Trait mods, Parts and attachments

cargo horizon-mod new <path> --template native pins an exact Horizon commit (the newest prebuilt game's, or --horizon <commit>'s; cargo horizon-mod update repins) and writes a flat project: horizon-mod.toml with [native], Cargo.toml, src/lib.rs, and empty assets/ and data/ directories. The template greets each player who joins. Build it with horizon-launcher native-build <path> --trust-native-code; cargo horizon-mod build packages the same project into a .hmod without compiling it (the manifest).

The root Rust package depends on horizon-mod-api (lib mod_api), never on the game. Its root src/lib.rs marks one impl Hooks with the attribute:

use mod_api::{self, Hooks};

#[derive(Default)]
struct Mod;

#[mod_api::horizon_mod]
impl Hooks for Mod {
    // Implement the hooks this mod needs.
}

The attribute generates the hooks() factory and derives optional hook subscriptions from this impl. The mod type implements Default; do not write a second factory. Keep the marked impl at the crate root. Rustc's "cannot find function hooks" at the launcher's generated call means the marked implementation is not at the crate root. The launcher links this package into a generated game executable and calls the generated factory in dependency order (a mod after the mods it depends on, else in bundle order). A mod with no raw injections skips horizon-mixins; typed hooks need no injection declarations. Dependencies follow the pinned Horizon Cargo.lock rules in The mod's crate.

Chapters

• Dependencies between trait mods
• Load phases and access
• Native entry point and diagnostics
• Hook dispatch and level hosts
• The typed API from mixin code
• Parts
• Registry keys
• Block Parts
• Block entity types
• Item and tag Parts
• Capability providers
• Item places and components
• An entity's items
• Entity energy and fluids
• Entity automation
• A menu's slots
• A block's fluids
• A block's energy
• Capability answer limits
• Consumable effects
• Transactions
• A mod's own capability
• Entity parts and mob goals
• Block-state facts
• Fake players
• Testing a trait mod
• Adding a hook
• Server attachments
• Host helpers and remaining gaps
• Camera and collision reads
• Item model values
• Owned item values
• Delayed tasks
• Extinguishing fire