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Domphy

Horizontal Rule

Use horizontalRule on an hr element. It renders a thematic break as a thin 1px themed line with vertical margin. The color prop controls the rule color tone.

Props

PropTypeDefaultDescription
colorValueOrState<ThemeColor>"neutral"Theme color tone for the rule.
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:

  1. Patch props. Each patch exposes a small, stable set of props—typically fewer than five. Lowest friction.
  2. Context attributes. Use dataTone, dataSize, and dataDensity on a container to shift tone, size, or density for an entire subtree without touching individual elements.
  3. Inline override. Native-wins merge strategy: any property set directly on the element overrides the patch value.
  4. 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:

Uw=0w=1w=2w=3
height (n = 1)691215
paddingBlock01.534.5
paddingInline34.564.5
radius01.534.5

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

RoleShiftn=0
Backgroundparent +/- n0
Textbg + K6
Borderbg + K/23
Hoverbg + 2K/34
Selected / Focusabove +/- K/32-4

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

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

/**
 * A thematic break rendered as a thin 1px themed line with vertical margin.
 * Apply to an `<hr>` element.
 *
 * @hostTag hr
 * @param props.color - Theme color tone (`ValueOrState<ThemeColor>`) for the rule. Defaults to "neutral".
 * @example { hr: "", $: [horizontalRule()] }
 */
function horizontalRule(
  props: { color?: ValueOrState<ThemeColor> } = {},
): PartialElement {
  const color = toState(props.color ?? "neutral", "color");

  return {
    _onInsert: (node) => {
      if (node.tagName !== "hr") {
        console.warn(`"horizontalRule" primitive patch must use hr tag`);
      }
    },
    // Soft rule surface — edge anchor (shift-3 = border) + inherit paint.
    dataTone: "shift-3",
    style: {
      border: 0,
      height: "1px",
      marginInline: 0,
      marginTop: themeSpacing(3),
      marginBottom: themeSpacing(3),
      backgroundColor: (listener) =>
        themeColor(listener, "inherit", color.get(listener)),
      color: (listener) => themeColor(listener, "text", color.get(listener)),
    },
  };
}

export { horizontalRule };