Distant Horizons - Make it compatible

A compatibility patch for Distant Horizons on Forge 1.20.1, so far for one mod: TerraFirmaCraft. Far terrain that Distant Horizons generates there gets its trees and plants instead of coming out bare. It only acts when TerraFirmaCraft is installed, and it contains no code from either mod.

TerraFirmaCraft

• With TerraFirmaCraft, and so TerraFirmaGreg, terrain that Distant Horizons generated itself had no trees, plants or boulders until a player walked close enough for the real chunks to exist.
• TerraFirmaCraft decorates a chunk from the biomes of its neighbours, and Distant Horizons hands it blank ones, so decoration failed for 15 of every 16 chunks. The blank neighbours now get their real biomes first.
• Chunks generated the normal way already have those biomes, so nothing changes for them.

Terrain generated earlier

• Far terrain made before the mod was installed is not repaired: Distant Horizons has marked those bare chunks as finished.
• To redo it, stop the server and delete world/data/DistantHorizons.sqlite*. Distant Horizons rebuilds from the region files and generates the rest again.

Generator modes

• The patch is for Distant Horizons' FEATURES generator, which builds far chunks in 3x3 windows and stands in blank chunks around them.
• INTERNAL_SERVER never had the problem: it generates and saves real chunks through the server. It is far slower and writes every far chunk to the region files.

In the log

• On start: Patched TerraFirmaCraft's chunk decoration for Distant Horizons.
• On first use: Filled biomes for N blank chunk(s) around [x, z]. The Unexpected issue when generating features warnings stop.
• If a TerraFirmaCraft update no longer matches, the patch stays off and says so in a warning. It cannot crash world generation.

Requirements

Minecraft 1.20.1, Java 17, Forge 47. Install it where the world is generated: on the server, or on the client for single-player. The other side does not need it. Written against TerraFirmaCraft 3.2.25 and Distant Horizons 3.3.3; neither is a hard dependency.

Related mods

Forge 1.20.1, on the side that generates the world. Free to use in modpacks.