---
id: T01
parent: S03
milestone: M002
provides: []
requires: []
affects: []
key_files: ["app/src/utils/fontService.ts", "app/src/utils/__tests__/fontService.test.ts", "app/public/fonts/Roboto-Regular.ttf", "app/public/fonts/OpenSans-Regular.ttf", "app/public/fonts/Lato-Regular.ttf", "app/src/App.css", "app/package.json"]
key_decisions: ["Used opentype.js v1.3.4 with dynamic import() and local type declarations (no @types package exists)", "Variable font .ttf files for Roboto/OpenSans validated to work with opentype.js glyph extraction", "Y-axis flip (canvas_y = ascender - font_y * scale) for canvas-compatible SVG path coordinates", "Manual per-character glyph positioning for letter spacing since opentype.js getPath() lacks native support"]
patterns_established: []
drill_down_paths: []
observability_surfaces: []
duration: ""
verification_result: "Ran: cd app && npx vitest run src/utils/__tests__/fontService.test.ts --reporter=verbose && npx tsc --noEmit && ls public/fonts/*.ttf | wc -l. All 24 tests pass, TypeScript compiles cleanly under strict mode, 3 font files confirmed in public/fonts/."
completed_at: 2026-03-26T05:52:47.243Z
blocker_discovered: false
---

# T01: Built fontService with opentype.js font loading, caching, text-to-path conversion, bundled 3 OFL Google Fonts, and added 24 passing unit tests

> Built fontService with opentype.js font loading, caching, text-to-path conversion, bundled 3 OFL Google Fonts, and added 24 passing unit tests

## What Happened
---
id: T01
parent: S03
milestone: M002
key_files:
  - app/src/utils/fontService.ts
  - app/src/utils/__tests__/fontService.test.ts
  - app/public/fonts/Roboto-Regular.ttf
  - app/public/fonts/OpenSans-Regular.ttf
  - app/public/fonts/Lato-Regular.ttf
  - app/src/App.css
  - app/package.json
key_decisions:
  - Used opentype.js v1.3.4 with dynamic import() and local type declarations (no @types package exists)
  - Variable font .ttf files for Roboto/OpenSans validated to work with opentype.js glyph extraction
  - Y-axis flip (canvas_y = ascender - font_y * scale) for canvas-compatible SVG path coordinates
  - Manual per-character glyph positioning for letter spacing since opentype.js getPath() lacks native support
duration: ""
verification_result: passed
completed_at: 2026-03-26T05:52:47.258Z
blocker_discovered: false
---

# T01: Built fontService with opentype.js font loading, caching, text-to-path conversion, bundled 3 OFL Google Fonts, and added 24 passing unit tests

**Built fontService with opentype.js font loading, caching, text-to-path conversion, bundled 3 OFL Google Fonts, and added 24 passing unit tests**

## What Happened

Installed opentype.js v1.3.4 as a production dependency. Downloaded three OFL-licensed Google Fonts (Roboto, Open Sans, Lato) as .ttf files into app/public/fonts/. Created app/src/utils/fontService.ts with loadFont, loadFontByFamily, textToPathData, getAvailableFonts, clearFontCache, and isFontCached exports. The service fetches .ttf files, parses them with opentype.js, caches parsed Font objects with in-flight deduplication, and converts text to SVG path data with manual per-character glyph positioning for letter spacing and Y-axis coordinate flip for canvas compatibility. Added @font-face declarations in App.css for all three fonts. Wrote 24 comprehensive unit tests covering font registry, loading/caching/deduplication/errors, family resolution, and text-to-path conversion with dimension scaling, letter spacing arithmetic, coordinate system validation, and edge cases.

## Verification

Ran: cd app && npx vitest run src/utils/__tests__/fontService.test.ts --reporter=verbose && npx tsc --noEmit && ls public/fonts/*.ttf | wc -l. All 24 tests pass, TypeScript compiles cleanly under strict mode, 3 font files confirmed in public/fonts/.

## Verification Evidence

| # | Command | Exit Code | Verdict | Duration |
|---|---------|-----------|---------|----------|
| 1 | `npx vitest run src/utils/__tests__/fontService.test.ts --reporter=verbose` | 0 | ✅ pass | 1050ms |
| 2 | `npx tsc --noEmit` | 0 | ✅ pass | 2200ms |
| 3 | `ls public/fonts/*.ttf | wc -l` | 0 | ✅ pass | 100ms |


## Deviations

None. Variable font files used for Roboto and Open Sans instead of static weights — validated they work correctly with opentype.js.

## Known Issues

None.

## Files Created/Modified

- `app/src/utils/fontService.ts`
- `app/src/utils/__tests__/fontService.test.ts`
- `app/public/fonts/Roboto-Regular.ttf`
- `app/public/fonts/OpenSans-Regular.ttf`
- `app/public/fonts/Lato-Regular.ttf`
- `app/src/App.css`
- `app/package.json`


## Deviations
None. Variable font files used for Roboto and Open Sans instead of static weights — validated they work correctly with opentype.js.

## Known Issues
None.
