ltk_overlay 0.2.1

WAD overlay/profile builder for League of Legends mods
Documentation

ltk_overlay

WAD overlay/profile builder for League of Legends mods.

Overview

ltk_overlay is a Rust library that builds WAD overlay directories from enabled mods, allowing the League of Legends patcher to load modded assets. It provides:

  • Incremental rebuilds: Only rebuild WADs that have changed
  • Cross-WAD matching: Distribute mod files to all affected WADs (e.g., champion assets in Map WADs)
  • Layer system: Respect mod layer priorities for proper override resolution
  • String overrides: Apply metadata-driven string table modifications
  • Conflict resolution: Detect and resolve conflicts between multiple mods

Architecture

The overlay builder follows this workflow:

  1. Index game files: Scan the DATA/FINAL directory and build:

    • WAD filename index (case-insensitive lookup)
    • Hash index (path_hash → list of WADs containing that chunk)

  2. Collect mod overrides: Walk enabled mods and collect all override files with their hashes

  3. Distribute to WADs: Use the hash index to find all WADs that need each override

  4. Build WADs: For each affected WAD:

    • Load base WAD from game directory
    • Apply overrides
    • Write patched WAD to overlay directory
    • Preserve compression types and metadata

  5. Apply string overrides: Modify string tables based on mod metadata

Usage

use ltk_overlay::{OverlayBuilder, EnabledMod, FsModContent};
use camino::Utf8PathBuf;

let game_dir = Utf8PathBuf::from("C:/Riot Games/League of Legends/Game");
let profile_dir = Utf8PathBuf::from("C:/Users/.../profiles/default");
let overlay_root = profile_dir.join("overlay");

let mut builder = OverlayBuilder::new(game_dir, overlay_root, profile_dir)
    .with_progress(|progress| {
        println!("Stage: {:?}, Progress: {}/{}",
            progress.stage, progress.current, progress.total);
    });

builder.set_enabled_mods(vec![
    EnabledMod {
        id: "my-mod".to_string(),
        content: Box::new(FsModContent::new(Utf8PathBuf::from("/path/to/mod"))),
        enabled_layers: None,
    },
]);

let result = builder.build()?;
println!("Built {} WADs in {:?}", result.wads_built.len(), result.build_time);

Integration

This crate is used by:

  • ltk-manager: Tauri-based GUI mod manager
  • league-mod: CLI tool for mod developers

Implementation Status

  • Core types and API design
  • Game indexing (Phase 1)
  • WAD patching (Phase 1)
  • Incremental rebuild (Phase 2)
  • String overrides (Phase 3)
  • Conflict resolution (Phase 4)
  • Health checks (Phase 4)

See docs/overlay-implementation-plan.md for the full roadmap.

License

Licensed under either of:

at your option.