Intentional deviation from Ghostty 1.3.1 (DEVIANT_FIXES.md row 34).
When a Metal buffer grows, Zig's renderer/metal/buffer.zig:89 and :146
compute the new size as twice the required *byte* count and then
multiply by @sizeOf(T) again, so large cell buffers allocate
sizeof(T) times more GPU memory than intended. The Rust Metal backend
(since bab49ee) allocates exactly twice the required bytes; this commit
factors the computation into metal_layout::grown_buffer_bytes, adds a
regression test and records the deviation.
Test Plan:
- cargo test -p ghostty-renderer
grown_buffer_bytes_is_double_the_required_bytes_not_scaled_by_size_of_t
- just check-macos
Resolves the parity items of docs/rewrite/notes/review-rv17-codex.md
(final-Z20.md):
- FreeType-only font backend is also available on Apple targets
(discovery-free, embedded emoji fonts); ghostty_surface_quicklook_font
returns null for every backend except plain CoreText like Zig.
- The +list-fonts test keys off the font crate's selected backend
(HAS_DISCOVERY), correct under feature unification and on Apple.
- Inspector font: 32 px rasterized with FreeType (dear-imgui freetype)
like Ghostty; a new `visual-parity.sh inspector` scenario shows 0.031%
differing pixels (hover highlight) vs the original on Linux. Windows,
Apple and wasm keep stb_truetype at 32 px (registered as a deliberate
deviation).
- Inspector DCS/APC descriptions follow Zig 0.15.2's formatting
(checked by running Zig), incl. the terminal.Parser.Action prefix.
- The ImGui demo window appears only in dev-profile builds, mirroring
Zig's .Debug-only gate.
Test Plan:
- cargo test --workspace --no-fail-fast (3582 passed)
- just check-macos (both, also with --features font-backend-freetype)
- scripts/visual-parity.sh inspector
Intentional deviation from Ghostty 1.3.1 (DEVIANT_FIXES.md row 33).
Zig's os/systemd.zig:116 accepts a NOTIFY_SOCKET path of exactly 108
bytes and then writes the terminating NUL to path[108], one past the
end of sockaddr_un.sun_path (out-of-bounds write). The Rust port's
socket address construction (since f8c5ce0) accepts at most 108 bytes
without a NUL and rejects longer paths, so it never writes out of
bounds; this commit records that deviation and adds a regression test.
Test Plan:
- cargo test -p ghostty-os notify_maximum_length_socket_path_is_rejected_safely
Ghostty can be built with -Dfont-backend=freetype, which uses FreeType
without any font discovery. The Rust port only had fontconfig+freetype
(default on Linux) and the CoreText variants. The new cargo feature
`font-backend-freetype` on ghostty-font (forwarded by ghostty-cli and
the root crate; non-Apple, non-wasm targets) behaves like Zig's mode:
font-family discovery, fallback search and codepoint-map overrides are
skipped (embedded fonts only); +list-fonts and +show-face print Zig's
"built without a font discovery mechanism" message and exit 1; +version
reports `.freetype`. The default backend is unchanged.
Also registers the Rust-only benchmark tooling extensions (--time,
--handler=full, ghostty-synthetic +sgr) in DEVIANT_FIXES.md.
Note: `--all-features` now selects this backend for the workspace.
Test Plan:
- cargo test -p ghostty-font --features font-backend-freetype (198)
- cargo build --features font-backend-freetype && ghostty +list-fonts
Intentional deviation from Ghostty 1.3.1 (DEVIANT_FIXES.md row 32).
Zig's os/open.zig runs `try collectOutput(...)` before `wait()`: when
collection fails (e.g. a stream exceeds the 50 KiB limit), the error
returns early and the child is never waited for, leaving a zombie
process for the lifetime of Ghostty.
The Rust opener thread now always waits for the child (the pipes are
already closed at that point) and still logs the collection error.
Test Plan:
- cargo test -p ghostty-os open
Intentional deviation from Ghostty 1.3.1 (DEVIANT_FIXES.md row 31).
