Trait ThemeTokens 

pub trait ThemeTokens: 'static {
    // Provided methods
    fn primary(&self) -> Color { ... }
    fn on_primary(&self) -> Color { ... }
    fn radius(&self) -> f32 { ... }
    fn radius_sm(&self) -> f32 { ... }
    fn radius_md(&self) -> f32 { ... }
    fn radius_lg(&self) -> f32 { ... }
    fn spacing(&self) -> f32 { ... }
    fn font_size(&self) -> f32 { ... }
    fn icon_size(&self) -> f32 { ... }
    fn muted(&self) -> Color { ... }
    fn scrollbar(&self) -> Color { ... }
    fn ink(&self) -> Color { ... }
    fn surface(&self) -> Color { ... }
    fn surface_alt(&self) -> Color { ... }
    fn border(&self) -> Color { ... }
    fn success(&self) -> Color { ... }
    fn warning(&self) -> Color { ... }
    fn error(&self) -> Color { ... }
    fn info(&self) -> Color { ... }
    fn highlight_low(&self) -> Color { ... }
    fn highlight_med(&self) -> Color { ... }
    fn highlight_high(&self) -> Color { ... }
}

Opt-in semantic-token contract the built-in component catalogue reads through, so a component can resolve a token without knowing the concrete theme type.

Every method carries a default, which makes impl ThemeTokens for MyTheme {} valid and each token an independent opt-in: a theme answers the questions it cares about and lets the catalogue keep its own answer for the rest. This trait is deliberately not where a theme’s vocabulary lives — that belongs to the theme’s own type, reachable in full through use_theme. What is here is only the subset a component written without knowledge of that type has to be able to ask for.

The metric tokens are bases, not a size scale. A catalogue component derives its own proportions from font_size rather than asking for a named role, because naming the roles would decide for every application which roles may exist. One number scales the type; the component keeps its own ratios.

Provided Methods

fn primary(&self) -> Color

fn on_primary(&self) -> Color

fn radius(&self) -> f32

Base corner radius in px. A component rounds by this, or by a step of the scale below where its shape asks for one (a pill is not a card).

fn radius_sm(&self) -> f32

The steps either side of radius, so a theme owns how round everything is instead of each component keeping its own literal.

This is the axis an application actually restyles, and a scale of three steps derived from one base is what a design system needs to be reachable from outside. A component that hardcodes BorderRadius::all(8.0) is not themeable at all — the caller can change the base radius and watch nothing move — and the fix is not a prop per component but a token they all read.

A theme that wants a flat scale returns the same number from all three; one that wants a rounder language moves the base and the steps follow.

fn radius_md(&self) -> f32

fn radius_lg(&self) -> f32

fn spacing(&self) -> f32

Base gap between adjacent things in px, and the unit a component derives its own padding from.

fn font_size(&self) -> f32

Base body text size in px. Every catalogue component scales its own text off this, so changing it scales the whole type ramp.

fn icon_size(&self) -> f32

Default size of a standalone icon in px.

fn muted(&self) -> Color

fn scrollbar(&self) -> Color

fn ink(&self) -> Color

Primary text ink for component labels/titles/values. A theme should override it, but the default follows the active light/dark mode rather than assuming light: a theme that overrides surface and forgets ink used to paint near-black text on its own dark panel.

fn surface(&self) -> Color

The background a floating panel sits on — a menu, a dropdown, a dialog. Opaque by default, because the thing it covers must not read through it, and mode-following for the same reason as ink.

fn surface_alt(&self) -> Color

A quiet, low-contrast surface tone for chip/tag backgrounds. Defaults to a faint neutral wash.

fn border(&self) -> Color

Hairline border/divider tone. Defaults to a faint neutral.

fn success(&self) -> Color

Semantic status colours. Defaults are conventional hues; a theme should override to match its palette.

fn warning(&self) -> Color

fn error(&self) -> Color

fn info(&self) -> Color

fn highlight_low(&self) -> Color

Three progressively stronger highlight/elevation tints for hover, selection, and pressed states. Defaults to faint neutral washes a theme can override with palette-specific tones.

fn highlight_med(&self) -> Color

fn highlight_high(&self) -> Color

Dyn Compatibility

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors