Heading

Styles a heading, scaling font size by level relative to the theme base size. Apply to <h1>–<h6>.

Props

Prop	Type	Default	Description
`color`	`ValueOrState<ThemeColor>`	`"neutral"`	Theme color tone for the heading text.
`size`	`ElementSize`	tag-based HeadingShift (`h1` `increase-4` … `h6` `decrease-1`)	Optional. When set, `fontSize` is `themeSize(listener, size)` (`"inherit"` \| `"increase-N"` \| `"decrease-N"`, N ≤ 7) with no tag bump. When omitted, follows the host tag.

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.

heading

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

const HeadingShift: Record<string, ElementSize> = {
  h6: "decrease-1",
  h5: "inherit",
  h4: "increase-1",
  h3: "increase-2",
  h2: "increase-3",
  h1: "increase-4",
};

/**
 * Styles a heading, scaling its font size by level (h1 largest … h6 smallest)
 * relative to the theme base size. Apply to a heading element `<h1>`–`<h6>`.
 *
 * @hostTag h1-h6
 * @param props.color - Theme color tone (`ValueOrState<ThemeColor>`) for the heading text. Defaults to "neutral".
 * @param props.size - Optional `ElementSize` (`"inherit"` | `"increase-N"` | `"decrease-N"`, N ≤ 7). When set, font size is `themeSize(listener, size)` including `"inherit"` (no tag bump). When omitted, follows the host tag (`h1` increase-4 … `h6` decrease-1).
 * @example { h2: "Section title", $: [heading()] }
 * @example { h3: "Panel title", $: [heading({ size: "inherit" })] }
 */
function heading(
  props: { color?: ValueOrState<ThemeColor>; size?: ElementSize } = {},
): PartialElement {
  const color = toState(props.color ?? "neutral", "color");
  const size = props.size;

  return {
    _onInsert: (node) => {
      if (!["h1", "h2", "h3", "h4", "h5", "h6"].includes(node.tagName)) {
        console.warn(
          `"heading" primitive patch must use heading tags [h1...h6]`,
        );
      }
    },
    style: {
      color: (listener) =>
        themeColor(listener, "shift-11", color.get(listener)),
      marginTop: 0,
      marginBottom: themeSpacing(2),
      fontSize: (listener) => {
        if (size !== undefined) {
          return themeSize(listener, size);
        }
        const offset = HeadingShift[listener.elementNode.tagName] || "inherit";
        return themeSize(listener, offset);
      },
    },
  };
}

export { heading };

Heading#

Props#

Heading

Props