[QGIS-Developer] Split features tool behavior

[Andreas Wicht]

Hi all,

I have a question regarding the behavior of the "split features" tool
when it comes to multipart polygons.
For that I created a small example (see split_features_1.png).

The polygon "1" is a multipart polygon as shown in the screenshot.
Let's say a user wants to split the lower polygon into two in order to
merge one part to the polygon "3" (here the workaround would be the
usage of the reshape features tool) or to create an entirely new
feature. (see split_features_2.png).

The expected result would be a the separated polygon (here on the
right) and the rest of the polygon including the part on the top. 1
Multipart Polygon and 1 Polygon.

The QGIS result is three separate Polygons. This behavior can be
dangerous when editing complex layers.
If furthermore attributes are being changed and aggregations happen
potential errors or unexpected results for a user are imminent.

Other GIS produce the expected output of 1 Multipart Polygon and 1 Polygon.

What is the specific intention behind this behavior as it seems not
quite intuitive?

Cheers
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