FAB (Floating Action Button)

Apply fab to a <button> to render a circular elevated button — the standard Material-style primary-action button. Three size presets and full theme-color support.

Props

Prop	Type	Default
`color`	`ValueOrState<ThemeColor>`	`"primary"`
`size`	`"small" \| "medium" \| "large"`	`"medium"`

Customization

Must see the source of patch at the bottom of each patch page to understand the structure then code it still code as html native element.

There are four levels of customization, in increasing order of effort:

Patch props. Each patch exposes a small, stable set of props—typically fewer than five. Lowest friction.
Context attributes. Use dataTone, dataSize, and dataDensity on a container to shift tone, size, or density for an entire subtree without touching individual elements.
Inline override. Native-wins merge strategy: any property set directly on the element overrides the patch value.
Create a variant. Clone a similar patch and edit it. Use this only when you need a reusable custom version.

Formulas

Unit - U = fontSize / 4 - convert final values with themeSpacing(n).

Size - n = intrinsic text lines, w = wrapping level, d = density factor:

height        = (n * 6 + 2 * d * w) * U
paddingBlock  = d * w * U
paddingInline = ceil(3 / w) * d * w * U
radius        = d * w * U

Base density d = 1.5:

U	w=0	w=1	w=2	w=3
height (`n = 1`)	6	9	12	15
paddingBlock	0	1.5	3	4.5
paddingInline	3	4.5	6	4.5
radius	0	1.5	3	4.5

Tone - K = N / 2 where N is the palette length. For N = 18, K = 9.

Role	Shift	n=0
Background	parent +/- n	0
Text	bg + K	6
Border	bg + K/2	3
Hover	bg + 2K/3	4
Selected / Focus	above +/- K/3	2-4

State shift range: K/3 <= delta <= 2K/3.

fab

import { type PartialElement, toState, type ValueOrState } from "@domphy/core";
import {
  type ThemeColor,
  themeColor,
  themeSize,
  themeSpacing,
} from "@domphy/theme";

const SIZE_MAP = { small: 8, medium: 10, large: 14 } as const;

/**
 * Floating Action Button — a circular elevated button typically used for the
 * primary action on a screen. Apply to a `<button>` element.
 *
 * @hostTag button
 * @param props.color - Button color tone. Optional `ValueOrState<ThemeColor>`, defaults to `"primary"`.
 * @param props.size - Button size preset. Optional `"small" | "medium" | "large"`, defaults to `"medium"`.
 * @example { button: "+", $: [fab()] }
 * @example { button: "+", $: [fab({ size: "small", color: "neutral" })] }
 */
function fab(
  props: {
    color?: ValueOrState<ThemeColor>;
    size?: "small" | "medium" | "large";
  } = {},
): PartialElement {
  const color = toState(props.color ?? "primary", "color");
  const dim = themeSpacing(SIZE_MAP[props.size ?? "medium"]);

  return {
    _onInsert: (node) => {
      if (node.tagName !== "button") {
        console.warn('"fab" patch must use button tag');
      }
    },
    style: {
      appearance: "none",
      border: "none",
      cursor: "pointer",
      display: "inline-flex",
      alignItems: "center",
      justifyContent: "center",
      flexShrink: 0,
      width: dim,
      height: dim,
      borderRadius: "50%",
      fontSize: (listener) => themeSize(listener, "inherit"),
      backgroundColor: (listener) =>
        themeColor(listener, "shift-9", color.get(listener)),
      color: (listener) => themeColor(listener, "shift-0", color.get(listener)),
      boxShadow: (listener) =>
        `0 ${themeSpacing(1)} ${themeSpacing(4)} ${themeColor(listener, "shift-4", "neutral")}`,
      transition: "background-color 200ms ease, box-shadow 200ms ease",
      "&:hover:not([disabled])": {
        backgroundColor: (listener) =>
          themeColor(listener, "shift-10", color.get(listener)),
        boxShadow: (listener) =>
          `0 ${themeSpacing(2)} ${themeSpacing(6)} ${themeColor(listener, "shift-5", "neutral")}`,
      },
      "&:focus-visible": {
        outline: (listener) =>
          `2px solid ${themeColor(listener, "shift-6", color.get(listener))}`,
        outlineOffset: "2px",
      },
      "&[disabled]": { opacity: 0.5, cursor: "not-allowed" },
    },
  };
}

export { fab };

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