ui/src/frontend/widgets/virtual_scroll_container.ts

// Copyright (C) 2023 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

import m from 'mithril';

import {findRef, toHTMLElement} from '../../base/dom_utils';

interface VirtualScrollContainerAttrs {
  // Called when the scrolling element is created, updates, or scrolls.
  onScroll?: (dom: HTMLElement) => void;
}

export class VirtualScrollContainer implements
    m.ClassComponent<VirtualScrollContainerAttrs> {
  private readonly REF = 'virtual-scroll-container';
  view({attrs, children}: m.Vnode<VirtualScrollContainerAttrs>) {
    const {
      onScroll = () => {},
    } = attrs;

    return m(
        '.pf-virtual-scroll-container',
        {
          ref: this.REF,
          onscroll: (e: Event) => onScroll(e.target as HTMLElement),
        },
        children);
  }

  oncreate({dom, attrs}: m.VnodeDOM<VirtualScrollContainerAttrs, this>) {
    const {
      onScroll = () => {},
    } = attrs;

    const element = findRef(dom, this.REF);
    if (element) {
      onScroll(toHTMLElement(element));
    }
  }
}