> _______________________________________________
> Qgis-developer mailing list
> Qgis-developer at lists.osgeo.org
> List info: http://lists.osgeo.org/mailman/listinfo/qgis-developer
> Unsubscribe: http://lists.osgeo.org/mailman/listinfo/qgis-developer

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/qgis-developer/attachments/20160725/69fb4b0a/attachment-0001.html>