leaflet-components/src/elements/leaflet-control-layers.ts

import { Control, type ControlPosition } from 'leaflet';
import { bool, choice } from '../core/props.ts';
import { WithProps } from '../core/with-props.ts';
import type { LeafletRegisterEvent } from '../core/register.ts';

export default class LeafletControlLayersElement extends WithProps(
  {
    position: choice<ControlPosition>('topright'),
    collapsed: bool(true),
    autoZIndex: bool(true),
    hideSingleBase: bool(),
    sortLayers: bool(),
  },
  { attach: 'self' },
) {
  declare readonly leafletObject?: Control.Layers;

  createLeafletObject(options: Control.LayersOptions): Control.Layers {
    return new Control.Layers({}, {}, options);
  }

  connectedCallback(): void {
    super.connectedCallback();
    this.addEventListener('leaflet-register', this.#onChildRegister);
  }

  disconnectedCallback(): void {
    this.removeEventListener('leaflet-register', this.#onChildRegister);
    super.disconnectedCallback();
  }

  // Every child -- present at construction or added later -- announces
  // itself this way: a parent's connectedCallback always finishes before a
  // child's does (even for an already-built subtree attached in one go), so
  // there is no "read the children that are already here" case to handle
  // separately.
  #onChildRegister = (e: LeafletRegisterEvent) => {
    e.stopPropagation();
    const el = e.detail.element;
    const layer = e.detail.leafletObject;
    const name = el.getAttribute('name');
    if (!name) return;
    if (el.getAttribute('type') === 'base') this.leafletObject?.addBaseLayer(layer, name);
    else this.leafletObject?.addOverlay(layer, name);
    if (el.hasAttribute('active')) {
      this.dispatchEvent(
        new CustomEvent('leaflet-add-layer', { bubbles: true, detail: { layer } }),
      );
    }
  };
}