[Qgis-developer] Re: [Qgis-user] QGIS mapserver project

[Marco Hugentobler]

Hi Martin,

> Btw. is it necessary to link also to gui library?

You're right, it works only with core. I had the link to gui in the makefile 
from the 0.8 time on and didn't realize it is not needed anymore.

> > QGIS mapserver doesn't (yet) have the same number of features as the
> > maperservers which are around for many years. But it is already usable as
> > a basic WMS server with SLD styling capabilities. It already supports
> > GetCapabilities and GetMap over HTTP GET and allows client defined
> > styling with SLD.
>
> How would you compare SLD with QGIS display capabilities? Is SLD a
> subset or superset of what can be displayed with QGIS libs? I'm
> wondering whether SLD could be useful also for saving layer's
> symbology...

The SLD specifications contain more than QGIS provides. But for me it seems 
that the idea was to cover everything and so most existing software only 
supports a subset of SLD (e.g. for UMN mapserver, see 
http://mapserver.gis.umn.edu/docs/howto/sldhowto/#server-side-support).

Some examples what SLD containes and QGIS does not provide:

Complex filters possible for categories, combinations of spatial filters, 
and/or, equals, greater, lesser, greater or equal, lesser or equal, between, 
like

lines: graphic fill, custom fill/gap

polygons: graphic fill (repeated texture)

point: the URL of any graphic file can be given as symbol

And there are also raster and label contained in SLD spec...

For qgis internal purposes, I think it would be easier to use the qgis xml 
format. But for exchange of symbologies with other applications, SLD would be 
better.
Some time ago, I started to write a plugin which generates an SLD 
configuration file for the server from loaded QGIS layers. But maybe 
import/export from/to SLD would also be interesting for QGIS gui?

> At some point in future I should deploy a web application with mapping
> support, so I'll take a look if this mapserver is usable enough. It's
> a pity that QGIS doesn't support advanced symbology and the labeling
> is still very inmature - these features are quite important for a good
> mapserver.

Yes, lots of work to be done :-)

What do you think are the most important missing symbology capabilities?

cheers,
Marco


-- 
Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
marco.hugentobler at karto.baug.ethz.ch