fix(tui): align wrapped composer cursor#25860
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XpeRIall
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May 17, 2026
…e cursor drift The composer's `cursorLayout` (in `ui-tui/src/lib/inputMetrics.ts`) used a hand-rolled word-wrap algorithm to decide where `useDeclaredCursor` should park the hardware cursor. But Ink's `<Text wrap="wrap">` renders the same text via `wrap-ansi`. The two algorithms disagreed on common real-world inputs — `"branch investigate"` at cols=20, `"hello world"` at cols=8, exact-fill strings like `"abcdefgh"` at cols=8 — so the hardware cursor parked several cells past where Ink actually rendered the last character. Users saw a multi-cell blank gap between their last-typed letter and the cursor block, especially on narrow terminals (the Cursor IDE built-in terminal was the worst offender). Three previous PRs (NousResearch#26717, NousResearch#25860, NousResearch#22197) chased fast-echo displayCursor/cursorDeclaration drift and in-band-vs-native cursor heuristics. None of them touched the underlying wrap-algorithm mismatch, which is why the bug kept resurfacing. Fix: source cursorLayout's line breaks from wrap-ansi directly. Walk its emitted string char-by-char, tracking original-string offsets, push a VisualLine at each '\n'. Also drop the buggy `column >= w` overflow rule in cursorLayout — that's what pushed exact-fill text onto a phantom next row. canFastBackspaceShape now detects the wrap boundary in BOTH coordinate conventions (column === 0 OR column >= columns), since exact-fill now reports as (0, columns) instead of the previous (1, 0). The physical state is identical — the terminal auto-wraps at column N either way — but the layout function reports the position more honestly. Tests: - ui-tui/src/__tests__/textInputWrap.test.ts: 3 tests that pinned the BUGGY behavior were updated to assert wrap-ansi parity (the real invariant). Added a typing-prefix invariant: cursorLayout must agree with wrap-ansi at every character of a long input. - ui-tui/src/__tests__/cursorDriftRegression.test.ts: new file. Walks the user-reported bug message char-by-char at 7 widths and asserts agreement with wrap-ansi at every prefix. Verification: - 791/791 vitest tests pass. - 84/84 tui-gateway pytest tests pass via scripts/run_tests.sh. - PTY repro (typing into a real `hermes --tui` PTY at cols=50/55/60): cursor lands exactly 1 cell past the last typed char in every case the bug previously drifted.
aashizpoudel
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May 21, 2026
…e cursor drift The composer's `cursorLayout` (in `ui-tui/src/lib/inputMetrics.ts`) used a hand-rolled word-wrap algorithm to decide where `useDeclaredCursor` should park the hardware cursor. But Ink's `<Text wrap="wrap">` renders the same text via `wrap-ansi`. The two algorithms disagreed on common real-world inputs — `"branch investigate"` at cols=20, `"hello world"` at cols=8, exact-fill strings like `"abcdefgh"` at cols=8 — so the hardware cursor parked several cells past where Ink actually rendered the last character. Users saw a multi-cell blank gap between their last-typed letter and the cursor block, especially on narrow terminals (the Cursor IDE built-in terminal was the worst offender). Three previous PRs (NousResearch#26717, NousResearch#25860, NousResearch#22197) chased fast-echo displayCursor/cursorDeclaration drift and in-band-vs-native cursor heuristics. None of them touched the underlying wrap-algorithm mismatch, which is why the bug kept resurfacing. Fix: source cursorLayout's line breaks from wrap-ansi directly. Walk its emitted string char-by-char, tracking original-string offsets, push a VisualLine at each '\n'. Also drop the buggy `column >= w` overflow rule in cursorLayout — that's what pushed exact-fill text onto a phantom next row. canFastBackspaceShape now detects the wrap boundary in BOTH coordinate conventions (column === 0 OR column >= columns), since exact-fill now reports as (0, columns) instead of the previous (1, 0). The physical state is identical — the terminal auto-wraps at column N either way — but the layout function reports the position more honestly. Tests: - ui-tui/src/__tests__/textInputWrap.test.ts: 3 tests that pinned the BUGGY behavior were updated to assert wrap-ansi parity (the real invariant). Added a typing-prefix invariant: cursorLayout must agree with wrap-ansi at every character of a long input. - ui-tui/src/__tests__/cursorDriftRegression.test.ts: new file. Walks the user-reported bug message char-by-char at 7 widths and asserts agreement with wrap-ansi at every prefix. Verification: - 791/791 vitest tests pass. - 84/84 tui-gateway pytest tests pass via scripts/run_tests.sh. - PTY repro (typing into a real `hermes --tui` PTY at cols=50/55/60): cursor lands exactly 1 cell past the last typed char in every case the bug previously drifted. (cherry picked from commit 3b4dd68)
gweeteve
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Jun 2, 2026
…e cursor drift The composer's `cursorLayout` (in `ui-tui/src/lib/inputMetrics.ts`) used a hand-rolled word-wrap algorithm to decide where `useDeclaredCursor` should park the hardware cursor. But Ink's `<Text wrap="wrap">` renders the same text via `wrap-ansi`. The two algorithms disagreed on common real-world inputs — `"branch investigate"` at cols=20, `"hello world"` at cols=8, exact-fill strings like `"abcdefgh"` at cols=8 — so the hardware cursor parked several cells past where Ink actually rendered the last character. Users saw a multi-cell blank gap between their last-typed letter and the cursor block, especially on narrow terminals (the Cursor IDE built-in terminal was the worst offender). Three previous PRs (NousResearch#26717, NousResearch#25860, NousResearch#22197) chased fast-echo displayCursor/cursorDeclaration drift and in-band-vs-native cursor heuristics. None of them touched the underlying wrap-algorithm mismatch, which is why the bug kept resurfacing. Fix: source cursorLayout's line breaks from wrap-ansi directly. Walk its emitted string char-by-char, tracking original-string offsets, push a VisualLine at each '\n'. Also drop the buggy `column >= w` overflow rule in cursorLayout — that's what pushed exact-fill text onto a phantom next row. canFastBackspaceShape now detects the wrap boundary in BOTH coordinate conventions (column === 0 OR column >= columns), since exact-fill now reports as (0, columns) instead of the previous (1, 0). The physical state is identical — the terminal auto-wraps at column N either way — but the layout function reports the position more honestly. Tests: - ui-tui/src/__tests__/textInputWrap.test.ts: 3 tests that pinned the BUGGY behavior were updated to assert wrap-ansi parity (the real invariant). Added a typing-prefix invariant: cursorLayout must agree with wrap-ansi at every character of a long input. - ui-tui/src/__tests__/cursorDriftRegression.test.ts: new file. Walks the user-reported bug message char-by-char at 7 widths and asserts agreement with wrap-ansi at every prefix. Verification: - 791/791 vitest tests pass. - 84/84 tui-gateway pytest tests pass via scripts/run_tests.sh. - PTY repro (typing into a real `hermes --tui` PTY at cols=50/55/60): cursor lands exactly 1 cell past the last typed char in every case the bug previously drifted.
Contributor
|
Automated hermes-sweeper review found this is now implemented on main by the later merged cursor-drift fix. Evidence:
Thanks for the original fix attempt — it helped identify the TUI cursor area that the later root-cause fix resolved. |
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Rationale
Long pasted composer input can wrap across multiple terminal rows. The TUI previously parked the native terminal cursor separately from Ink's wrapped text layout, which could make the cursor drift or show a second cursor after paste. Switching wrapped input to an in-band cursor fixed the double cursor, but the fallback inverse-video cursor lost the Hermes cursor color.
Summary
TextInputso the synthetic cursor remains visually consistent on multiline input.Test Plan
npm run build --prefix packages/hermes-inknpm run test -- textInputWrap.test.tsnpm run type-checknpm run buildgit diff --checknpm exec eslint -- src/components/textInput.tsx src/components/appLayout.tsx src/__tests__/textInputWrap.test.ts(0 errors; existing warnings only)