Conflating Subject Data Beyond the Downloaded Area Causes JOSM to Softlock

[Gregory]

Problem

When conflating data that has only been partially downloaded JOSM softlocks, becomes unresponsive, and the only way out I've found is to kill the process/application via tasking manager or simmilar.

This is a big problem, becasue the conflation plugin is one of the best ways I've found to improve feature geometries at scale. When manually improving feature geometries i.e. not importing from an existing data base, if this error occurs it can mean that all of a users work is lost if the layer was not saved prior to conflation (recovery is not always possible). Saving before every conflation is however, an inefficiency and one can easily forget to do this. The conflation plugin gives no indication/warning that anything is wrong until you trigger the error.

Even when importing from an existing database this could cause problems depending on the workflow used, becasue the plugin generates matches just fine even if features are not entirely within the downloaded area.

If you map without the hatched background in undownloaded areas it's very easy to trigger this error. The entire footprint of a building will be visible (even if you only downloaded one node).

It's also easy to misclick and trigger the error, because the conflation button is adjacent to the configure button and remove button.

Reproduction steps;

1. Partially download some data e.g. one node of a building footprint.
2. Open a new layer to use as a reference.
3. Draw the building's footprint on the reference layer
4. configure the conflation plugin
5. conflate
6. See error

Solution

Please make it so that when the conflation plugin attempts to repace the geometry of a feature, that it shows a pop-up warning about features not being completely in the downloaded area (as the replace geomerty tool does currently), instead of failing in such a catastrophic way.

I noticed that when conflating a larger number of features that those which were entirely within the downloaded area and were to be conflated before the error triggered would successfully conflate. Maybe it's possible to ignore the matched which are unable to be conflated.

Perhaps it would be possible to introduce a test/check that will show if conflation would fail due to features not being fully in the downloaded area, and which matches would fail to conflate to make locating them easier.

My initial thought is that solutions which require the user to resolve the error before conflating would be prefered, because it would increase the likelihood that those conflating using an existing source spot errors before conflating.

of course evaluate the possible solutions. I'm giving some suggestions of possible solutions here, but I haven't thouroughly analysed them all.

Revision:19277
Build-Date:2025-01-03 15:21:53

Identification: JOSM/1.5 (19277 en_GB) Windows 10 64-Bit
OS Build number: Windows 10 Home 22H2 (19045)
Java version: 22.0.2+9, Azul Systems, Inc., OpenJDK 64-Bit Server VM

Plugins:
+ conflation (0.6.11)

[Gregory]

Images Relevant to This Error