Struct TexturePool 

pub struct TexturePool {
    textures: Vec<Arc<UserTexture>>,
    by_name: HashMap<String, usize>,
    fallback: Arc<UserTexture>,
}

Texture pool. Hold one per renderer; the comp pipeline borrows it whenever a preset’s user shader needs to bind disk-loaded textures.

Fields

textures: Vec<Arc<UserTexture>>

All loaded textures in disk-walk order. The order is stable across runs as long as the underlying filesystem returns the same listing — used by pick_rand to make sampler_rand0X deterministic.

by_name: HashMap<String, usize>

Lookup by canonicalised name.

fallback: Arc<UserTexture>

1×1 opaque white. Bound into unfilled slots and returned when a preset references a name that isn’t on disk. Keeps every user shader compileable + drawable even when the texture pool is empty.

Implementations

impl TexturePool

pub fn new(device: &Device, queue: &Queue) -> Self

Build a pool with only the 1×1 white fallback. Tests and headless CI paths use this; the real engine calls from_dirs after.

pub fn from_dirs(device: &Device, queue: &Queue, dirs: &[PathBuf]) -> Self

Build a pool by scanning each directory in dirs for image files. Earlier directories shadow later ones — pass user dirs before system dirs if you want overrides.

Decode errors are logged and the offending file skipped; missing directories are silently treated as empty.

pub fn scan_dir(&mut self, device: &Device, queue: &Queue, dir: &Path)

Append textures from one directory. Doesn’t recurse — flat layout matches MD2’s Textures/ convention.

pub fn get(&self, name: &str) -> Option<&Arc<UserTexture>>

Lookup by canonicalised name. name is compared against the lowercase stem of the source filename — get("clouds") matches both clouds.png and Clouds.PNG.

pub fn fallback(&self) -> &Arc<UserTexture>

Always-non-None fallback — bound into unfilled user-texture slots so the comp pass’s bind group is complete even when the pool is empty or a preset references a name we don’t have.

pub fn is_empty(&self) -> bool

true when the pool has no user textures (only the fallback). The renderer uses this to skip the disk-load scan path entirely on sampler_rand0X resolution.

pub fn len(&self) -> usize

Number of user textures (excludes the fallback).

pub fn pick_rand( &self, seed: u64, prefix: Option<&str>, ) -> Option<&Arc<UserTexture>>

Deterministic-per-seed pick from the pool, optionally filtered by name prefix. Returns None when no texture matches (caller can substitute the fallback).

MD2’s sampler_rand0X slots want a stable choice for the lifetime of a preset but a different choice across presets. The caller seeds with hash(preset_name) ^ slot_index to achieve that.