Skeleton

Use the skeleton patch on any block element to show a loading placeholder. The animation pulses between full and reduced opacity.

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.

skeleton

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

/**
 * A loading placeholder block with a pulsing opacity animation. Marked `aria-hidden`, themed
 * background/foreground, fixed height, slight rounding. No host-tag check; typically applied
 * to a block-level element such as a `div` or `span`.
 *
 * @param props.color - Theme color tone for the placeholder. Accepts a value or reactive state.
 *   Defaults to `"neutral"`.
 * @example { div: null, $: [skeleton()] }
 */
function skeleton(
  props: { color?: ValueOrState<ThemeColor> } = {},
): PartialElement {
  const color = toState(props.color ?? "neutral", "color");

  const keyframes = {
    "0%,100%": { opacity: 1 },
    "50%": { opacity: 0.4 },
  };
  const animationName = hashString(JSON.stringify(keyframes));
  return {
    ariaHidden: "true",
    dataTone: "shift-2",
    style: {
      fontSize: (listener) => themeSize(listener),
      color: (listener) => themeColor(listener, "shift-9", color.get(listener)),
      height: themeSpacing(6),
      display: "block",
      borderRadius: themeSpacing(1),
      backgroundColor: (listener) =>
        themeColor(listener, "inherit", color.get(listener)),
      animation: `${animationName} 1.5s ease-in-out infinite`,
      [`@keyframes ${animationName}`]: keyframes,
    } as StyleObject,
  };
}

export { skeleton };

</div>