Snapping line vertex on curved line segment results in an offset

[j-briant]

What is the bug or the crash?

When moving a vertex from a line geometry (linestring, compoundcurve) and snapping it on a segment of a curved geometry, the point is placed next to the curve, where the line would be if the geometry was not curved.
Occured on PostGIS and temporary layers.

Expected: the moved point would be on the curved segment.

Steps to reproduce the issue

1. Create a line geometry (curved or not)
2. Create a curved geometry
3. Activate Snapping
4. Vertex Tool (current layer)
5. Move a vertex from [1. line geometry] onto a segment of [2. curved geometry]

Versions

Observed on QGIS 3.16.10 and 3.16.11, reproduced on 3.22.1

Supported QGIS version

• I'm running a supported QGIS version according to the roadmap.

New profile

• I tried with a new QGIS profile

Additional context

No response

[gioman]

@j-briant does it happens also if you use a projected CRS for the layers?

[j-briant]

@gioman Well now I'm confused, I can't reproduce this exact bug on Windows. But it does happen with both geographic and projected systems on Ubuntu 20.04 with QGIS 3.22.1
However on Windows 10, the Snapping Tool keeps having an offset when zooming after the snap, the moved point doesn't touch the curved line, both in geographic and projected systems (see gif). But maybe I'm missing something here.

[gioman]

@j-briant I can replicate the problem. It happens when snapping to segment, if you snap to vertexes it work as expected.

[alexbruy]

Duplicates #53197.