[Qgis-user] Snapping options logic

[Gerhardus Geldenhuis]

Hi
I am having a bit of trouble understanding the logic behind when I get an
error message or not when I set snapping options.

I have taken the following steps:
Create New Raster Layer
Create new Shapefile layer 01 (Polygon)
Set snapping options for Shapefile to:
Mode: to vertex
Tolerance:15
Units: pixels
Avoid Int: Checked

Draw some vectors and get intersections working. ( very cool feature ! )

Create new Shapefile layer 02 (Polygon)
toggle edit mode for layer 01
select new Shapefile layer and toggle edit mode
draw a triangle

Now I get an error message:
The feature could not be added because removing the polygon intersections
would change the geometry type.

So I thought it might have to do with the snapping settings so I set the
snapping settings for layer02 the be the same as layer01.

Draw triangle still get the same error.

Uncheck the Avoid Int checkbox for layer01

Draw Triangle, no error message.

I don't understand why that would cause the error message to go away. Is
avoid intersections not supposed to be limited to a specific layer?

Regards

-- 
Gerhardus Geldenhuis
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