| fix(tui): keep Ink displayCursor in sync with fast-echo writes so cursor stops drifting (#26717)
* fix(tui): keep Ink displayCursor in sync with fast-echo writes so cursor stops drifting
TextInput's fast-echo bypass writes characters directly to stdout to
avoid waiting on a React re-render for each keystroke. The hardware
cursor advances by text.length cells, but Ink's cached displayCursor
(the basis for the next frame's relative cursor-move preamble in
log-update) stayed unchanged. When ANY unrelated component re-rendered
between the fast-echo write and the deferred composer setCur/setParent
flush — status bar timer, streaming reasoning, etc. — the next frame's
preamble emitted a relative cursor move from a stale parked position
and the hardware cursor parked N cells offset from the actual caret.
Visible symptom: extra whitespace between the just-typed character and
the cursor block, intermittent, worse on long sessions during streaming.
Alt-screen was immune because frames begin with absolute CSI H.
This adds a small API in @hermes/ink:
- Ink.noteExternalCursorAdvance(dx, dy?) — bumps displayCursor if
set, otherwise seeds from frontFrame.cursor so the next preamble's
relative move correctly cancels the external advance. No-op on
alt-screen.
- CursorAdvanceContext + useCursorAdvance() hook to expose it.
TextInput then calls noteCursorAdvance(text.length) after the
fast-echo stdout.write(text) append, and noteCursorAdvance(-1)
after the fast-backspace \b \b sequence.
Tests: 4 new vitest cases pin the API contract (bumps when set, seeds
from frontFrame.cursor when null, alt-screen no-op, zero-delta no-op).
All 751 ui-tui tests pass; tests/test_tui_gateway_server.py (177) pass.
* fix(tui): also advance cursorDeclaration so fast-echo survives deferred React state
Copilot review on PR #26717 flagged a gap in the original fix:
TextInput's fast-echo path defers the React cur state update by
16ms (perf optimization that batches re-renders during heavy typing).
Inside that window, useDeclaredCursor still publishes a target
computed from the PRE-keystroke cur — `cursorLayout(display, cur,
columns). Advancing only displayCursor` would let any unrelated
re-render in that 16ms window run onRender's cursor-park branch with
the stale declaration and visually undo the fast-echo's advance.
The fix is symmetric: noteExternalCursorAdvance now bumps BOTH
displayCursor (the log-update relative-move basis) AND, if non-null,
cursorDeclaration.relativeX/Y (the target the cursor parks at after
every frame). When React finally flushes setCur, useDeclaredCursor
publishes a fresh declaration that supersedes our bumped one — exactly
what we want.
Adds two new vitest cases covering both halves:
- active declaration advances in lock-step with displayCursor
- null declaration stays null (no spurious bump)
All 753 ui-tui tests pass; tests/test_tui_gateway_server.py (177) pass.
Closes review threads:
PRRT_kwDOPRF1G86ChKtD (textInput.tsx:1016 fast-echo append)
PRRT_kwDOPRF1G86ChKtF (textInput.tsx:924 fast-backspace)
PRRT_kwDOPRF1G86ChKtG (ink-cursor-advance.test.ts:57 missing coverage)
* fix(tui): make fast-echo survive TextInput rerenders + alt-screen (Copilot round 2)
Round 2 of PR #26717 review. Three real holes Copilot flagged after the
initial cursorDeclaration bump:
1. alt-screen early-return skipped BOTH halves of the notifier. But the
default TUI wraps the composer in <AlternateScreen> — that IS the
production path. CSI H resets log-update's relative-move basis, but
the alt-screen park branch uses absolute CUP =
rect.x + decl.relativeX, so a stale declaration there still parks
the cursor at the pre-keystroke caret. Fix: skip ONLY the
displayCursor half on alt-screen; still bump cursorDeclaration.
2. TextInput's own rerender could clobber the Ink-level bump. The fast-
echo path defers setCur by 16ms; if a parent state change rerenders
TextInput in that window, the layout effect inside useDeclaredCursor
reads the stale React cur state and re-publishes a declaration at
the OLD column. Fix:
cursorLayout(display, curRef.current, columns) — read the always-
up-to-date ref, not the deferred state. useMemo dropped (compute is
cheap, single-line wrap-text in the common case).
3. Tests bypassed the production wiring. Added two structural tests:
- still advances cursorDeclaration on alt-screen in the Ink-level
suite, asserting displayCursor stays put but the declaration
advances by the delta.
- textInputCursorSourceOfTruth.test.ts pins three structural
invariants: layout reads curRef.current, never the bare cur
state, and the fast-echo stdout.write calls remain paired with
noteCursorAdvance(±N). Source-grep invariants > flaky Ink mount
tests for this kind of regression.
757/757 ui-tui tests pass (+3 over round 1). type-check clean. lint
introduces zero new errors on touched files. tests/test_tui_gateway_server.py
(177) pass.
