[Qgis-user] Vertex Tool instabilities

[Andreas Wicht]

Hi there,

lately I observed the following:
I was using the Vertex Tool quite a lot lately as I had to adjust
polygon boundaries in a larger layer (PostGIS table ~60.000 polygons).
The layer and the QGIS project use CRS 3857.
As I am aware of snapping issues I usually take care that snapping is
only enabled for layers where I really need it.
As QGIS enables snapping for each layer loaded (when setting enable
snapping by default in the settings, I guess) I forgot to turn it off
for some point layers (millions of features - address point layer) I
added later as a background reference. Those layers were using CRS
4326 and therefore re-projecting on-the-fly.
As soon as those were in the mix QGIS started to crash very frequently
(>10x per hour) when using the Vertex Tool.
After some time and frustration I noticed the snapping options and
disabled snapping for those point layers and the crashes stopped
immediately (no crashes for days).
The crashes appeared ONLY when using the Vertex Tool for me. Splitting
or reshaping features worked just as expected.

I know this is a very vague and not very technical description of a
problem which can be very frustrating to users who do not see the
connection between the snapping options, re-projecting on-the-fly and
those crashes.

I do not know if it is a Vertex Tool or re-projecting issue... or a
combination of both as other tools work fine.

QGIS Version 3.8.0 (OSGeo4W installer)
Win10
PostGIS 2.5.2

Cheers
Andreas