Zig's apprt/gtk/ipc/new_window.zig:49-53 builds the D-Bus argument
array from raw bytes as a *trusted* GVariant; an argument with invalid
UTF-8 or an interior NUL violates GVariant's string invariants, which
GLib turns into a process abort. The Rust port mirrored this with an
explicit abort().
new_window now validates every argument before touching the bus: a bad
argument prints an error to stderr and returns Error::IpcFailed, so the
CLI exits with failure and nothing crashes. Valid arguments are sent
byte-identically to Ghostty.
Test Plan:
- cargo test -p ghostty-apprt-gtk new_window
(invalid_dbus_strings_are_rejected_without_abort)
Resolves the parity items of docs/rewrite/notes/review-rv15-codex.md
(final-Z18.md):
- os::open inherits stdin like Zig's Child.init, strips LD_LIBRARY_PATH
only in Snap builds (new `snap` cargo feature, off by default, like
Zig's snap build option) and bounds output collection to 50 KiB per
stream (StdoutStreamTooLong/StderrStreamTooLong).
- +show-face writes diagnostics and lookup lines in the exact fragments
Zig's formatter produces, so buffer drains happen at the same byte
positions (0 diffs vs /usr/bin/ghostty over 0-44 bad options for
three codepoints); its tests no longer parse the test runner's argv.
- DEVIANT_FIXES.md: five entries reworded and four removed that were no
longer deviations (verified against code and oracle).
Test Plan:
- cargo test -p ghostty-os open; cargo test -p ghostty-cli show_face
Adds docs/rewrite/DEVIANT_FIXES.md, the single list of places where the
Rust port deliberately behaves differently from Ghostty 1.3.1:
- 30 upstream bugs fixed instead of replicated (memory safety/UB,
infinite loops, crashes, data loss), each with Zig file:line, both
behaviours, the commit that introduced the Rust behaviour and its test
(a few Zig locations are marked unverified);
- 11 upstream quirks deliberately kept as in Zig;
- 18 other deliberate deviations (out-of-scope Swift app, platforms that
are only compile-checked, library substitutions with observable
differences).
Deviations made from now on are committed alone as fix-deviant(<scope>)
and added here; earlier ones are bundled in larger commits, which is why
the register records their hashes.
Intentional deviation from Ghostty 1.3.1 (upstream data-loss bugs, see
docs/rewrite/DEVIANT_FIXES.md and docs/rewrite/notes/final-Z17.md):
- Zig 0.15's File.writer writes positionally (pwrite) at each writer's
own offset, starting at 0, while the file is seekable. When stdout is
a regular file, two writers (e.g. +show-face) overwrite each other and
any existing content, and File.Writer.end truncates. ZigWriter always
appends at the current end and end() only flushes.
- Writers that are never flushed lose their buffered output in Zig, e.g.
+list-themes' stderr buffer, so "No themes found..." is never printed.
ZigWriter flushes on drop.
Zig's buffering and flush order (and thus pipe/tty interleaving) is kept
unchanged; only the data loss is not replicated.
Test Plan:
- cargo test -p ghostty-cli zig_writer
(regular_file_output_is_complete_and_appended,
unflushed_buffer_is_flushed_on_drop)
- ghostty +list-themes with a missing resources dir prints the message
Resolves RV14 (docs/rewrite/notes/review-rv14-codex.md, final-Z17.md):
- +show-face --cp parses as u21 (new U21 field type): out-of-range
values give an invalid-value diagnostic and exit 1 instead of a panic;
--string accepts raw bytes and fails with error.InvalidUtf8 after the
codepoint lookup like Zig.
- CLI actions write through ZigWriter, a model of Zig 0.15's buffered
File.writer (fixed buffer, drain on overflow, explicit flush), so
stdout/stderr interleave in Zig's flush order (+show-face, help,
version, validate-config, show-config, list-*, ssh-cache, crash-report,
edit-config, new-window).
- Zig 0.15.2 std.fs.path.isAbsolute port (Windows: \theme and /theme are
absolute) replaces Path::is_absolute at every Zig isAbsolute site.
