typography

# Typography Type is most of your UI. The system does the hard parts — optical sizes, tracking tables, Dynamic Type — *if* you use its APIs. This skill covers when to trust the system, how to build hierarchy deliberately, and what custom fonts owe you back. ## When This Skill Activates - Choosing fonts or building a type hierarchy for a screen or app - Text truncating, cramping, or breaking under larger Dynamic Type sizes - Adopting a custom/brand font (and keeping accessibility) - Display typesetting: hero numbers, stats, editorial headlines ## Rule 1: text styles first Predefined styles (Large Title → Caption 2) are weight + size + leading combos with Dynamic Type support built in — and different styles scale *differently* (body grows more than footnote), which manual font sizes can't replicate. - Build hierarchy from 2–3 text styles + emphasized variants (bold trait — the actual weight varies per style: some go medium→semibold, others bold→heavy) before reaching for new fonts. - Semantic colors + text styles together give dark mode, contrast, and Dynamic Type for free. - macOS supports text styles (without Dynamic Type); design Mac type at 100% — no iOS-style scaling assumptions. ## Rule 2: let optical sizes and tracking work - San Francisco blends Text→Display designs **continuously between 17 and 28pt** (below: sturdier letterforms, looser tracking for legibility; above: tighter, more refined). System font APIs do this automatically — hardcoded single-cut fonts don't. - **Tracking, not kerning**, for letterspacing — tracking is size-specific and lets the OS disable clashing features (ligatures). Override system tracking only in exceptional cases. - Truncation pressure? Use `allowsTightening` (default-tightening-for-truncation) instead of manually squeezing — and prefer wrapping to truncating (line limit 0 on labels that matter). - Line height moves only via leading traits: tight = −2pt, loose = +2pt (±1pt on watchOS); the system adds leading automatically for tall scripts (Arabic, Devanagari). ## The Dynamic Type ladder (WWDC24 10074) 12 sizes: 7 default + 5 accessibility (AX1–AX5). `.body` runs 17pt at default up to 53pt at AX5 — roughly 3× taller, and layouts must expect that. Escalate in order: 1. **Text styles** — `.font(.title)` / `preferredFont(forTextStyle:)` + adjusts-for-content-size, line count 0 so text wraps instead of truncating. 2. **`@ScaledMetric`** for the non-text riding alongside (icon frames, spacing); SF Symbols scale via `UIImage.SymbolConfiguration(textStyle:)`. Prioritize scaling essential content over decoration. 3. **Switch layout axis at accessibility sizes** — branch on `dynamicTypeSize.isAccessibilitySize` with `AnyLayout(HStackLayout())` / `AnyLayout(VStackLayout())` (UIKit: flip the stack axis on `preferredContentSizeCategory.isAccessibilityCategory`); give text the full line width and relax `lineLimit`. 4. **Large Content Viewer** — only for bars that legitimately can't grow: a tab bar takes under 10% of screen height, and scaled to accessibility sizes it would eat almost a quarter (WWDC24 10074). Scaling is always preferred; the viewer is the fallback, not the fix. Test at all 12 sizes (Xcode Previews → Variants → Dynamic Type Variants), not just the biggest — mid-range accessibility sizes catch different wrap points. ## The San Francisco family — pick by job | Face | Job | |---|---| | SF Pro | The default; UI text everywhere | | SF Pro Rounded | Friendlier numerals/labels — widgets, health/fitness data | | SF Compact | watchOS (space-efficient counterpart) | | SF Mono | Code, tabular alignment | | New York | Serif — reading experiences, editorial contrast | | SF Arabic / SF Arabic Rounded | Arabic script with its own optical sizes | **The width axis** (Condensed / Regular / Compressed / Expanded): - Default Regular; every non-Regular choice is a legibility decision — check it. - Condensed: fit more text comfortably (long headlines wrap one line fewer). - Compressed: display-only density, not body text. - Expanded: display typesetting AND small secondary labels (wide + loose tracking). - Width is a **fourth hierarchy lever** beside weight, size, color; all widths share identical vertical proportions, so mixing them never misaligns baselines. 2–3 styles are enough — pair one width with contrasting weights, one weight with contrasting widths, or oppose both for maximum display contrast. ## Custom fonts: what you owe back System fonts get Dynamic Type free; a brand font makes *you* the type engine: - Scale with `UIFontMetrics(forTextStyle:).scaledFont(for:)` + adjusts-for-content-size, or SwiftUI `Font.custom(_:size:relativeTo:)`; scale layout constants with `@ScaledMetric`. - Test at the largest accessibility sizes — wrap to multiple lines rather than truncate. - Verify script coverage for your locales; have a fallback plan for writing systems the brand font doesn't cover (the system stacks: `system-ui`, `ui-rounded`, `ui-serif`, `ui-monospace` on the web). - Budget for the maintenance: tracking tables, optical sizing, and weight ramps are things SF does that a licensed font usually doesn't. ❌ Anti-patterns: hardcoded point sizes on user-facing text · kerning APIs for tracking jobs · custom font without `relativeTo:` (frozen size) · Compressed body text · truncation where wrapping was possible. ## Output Format Type review: `Element | Current (font/size/style) | Issue (hierarchy/scaling/legibility) | Fix` — check Dynamic Type at XXL + AX sizes before signing off; pairs with the contrast rules in `generators/accessibility-generator`. ## References - https://developer.apple.com/videos/play/wwdc2020/10175/ (The details of UI typography) - https://developer.apple.com/videos/play/wwdc2022/110381/ (The expanded San Francisco family) - https://developer.apple.com/fonts/ (SF + New York downloads) - https://developer.apple.com/design/human-interface-guidelines/typography - Related skills: `design/sf-symbols` (symbols align to text styles), `foundation/attributed-string` (rich text mechanics), `generators/accessibility-generator`