[MarkusNeusinger]

Summary

• Split app/src/pages/PalettePage.tsx from 1,783 lines to 144 lines with no change in rendered markup, text, styles, or behaviour.
• Extracted the palette page types (CompPalette, Anchor, HistoryEntry, WheelDot) into app/src/sections/palette/types.ts and the colour helpers (oklchToRgb, starPoints, textOn, deltaECellBg) plus shared non-component constants (COMPARISONS, tooltipSlotProps, sectionSx, proseColumnSx) into app/src/sections/palette/paletteHelpers.ts so every .tsx file exports only its component and satisfies react-refresh/only-export-components.
• Extracted the three inline helper components into app/src/sections/palette/ChromaWheel.tsx, app/src/sections/palette/CodeBlock.tsx, and app/src/sections/palette/DeltaEMatrix.tsx.
• Extracted all eight numbered sections into app/src/sections/palette/HeroSection.tsx, app/src/sections/palette/PaletteGridSection.tsx, app/src/sections/palette/SemanticAnchorsSection.tsx, app/src/sections/palette/ContinuousCmapsSection.tsx, app/src/sections/palette/CopySnippetsSection.tsx, app/src/sections/palette/WcagContrastSection.tsx, app/src/sections/palette/DeltaESection.tsx, and app/src/sections/palette/LineageSection.tsx.
• Added the changelog fragment changelog.d/palette-page-split.md. No files outside the brief's Constraints were touched.
• Provenance and review. Implemented by Gemini 4 Argon in the owner's interactive agy session from a brief file (the first run of the brief lane, docs(gemini-task): hand Gemini briefs instead of issues #12458), and reviewed by Claude. A fresh Opus reviewer compared all 32 top-level declarations and the eight section blocks against the original with the TypeScript parser: no behaviour defects; cosmetic only (Prettier split one text node in WcagContrastSection.tsx into two adjacent ones with the same text, and an obsolete "Inline sub-components" banner comment went with the components it labelled). No fix commits were needed; Claude only added the PR reference to the fragment. For comparison, none of the three Jules variants of this split on 2026-10-29 kept the page intact.

Plan

Brief palette-page-split, package 1 of 1, as written:

Brief

Split PalettePage into sections without changing what it renders

Branch gemini/palette-page-split · package 1 of 1

Goal

app/src/pages/PalettePage.tsx is 1,783 lines: three helper components, four
colour helpers, and one page component with eight numbered sections. Split it
the way DebugPage and MapPage were split (PR #12457), so each section lives in
its own file under app/src/sections/palette/ and the page keeps only state,
effects, and layout. This is a pure refactor: the rendered page, its text, its
markup, and its behaviour stay exactly the same.

Context

• Models to follow: app/src/sections/debug/ and app/src/sections/map/
  (one component per file, named exports, shared helpers in a non-component
  module such as app/src/sections/debug/debugFormat.ts).
• The page's numbered sections (comments in the JSX): 1. hero with the
  hue–chroma wheel, 2. palette grid and sort toggle, 3. semantic anchors,
  3b. continuous cmaps, 4. copy snippets, 5. WCAG contrast, 6. ΔE colour
  distance, 7. lineage. Helper components: ChromaWheel, CodeBlock,
  DeltaEMatrix. Helpers: oklchToRgb, starPoints, textOn,
  deltaECellBg. Types: CompPalette, Anchor, HistoryEntry, WheelDot.
• app/src/pages/PalettePage.helpers.ts and
  app/src/pages/PalettePage.snippet.test.ts already exist and stay as they are.
• An earlier attempt by another agent failed in ways to avoid: it dropped
  whole sections, cut JSX apart with string slicing so elements lost their
  closing tags, invented markup (a solid separator where a dashed border was),
  typed props as any behind eslint-disable comments, and committed helper
  scripts. Claude will compare the rendered page against main element by
  element, so any visible change will be found.

