fix(export): stop counting letterbox rows as an upscale

[EtienneLescot]

Reported from the export dialog: with a 1920x1032 window capture on the timeline, the Source tile reads 1920 × 1080.

That number is right — it is the output frame, and the smallest 16:9 frame holding a 1920-wide source without shrinking it is 1920x1080. The source's real 1032 was never lost either: it is what makes the 720p tile read as a downscale. So the size SSOT is fine.

What was wrong is next to it: 1080p and Source resolve to the exact same 1920x1080 frame, and only one of them carries the "Upscale" warning.

	before	after
720p	1280 × 720	1280 × 720
1080p	1920 × 1080 · Upscale	1920 × 1080
Source	1920 × 1080	1920 × 1080

The badge compared short sides (1080 > 1032), which counts the letterbox rows a non-16:9 source gets in a 16:9 project as if they were stretched pixels. Those 48 rows are wallpaper; the clip is contain-fitted and still renders at 1:1.

wouldUpscale() now asks the contain-fit question the compositor actually answers:

min(out.w / src.w, out.h / src.h) > 1

A source whose shape matches the project ratio is unaffected — which is why a full-screen capture never showed this and a window capture did. A tier that genuinely stretches the source (1280x720 → 1080p, scale 1.5) is still flagged.

The q.value !== "source" exemption is gone: Source's frame is the source's long side at the project ratio, so its contain scale is never above 1 and the general test covers it. The MEDIUM_SHORT_SIDE/HIGH_SHORT_SIDE constants (duplicated from mp4ExportSettings.ts) and the write-only targetShortSide field they fed go with it.

Verification

• src/lib/exporter/mp4ExportSettings.test.ts — 8/8, two new cases: the reported 1920x1032 @ 16:9 (all three tiers unflagged) and a real stretch that must stay flagged.
• src/components/ai-edition/ExportDialog.test.ts — 8/8.
• biome check clean on the three files (also via the pre-commit hook).
• Not exercised in the running app: it needs a real 1920x1032 window recording loaded in the editor. The unit test replays that exact case.

tsc --noEmit reports one pre-existing unrelated error, src/i18n/loader.ts: Cannot find module 'i18next' — the local node_modules predates that dependency and needs an npm install.

Summary by CodeRabbit

• Bug Fixes
  • Improved export quality warnings by accurately accounting for letterboxed video dimensions.
  • Prevented false upscale warnings when source footage fits within the selected output without enlargement.
  • Continued warning users when genuinely smaller source footage would be enlarged during export.
  • Updated quality handling consistently across medium, good, and source export options.

[coderabbitai]

📝 Walkthrough

Walkthrough

The export flow now uses contain-fit output dimensions to detect upscaling. The dialog removes fixed target-size metadata and applies the shared check to all quality tiers. Tests cover letterboxed captures and genuine source upscaling.

Changes

Upscale detection

Layer / File(s)	Summary
Contain-fit upscale helper and coverage src/lib/exporter/mp4ExportSettings.ts, src/lib/exporter/mp4ExportSettings.test.ts	Adds Dims and the exported wouldUpscale helper. Tests cover letterboxed captures and smaller sources.
Export dialog warning integration src/components/ai-edition/ExportDialog.tsx	Removes fixed target short-side metadata and uses wouldUpscale for quality warnings, including the Source tier.

Estimated code review effort: 2 (Simple) | ~15 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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 export bug and the correction for letterbox rows being counted as an upscale.
Description check	✅ Passed	The description clearly explains the bug, implementation, affected behavior, and verification, but it does not complete the template checkboxes or related-issue field.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/export-upscale-badge

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[coderabbitai]

🧹 Nitpick comments (1)

src/components/ai-edition/ExportDialog.tsx (1)

409-417: 🎯 Functional Correctness | 🔵 Trivial | ⚡ Quick win

Add a same-package test for the ExportDialog upscale badge path.

src/components/ai-edition/ExportDialog.test.ts does not cover willUpscale(dims, smallestSource) or qualityUpscaleWarning, while the exported badge uses wouldUpscale on the dialog’s tier output dimensions. Add integration coverage for the letterboxed source case and a genuine upscale case across the relevant quality options.

🤖 Prompt for AI Agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@src/components/ai-edition/ExportDialog.tsx` around lines 409 - 417, Add
same-package integration tests in ExportDialog.test.ts covering the exported
upscale badge path that calls wouldUpscale(dims, smallestSource), including a
letterboxed source case that remains unflagged and a genuine upscale case that
is flagged. Exercise the relevant quality options and verify
qualityUpscaleWarning behavior using the dialog’s tier output dimensions.

Source: Coding guidelines

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Nitpick comments:
In `@src/components/ai-edition/ExportDialog.tsx`:
- Around line 409-417: Add same-package integration tests in
ExportDialog.test.ts covering the exported upscale badge path that calls
wouldUpscale(dims, smallestSource), including a letterboxed source case that
remains unflagged and a genuine upscale case that is flagged. Exercise the
relevant quality options and verify qualityUpscaleWarning behavior using the
dialog’s tier output dimensions.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: e04c0496-2993-482a-9a92-ac78c92ab642

📥 Commits

Reviewing files that changed from the base of the PR and between e383f9b and ee28154.

📒 Files selected for processing (3)

• src/components/ai-edition/ExportDialog.tsx
• src/lib/exporter/mp4ExportSettings.test.ts
• src/lib/exporter/mp4ExportSettings.ts