prometeu-runtime/discussion/workflow/plans/PLN-0116-implement-fake-local-render-backend.md

id	ticket	title	status	created	completed	ref_decisions	tags
PLN-0116	real-render-worker-establishment	Implement Fake Local Render Backend	done	2026-06-15		DEC-0033	runtime renderer worker backend drivers

Briefing

DEC-0033 requires fake/local backend behavior before desktop integration so worker semantics can be proven without a window.

Decisions de Origem

• DEC-0033: Real Render Worker Contract.

Alvo

Implement backend contracts that consume RenderSubmission plus read-only resources and produce OwnedRgba8888Frame.

Escopo

• Define or finalize a backend trait for worker rendering.
• Add a fake backend for deterministic tests.
• Add a local framebuffer backend that can rasterize through existing driver/GFX logic without exposing mutable Hardware as the worker contract.
• Verify output frame ownership and pixels.

Fora de Escopo

• No desktop upload/present.
• No runtime tick integration.
• No resource mutation policy changes.

Plano de Execucao

Step 1 - Define backend trait

What: Encode backend consumption contract. How: Trait consumes RenderSubmission and read-only resource access and returns OwnedRgba8888Frame or RenderWorkerError. File(s): HAL if shared, or system if internal; prefer HAL if host/drivers implement it.

Step 2 - Implement fake backend

What: Provide test backend. How: Fake backend returns deterministic frames, can block through harness, and can return typed errors. File(s): system test module or driver test utility.

Step 3 - Implement local framebuffer backend

What: Provide non-window raster backend. How: Use existing GFX rendering internally to turn submissions into OwnedRgba8888Frame, but expose only the backend trait and read-only resources. File(s): prometeu-drivers rendering modules, possibly a new backend module.

Step 4 - Add output tests

What: Prove frame content and metadata. How: Render simple Game2D and ShellUi submissions and compare OwnedRgba8888Frame pixels/metadata. File(s): driver/system tests.

Criterios de Aceite

• Backend trait does not expose mutable Hardware, Gfx, FrameComposer, or VM state.
• Fake backend supports deterministic blocking/error behavior.
• Local backend produces OwnedRgba8888Frame.
• Game2D and ShellUi submissions can produce frame output without a native window.

Tests / Validacao

• cargo test -p prometeu-drivers -p prometeu-system
• rg "&mut Hardware|&mut Gfx|FrameComposer" crates/console/prometeu-hal crates/console/prometeu-system/src/services/vm_runtime -n

Riscos

• Local backend may be tempted to reuse Hardware directly as the public worker contract.
• Resource access gaps may surface when moving from fake to local rasterization.