element-web/src/components/views/emojipicker/Category.js

/*
Copyright 2019 Tulir Asokan <tulir@maunium.net>

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 React from 'react';
import PropTypes from 'prop-types';
import { CATEGORY_HEADER_HEIGHT, EMOJI_HEIGHT, EMOJIS_PER_ROW } from "./EmojiPicker";
import * as sdk from '../../../index';

const OVERFLOW_ROWS = 3;

class Category extends React.PureComponent {
    static propTypes = {
        emojis: PropTypes.arrayOf(PropTypes.object).isRequired,
        name: PropTypes.string.isRequired,
        id: PropTypes.string.isRequired,
        onMouseEnter: PropTypes.func.isRequired,
        onMouseLeave: PropTypes.func.isRequired,
        onClick: PropTypes.func.isRequired,
        selectedEmojis: PropTypes.instanceOf(Set),
    };

    _renderEmojiRow = (rowIndex) => {
        const { onClick, onMouseEnter, onMouseLeave, selectedEmojis, emojis } = this.props;
        const emojisForRow = emojis.slice(rowIndex * 8, (rowIndex + 1) * 8);
        const Emoji = sdk.getComponent("emojipicker.Emoji");
        return (<div key={rowIndex}>{
            emojisForRow.map(emoji =>
                <Emoji key={emoji.hexcode} emoji={emoji} selectedEmojis={selectedEmojis}
                    onClick={onClick} onMouseEnter={onMouseEnter} onMouseLeave={onMouseLeave} />)
        }</div>);
    };

    render() {
        const { emojis, name, heightBefore, viewportHeight, scrollTop } = this.props;
        if (!emojis || emojis.length === 0) {
            return null;
        }
        const rows = new Array(Math.ceil(emojis.length / EMOJIS_PER_ROW));
        for (let counter = 0; counter < rows.length; ++counter) {
            rows[counter] = counter;
        }
        const LazyRenderList = sdk.getComponent('elements.LazyRenderList');

        const viewportTop = scrollTop;
        const viewportBottom = viewportTop + viewportHeight;
        const listTop = heightBefore + CATEGORY_HEADER_HEIGHT;
        const listBottom = listTop + (rows.length * EMOJI_HEIGHT);
        const top = Math.max(viewportTop, listTop);
        const bottom = Math.min(viewportBottom, listBottom);
        // the viewport height and scrollTop passed to the LazyRenderList
        // is capped at the intersection with the real viewport, so lists
        // out of view are passed height 0, so they won't render any items.
        const localHeight = Math.max(0, bottom - top);
        const localScrollTop = Math.max(0, scrollTop - listTop);

        return (
            <section className="mx_EmojiPicker_category" data-category-id={this.props.id}>
                <h2 className="mx_EmojiPicker_category_label">
                    {name}
                </h2>
                <LazyRenderList
                    element="ul" className="mx_EmojiPicker_list"
                    itemHeight={EMOJI_HEIGHT} items={rows}
                    scrollTop={localScrollTop}
                    height={localHeight}
                    overflowItems={OVERFLOW_ROWS}
                    overflowMargin={0}
                    renderItem={this._renderEmojiRow}>
                </LazyRenderList>
            </section>
        );
    }
}

export default Category;