[Qgis-developer] QGIS Server and OL3 GetFeatureInfo requests issue

[G. Allegri]

Thanks Mathias!
I will investigate it. Maybe an heuristic for the tolerance could be used
on the base of the BBOX coordinates...

giovanni

2015-09-17 15:39 GMT+02:00 Mathias Walker <mwa at sourcepole.ch>:

> Hi Giovanni
>
>
>
> QGIS Server uses a fixed percentage (1 or 2%) of the image size as a
> default tolerance for GetFeatureInfo requests. This works nicely with a
> full sized image e.g. in the QGIS WebClient. But with the smaller image
> size in the OL3 GetFeatureInfo request this results in a single pixel
> tolerance which requires pixel perfect clicks.
>
>
>
> There are new parameters in QGIS Server to set the tolerance in
> GetFeatureInfo requests (should be available from QGIS 2.10):
>
>
>
> FI_POINT_TOLERANCE
>
> FI_LINE_TOLERANCE
>
> FI_POLYGON_TOLERANCE
>
>
>
> The tolerances can be set in pixels per geometry type.
>
>
>
> If you add these parameters to your OL3 getGetFeatureInfoUrl() calls, the
> feature info requests should respond to less precise clicks.
>
>
>
> Cheers
>
> Mathias
>
>
>
> Am Donnerstag, 17. September 2015, 12.07:32 schrieb G. Allegri:
>
> OL3 has changed the way GetFeatureInfo request parameters are generated.
>
> The nre way uses fixed WIDTH/HEIGHT and X/Y (I/J) params: 101 for the
> first and 50 latters. Then it builds the BBOX parameter consequently.
>
>
> The old way they were built from the size and extent of the map, and the
> query coordinate.
>
>
> The new style makes QGIS Server respond with empty results if the click is
> not exactly on the feature coordinates.
>
> I've tested the same request on the same layer served by Geoserver, which
> responds even with not so precise clicks.
>
>
> Can this be caused by coordinates rounding happening inside QGIS Server?
>
>
> giovanni
>
>
> --
>
> Giovanni Allegri
> http://about.me/giovanniallegri
>
> Gis3W - http://gis3w.it
>
> Ikare - http://ikare.it
>
> Twitter: https://twitter.com/_giohappy_
>
> blog: http://blog.spaziogis.it
> GEO+ geomatica in Italia http://bit.ly/GEOplus
>
>
>
> --
>
> Sourcepole - Linux & Open Source Solutions
>
> Weberstrasse 5, 8004 Zürich, Switzerland
>
> Tel: 044 440 77 11 Direkt: 044 515 67 71
>
> mwa at sourcepole.ch http://www.sourcepole.ch
>



-- 
Giovanni Allegri
http://about.me/giovanniallegri
Gis3W - http://gis3w.it
Ikare - http://ikare.it
Twitter: https://twitter.com/_giohappy_
blog: http://blog.spaziogis.it
GEO+ geomatica in Italia http://bit.ly/GEOplus
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