CompositionHelper.keydown exempted keyCodes 16/17/18 from tearing a composition
down, which covers Shift/Ctrl/Alt but not macOS Meta — 91/93 in Chromium, 224 in
Firefox. A lone Cmd press mid-composition therefore reached
_finalizeComposition(false), which dropped the preedit overlay's `active` class
and committed the live syllable early. macOS keeps the marked text alive across
that press, so no later compositionstart re-arms the overlay and the rest of the
word composes invisibly.
Measured on hardware (m4air, macOS 26.5.2, Apple M4, 2-Set Korean) with the Cmd
posted as a CGEventType.flagsChanged, which is what a physical modifier emits.
AppleScript `key code 55` posts nothing a browser can see — a bare `key code 56`
for Shift is equally silent — which is why no capture in the corpus ever reached
this branch. Three arms, same build otherwise: overlay live throughout with the
exemption, dark and prematurely committed without it, live again with it
restored. Evidence under
.tmp/ime-handoff/swarm-scratch/wave31-cmd-preedit/evidence/.
The fix cannot widen past a lone modifier: only a standalone press reports these
keyCodes, and a Cmd chord during composition is reported by Chromium as 229,
which was already exempt. Cmd+A still ends the composition, via the IME's own
compositionend. Ghostty draws the same line, returning early from flagsChanged
under hasMarkedText() for every modifier including Super.
Orca's terminal pane was never affected — shouldSuppressTerminalModifierKeyboardEvent
drops a standalone Meta keydown before xterm sees it, and deleting only 'Meta'
from that set is what flipped the hardware arm to broken. The popout preview
terminal and mobile's webview install no such guard and did reach the teardown.
terminal-ime-xterm-composition-commit-overlap.test.ts asked its fixer to update
the two Cmd arms to the values it named as correct; both now emit a single ['한'].
updateCompositionElements computed the overlay's left edge from the grid
but never its width, so the preedit rendered at the font's natural advance
while the committed text takes two cells per wide glyph. Measured in
Chromium 150: 가나다라 drew 48.45px as a preedit and 69.20px once committed
— the same characters, same font, 30% narrower, and drifting further with
each syllable. Every macOS mono font carrying Hangul measured 0.49–0.72 of
two cells; never 1.0.
Deriving the width from wcwidth and the cell measure moves Korean, Japanese
and Chinese to 1.000 and leaves ASCII at 1.000, which it already was:
한 12.125 -> 17.297 (17.30 expected)
가나다라 48.453 -> 69.188 (69.20)
안녕하세요 60.563 -> 86.500 (86.50)
日本語 42.000 -> 51.906 (51.90)
abcdefgh 69.234 -> 69.203 (69.20, unchanged)
Edited in config/patches/xterm-src/ and regenerated through the harness, so
the emitted patch and lockfile hash are derived rather than hand-written.
The unit test asserts the arithmetic, which is what CI can run. The pixel
consequence was measured on macOS with SF Mono in an Electron harness, not
on the Windows font stack STA-3232 reports from — so this demonstrates the
mechanism and does not stand as that row's platform evidence.
Type a Japanese segment, convert it, then press a key one macrotask later
and that key was lost. No modifier, nothing exotic — every user who keeps
typing straight after converting. Korean surfaced it first only because
2-Set composes on nearly every keystroke.
handleCompositionInput discarded the payload unconditionally in the window
after the deferred send: _isSendingComposition stays true for one macrotask
after the timer cleared _pendingCompositionStart, and the branch substituted
'' for whatever arrived. The suppression is not itself wrong — it
de-duplicates IMEs that deliver their commit an event-loop turn late, which
terminal-stock-composition.test.ts pins. It just could not tell a duplicate
from new input, because the two events are identical apart from payload.
Now it compares against _sentComposition, the text the deferred send
actually emitted, and discards only a match. A flag-timing redesign was
measured first and rejected: it fixed this and duplicated on IBus, because
no timing change can separate events that differ only in content.
Edited in config/patches/xterm-src/ and regenerated through the harness, so
the emitted patch and the lockfile hash are derived, not hand-written.
The commit-overlap pin's swallow arm now asserts the repaired contract —
the value its own comment already named as correct and as what stock
beta.287 emits. #11504's arm at :184 flips too; it never covered that
report, as its own prior note recorded, and the reporter's +149ms arm is
untouched and still asserting the defect. Provenance hashes in three test
docblocks are updated, since regenerating changes the patch hash and with it
the resolved install directory.
The five dependency patches under config/patches/ shipped with no tracked
way to regenerate any of them. The xterm one is the hard case: it is derived
from an upstream build, so no fix could be made without rebuilding, and the
tooling to rebuild lived only in one machine's scratch directory. That
blocked a measured fix for a live keystroke-loss bug, and the EditContext
reduction an OSS survey identified as the only real one available.
Adds the regenerator, the upstream pin, the hand-written source patch the
bundle hunks derive from, tests, docs, and a PR job that verifies the
shipped patches still match the pinned build. The job caches the shallow
clone keyed on the manifest, so a cold run is minutes and a warm one under
one. Round-trip verified: regenerating from a clean checkout reproduces the
shipped patch byte-for-byte.
Marks the emitted patch -diff -text. pnpm hashes it byte-for-byte, so a
CRLF checkout would break install on Windows, and its minified bundle lines
make a diff nobody can read — review the source patch instead.
Also rejects unknown flags. --check was the fallback for any unrecognised
argument, so a typo, or --help, silently triggered a full upstream build
instead of what the caller asked for.
Neil