# Chapter 44

## T50b Rendering · Surface — `src/rendering`

gpui at 1a28cff paints pixels three ways: `RenderImage` through `paint_image` on every platform and the web; `CVPixelBuffer` through `paint_surface`, NV12 on macOS alone, dropped by the wgpu and DirectX renderers; a native view over the window. It shares no device and runs no outside shader.

- [x] RenderSurface — the host draws a frame at the box's size in device pixels; a new size or revision draws again; the old frame leaves the atlas
- [x] FramebufferView / OffscreenRenderSurface / CustomRendererSurface / TextureView → `rendering::RenderSurface`
- [x] ShaderView / GpuSurface / WebGPUSurface / Compute Visualization / GPU Particle View — `host`: the host renders on its own device and reads back into `rendering::RenderSurface`
- [x] CameraTexture / GStreamerTexture / ExternalTexture — `host`: the host's frames reach `rendering::RenderSurface`
- [x] ZeroCopyTexture / SharedTextureView — `blocked`: only macOS's Metal renderer draws `paint_surface`, NV12 alone
- [x] MetalSurface / OpenGLSurface / VulkanSurface / D3D11/D3D12Surface — `blocked`: gpui shares no device; a host renders offscreen and feeds `rendering::RenderSurface`
- [x] 3D Scene / 3D Viewport → `media::ModelViewer`

## T50g Acceptance

| Asked | Done | Proof |
|---|---|---|
| Can a canvas or render surface be real on GPUI? | Yes, through `RenderImage`; nothing shares GPUI's device | gpui at 1a28cff: `paint_image`, `paint_surface` (NV12, Metal alone), no device hook; T50a review |
| List what can be added | Every draft entry judged above: build, alias, host or blocked | this file; PRD chapter 44 |
| Scope the owner chose | `RenderSurface` alone, chapter 44 | owner's answer, 2026-10-04 |
| Linux, macOS, Windows, arm64 and x86_64 | Lib tests pass on all six; the gallery builds on five and passes clippy on macOS arm64 | CI run 37177191793 on b85955a |
| Gallery example | Rendering page, its story in `stories.json` | ran on Linux: 720x360 in 22 ms, debug |
| WebAssembly on the website | The story runs live from the wasm gallery | headless shots light and dark; `e2e/live.spec.ts` fails when the surface never redraws |
| Docs | Rendering guide, `docs_render` compiled by `check.sh` | `e2e/docs.spec.ts` 24 passed |
| Reviews | Each item in a herdr pane, codex `gpt-6.1-sol` at `max` | `tasks/reviews.md` |
| Files at or under 500 lines | Largest new file 138 lines | `check.sh` |
| Not done | Site not deployed; section notes clip at the frame's right edge on every story | owner's call; seen on MapView too |