fix(ios): scroll short source files from blank space

[juliusmarminge]

Horizontal dragging below the last line of a short iOS source file does nothing, even when its lines overflow. Starting the same gesture over a code row works.

Let that trailing blank area target the existing single, expanded, headerless file. Reuse the current pan, overflow and back-navigation guards. The full review screen keeps its existing hit testing because its file headers exclude this fallback. Headerless single-file snippets in inline review-comment cards also gain blank-area scrolling. No new state or row scan.

Related #5157. This reproduces the narrower blank-area failure, not the author's unspecified touch path on iOS 27.

Verification

• Built baseline 62ed748a and candidate 2d39d4fd independently for the same iPhone 17 Pro Max simulator, iOS 26.5. The mobile source is unchanged on latest main cb9a6942.
• Same synthetic C# file, unwrapped rows, 440×956 viewport. Two leftward drags from (360,650) to (80,650) do nothing before and reach all three right-hand line endings after. Reverse drags restore the left edge. Row-origin scrolling works in both builds.
• A nonoverflowing source stays stationary on a leftward blank-area drag. A rightward drag returns to Files. Reopening the overflowing file starts at its left edge.
• Focused SwiftLint with the existing mobile configuration passes. No JavaScript test was added to mirror a native gesture implementation.
• Native syntax highlighting fell back to JavaScript in both builds; the native source canvas was separately confirmed through accessibility. Existing test-state storage warnings were dismissed without deleting records. Android, the reporter's iOS 27 device, inline review-comment cards, long-file vertical scrolling, and a full multi-file review gesture matrix were not native-tested. All three callers, full-review header exclusion, and vertical gesture guards were source-reviewed.

Before and after

After the same two blank-area drags:

Before	After

Before recording: blank-area drags ignored, followed by a working row drag

After recording: blank-area drags scroll right and back left

Hold for native-release timing. This native change should be coordinated with the next store build under the repository's fingerprint workflow. Do not automatically close the original report on this narrower reproduction.

Prepared by GPT 6 Astra via Codex in T3 Code.

Note

Fix horizontalPanTarget to scroll short source files from blank space on iOS

Adds a fallback in T3ReviewDiffView.swift for pan points that do not map to a row. When the point is at or below the content end, no file-header rows exist, exactly one file has measured content width, and that file is expanded, the method now returns a code-scrolling target so horizontal pans in the bottom blank area scroll the file.

^{Macroscope summarized 2d39d4f.}

[macroscopeapp]

Approvability

Verdict: Approved at 2d39d4f

Macroscope's review found this PR approvable — This is a narrowly scoped native iOS bug fix that reuses the existing horizontal scrolling path only for trailing blank space in a single expanded source file. Existing multi-file, collapsed, header, and review-diff interactions are explicitly excluded, with no schema, security, deployment, or default-behavior changes.

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

[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	13.5 KiB	13.5 KiB	+15 B (+0.1%)	15.1 KiB	✅
Codex	Thread snapshot wire	7.0 KiB	7.0 KiB	+1 B (+0.0%)	7.3 KiB	✅
Codex	Live turn WebSocket wire	6.5 KiB	6.5 KiB	+14 B (+0.2%)	7.8 KiB	✅
Codex	Live turn WebSocket decoded	57.0 KiB	57.0 KiB	0 B (0.0%)	66.4 KiB	✅
Codex	Live turn messages	8	8	0 (0.0%)	21	✅
Claude	Total thread wire	13.6 KiB	13.6 KiB	+24 B (+0.2%)	15.1 KiB	✅
Claude	Thread snapshot wire	7.0 KiB	7.0 KiB	−8 B (−0.1%)	7.3 KiB	✅
Claude	Live turn WebSocket wire	6.5 KiB	6.6 KiB	+32 B (+0.5%)	7.8 KiB	✅
Claude	Live turn WebSocket decoded	57.8 KiB	57.9 KiB	+44 B (+0.1%)	66.4 KiB	✅
Claude	Live turn messages	9	10	+1 (+11.1%)	21	✅

Baseline: cb9a694 · PR result: 2d39d4f · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 113.8 KiB
• Claude decoded thread snapshot: 114.5 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.