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oak-editor/crates/oakrender/README.md
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Mike-Solar 013a175707 refactor: workspace layout — crates/, app at root, legacy C++ removed
Single mechanical restructure commit:
- root Cargo.toml = oakapp bin + workspace; one cargo build produces
  oakapp, oak-cli, oak-worker, liboakengine.dylib
- app/rust/src -> src/ (app at repo root, no rust/ nesting)
- src/<mod>/rust -> crates/oak<mod>; src/oakcore-rs -> crates/oakcore;
  src/bindings/oakotio -> crates/oakotio; src/engine/rust ->
  crates/oakengine (keeps cdylib+staticlib+rlib)
- public C headers include/<mod>/ -> crates/oakengine/include/<mod>/
- OFX SDK headers vendored into crates/oakplugin/ofx/ (HostSupport gone)
- legacy deleted: old src/ C++ modules, engine/, core/, ffmpeg_bridge/,
  app/ (Qt), cli/worker C++, root CMakeLists, third_party/KDDockWidgets
  submodule, otio-install, all build-* output (~40GB)
- oakstorage kept but excluded from the workspace (skeleton w/ todos);
  gpui excluded (own workspace)
- verified: cargo build green, cargo test --workspace 1845/0
  (with the documented OCIO_RS_* env override for the homebrew OCIO)
2026-08-10 20:24:25 +08:00

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# oakrender Rust crate
> Status: **implemented (M7 render wave)**. Every `todo!()` from the
> declaration draft is implemented; the crate builds, tests green
> (`cargo test`), and the C ABI surface in `include/render/*.h` is
> exported from `src/ffi.rs`. Deferred items are documented inline and
> in the **Deferred** section below.
## Scope
Replaces the C++ oakrender module (`src/render/src`): render manager,
ticket system + worker pool, textures and GPU backend dispatch, playback/
frame-hash caches, color processing (OCIO), the preview auto-cacher, and
the blit/display path.
Public contract: `include/render/*.h` (8 headers, ~165 functions) —
frozen, implemented verbatim by `src/ffi.rs`.
## Key architectural decisions (C++ → Rust mapping)
1. **The ProjectCopier inversion disappears.** C++ render deep-copied
the node project with raw C++ calls (the biggest render→node
coupling). In Rust this is impossible by construction: the copier
calls `oaknode_project_deep_copy` / `sync_copy` (designed in the
oaknode crate) through the C ABI. `copier.rs` here is a thin client.
2. **RenderProcessor's inheritance disappears.** C++
`RenderProcessor : NodeTraverser` becomes `eval.rs` (the closed
`JobSpec` set + the CPU-side hook implementations; graph traversal
stays in oaknode).
3. **Ticket/watchers.** C++ RenderTicket/RenderTicketWatcher (Qt
signals) become a ticket arena with completion callbacks —
exactly-once delivery (`ticket.rs`), `FnOnce` boxes fired on the
worker thread.
4. **GPU backend = wgpu (v25).** The C++ tree's backend plugin split
(liboakgl2/liboakvulkan behind `renderbackend_c.h`) exists because
C++ had no portable GPU abstraction. Rust has `wgpu` (Metal/Vulkan/
GL/DX12 in one safe API), so the Rust crate uses `wgpu` directly —
no backend plugins, no `renderbackend_c.h`, no dlopen. `backend.rs`
owns the wgpu instance/device/queue, the texture registry and the
WGSL blit pipeline. **Headless status: verified** — texture
create/upload/download and the plain-copy blit run without any
surface or event loop on macOS Metal (the GPU tests exercise them
and skip gracefully when no adapter is available).
5. **Threading.** The worker pool is scoped threads with a job
channel; every shared structure is `Mutex`/`RwLock`. Process
isolation (`ProcessPool`) is preserved as a documented stub: it
needs the oakengine_ipc worker binary, which is not wired this pass.
