gotnukesgit/journeymap-biome-reveal

Biome Reveal is a companion mod for JourneyMap, a popular Minecraft mapping mod, built for the same GTNH modpack setup as version 1.7.10 with Forge. Its job is to show the biome name and its Forge biome tags for any part of the map you have already explored, not just the chunks currently loaded around you, when you hover your mouse over the fullscreen map. Normally JourneyMap will not show a biome for chunks that are not currently loaded, because the game's usual method for looking up a biome falls back to a generic, seedless calculation that returns the wrong answer for unloaded areas. Biome Reveal works around this by keeping its own small persistent record of every biome it has seen, built by periodically scanning the chunks near the player about once per second while you play, since scanning on the moment a chunk loads turns out to be too early to read real biome data. For single player worlds, the mod goes further: the first time it loads a world, it reads biome information directly from the save files on disk, so your entire already explored map works immediately, even areas you explored before installing the mod. This backfill trick does not work on multiplayer servers, since those save files live on the server rather than your own computer, so on a server the mod can only track chunks you load after installing it. Technically, the mod stores one byte per map column, grouped into gzip compressed region files, and changes a single piece of JourneyMap's own code using a technique called Mixin to redirect where the hover label's text comes from. Building it requires either using an automatic GitHub Actions pipeline that needs no local setup, or building locally with Java 21 for the build tools, while the mod itself still targets the older Java 8. The project is written in Java, requires JourneyMap version 5.2.19 FairPlay and the UniMixins loader already present in GTNH 2.9, and has no stars yet.