perf(screenshot): Phase D — native server-side region crop - #3
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…to JS) The in-tool region flow captured the frozen full-res screen, shipped the whole PNG to JS (10-30MB on a 5K display), base64'd it, decoded it, and cropped in a canvas — even for a tiny region. Now: capture_hold captures the frozen full frame once (while the main window is hidden) and keeps it in Rust; after selection, crop_held crops server-side with HiDPI scaling and returns only the small region as raw PNG bytes. release_held frees it on cancel. Memory is bounded to one held frame (cleared on next capture). physical_crop_rect (logical→physical, clamped) is a pure fn with 6 unit tests. Screenshot.tsx loads the crop via createImageBitmap — no base64, no full-res decode. Region button is Tauri-only so there's no browser path to preserve. cargo test: 19 passed; JS: 385 passed. Manual test: crop is pixel-accurate on HiDPI and correct on a secondary display. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_013dqouzFP8vy9jaKhTDFj5H
This was referenced Jul 21, 2026
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Summary
Completes the screenshot optimization plan. The in-tool region flow no longer ships a full-res PNG to JS to crop in canvas — it holds the frozen full frame in Rust and crops server-side, so only the small region crosses IPC.
Before → after
<img>decode → canvas crop.capture_holdkeeps the frozen frame in Rust; after selectioncrop_heldcrops with HiDPI scaling and returns just the region as PNG;release_heldfrees it on cancel. Memory bounded to one held frame.Details
physical_crop_rect(logical→physical, clamped) is a pure fn with 6 unit tests (identity, 2× retina, edge-clamp, negative-origin, zero-dims, zero-logical fallback).Screenshot.tsxloads the crop viacreateImageBitmap— no base64, no full-res decode.Testing
cargo test→ 19 passed (incl. the 6 new crop tests); JS → 385 passed.Note
capture_hold/crop_heldare macOS-only, consistent with the rest of desktop capture (Windows/Linux capture is still unimplemented).🤖 Generated with Claude Code