Module layer_cache 

Render-layer cache for GPU-backed subtree caching.

LayerCache manages a pool of RenderTargets keyed by a caller-provided u64 layer_id. When a widget subtree is rendered, its output is saved to a RenderTarget; subsequent frames can composite the cached layer texture directly without replaying the full draw list, as long as the layer hasn’t been invalidated.

Invalidation model

• Each layer has a generation counter. The caller bumps the generation (via LayerCache::invalidate) when the subtree’s content changes.
• Layers that haven’t been accessed for max_idle_frames frames are evicted to reclaim GPU memory.

Usage

let mut cache = LayerCache::new(16);    // keep up to 16 layers
cache.begin_frame();

let layer_id = widget.stable_id();
if let Some(target) = cache.get(layer_id) {
    if !target.is_dirty() {
        // composite cached layer texture into the parent pass
        composite_layer(target.texture_view(), ...);
        return;
    }
}
// Layer is dirty or absent — render the subtree into it.
let target = cache.get_or_create(device, layer_id, width, height, 1)?;
render_subtree_into(target, ...);
target.mark_clean();

Structs

LayerCache

A pool of off-screen render targets, keyed by layer_id: u64.