- io_uring is available iff a 256-entry ring can be created, like
libxev; the reactor falls back to IORING_OP_TIMEOUT without EXT_ARG.
- Windows basename (`λ:theme`) verified against 0.15.2 (test added).
Test Plan:
- cargo test --workspace --no-fail-fast
- diff +show-face outputs (pipe) against /usr/bin/ghostty
The first basename port followed Zig 0.16's ComponentIterator-based
implementation (the system std); Ghostty 1.3.1 builds with 0.15.2. The
theme-name check now ports 0.15.2's basenamePosix/basenameWindows: a ':'
at byte 1 ends the drive designator for any first byte, so '1:theme'
yields 'theme'. Tests use the 0.15.2 cases.
Resolves the 4 P3 items in docs/rewrite/notes/review-rv13-codex.md
(final-Z16.md):
- async-backend now takes effect like Ghostty: ghostty_os::xev ports
libxev's backend detection (io_uring, then epoll); global init detects
and logs it, the GTK startup applies the config with Zig's messages,
and +version reports the real backend. The termio IO loop runs on a
new reactor with epoll, io_uring (io-uring crate) and poll(2) (kept
for macOS, where libxev uses kqueue). The 21 exec integration tests
run under every backend; io_uring was exercised here.
- auto-update-channel defaults to the build's release channel.
- Windows error names: sharing violation -> AccessDenied, plus
ERROR_FILE_EXISTS -> PathAlreadyExists and virus errors ->
AntivirusInterference, mirroring std.os.windows.OpenFile's NTSTATUS
mapping in Zig 0.15.2 (verified against its source by the
orchestrator).
- Exact ports of std.fs.path.basenameWindows/basenamePosix for theme
name validation (drive, UNC and device roots).
Test Plan:
- cargo test --workspace --no-fail-fast (3555 passed, exit 0)
- just check-macos (both), just check-windows, just check-wasm
- +show-config --default --docs vs /usr/bin/ghostty (only the
build-specific gtk-opengl-debug line differs)
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
Resolves the 3 remaining gaps in docs/rewrite/notes/review-rv11-codex.md
(final-Z14.md):
- ghostty-bench validates every occurrence of enum options in order
(Args::take_enum; empty value resets) like cli/args.zig, so
`--mode=bad --mode=noop` fails as in Zig.
- Theme paths with an interior NUL open the prefix like Zig's C-string
path handling (verified against /usr/bin/ghostty).
- Filesystem diagnostics print Zig's error names (error.FileNotFound,
NotDir, AccessDenied, IsDir, NameTooLong, SymLinkLoop, ...) via a
shared ghostty_os::zig_error mapping used by theme/path/config-file/
file_load/edit-config/list-themes; messages match the oracle.
Test Plan:
- cargo test --workspace --no-fail-fast
- just check-macos (both), just check-windows, just check-wasm
Adds scripts/visual-parity.sh (`just visual-parity`): launches the
installed Ghostty 1.3.1 and the Rust build in an isolated headless
nested weston (GL renderer, Mesa forced, weston-screenshooter via
--debug), with identical isolated config, a deterministic test page
(ASCII, ligatures, all SGR styles and underline kinds, 16/256/truecolor,
box/block/braille/powerline/nerd icons, CJK, emoji, wide chars,
cursor) and a tabs+splits scenario driven through Xwayland, then diffs
the captures (terminal area and chrome separately, heatmaps).
Fixes found by comparing against the original:
- A pane stayed blank after a nested split: the GTK render path called
draw_frame(false) where Ghostty uses drawFrame(true) (a re-realized
GLArea has a new swap chain that nothing else redraws).
- Sprite glyph antialiasing now ports z2d's default 4x4 multisample
rasterizer instead of tiny-skia's analytic coverage (pixels differing
from Ghostty's reference sprite sheets: 5.76% -> 1.20%, none off by
more than 96 levels); the sheet test tolerance is tightened to 0.1%.
Result vs Ghostty 1.3.1: test page 0.020% of pixels differ (196 px at
curly-underline ends and diagonal box strokes, max delta 86 levels);
tabs+splits and headerbar/tab bar are bit-identical. Details in
docs/rewrite/notes/visual-parity-VP.md.
