[QGIS-Developer] Fwd: [Qgis-user] Editing a multipolygon object changes type from Multipolygon to Polygon

[Bo Victor Thomsen]

I'll just add that  I have observed the same behaviour using a 
GeoPackage based layer. It was during a teaching session with 10-15 
students, so I can't remember exactly how and which editing tool that 
was the cause of the error.

Windows 10 / QGIS 3.22.3


Med venlig hilsen / Kind regards

Bo Victor Thomsen

Den 01-04-2022 kl. 17:38 skrev Jörg Höttges via QGIS-Developer:
> Hi everyone,
>
> I'm using QGIS 3.16 to 3.22. I created a table with multipolygon 
> objects in a SpatiaLite database. When editing one of the polygons 
> there appears a warning "Die Operation würden Geometrietyp ändern" 
> ("The operation would change geometry type") and saving of the 
> changings failes.
>
> Following are the objects before and after the modification:
>
> before editing:
> wkt_geom: MultiPolygon (((379698.83699999999953434 
> 5709466.37000000011175871, 379705.34999999997671694 
> 5709460.93499999959021807, 379703.7970000000204891 
> 5709459.07600000035017729, 379697.34799999999813735 
> 5709464.77400000020861626, 379698.83699999999953434 
> 5709466.37000000011175871)))
>
> after adding the point (379701.02700000000186265 
> 5709464.54299999959766865):
> wkt_geom: Polygon ((379701.02700000000186265 
> 5709464.54299999959766865, 379705.34999999997671694 
> 5709460.93499999959021807, 379703.7970000000204891 
> 5709459.07600000035017729, 379697.34799999999813735 
> 5709464.77400000020861626, 379698.83699999999953434 
> 5709466.37000000011175871, 379701.02700000000186265 
> 5709464.54299999959766865))
>
> how can I make sure that the type does not change due to editing? The 
> only idea i have is to remove or modify the geometry constraint in the 
> Spatialite database table for the geometry column. The warning still 
> appears but saving is successful.
>
> Interesting fact: The problem didn't appear with QGIS 3.16.
>
> Many thanks for your help!
>
> Jörg Höttges
>
> -------
> FH Aachen
> University of Applied Sciences
> Bayernallee 9
> 52066 Aachen | Germany
> www.fh-aachen.de/menschen/hoettges
>
>
>
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