Design

An app's design system as Swift, from compact lines, shipped as a Granite agent package. A call says the brand's colours, the colour roles views read, its gradients, spacing, radii, type scale and fonts the way a person would jot them down; the package writes them into the folder the call names, in the shape Loom keeps its design: Brand.swift, Brand.Color.swift, Style.swift and Fonts/. A light/dark pair, an asset catalog's colour set and every colour the platform supplies switch with the appearance; every type style follows Dynamic Type; the code builds for iOS 17 and macOS 14 in Swift 5 and Swift 6.

It is one of the Rao Craft Agents: independent packages that, tagged in prompts along the life of a project, build an app of Loom's quality. design writes what every view reads: Color.background, .padding(.layer4), .font(.brandTitle), Brand.Colors.cream.

How an app finds it

DesignAgent is a GraniteAgentPackage, and it carries a record in its binary:

@used @section("__DATA_CONST,__granite")
let designRecord: GraniteRoster.Record = { GraniteRoster.record(DesignAgent.self) }

In Craft, install it from the Agent Store or with craft agents add https://github.com/Rao-Craft-Agents/DesignAgent.git, then say $design in a request:

$design the recipe app's look: a cream page, ink text, basil for the accent and tomato for danger,
a serif large title, rounded cards, and the card and section styles

The model writes the lines; the call shows on Craft's agent map as design-1, and the files it names are built and tested with the turn.

What a call takes and answers

The answer is a DesignResult: every file written (path, paths, absolute, the copied fonts included), the names views write (colors, roles with what each reads, layers, radii, type, gradients), the font faces, and a sentence for anything the call should know.

The lines

palette    cream: #FBF7F0/#1A1714          light/dark
           saffron "the spice jar": #E8A33D   one for both, with a doc
           ink: brandInk                     a colour set of the project's asset catalogs
           scrim: #000000 40%                any of them, less opaque
roles      background = cream
           secondaryForeground = ink 60%
           accent = #3F7D58/#6FBF8E
           highlight = saffron "a recipe someone starred"
type       title: 28 bold rounded            size, weight, design, `italic`, text style, in any order
           display: 44 heavy                 scales with the style nearest its size (largeTitle)
radii      card: 14
gradients  sunrise: saffron tomato vertical

• A name is said as a person says it (brand blue, brand-blue) and written as Swift says it (brandBlue); : and = read the same.
• A role left out reads, in order, the asset catalog's colour set of its name (colors/background, namespaces kept; AccentColor is the accent, as Xcode names it), the palette colour of its name, then the platform's own (systemBackground on iOS, windowBackgroundColor on macOS). The roles every design has: background, secondaryBackground, tertiaryBackground, alternateBackground, foreground, secondaryForeground, accent, separator, success, warning, danger.
• Radii and the type scale start from four radii (small 4, medium 8, card 12, large 16) and Apple's text styles; a line of a name they have changes it, any other adds to them.
• A line it cannot read, a colour set or a font file it cannot find, is refused with the reason, every one at once, and nothing is written.

How the files are made

Two things it reads of the project so the code builds the first time: when an Xcode project turns on Swift asset symbol extensions, Xcode writes Color.accent from an AccentColor set itself, so that role is left to it (a line against it is refused); and another file that declares Brand, a .layer, a role or Font.brand is named in a note.

No model is asked: the same lines make the same files every time.

Testing

swift test                    # the record, the schema, the lines, the files, the project read, a call through the roster
DESIGN_BUILD=1 swift test     # three designs (hex with fonts, an asset catalog, Xcode's asset symbols) built for macOS
                              # and the iOS simulator in Swift 6 and 5, and run: each colour drawn in light and dark,
                              # the fonts registered from the bundle

MIT licensed.