snapgeometries only snaps to vertices, not segments

[Martin-BKT]

What is the bug or the crash?

When snapping a point layer to a line layer, QGIS 3.16 snapped the points to the closest segment when using parameter 1, as seen in the example (yellow line layer as reference layer, red point layer, green result layer)

In QGIS 3.26, the same algorithm with the same parameter and inputs no longer snaps to segments, but only to vertices:

Steps to reproduce the issue

Create a point and a line layer. use snapgeometries to snap points to the lines using parameter 1.

Versions

QGIS 3.16.16: OK
QGIS 3.26.2: Not OK.

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

[nyalldawson]

Create a point and a line layer. use snapgeometries to snap points to the lines using parameter 1.

Can you clarify what you mean by "using parameter 1"?

[Martin-BKT]

Yes, of course. It’s the behaviour parameter, in full text: "Prefer closest point, insert extra vertices where required"

[roya0045]

Pretty sure this is a user error and not a QGIS one, did you check https://docs.qgis.org/3.22/en/docs/user_manual/working_with_vector/editing_geometry_attributes.html#snapping-and-digitizing-options ?

[Martin-BKT]

Pretty sure this is a user error and not a QGIS one, did you check https://docs.qgis.org/3.22/en/docs/user_manual/working_with_vector/editing_geometry_attributes.html#snapping-and-digitizing-options ?

The issue is not about snapping during edit, but when using snapgeometries in processing mode. Just open QGIS 3.16 and QGIS 3.26 with an initial user profile, create the 2 layers and use snapgeometries processing, and I would be surprised if you would get identical results.

[roya0045]

The issue is not about snapping during edit, but when using snapgeometries in processing mode. Just open QGIS 3.16 and QGIS 3.26 with an initial user profile, create the 2 layers and use snapgeometries processing, and I would be surprised if you would get identical results.

Ah right, it seems the 'closest' point' is now the closest vertex and not closest point on surface. And that's delegated to the QgsGeometrySnapper.

[github-actions]

The QGIS project highly values your report and would love to see it addressed. However, this issue has been left in feedback mode for the last 14 days and is being automatically marked as "stale".
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[Martin-BKT]

Ah right, it seems the 'closest' point' is now the closest vertex and not closest point on surface. And that's delegated to the QgsGeometrySnapper.

Yes, that's the issue. Unfortunately, the function is quite important for us, so we cannot update to the newest version until the issue is resolved.

[roya0045]

Yes, that's the issue. Unfortunately, the function is quite important for us, so we cannot update to the newest version until the issue is resolved.

Your options are to keep using your current version. Hope someone wants to fix the bug eventually, or try to get it fixed (by submitting a fixing or funding a dev to fix it for you.)

[github-actions]

The QGIS project highly values your report and would love to see it addressed. However, this issue has been left in feedback mode for the last 14 days and is being automatically marked as "stale".
If you would like to continue with this issue, please provide any missing information or answer any open questions. If you could resolve the issue yourself meanwhile, please leave a note for future readers with the same problem and close the issue.
In case you should have any uncertainty, please leave a comment and we will be happy to help you proceed with this issue.
If there is no further activity on this issue, it will be closed in a week.

[github-actions]

While we hate to see this happen, this issue has been automatically closed because it has not had any activity in the last 42 days despite being marked as feedback. If this issue should be reconsidered, please follow the guidelines in the previous comment and reopen this issue.
Or, if you have any further questions, there are also further support channels that can help you.

[untsvn]

Sorry I'm new to logging issues like this - is it possible to reopen this as an issue or is the etiquette to open a new issue?

Have just encountered this issue in v3.22 so tried an upgrade to v3.24. Appears the "Prefer closest point" options are not working and is falling back to "Prefer aligning nodes"

See below screen shot for what I expect snap to nearest point to do with a 3m tolerance. I would expect the input vertices to snap to the closest point on the segment (indicated by arrows) and add vertices to that line depending on which behaviour was selected.

processing.run("native:snapgeometries", {'INPUT':'S:/OneDrive/Desktop/temp.gpkg|layername=ref_1_input','REFERENCE_LAYER':'S:/OneDrive/Desktop/temp.gpkg|layername=ref_2a','TOLERANCE':3,'BEHAVIOR':1,'OUTPUT':'TEMPORARY_OUTPUT'})

GPKG with embedded QGIS project attached whcih demonstrates this exmaple.

qgis_snap_issue.zip

[gacarrillor]

This issue should still be open. Feedback was provided by the OP in due time.

Reopening, since I just confirmed the issue on QGIS master rev 51d8e5d7982.

[uclaros]

Fixed in #56426