Closes review threads:
PRRT_kwDOPRF1G86ChOG2 (ink.tsx alt-screen guard)
PRRT_kwDOPRF1G86ChOG9 (textInput.tsx fast-backspace rerender window)
PRRT_kwDOPRF1G86ChOHC (textInput.tsx fast-append rerender window)
PRRT_kwDOPRF1G86ChOHJ (alt-screen test asserts wrong invariant)
PRRT_kwDOPRF1G86ChOHP (missing integration-style coverage)
* fix(tui): reject fast-backspace at soft-wrap boundary (Copilot round 3)
PR #26717 round 3. Copilot caught two real things:
1. \b \b cannot move the terminal cursor onto the previous visual
row across a soft-wrap boundary. When the caret sits at visual
column 0 of a wrapped row (e.g. value 'hello ' at width 6 →
cursorLayout produces (line 1, col 0)), backspace would leave the
physical cursor in place while the logical caret moves up to the
end of the previous visual line. noteCursorAdvance(-1) would then
feed Ink a wrong delta. Fix: canFastBackspaceShape now takes the
composer width and rejects when cursorLayout(value, cursor, columns).column === 0.
The fast path falls through to the normal Ink render, which
correctly lays out the new caret position. The PR-description
inconsistency about alt-screen is fixed in a separate gh pr edit.
Adds 4 new tests in textInputFastEcho.test.ts pinning the rejection at
exact-multiple wrap boundaries plus a positive control inside a
wrapped line and a back-compat case where columns is omitted.
761/761 ui-tui tests pass. type-check / lint clean. 177/177 Python
tests/test_tui_gateway_server.py pass.
Closes review threads:
PRRT_kwDOPRF1G86ChxE5 (textInput.tsx:933 wrap-boundary regression)
* fix(tui): polish doc + tests after Copilot round 4
Three polish points Copilot raised:
1. canFastBackspaceShape doc comment overstated the legacy contract —
said it conservatively rejects potential wrap boundaries when
columns is omitted, but the implementation actually skips the
wrap-boundary check entirely. Reworded to make the legacy behavior
explicit and warn callers not to rely on protection they don't get.
2. ink-cursor-advance.test.ts rationale comment for the
'advances cursorDeclaration in lock-step' case still referenced
the pre-fix cursorLayout(display, cur, columns) expression. Now
accurately describes the current source of truth — curRef.current
in textInput.tsx — and explains the window the bump is bridging.
3. Removed the three __get*ForTest accessors from Ink. The test
file already cast the instance to inspect private state in the
couple of tests that needed declaration mutation; the rest now use
a small peek(ink) helper that does the same cast for reads. No
test-only API surface ships in production.
761/761 ui-tui tests pass. type-check clean. lint introduces zero new
errors on touched files. 177/177 tests/test_tui_gateway_server.py pass.
Closes review threads:
PRRT_kwDOPRF1G86Ch23W (canFastBackspaceShape doc accuracy)
PRRT_kwDOPRF1G86Ch23f (stale test rationale)
PRRT_kwDOPRF1G86Ch23p (test-only API surface in production)
* fix(tui): tighten doc + add dy test coverage (Copilot round 5)
Two polish points from round 5:
1. canFastBackspaceShape doc had two paragraphs that conflicted —
the main 'Additionally rejects when the physical cursor sits at
visual column 0' was stated unconditionally, then the columns-param
paragraph qualified that it only happens when columns is passed.
Reworked into clear 'When supplied / When omitted' branches with a
concrete example value ('hello ' returns true without columns even
though it would be unsafe at width 6). No more inconsistency.
2. Added a test asserting cursorDeclaration.relativeY advances when dy
is non-zero. Existing tests exercised dy on displayCursor only.
Newlines in fast-echoed text don't currently hit the bypass
(canFastAppendShape rejects '\n'), but dy is part of the public
notifier contract and must propagate symmetrically with dx so
future callers get a fully-implemented contract.
762/762 ui-tui tests pass (+1). type-check / lint / build clean.
Closes review threads:
PRRT_kwDOPRF1G86Ch6Sz (doc inconsistency)
PRRT_kwDOPRF1G86Ch6TE (missing dy coverage on declaration)
* fix(tui): doc polish (Copilot round 6)
Four small but valid points:
1. textInputCursorSourceOfTruth.test.ts used bare 'fs'/'path'/'url'
imports; the rest of ui-tui consistently uses the 'node:' prefix
(see src/__tests__/useSessionLifecycle.test.ts, src/lib/editor.test.ts).
Switched to node:fs / node:path / node:url to match convention.
2. CursorAdvanceContext.ts type-level doc described only displayCursor.
The notifier intentionally also mutates the active cursorDeclaration
and that's the only part that matters on alt-screen. Reworked the
doc into a two-part 'updates both' summary with the alt-screen
asymmetry called out explicitly.
3. use-cursor-advance.ts hook doc had the same problem. Same fix —
document both pieces of state, both screen modes.
4. App.tsx onCursorAdvance prop comment was incomplete. Same fix —
describe both state updates and the screen-mode asymmetry.
No behavior change. 762/762 ui-tui tests pass. type-check / lint /
build clean.
Closes review threads (auto-resolved on PR but valid critiques):
PRRT_kwDOPRF1G86Ch926 (node: prefix on built-in imports)
PRRT_kwDOPRF1G86Ch92_ (use-cursor-advance.ts doc)
PRRT_kwDOPRF1G86Ch93H (CursorAdvanceContext.ts type doc)
PRRT_kwDOPRF1G86Ch93J (App.tsx prop comment) | 20 天前 |