forgotten_caves/notes/02-asset_loader.md

Asset Loader

Current state

TGA loading is implemented in game/src/assets.rs. Image::from_tga(path) reads the file, parses the 18-byte header, skips the colormap block, and returns an Image — supporting type 1 (uncompressed) and type 9 (RLE) via the private decode_rle() function in the same module. game.rs uses it directly: Image::from_tga("assets/tilesets/overworld.tga").

Image also provides to_tileset() -> Vec<[u8; 64]>, which splits the image into 8×8 tiles row-major. Every tile is emitted; tile ID is the flat row-major index into the Vec, so tiles are never skipped or reordered. (Transparency is a per-pixel concern handled at blit time by blit_tile, not by the splitter.)

AssetStore (a named registry) is not yet implemented. Assets are currently loaded inline in Game::start().

Goal

Add an AssetStore so that game code can ask for an asset by name rather than loading files directly at the call site.

Design notes

• Image struct: width: u32, height: u32, pixels: Vec<u8> — done.
• A simple AssetStore could be a HashMap<&'static str, Image> loaded at startup.
• No streaming needed — the whole game is small enough to load everything upfront in start().
• Palette index 0 is transparent when blitting sprites. This convention is enforced by blit_tile() in pixelhelper.rs; the loader itself does not need to handle it.
• Pixel assets are stored as flat Vec<u8> of palette indices, row-major, width × height bytes.
• Future: consider embedding assets with include_bytes! to produce a single binary.

Open questions

• Should AssetStore hold pre-split tilesets too, or just raw Image values?