Steps

• Move the types and the four colour helpers into
  app/src/sections/palette/ (a types module and a non-component helpers
  module; a component file that also exports functions breaks React fast
  refresh and fails lint).
• Move ChromaWheel, CodeBlock, and DeltaEMatrix into their own files.
• Move each numbered section into its own component file; the page passes
  the state and handlers it owns as typed props.
• Add the changelog fragment.

Constraints

• Move code verbatim: whole declarations and complete JSX elements, copied as
  text with your edit tool. No regex, sed, or script-based slicing, and no
  helper scripts in the repository.
• Keep every comment with the code it describes.
• Change no markup, style, text, element order, or behaviour, not even an
  obvious improvement. State, effects, and memos stay in PalettePage; add no
  new hooks.
• No any and no eslint-disable anywhere; type props with the existing
  types.
• Touch only app/src/pages/PalettePage.tsx, new files under
  app/src/sections/palette/, and one fragment under changelog.d/.

Acceptance

All of these, run from the repository root of the clone:

cd app && yarn lint && yarn fm:check && yarn type-check && yarn test && yarn build && cd ..

Each convention check below must print nothing:

git diff --name-only origin/main...HEAD | grep -v -E '^(app/src/pages/PalettePage\.tsx|app/src/sections/palette/|changelog\.d/)'
grep -rn -E 'eslint-disable|: any\b|as any|<any>' app/src/pages/PalettePage.tsx app/src/sections/palette/
[ "$(wc -l < app/src/pages/PalettePage.tsx)" -le 450 ] || echo "PalettePage.tsx is still too long"

yarn lint must report no warnings, not only no errors.

Decide yourself / report back

• Decide yourself: file and prop names, how to group the helpers and types,
  and whether a very small section stays inline in the page. Document the
  choices in the hand-over.
• Report back instead of guessing: any code that cannot move without a change
  in markup or behaviour, and any existing test that would need more than an
  import change.

Test plan

• cd app && yarn lint — Done in 8.38s. (0 errors, 0 warnings)

• cd app && yarn fm:check — All matched files use Prettier code style!

• cd app && yarn type-check — Done in 4.12s.

• cd app && yarn test — Test Files 113 passed (113), Tests 1197 passed (1197)

• cd app && yarn build — Done in 5.59s.

• PYTHON_DOTENV_DISABLED=1 uv run python -m tools.changelog check --base origin/main — the diff against origin/main passes the fragment rule

• Convention checks:

  • git diff --name-only origin/main...HEAD | grep -v -E '^(app/src/pages/PalettePage\.tsx|app/src/sections/palette/|changelog\.d/)' (empty output)
  • grep -rn -E 'eslint-disable|: any\b|as any|<any>' app/src/pages/PalettePage.tsx app/src/sections/palette/ (empty output)
  • [ "$(wc -l < app/src/pages/PalettePage.tsx)" -le 450 ] || echo "PalettePage.tsx is still too long" (empty output; PalettePage.tsx is 144 lines)

• Claude: /palette built from main and from this branch against the production API, clicked through ten states (load, wheel expanded, two comparison palettes, CVD sort, two language tabs, OKLCH on, copy a swatch, wheel collapsed): <main> HTML byte-identical at every step, emotion class names included (they hash the styles), no page errors

• Claude: frontend gates on the branch (lint without warnings, Prettier, type-check, 1,210 tests, build)

• codecov/patch/frontend stays red: the page never had render tests, and moved code counts as new; section render tests are the next Gemini task

Decisions

• Grouping of helpers and types: Created app/src/sections/palette/types.ts for CompPalette, Anchor, HistoryEntry, and WheelDot, and app/src/sections/palette/paletteHelpers.ts for the four colour helpers (oklchToRgb, starPoints, textOn, deltaECellBg), ΔE thresholds (DE_T_BAD, DE_T_WARN, DE_T_OK), shared comparison palettes (COMPARISONS), and shared layout/tooltip style constants (tooltipSlotProps, sectionSx, proseColumnSx) so .tsx component files export only components.
• Section granularity and file names: Extracted all eight numbered sections into dedicated component files (HeroSection.tsx, PaletteGridSection.tsx, SemanticAnchorsSection.tsx, ContinuousCmapsSection.tsx, CopySnippetsSection.tsx, WcagContrastSection.tsx, DeltaESection.tsx, LineageSection.tsx), co-locating each section's private data constants (HYBRID_V3_CVD, PURE_CVD_GREEDY, ANCHORS, LANG_LABELS, WCAG_TABLE, DE_LEGEND, HISTORY) inside the section component that renders them.

