Parallel tool (Advanced Digitizing) snaps to curved segment in the wrong place

[bencahill]

What is the bug or the crash?

When drawing a parallel line, the line does not correctly snap to a curved segment (whether part of a line or a polygon). Instead it snaps to a light blue line showing where the line would be if it wasn't curved.

Example with snapping to a curved line:

Examples with snapping to curved polygon segments:

_Untitled.Project.QGIS.test2025-01-06.2025-01-24.09-47-31.mp4

_Untitled.Project.QGIS.test2025-01-06.2025-01-24.10-13-01.mp4

Steps to reproduce the issue

1. Enable snapping to segment.
2. Make a new temporary layer with CompoundCurve geometry type.
3. Draw a curved line and a straight line.
4. Draw a line between the straight line and the curved line (using segment snapping).
5. Draw a second line starting from the straight line and ending on the curved line (using segment snapping), using the Advanced Digitizing Parallel tool to make the line parallel to the previous line.
6. Observe that the new line does not snap to the curve as expected. Instead it snaps to where the line would be if it wasn't curved.

Versions

QGIS version
3.34.14-Prizren
QGIS code revision
0cdaf6d
Qt version
5.15.13
Python version
3.12.8
GDAL/OGR version
3.9.3
PROJ version
9.5.0
EPSG Registry database version
v11.016 (2024-08-31)
GEOS version
3.13.0-CAPI-1.19.0
SQLite version
3.46.1
PDAL version
2.8.1
PostgreSQL client version
16.2
SpatiaLite version
5.1.0
QWT version
6.3.0
QScintilla2 version
2.14.1
OS version
Windows 10 Version 2009

Active Python plugins
db_manager
0.1.20
grassprovider
2.12.99
MetaSearch
0.3.6
processing
2.12.99

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

This appears to be very similar to #53197 . That issue affected the Vertex Tool. This issue affects the Advanced Digitizing Parallel tool.

[agiudiceandrea]

The issue also occurs using QGIS 3.40.2.