name: figui3 description: Guides development and maintenance of the FigUI3 web components library for Figma-style plugin UIs. Applies when adding or modifying fig-* custom elements, updating docs/demo pages, adjusting theme tokens, improving accessibility, or debugging component behavior in fig.js, components.css, index.html, and README.md. user-invocable: false

FigUI3

A lightweight web components library for Figma UI3-style plugin and widget interfaces.

IMPORTANT: Prefer the project's native scripts and structure. Use bun dev for local docs/demo work and bun build for production output.

Current Project Context

!`node -e "const p=require('./package.json'); console.log(JSON.stringify({name:p.name,version:p.version,scripts:p.scripts,exports:p.exports},null,2))" 2>/dev/null || echo '{"error":"package.json not found"}'`

The JSON above is the source of truth for package name, build commands, and exported files.

Principles

1. Preserve native Web Components patterns. Keep components framework-agnostic and rooted in custom elements.
2. Prefer existing fig-* components over one-off markup. Compose from current primitives before inventing new ones.
3. Keep Figma UI3 visual consistency. Use existing CSS variables and spacing/radius conventions.
4. Honor interaction semantics. Emit input while interacting and change on committed value changes.
5. Treat accessibility as required behavior. Preserve labels, keyboard support, ARIA attributes, and disabled states.

React + Vite Integration

Install and bootstrap in React

• Install package: npm i @rogieking/figui3 (or pnpm add / bun add).
• Import CSS once in app entry (main.tsx / main.jsx): import "@rogieking/figui3/fig.css";
• Register custom elements before first render. In Vite/React, prefer an explicit bootstrap:

import "@rogieking/figui3/fig.css";

const bootstrap = async () => {
  // Prevent production tree-shaking from dropping registration side effects.
  await import("@rogieking/figui3/fig.js");
  createRoot(document.getElementById("app")!).render(<App />);
};

bootstrap();

Vite config guidance

• Standard React Vite config is usually enough:

import { defineConfig } from "vite";
import react from "@vitejs/plugin-react";

export default defineConfig({
  plugins: [react()],
});

• Keep FigUI3 registration import at the top-level app bootstrap (not inside leaf components).
• If a production build appears to tree-shake element registration, use the explicit dynamic import pattern above.

React usage rules for web components

• Use DOM attrs on custom elements (<fig-slider text="true" />) and read values from e.target / e.detail.
• In React, use class (not className) for all FigUI3 web components (fig-* and <dialog is="fig-...">) to keep attribute behavior consistent.
• Prefer refs + addEventListener when wiring complex input/change behavior.

React + color picker modes (fig-input-color / fig-fill-picker)

• fig-input-color supports custom mode workflows only through picker="figma" (internally uses fig-fill-picker).
• The mode attribute on fig-input-color is pass-through to inner fig-fill-picker; mode logic lives in fig-fill-picker.
• picker-* attrs on fig-input-color are forwarded to fig-fill-picker (except picker-anchor, which is handled separately).
  • Example: picker-dialog-position, picker-experimental, etc.
• For React custom modes, use fig-fill-picker + slot API:
  • Add a child with slot="mode-<name>" (and optional label).
  • Include <name> in the mode attribute (e.g. mode="solid,react-demo").
  • Listen for modeready and render into e.detail.container.
• Do not reparent React-owned DOM into the picker after render; use the provided modeready container as mount target.
• Keep React lifecycle cleanup explicit for custom mode mounts:
  • keep one root per mode container
  • call root.unmount() when the host component unmounts
  • remove modeready listeners in cleanup to avoid duplicate mounts
• Custom mode content must dispatch input / change with detail payload so picker can store mode data and propagate events.
• Preserve value shape expectations:
  • fig-input-color expects solid color data (detail.color, optional detail.alpha) from the picker.
  • fig-fill-picker custom modes use JSON with type set to mode name and remaining data in payload.
• Keep picker-anchor behavior explicit in React:
  • picker-anchor="self" anchors to the color input element itself.
  • Selector values anchor to another DOM element (resolved via document.querySelector).

Experimental Attribute Guidance

• Use experimental as a feature-flag string for opt-in behavior. Treat it as progressive enhancement, not guaranteed baseline behavior.
• Prefer experimental="modern" when enabling modern customizable select/picker UI behavior.
• Keep usage explicit on the component that needs it (for example fig-dropdown, fig-fill-picker, fig-input-fill, fig-input-color).
• Preserve pass-through behavior:
  • fig-input-color and fig-input-fill forward experimental-related picker settings into internal fig-fill-picker usage.
  • Avoid adding hidden implicit defaults that enable experimental behavior globally.
• Backward-compat rule:
  • Do not reintroduce variant="neue" for dropdown experimental behavior.
  • Keep variant="neue" handling only where it is still intentionally supported (for example slider visuals).
• Documentation rule: any new experimental token must be documented with activation syntax, intended scope, and fallback behavior in demos + README + changelog.

