Struct RenderPassDescriptorCache 

pub struct RenderPassDescriptorCache { /* private fields */ }

OPT 34: persistent render-pass descriptor and its inner attachments, reused across begin_render_pass_full calls.

Why

begin_render_pass_full historically allocated a fresh descriptor Object, a colorAttachments Array, and one inner color_attachment Object (plus an optional clearValue Object) on every frame, then ran 8-15 Reflect::set calls to populate them. WebGPU re-validates the descriptor each call, but the JS-side Object / Array allocations and the per-property Reflect::set crossings are pure overhead — only the clearValue and (rarely) view / loadOp / storeOp fields change between frames.

What we cache

• The top-level descriptor Object (the one passed to beginRenderPass).
• The colorAttachments Array (always exactly one element — we keep the same Array reference and mutate its slot 0 in place).
• The inner color attachment Object (slot 0 of colorAttachments).
• The clearValue Object (the {r, g, b, a} dictionary that is the actual per-frame mutating field).
• Last-applied loadOp / storeOp string slices, to detect when the caller switched ops and the cached descriptor must be rebuilt (rare; WebGPU does not hot-swap ops every frame).
• Last-applied depth-stencil shape (present / absent), to detect when the depth-stencil shape changes.

Invalidation

The cache is invalidated (rebuilt from scratch) when any of:

• load_op changes between calls,
• store_op changes between calls,
• the depth-stencil shape changes (None → Some / Some → None),
• the resolve-target shape changes (MSAA on/off).

view / resolveTarget / clearValue are refreshed on every call (the swap-chain view expires after each presented frame, so caching it across frames silently invalidates every subsequent render pass).

These are all &'static str (they come from WEBGPU_*_OP_* constants), so invalidation is a pointer-compare.

Clone is derived so the parent WebGpuRenderer’s Data derive (which adds a Clone bound on every field) keeps compiling; js_sys::Object and js_sys::Array both derive Clone, so the derived Clone impl just clones the inner JS-side references (cheap, no JS allocation).

Trait Implementations

impl Clone for RenderPassDescriptorCache

fn clone(&self) -> Self

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for RenderPassDescriptorCache

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.