[Qgis-user] Split features tool behavior

[Andreas Wicht]

On 29 May 2017 at 13:16, Andreas Wicht <a.wicht at gmail.com> wrote:
> On 28 May 2017 at 14:43, James Wood <jwood911 at gmail.com> wrote:
>> On the digitizing toolbar, try "Split Parts" instead of "Split Features" on multipart polygons.
>
> Thank you for the hint, James. Somehow I always thought that this
> function is only suitable for separating an existing part from a
> feature (never used it though).
> Yet, if you cut a polygon with the "Split Parts" tool, the output will
> be an invalid geometry (I observed self-intersections). This as well
> can not be the intended behavior. I could observe those errors in
> simple scratch layers as well as in PostGIS layers.
>
> Has anybody else experienced this behavior?

Is my assumption right, that according to this issue
(https://issues.qgis.org/issues/12799) the current workflow would have
to look somewhat like this:
- use split parts tool to split the multipart polygon
- delete the newly created part (-> invalid geometry) using the
"Delete Part" tool

either
- create a new feature/new part (depending on the use case) inside the
hole created by deleting the part
- optional: attribute merging with other features surrounding the new
feature (depends on the complexity of the attribute table)
- change desired attribute(s) (which led to the decision to separate the area)

or
- use the "Reshape Features" tool to enlarge a neighbouring polygon by
the cut off area

or
- create new feature inside the hole and merge it ("Merge Selected
Features" tool) to enlarge a neighbouring polygon by the cut off area

Isn't that a bit too much post-processing for that cause?

Any thoughts?