fix(mobile): show complete unwrapped diff lines containing tabs

[jakeleventhal]

Replacement for #12234. That PR was closed under the verification rule because its screenshots predated the renderer rework and its layout tests never scrolled the view. This is the same fix on current main, with a recording of the current view panning to the ends of the tab-indented lines.

Problem

With word wrap off, the iOS review diff counts each tab as one column and draws the row into that narrower rectangle. Tab-indented lines such as a TSConfig extends value wrap inside the rectangle, and horizontal panning never reaches the real end. Word wrap is off by default in the mobile review diff, and review comment cards always pass wordWrap: false, so both surfaces hit this path. #12590 fixed the wrapped path.

This is a focused repair of that drawing bug. It does not change a product default, add a setting, or introduce a workflow. The iOS renderer is the only code that has the defect this patch addresses. Android keeps its own renderer.

Fix

Unwrapped rows are laid out on one line. ReviewDiffCodeLayout records the widest visual line, including tab stops and non-ASCII glyphs. The view sizes horizontal scrolling from that width, without the previous contentWidth cap, and draws native rows at codeStartX - horizontalOffset, so the glyphs move with the pan. Wrapped rows still wrap to the viewport and do not pan.

Evidence

Word wrap off, viewport 390×250, contentWidth 2800. The rows are the tab-indented lines from the original report:

"\t\t\"extends\": \"@riptech/tsconfig/tsconfig.json\","
"\t\t\"extends\": \"@riptech/tsconfig/tsconfig.test.json\","

The shots are the production T3ReviewDiffView, panned through its handleHorizontalPan handler. Before is main at bd89c13020. After is this branch. Host is Mac Catalyst. This machine has Command Line Tools only, so xcrun simctl is unavailable and the T3 device panel cannot boot an iPhone Simulator. The full T3 Code Dev app was not launched.

On current main, panning does not move the lines. Both extends values stay cut off (tscon and tsconfig/).

On this branch the same lines start clipped at the viewport edge, then the pan reaches the closing quote and comma on both filenames.

Start	Panned to the end

The recording is that same pan. Both lines stay in frame, from the clipped start through the closing punctuation on tsconfig.test.json.

scroll-both-lines.mp4

apps/mobile/modules/t3-review-diff/tests/run-ios.sh passed: 18 cases, including unwrapped tab, CJK, and Arabic rows that stay on one line and whose ink falls inside usedWidth. T3ReviewDiffView.swift typechecks for Mac Catalyst against a stubbed ExpoModulesCore.

Not checked: a booted iPhone Simulator, the full mobile app, and Android.

Model: grok-4.7-build-fast. Harness: Grok in T3 Code.

[macroscopeapp]

Approvability

Verdict: Approved at b05f3b9

Macroscope's review found this PR approvable — This is a localized iOS diff-rendering fix that makes existing horizontal scrolling account for tabs and shaped text without changing wrapping defaults or introducing a new workflow. The production changes are small and accompanied by focused layout coverage.

Notes:

• Diff unchanged. Approvability was decided on eligibility alone.

No code changes detected at 2d2343f. Prior analysis still applies.

^{You can add or adjust custom eligibility rules. Learn more.}

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📥 Commits

Reviewing files that changed from the base of the PR and between 5cc99e1 and b05f3b9.

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📒 Files selected for processing (3)

• apps/mobile/modules/t3-review-diff/ios/ReviewDiffCodeLayout.swift
• apps/mobile/modules/t3-review-diff/ios/T3ReviewDiffView.swift
• apps/mobile/modules/t3-review-diff/tests/ios/main.swift

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📝 Walkthrough

Walkthrough

The iOS diff view now supports unwrapped code layout. It measures code and hunk content widths from rendered text and applies the horizontal scroll offset when drawing native-layout text. The iOS layout tests cover unwrapped tabbed and ASCII text.

Changes

iOS diff code layout

Layer / File(s)	Summary
Code layout width metrics apps/mobile/modules/t3-review-diff/ios/ReviewDiffCodeLayout.swift	ReviewDiffCodeLayout supports unbounded width and records the widest visual line for ASCII and native TextKit layouts.
Diff view sizing and rendering apps/mobile/modules/t3-review-diff/ios/T3ReviewDiffView.swift, apps/mobile/modules/t3-review-diff/tests/ios/main.swift	ReviewDiffContentView uses a shared width policy to prepare layouts and measure code and hunk text. Native-layout drawing applies the horizontal scroll offset. Tests check unwrapped tabbed text and ASCII width.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix

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Merge Risk

Merge Risk: ⚪ Minimal · up to b05f3

The change makes unwrapped iOS diff lines horizontally reachable using measured text widths. No actionable merge-blocking issue is established; normal checks remain appropriate, with full-app and iPhone validation still limited.

Security Architecture Review

Security architecture risk: 🔵 Low · up to b05f3

The fix remains within the iOS code display. Large or rapidly replaced content may require more processing than before, but an exploitable availability impact has not been established.

Retained concerns

• Low · security · inferred: Preparing every unwrapped row expands input-sized native measurement work. Obsolete preparations continue through their row loop before replacement checks reject publication, so large non-ASCII payloads could delay newer content on the shared payload queue. Effective caller bounds and material availability impact remain unverified; this is not evidence that the removed horizontal-width cap was a security control.

Security review details

Security Blast Radius

• inferred — The identified concern is processing availability in the iOS application displaying supplied code content. The inspected path ends in text measurement and drawing, not a privileged operation or cross-service mutation; broader service or tenant impact is not established.

Security Findings and Attack Paths

• inferred — A potential availability path is large non-ASCII row content passed through the existing app bridge into eager TextKit measurement, compounded by repeated replacements. Native ingestion has no observed byte, row-count, or line-length bound. Whether an adversary can deliver a sufficiently costly payload through production callers remains unresolved; no exploit was verified.

Trust Boundaries and Controls

• observed — The bridge is invoked by the existing application wrapper, not a newly introduced network entrypoint. Generation checks prevent obsolete results from replacing current display state, and measurement reuse is thread-local. These controls protect publication identity and measurement ownership, but do not cancel queued work.

Hardening Proposals

• proposed — Establish an independent preparation budget for payload size and line complexity, and consider stopping obsolete measurement between rows. Preserve measured horizontal scrolling rather than treating the former drawing-width cap as an input-security limit.

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🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 40.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 5 functions across 3 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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.
Title check	✅ Passed	The title clearly identifies the mobile fix for displaying complete unwrapped diff lines that contain tabs.
Description check	✅ Passed	The description explains the problem, implementation, affected surfaces, visual evidence, focused tests, type-check result, limitations, and agent details. It uses “Fix” and “Evidence” instead of the …

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Dismissing prior approval to re-evaluate b05f3b9