[birkskyum]

+proj=krovak with different +x_0 and +y_0 doesn't round-trip. With +x_0=100 +y_0=0, 16.85°E 50.21°N comes back ~280 m away, because the inverse applies the false easting to the northing and the false northing to the easting. All EPSG Krovak CRSs use equal values, so they aren't affected.

This PR applies each offset to its own axis, the same way as the forward.

• AI (Copilot or something similar) supported my development of this PR. See our policy about AI tool use. Use of AI tools must be indicated. (Claude Opus 5.5)
• Tests added
• Added clear title that can be used to generate release notes

[jjimenezshaw]

Hi. Why were you testing krovak with false easting or northing? Is there any official CRS like that?

[birkskyum]

No, not that I know of. All the EPSG ones use the same value for both.

We're adding projection support in MapLibre, so I was fuzzing PROJ and proj4js for inconsistencies, and this was one of them. It still matters for custom strings, since the forward already handles different values correctly and only the inverse mixes them up. It's been like this since 9.4.0, when mod_krovak was added.