ddidderr
f68b11d469
Resolves the 3 P3 items in docs/rewrite/notes/review-rv12-codex.md (final-Z15.md): - Sprite strokes: tiny-skia is replaced by a port of z2d 0.10's stroke plotter (sprite/stroke.rs) plus z2d's arc segmentation and truncating integer compositing, feeding the ported 4x4 multisample rasterizer. All 36 reference sprite sheets now match Ghostty's byte for byte (test tolerance 0), and `just visual-parity` with a production build shows 0 differing pixels (max delta 0) against the installed Ghostty 1.3.1 for the test page (block and bar cursor) and the tabs+splits scenario, terminal area and chrome alike. tiny-skia dependency removed. - zig_error maps errno values per target via libc (Linux, Darwin/BSD) and Win32 codes the way Zig std does on Windows. - theme=. / theme=.. report "it is a directory" via a port of std.fs.path.basename, matching Ghostty. Test Plan: - cargo test --workspace --no-fail-fast (3498 passed, exit 0) - cargo build --profile production && just visual-parity - just check-macos (both), just check-windows, just check-wasm
63 lines
4.4 KiB
Markdown
63 lines
4.4 KiB
Markdown
# Visual parity vs original Ghostty 1.3.1 (agent VP)
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## Method (`scripts/visual-parity.sh`, `just visual-parity [scenario...]`)
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- A private headless `weston` (`--backend=headless --renderer=gl`, 1200x800, `desktop-shell`, no
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panel) per run, on its own socket in `$XDG_RUNTIME_DIR=/tmp/vp-runtime-$UID` (socket paths must be
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<108 bytes). The user's desktop is never touched. Mesa is forced for weston (`__EGL_VENDOR_LIBRARY_FILENAMES`
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-> 50_mesa.json); the NVIDIA EGL crashes Xwayland's glamor. `XWAYLAND_NO_GLAMOR=1`.
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- `weston --debug` is what authorizes `weston-screenshooter` (without it: "Output capture error: unauthorized").
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- Both apps run with `env -i`, `GSETTINGS_BACKEND=memory`, no D-Bus, isolated `XDG_CONFIG_HOME` with the
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same explicit config (JetBrains Mono 13, bg/fg, padding 8, `maximize = true` so the window geometry
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is deterministic, `cursor-style-blink = false`, `title = Ghostty`, no shell integration) and
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`LANG=C.UTF-8` (otherwise `printf '\U..'` in the test page prints literally).
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- Scenarios: `page` (block cursor), `page-bar` (bar cursor), `tabs` (new tab + split right + split down,
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driven with `xdotool` through Xwayland since the original Ghostty has no input replay; Rust is driven
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the same way so both apps are treated identically).
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Test page: `scripts/visual-parity/testpage.sh` (ASCII, ligatures, bold/italic/faint/inverse/strike/
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overline, all underline styles + colored, 16/256/truecolor, box drawing, blocks, braille, powerline,
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nerd font icons, CJK, emoji, wide chars, math, cursor). Not covered: mouse selection (no input
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injection into the original on Wayland; could be added through the Xwayland path).
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- `scripts/visual-parity/compare.py`: per-pixel max-channel delta, % differing, % > 8 / > 32 levels, max,
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mean, red heat-map PNG; run on the full frame, the terminal area and the headerbar strip.
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`scripts/visual-parity/zoom.py`: ref | rust | diff crops, upscaled.
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- Output (not committed): `target/visual-parity/<scenario>/{ref,rust,diff,diff-term,diff-chrome}.png`,
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`target/visual-parity/stats.txt`. `RUST_BIN` defaults to `target/production/ghostty`.
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Iteration build: `CARGO_TARGET_DIR=target/vp CARGO_PROFILE_PRODUCTION_LTO=off
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CARGO_PROFILE_PRODUCTION_CODEGEN_UNITS=16 CARGO_PROFILE_PRODUCTION_INCREMENTAL=true cargo build --profile production`.
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## Results (% of pixels differing at all; max channel delta)
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| scenario | before | after |
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|---|---|---|
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| page (full frame) | 0.130% (1250 px, max 93) | 0.000% (0 px; was 0.020% / 196 px before Z15) |
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| page-bar | same as page | 0.000% |
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| tabs + splits | 44.6% (a whole pane blank, bug) | 0.000% (bit-identical) |
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| chrome (headerbar, tab bar) | 0.000% | 0.000% |
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Sprite sheets (`ghostty-font` tests, Zig reference PNGs): differing pixels 5.76% -> 1.20% -> 0 (bit-exact after Z15;
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test tolerance is now zero).
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Font metrics, cell size, baseline, glyph rasterization, colors, cursor, underline positions, padding,
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GTK CSS/headerbar/tab bar were already pixel-identical; no change was needed there.
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## Fixes
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1. **Split rebuild blanked an unchanged pane** (`ghostty-core/src/surface/mod.rs`, `draw_frame`): the GTK
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`render` handler called `renderer.draw_frame(false)`; Zig's `glRender` uses `drawFrame(true)`. With
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`sync = false` and nothing dirty the renderer only re-presents the last target, which is cleared when
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the GLArea is re-realized (nested split = tree rebuild = unrealize/realize of every surface whose size
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did not change), so that pane stayed empty until something changed. Now `true` like Zig.
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2. **Sprite antialiasing** (`ghostty-font/src/sprite/canvas.rs`): replaced tiny-skia's coverage with a port of
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z2d 0.10's default `multisample_4x` rasterizer (4x4 samples, scanline spans with edge x rounded at
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sample row centers, non-zero filter, alpha = `coverage * 16 - 1`, full = 255, z2d's Bezier
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flattening with tolerance 0.1). (Stroke outlines were still tiny-skia's until Z15, which ported z2d's stroker.)
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## Remaining differences
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None (Z15). z2d's stroke plotter (pen, joins, caps, spline flattening), Cairo-style arc segmentation and
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z2d's truncating integer compositing were ported (`ghostty-font/src/sprite/stroke.rs`, `canvas.rs`;
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see `final-Z15.md`). Final `just visual-parity`: page, page-bar and tabs are 0 differing pixels on the
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full frame, the terminal area and the chrome (max delta 0). All sprite sheets in the `ghostty-font`
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reference test are bit-exact (tolerance now zero).
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