Critical Rules

Overlay Components (fig-dialog, fig-popup)

• Choose the overlay primitive intentionally:
  • <dialog is="fig-dialog"> for modal/light-dismiss dialog workflows.
  • <dialog is="fig-popup"> for anchored floating surfaces (menus, contextual panels, nested popups).
• Keep overlay semantics stable:
  • fig-dialog should remain dialog-first (title/header/footer patterns, modal semantics).
  • fig-popup should remain anchor/position-first (offset, collision handling, viewport margins).
• Preserve drag and positioning behavior on both fig-dialog and fig-popup; do not regress manual placement rules.
• For popup chains, maintain containment and dismissal logic across descendant popups.
• Document any overlay behavior change in demos and changelog with a concrete before/after note.

Component Architecture

• Extend HTMLElement and implement lifecycle cleanup in disconnectedCallback.
• Use observedAttributes + attributeChangedCallback for attribute-driven reactivity.
• Keep attribute names and behavior backward-compatible unless explicitly doing a breaking change.
• Support disabled behavior wherever interaction is possible.
• Avoid introducing framework-specific assumptions in component internals.

Events and Data Contracts

• Emit standard input and change events for form-like controls.
• Put rich payloads in event.detail when needed; keep names stable.
• Do not silently change event payload shape for existing components.
• When adding new events, document trigger timing and payload fields.

Styling and Theming

• Reuse established design tokens and CSS variables before adding new ones.
• Keep light/dark compatibility working with color-scheme and current token strategy.
• Avoid ad-hoc hardcoded colors when semantic tokens already exist.
• Preserve current sizing, spacing, and radius rhythm unless intentionally refactoring system-wide.

Documentation and Demos

• Update README.md component docs when public API or behavior changes.
• Update demo surfaces (index.html and playground/ routes where relevant) for visible behavior changes.
• Prefer realistic examples that mirror plugin/property panel usage.
• If introducing an experimental feature, document activation and fallback behavior clearly.

Compatibility and Safety

• Keep browser support expectations aligned with current README claims.
• Use progressive enhancement for bleeding-edge CSS features.
• Avoid regressions in existing attributes, defaults, and emitted events.

Color Picker Mode Extensibility

• Treat custom modes as a fig-fill-picker concern, not a standalone fig-input-color concern.
• When adding a new mode, update demos/docs with both:
  • vanilla slot usage (slot="mode-*")
  • React modeready usage
• Do not emit input from programmatic attribute writes (value updates); preserve current loop-avoidance behavior for React.

Key Patterns

<!-- Modal/dialog content container -->
<dialog is="fig-dialog" drag="true" handle="fig-header">
  <fig-header>
    Dialog Title
    <fig-button variant="ghost" icon close-dialog aria-label="Close dialog">
      <span class="fig-mask-icon" style="--icon: var(--icon-close)"></span>
    </fig-button>
  </fig-header>
  <div>Dialog body</div>
</dialog>

<!-- Anchored popup surface -->
<dialog is="fig-popup" anchor="#trigger" position="bottom left" offset="8 8">
  <div>Popup content</div>
</dialog>

// Event contract pattern: continuous + committed updates.
this.dispatchEvent(new CustomEvent("input", { detail, bubbles: true }));
this.dispatchEvent(new CustomEvent("change", { detail, bubbles: true }));

// Attribute-driven updates.
static get observedAttributes() { return ["value", "disabled"]; }
attributeChangedCallback(name, oldValue, newValue) {
  if (oldValue === newValue) return;
  // sync internal UI state
}

Event contract quick map:
- fig-slider: input/change -> current value on e.target.value
- fig-input-color: input/change -> value on e.target.value, structured color via e.detail (when available)
- fig-input-fill / fig-fill-picker: input/change -> fill payload in e.detail

<!-- Typical field composition -->
<fig-field direction="horizontal">
  <label>Opacity</label>
  <fig-slider value="75" min="0" max="100" text="true" units="%"></fig-slider>
</fig-field>

fig-popup vs fig-dialog

• Use fig-dialog when the UI is a dialog.
  • Best for modal or primary task flows.
  • Works well with explicit dialog structure and close policies.
• Use fig-popup when you need low-level floating control.
  • Best for anchored contextual surfaces and advanced positioning behavior.
  • Prefer this when you need explicit anchor/position/offset/viewport tuning.

Rule of thumb: fig-dialog = dialog UX, fig-popup = popup primitive.

Workflow

1. Read existing implementation first. Check fig.js, components.css, and related demo usage before editing.
2. Confirm API surface impact. Identify affected attributes, events, and slots.
3. Implement with compatibility in mind. Preserve defaults and old usage unless explicitly changed.
4. Update docs/demo in same pass. Keep examples and behavior synchronized.
5. Run project checks. Use bun dev for interactive verification and bun build for output sanity.
6. Verify accessibility and theming. Check keyboard flow, labels, disabled states, and both light/dark appearance.

Release-Ready Checklist

• Validate in a production build (bun build) and confirm custom elements are registered at runtime.
• Verify input vs change behavior for touched controls in both vanilla usage and React integration.
• Verify light/dark themes and keyboard navigation for any changed component.
• Verify overlay behavior (fig-dialog, fig-popup) including close/dismiss and drag behavior when applicable.
• Update README.md, demos, and CHANGELOG.md for any public API or behavior change.

Quick Reference

# Start docs/demo server
bun dev

# Build distributable files
bun build

Primary Files

• fig.js - component implementations and behavior
• components.css - component-level styling and states
• base.css - foundational styles and variables
• index.html - main interactive docs/demo
• README.md - public API and usage documentation
• CHANGELOG.md - release history and migration notes