Struct LayeredTileCache 

pub struct LayeredTileCache { /* private fields */ }

Read-through composite cache. get / contains try each layer in order until one hits; put only writes to the first layer (which must be writable). Use to overlay a writable user cache over a read-only bundled cache: the bundled tiles serve instantly, new fetches accumulate in the user cache without polluting the bundle.

Implementations

impl LayeredTileCache

pub fn new( writable: Box<dyn TileCache>, fallbacks: Vec<Box<dyn TileCache>>, ) -> Self

Build a layered cache. writable receives all puts; fallbacks are tried in order on read misses.

Trait Implementations

impl TileCache for LayeredTileCache

fn get(&self, key: TileKey) -> Option<Image>

Look up the cached tile, decoded as a slint::Image. Returns None if the tile isn’t cached (or if its bytes failed to decode). Implementations should be cheap on the miss path.

fn put(&self, key: TileKey, bytes: &[u8]) -> Result<(), CacheError>

Store raw bytes (typically a PNG payload exactly as the source served it — the cache is encoding-agnostic). Errors here are returned but a fetching source will typically just log and keep going.

fn contains(&self, key: TileKey) -> bool

Quick existence check that avoids the decode cost of get. Default implementation falls back to get(key).is_some() — override on backends where existence is cheaper to test.

fn get_bytes(&self, key: TileKey) -> Option<Vec<u8>>

Read the raw bytes for a tile, if cached. Used by sources that want to do their own (off-UI-thread) decoding rather than the in-thread decode that get performs. Default returns None — backends that store raw bytes (FileTileCache) should override.