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

/*
Copyright 2019 Tulir Asokan <tulir@maunium.net>
Copyright 2020 The Matrix.org Foundation C.I.C.

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, {RefObject} from 'react';

import { CATEGORY_HEADER_HEIGHT, EMOJI_HEIGHT, EMOJIS_PER_ROW } from "./EmojiPicker";
import LazyRenderList from "../elements/LazyRenderList";
import {DATA_BY_CATEGORY, IEmoji} from "../../../emoji";
import Emoji from './Emoji';

const OVERFLOW_ROWS = 3;

export type CategoryKey = (keyof typeof DATA_BY_CATEGORY) | "recent";

export interface ICategory {
    id: CategoryKey;
    name: string;
    enabled: boolean;
    visible: boolean;
    ref: RefObject<HTMLButtonElement>;
}

interface IProps {
    id: string;
    name: string;
    emojis: IEmoji[];
    selectedEmojis: Set<string>;
    heightBefore: number;
    viewportHeight: number;
    scrollTop: number;
    onClick(emoji: IEmoji): void;
    onMouseEnter(emoji: IEmoji): void;
    onMouseLeave(emoji: IEmoji): void;
}

class Category extends React.PureComponent<IProps> {
    private renderEmojiRow = (rowIndex: number) => {
        const { onClick, onMouseEnter, onMouseLeave, selectedEmojis, emojis } = this.props;
        const emojisForRow = emojis.slice(rowIndex * 8, (rowIndex + 1) * 8);
        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 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
                id={`mx_EmojiPicker_category_${this.props.id}`}
                className="mx_EmojiPicker_category"
                data-category-id={this.props.id}
                role="tabpanel"
                aria-label={name}
            >
                <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;