Flutter embedder step 3b: Metal zero-copy renderer - #33
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Design for switching the out-of-process guest from the software renderer to the Metal renderer, rendering directly into shared IOSurface-backed Metal textures with a GPU completion fence before FrameReady. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Replaces the cross-thread retired-ring mechanism with raster-thread reallocation inside get_next_drawable, where the engine holds no texture. Simpler and equally correct. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The out-of-process guest now renders directly into shared IOSurface-backed Metal textures instead of memcpy'ing software-rendered frames. FrameReady is sent from a GPU completion-handler fence; the surface ring is reallocated inside get_next_drawable on resize. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
Step 3b of the experimental Flutter engine embedder: the out-of-process guest
switches from the software renderer to the Metal renderer, rendering
directly into shared
IOSurface-backed Metal textures — a true zero-copy pathwith no per-frame
memcpyand no RGBA→BGRA swap.FlutterRendererConfigbecomeskMetal. Each ringIOSurfacealso backs anid<MTLTexture>the engine renders into viaget_next_drawable/present_drawable.present_drawablecommits an emptycommand buffer on the shared
present_command_queueand sendsFrameReadyfrom its completion handler, so the GUI never reads a half-rendered surface.
surface.c→surface.m(Objective-C, ARC).get_next_drawablewhen the requested size changes; at that point the engineholds no texture, so a resize never races an in-flight texture and no ring
mutex is needed.
--capture-rawsmoke now reads the IOSurfaceback via
IOSurfaceLock;decodeRawFramedecodes BGRA.embedded_engine.dart,protocol.dart,EmbedderTexturePlugin.swift) and the wire protocol are unchanged — theplugin already wraps the IOSurfaces as Metal-compatible
CVPixelBuffers.Design and plan:
docs/superpowers/specs/2026-05-15-flutter-embedder-step3b-design.md,docs/superpowers/plans/2026-05-15-flutter-embedder-step3b.md.Test plan
flutter test test/embedder— protocol + raw-frame unit tests pass (raw-frame fixtures updated to BGRA)dart run app/tool/embedder/run.dart) renders the scene with correct colors/tmpsocket because the worktree path exceeds the macOS AF_UNIX limitflutter analyze— no issuesflutter run -t lib/main_embedder_dev.dart -d macos …) and confirm the live scene renders, resizes, and takes pointer/keyboard input with no Metal/IOSurface console errors or tearing🤖 Generated with Claude Code