[Qgis-developer] WCS and Raster improvements for QGIS

[Marco Hugentobler]

Hi

In my opinion, it is better to use the Qt classes for the network 
requests than curl. In QGIS, we have QgsNetworkAccessManager, which 
picks up automatically the network settings from the options tab (proxy 
settings, exclusion list, password, disk cache). It has nice progress 
reporting by signal/slot, the possibility to interrupt the network 
request and a disk cache. And the possibility to provide custom 
implementations for all that if necessary.

Like this, WFS, WPS, WMS providers, plugin installer and open layers 
plugin (and third party python plugins) have a unified method to do 
network requests. No need to use a different network library for each 
one (and the mapping is never 1:1, there is always loss).

So while it might be quicker (in terms of development time) to use the 
GDAL provider, a standalone provider is always more native and flexible 
(that's also the reason there are QGIS vector providers for postgres, 
wfs, gpx, spatialite, grass while everything can be read with the OGR 
provider).

Regards,
Marco

Am 12.07.2012 15:51, schrieb Even Rouault:
>> Yes - Radim already made a first pass implementation using GDAL WCS
>> though he said there were some problems with it - I think the most
>> critical being that it doesn't support proxy access (I am speaking
>> under correction here as I haven't looked into it in that much detail
>> myself).
> This should be rather easy to add. It is just a matter of setting the right
> option to CPLHTTPFetch() (and thus the curl library), namely :
>
> <li>PROXY=val, to make requests go through a proxy server, where val is of the
>      form proxy.server.com:port_number
> <li>PROXYUSERPWD=val, where val is of the form username:password
>
> Note: They can also already be used by setting the GDAL_HTTP_PROXY and
> GDAL_HTTP_PROXYUSERPWD configuration options/environmenet variable, which will
> act on all GDAL/OGR drivers that go through the CPLHTTPFetch() function.
>
> I see Radim is already a GDAL committer, so there shouldn't be too much overhead
> if he wants to hack in the WCS driver.
>
>> I will let Radim comment on any other issues. I think from
>> the project perspective we don't mind too much which approach is used
>> if the result is efficient and integrates nicely into QGIS.
>>
>> Regards
>>
>> Tim
>>
>>
>>
>> --
>> Tim Sutton - QGIS Project Steering Committee Member (Release  Manager)
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee