test(tui): add Unicode glyph conformance invariants

[lawrencecchen]

Adds bounded behavior-level tests for UTF-8 chunking, combining marks, CJK graphemes, wide-cell spacer roles, and protocol run width accounting. No font-sensitive emoji widths are hard-coded.

Focused test: cargo test -p ghostty-vt --test unicode_glyphs (blocked locally because clean worktree Ghostty submodule lacks build.zig).

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Summary by cubic

Adds Unicode conformance tests for ghostty-vt that pin down grapheme cluster preservation (combining marks, CJK wide, Indic conjuncts), wide-cell spacer roles, UTF-8 chunking equivalence, and rows_to_runs column accounting. The chunked-write test now enables grapheme mode so partial UTF-8 writes render identically to a single write. No font-sensitive emoji widths are hard-coded; run cargo test -p ghostty-vt --test unicode_glyphs to execute.

^{Written for commit a703004. Summary will update on new commits.}

Summary by CodeRabbit

• Tests
  • Added coverage for Unicode grapheme rendering, including combining marks, wide characters, and Indic text.
  • Verified terminal column preservation and consistent rendering across chunked versus single UTF-8 writes.

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📝 Walkthrough

Walkthrough

Adds Unicode rendering tests for grapheme clusters, cell widths, spacer cells, row runs, and byte-chunked UTF-8 writes in ghostty-vt.

Changes

Unicode glyph rendering tests

Layer / File(s)	Summary
Frame setup and grapheme cell validation cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs	Creates terminal frames with mode 2027 enabled. Validates grapheme clusters, cell widths, and spacer placement.
Row runs and chunked UTF-8 writes cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs	Validates row column accounting and maximal runs. Confirms byte-by-byte writes match a single write.

Estimated code review effort: 2 (Simple) | ~10 minutes

Merge Risk: ⚪ Minimal · up to a7030

This PR adds localized Unicode rendering conformance tests without changing production behavior or system interfaces. No actionable merge-blocking risk remains after normal checks.

🚥 Pre-merge checks | ✅ 24 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 1 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (24 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly identifies the addition of Unicode glyph conformance tests for the TUI.
Description check	✅ Passed	The description explains what changed and why, identifies the focused test command, and documents the local test blockage. A demo video is not needed because this change adds tests rather than a user-…
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Cmux Swift Actor Isolation	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The inferred PR diff contains no Swift files and no production Swift changes. The custom fai…
Cmux Swift Blocking Runtime	✅ Passed	PASS: The complete PR diff from base 495477e to HEAD changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration-test file. It adds no Swift files or production Swift change…
Cmux Browser Automation Off-Main	✅ Passed	PASS. The PR changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust Unicode terminal test. The diff adds no browser.* socket command, WebKit/AppKit access, main-actor routing, wor…
Cmux Expensive Synchronous Load	✅ Passed	PASS: The complete diff from origin/main adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs (108 Rust test lines). It changes no Swift files and introduces no agent-history loader, synchro…
Cmux Cache Substitution Correctness	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration-test file. The visible five-commit range has no Swift, TypeScript, or JavaScript production…
Cmux No Hacky Sleeps	✅ Passed	PASS: The PR changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The diff adds deterministic terminal assertions and byte-chunk iteration. It adds no TypeScript, JavaS…
Cmux Algorithmic Complexity	✅ Passed	PASS. The PR adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration test. It changes no production Swift, TypeScript, JavaScript, shell, or runtime code. The custom check e…
Cmux Swift Concurrency	✅ Passed	PASS: The pull-request diff from the merge base adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust XCTest-unrelated test file. It changes no Swift files and adds no Dispatch, Combi…
Cmux Swift @Concurrent	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The diff contains no Swift files or Swift concurrency changes, so the @concurrent check is…
Cmux Swift Package Boundaries	✅ Passed	PASS. The complete main to HEAD diff contains one file: cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. It is Rust test code under a tests directory. The diff contains no Swift source, Swi…
Cmux Swiftpm Lockfiles	✅ Passed	PASS: The PR diff from the merge base contains only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration test. It changes no Package.swift, Package.resolved, .gitignore, Xcod…
Cmux Swift Logging	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The complete PR-range diff contains no Swift files and no added logging calls or file/stdout…
Cmux User-Facing Error Privacy	✅ Passed	PASS. The pull-request range adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. The file contains test helpers, assertions, and developer-only comments. It does not add or change producti…
Cmux Full Internationalization	✅ Passed	PASS. The full PR diff from origin/main adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs with 108 test lines. It changes no production UI, web, metadata, API, catalog, or locale files. T…
Cmux Swiftui State Layout	✅ Passed	PASS: The complete pull request diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. It changes no Swift or SwiftUI files and introduces none of the state or layout p…
Cmux Architecture Rethink	✅ Passed	PASS. The full pull-request diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. It contains no Swift changes and no architectural-rethink patterns. The custom check …
Cmux Swift Auxiliary Window Close Shortcuts	✅ Passed	PASS: The cumulative pull-request diff changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. It adds or updates Rust test code only. It does not add or materially change SwiftUI windows, …
Cmux Source Artifacts	✅ Passed	PASS: The merge-base diff contains only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. This is a hand-written Rust integration test in the crate's expected tests/ directory. It is a deliberat…
Cmux No Test Or Debug Seam In Production Source	✅ Passed	The cumulative PR diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test-target file. It changes no Swift file under a production Sources/ path and adds no production test/…
Cmux No Ambient Global State	✅ Passed	PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The inspected diff contains no Swift changes and no production Swift declarations. Therefore…

Full details: Description check

Explanation

The description explains what changed and why, identifies the focused test command, and documents the local test blockage. A demo video is not needed because this change adds tests rather than a user-facing UI change.

Full details: Cmux Swift Actor Isolation

Explanation

PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The inferred PR diff contains no Swift files and no production Swift changes. The custom failure conditions are therefore not applicable.

Full details: Cmux Swift Blocking Runtime

Explanation

PASS: The complete PR diff from base 495477e to HEAD changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration-test file. It adds no Swift files or production Swift changes. The test contains no semaphore, wait, sleep, delayed dispatch, polling, main-queue sync, or manual-lock primitives. The custom check therefore does not apply.

Full details: Cmux Browser Automation Off-Main

Explanation

PASS. The PR changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust Unicode terminal test. The diff adds no browser.* socket command, WebKit/AppKit access, main-actor routing, worker routing, or browser policy test changes. Therefore none of the rule's explicit failure conditions apply.

Full details: Cmux Expensive Synchronous Load

Explanation

PASS: The complete diff from origin/main adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs (108 Rust test lines). It changes no Swift files and introduces no agent-history loader, synchronous disk/JSON load, or interactive Swift path. The custom check is therefore inapplicable.

Full details: Cmux Cache Substitution Correctness

Explanation

PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration-test file. The visible five-commit range has no Swift, TypeScript, or JavaScript production changes, and it does not substitute a cached value for an authoritative read in a persistence, history, undo, or snapshot path.

Full details: Cmux No Hacky Sleeps

Explanation

PASS: The PR changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The diff adds deterministic terminal assertions and byte-chunk iteration. It adds no TypeScript, JavaScript, shell, or build/runtime changes, and no fixed sleeps, timers, polling, or wall-clock waits.

Full details: Cmux Algorithmic Complexity

Explanation

PASS. The PR adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration test. It changes no production Swift, TypeScript, JavaScript, shell, or runtime code. The custom check explicitly passes tests, and the test uses bounded fixtures with a fixed 16-column viewport.

Full details: Cmux Swift Concurrency

Explanation

PASS: The pull-request diff from the merge base adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust XCTest-unrelated test file. It changes no Swift files and adds no Dispatch, Combine, completion-handler, or fire-and-forget Task patterns. The cmux Swift concurrency check is therefore not applicable.

Full details: Cmux Swift `@Concurrent`

Explanation

PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The diff contains no Swift files or Swift concurrency changes, so the @concurrent check is not applicable.

Full details: Cmux Swift Package Boundaries

Explanation

PASS. The complete main to HEAD diff contains one file: cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. It is Rust test code under a tests directory. The diff contains no Swift source, SwiftPM manifest, Xcode project, or app-target change. The Swift package-boundaries rule does not apply, and test code is explicitly allowed.

Full details: Cmux Swiftpm Lockfiles

Explanation

PASS: The PR diff from the merge base contains only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust integration test. It changes no Package.swift, Package.resolved, .gitignore, Xcode project, workflow, or dependency files. The SwiftPM lockfile policy is therefore not triggered.

Full details: Cmux Swift Logging

Explanation

PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The complete PR-range diff contains no Swift files and no added logging calls or file/stdout diagnostics. The custom check applies only to production Swift logging changes.

Full details: Cmux User-Facing Error Privacy

Explanation

PASS. The pull-request range adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. The file contains test helpers, assertions, and developer-only comments. It does not add or change production user-facing errors, alerts, command output, API error bodies, or recovery copy.

Full details: Cmux Full Internationalization

Explanation

PASS. The full PR diff from origin/main adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs with 108 test lines. It changes no production UI, web, metadata, API, catalog, or locale files. The rule explicitly allows tests and fixtures, so no internationalization failure condition applies.

Full details: Cmux Swiftui State Layout

Explanation

PASS: The complete pull request diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. It changes no Swift or SwiftUI files and introduces none of the state or layout patterns in the rule.

Full details: Cmux Architecture Rethink

Explanation

PASS. The full pull-request diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. It contains no Swift changes and no architectural-rethink patterns. The custom check therefore does not apply.

Full details: Cmux Swift Auxiliary Window Close Shortcuts

Explanation

PASS: The cumulative pull-request diff changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. It adds or updates Rust test code only. It does not add or materially change SwiftUI windows, NSWindow, NSPanel, or window controllers. The check is therefore inapplicable, and scripts/lint_auxiliary_window_close_shortcuts.py is not relevant.

Full details: Cmux Source Artifacts

Explanation

PASS: The merge-base diff contains only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs. This is a hand-written Rust integration test in the crate's expected tests/ directory. It is a deliberate test-system source file, not local output, a generated log, cache, build artifact, dependency checkout, screenshot, recording, or scratch directory.

Full details: Cmux No Test Or Debug Seam In Production Source

Explanation

The cumulative PR diff adds only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test-target file. It changes no Swift file under a production Sources/ path and adds no production test/debug seam.

Full details: Cmux No Ambient Global State

Explanation

PASS: The pull request changes only cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs, a Rust test file. The inspected diff contains no Swift changes and no production Swift declarations. Therefore, the custom check for ambient global state in production Swift is not applicable.

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Actionable comments posted: 1

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Inline comments:
In `@cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs`:
- Around line 95-103: Update the text closure and assertion in the unicode glyph
test to compare the complete styled row as ordered (cell.text, cell.width)
pairs, retaining empty cells and CellWidth values instead of filtering or
concatenating text.

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Actionable comments posted: 1

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Inline comments:
In `@cmux-tui/crates/ghostty-vt/tests/unicode_glyphs.rs`:
- Around line 89-108: Update
unicode_conformance_utf8_chunking_preserves_rendered_text to enable mode 2027
with the DEC private-mode sequence before constructing expected via frame_for
and before writing chunks to terminal, so the chunked and unchunked comparisons
run with mode 2027 enabled.

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