Test Plan:
- just visual-parity (needs weston, weston-screenshooter, xdotool)
- cargo test -p ghostty-font (sprite sheet comparison)
Adds tools/difftest: a Zig driver built against a copy of Ghostty
1.3.1's own src/terminal (Zig 0.15.2, set up under target/ by
tools/difftest/setup.sh) and a Rust twin on ghostty-terminal, both
printing a canonical dump of every scrollback/active row (cells,
graphemes, styles, hyperlinks, row flags), cursor, modes, regions,
tabstops and colors. A seeded generator produces escape-heavy streams
(UTF-8/wide/combining/emoji, C0, CSI with edge params, SGR, modes, ESC,
OSC, DCS, margins, insert/delete); `just difftest` runs it with Zig
assertions on (ReleaseSafe vs debug Rust) and off (ReleaseFast vs
production Rust), with minimizers and a triage script.
Divergences found and fixed in Rust (each with a regression test):
- ill-formed UTF-8 decoding follows the SIMD path a default Ghostty
build uses (not Zig's scalar fallback)
- PageList::erase_rows keeps Zig's row-flag behavior on regrow
- grapheme move on wrap with left/right margins uses the original cell
Upstream bugs found and deliberately NOT replicated (per the project
rule): a stale cell pointer after page growth in Terminal.zig:482/539
that drops a grapheme, plus several Zig assertion failures/segfaults;
documented with minimized repros in docs/rewrite/notes/difftest-DF.md.
Final run: 390k cases across many geometries, 0 divergences (Zig-abort
cases, ~0.1-0.5%, are not compared).
Test Plan:
- just difftest 20000 "1 2 3"
- cargo test -p ghostty-terminal (regression tests)
Resolves the 8 gaps in docs/rewrite/notes/review-rv10-codex.md
(final-Z13.md):
- P1 memory safety: the C key-table action (and hovered-link/open-URL
payloads) could advertise a length larger than the NUL-truncated
allocation. A counted_bytes helper now passes the full bytes plus a
trailing NUL with len == byte count, like Zig's backing slices; all
C pointer+len structs were audited and tested to read exactly len.
- ghostty-bench args follow cli/args.zig (ordered duplicates, empty
value resets, first bad value errors, parseBool spellings); the C
benchmark tokenizer uses the ArgIteratorGeneral port.
- OSC 7 derived titles, desktop notifications and OSC 8 hover links
forward raw bytes to the runtime; GTK converts only for display.
- C diagnostic getter exports original bytes; escaped surrogates report
Utf8CannotEncodeSurrogateHalf; config float formatters print `nan`.
- Config::finalize_for(AppRuntime): GTK-only finalization (gtk-single-
instance=detect) and termio's cgroup hooks apply only to the GTK
runtime, so libghostty keeps `detect` like Zig.
Test Plan:
- cargo test --workspace --no-fail-fast (exit 0)
- cargo test -p ghostty-lib --features test-platform
- just check-wasm (macOS/Windows clippy re-run after the concurrent
terminal changes land)
Rust's str::parse accepts and rejects different inputs than Zig's
std.fmt.parseInt/parseFloat (underscores, base prefixes, signs). The
config layer already used the Zig ports; now the protocol parsers do
too (call site -> Zig reference -> status in final-Z12.md):
- zig_fmt moves into the leaf crate ghostty-zigfmt (ghostty-vt cannot
depend on ghostty-os); ghostty-os re-exports it unchanged.
- ghostty-vt: kitty graphics keys, kitty text sizing, OSC 4/5/10-19
color indices, hex color components and intensities, OSC 9 sleep and
progress, OSC 133 exit codes, OSC 3008 fields, kitty color palette.
- ghostty-terminal: tmux layout, format variables and pane tabs.
- ghostty-os: URI ports and %XX decoding; ghostty-bench CLI arguments.
Expected values were cross-checked against the real Zig toolchain.
Test Plan:
- cargo test --workspace --no-fail-fast
- just check-macos (both), just check-windows, just check-wasm
ddidderr