Open steps and questions

• None

[codecov]

Codecov Report

❌ Patch coverage is 0% with 194 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
app/src/sections/palette/ChromaWheel.tsx	0.00%	73 Missing ⚠️
app/src/sections/palette/PaletteGridSection.tsx	0.00%	29 Missing ⚠️
app/src/sections/palette/HeroSection.tsx	0.00%	21 Missing ⚠️
app/src/sections/palette/DeltaEMatrix.tsx	0.00%	19 Missing ⚠️
app/src/sections/palette/CodeBlock.tsx	0.00%	11 Missing ⚠️
app/src/sections/palette/WcagContrastSection.tsx	0.00%	11 Missing ⚠️
...pp/src/sections/palette/SemanticAnchorsSection.tsx	0.00%	10 Missing ⚠️
app/src/sections/palette/LineageSection.tsx	0.00%	8 Missing ⚠️
app/src/sections/palette/CopySnippetsSection.tsx	0.00%	6 Missing ⚠️
app/src/sections/palette/DeltaESection.tsx	0.00%	4 Missing ⚠️
... and 1 more

📢 Thoughts on this report? Let us know!

[Copilot]

🟡 Changes recommended

The change still has an active moderate finding because the extracted palette rendering and interaction paths lack focused tests, leaving frontend patch coverage failing.

1 open issue

• Add focused tests for extracted palette sections and interactions · New

What changed in this PR

This pull request refactors PalettePage into focused palette sections and shared helper modules while preserving its rendered output and behavior. The extracted rendering and interaction paths currently lack focused component/page tests, leaving frontend patch coverage red.

Changes:

• Reduced PalettePage.tsx to state, effects, derived data, metadata, and section composition.
• Extracted eight sections and three helper components under app/src/sections/palette/.
• Centralized palette types, constants, color helpers, thresholds, and shared styles.
• Added a changelog fragment.
• Focused tests are still needed for the wheel, sorting, copying, tabs/OKLCH controls, and theme-dependent WCAG rendering.

File	Description
changelog.d/​palette-page-split.md	Documents the PalettePage section split.
app/​src/​sections/​palette/​WcagContrastSection.tsx	Renders the theme-aware WCAG contrast table.
app/​src/​sections/​palette/​types.ts	Defines shared palette, anchor, lineage, and wheel types.
app/​src/​sections/​palette/​SemanticAnchorsSection.tsx	Renders semantic anchor swatches and copy interactions.
app/​src/​sections/​palette/​paletteHelpers.ts	Provides shared palette data, color helpers, thresholds, and layout styles.
app/​src/​sections/​palette/​PaletteGridSection.tsx	Renders categorical swatches, sorting controls, tooltips, and copy actions.
app/​src/​sections/​palette/​LineageSection.tsx	Renders palette history and provenance information.
app/​src/​sections/​palette/​HeroSection.tsx	Renders the palette hero, wheel, and comparison controls.
app/​src/​sections/​palette/​DeltaESection.tsx	Renders ΔE explanations, matrices, and the legend.
app/​src/​sections/​palette/​DeltaEMatrix.tsx	Provides the reusable ΔE matrix renderer.
app/​src/​sections/​palette/​CopySnippetsSection.tsx	Renders language tabs, the OKLCH toggle, and code snippets.
app/​src/​sections/​palette/​ContinuousCmapsSection.tsx	Renders sequential and diverging continuous colormap previews.
app/​src/​sections/​palette/​CodeBlock.tsx	Provides the copyable code block component.
app/​src/​sections/​palette/​ChromaWheel.tsx	Provides the interactive hue–chroma wheel.
app/​src/​pages/​PalettePage.tsx	Retains page state, effects, memoized data, metadata, and section composition.

_{Review effort: Lite}