6. **OFX disappears from render.** pluginrenderer.cpp's functionality
moves to the oakplugin crate; this crate only sees plugin jobs as
opaque C ABI calls.
## Dependencies (registered)
| Crate | Version | Reason |
|---|---|---|
| `oakcore-rs` | path | Rational/TimeRange/PixelFormat value types (crate-internal) |
| `wgpu` | 25 | portable GPU backend — the direct replacement for the C++ GL/Vulkan backend plugins |
| `ocio-rs` | 0.2 | safe Rust bindings for OpenColorIO v2.5.2 (bundled real-OCIO build); the ColorProcessor implementation — OCIO is never rewritten |
## Layout
```
src/
lib.rs crate doc + module map
error.rs error codes (mirrors include/render/error.h)
handle.rs refcounted-handle scaffolding + live-object accounting
texture.rs Texture value type (wraps backend textures / CPU frames)
frame.rs VideoParamsPod + Frame helpers
cache.rs PlaybackCache / FrameHashCache family + C++-parity disk state
color.rs ColorProcessor over ocio-rs + default config + LUT library
manager.rs RenderManager singleton + lifecycle + disk cache
ticket.rs Ticket arena, params, exactly-once completion delivery
worker.rs Worker pool + process pool (stub) + graph snapshot store
autocacher.rs PreviewAutoCacher
eval.rs RenderHooks impl: the CPU evaluation seam
backend.rs wgpu device/queue/texture management + DisplayRenderer
copier.rs Render-side project copy client (bridge::node)
cancelatom.rs the cancellation primitive
bridge/ C ABI imports: node.rs, common.rs, codec.rs (dlsym-resolved)
ffi.rs include/render/*.h export layer
tests/ contract + golden tests (common/ has shared helpers)
```
## Hard rules
1. Every export goes through `handle::guard*`.
2. No `unsafe` outside `backend.rs` (GPU FFI) and `bridge/`.
3. F32 + ACEScg pipeline invariants are asserted in tests, not in
comments (see tests/pipeline_test.rs).
## Deferred (documented; tests gated with `#[ignore]`)
- **oakcodec frame payload I/O** — disk frame-cache read/write
(`oakrender_frame_cache_load/save`) and footage decode go through the
`bridge::codec` C ABI (EXR/JPEG). The oakcodec crate is a concurrent
wave; until it lands these fail explainably and the success-path
tests are `#[ignore = "needs oakcodec final"]`.
- **oaknode C ABI** — `oakrender_project_copier_set_project` /
`get_copy` success paths need `oaknode_project_deep_copy`; the
success-path copier tests are `#[ignore = "needs oaknode C ABI"]`.
- **Color-managed GPU blit** — the OCIO→WGSL shader generation is not
in this pass: `GpuContext::blit` handles the plain copy and returns
`Error::Failed` for a processor; the CPU path applies the processor
in float. `oakrender_color_processor_create_transform` resolves the
destination transform against the default config's reference role
until the oakcommon color-transform bridge lands.
- **Worker process isolation** — `ProcessPool` (oakengine_ipc worker
binary) is a stub; `start/post` fail explainably; the crash-isolation
tests are `#[ignore]`.
- **Audio rendering** — audio tickets complete with `Error::Failed`
(the audio graph path is not implemented); `oakrender_ticket_get_samples`
fails explainably.
- **Borrowed caches** — `oakrender_cache_wrap_borrowed` boxes an
opaque marker; queries on borrowed caches return `OAKRENDER_E_INVALID`
until the C++ interop layer lands.
- **`RenderManager::global()` returns `Option<Arc<…>>`** instead of the
draft's `Option<&'static …>` — a resettable singleton cannot hand out
stable references safely.
## Coverage
`COVERAGE.md` maps every C++ class of `src/render/src` to its Rust
home. `cargo tarpaulin` ≥ 80% excluding the deferred areas listed
above.