ArtPlayer/packages/artplayer-plugin-danmuku/src/getDanmuTop.js

export default function getDanmuTop(ins, danmu) {
    const { $player } = ins.art.template;

    const danmus = ins.queue
        .filter((item) => {
            return (
                item.$ref &&
                item.$state === 'emit' &&
                item.mode === danmu.mode &&
                item.$ref.offsetTop <= $player.clientHeight - ins.marginBottom
            );
        })
        .map((item) => {
            return {
                top: item.$ref.offsetTop,
                left: item.$ref.offsetLeft,
                height: item.$ref.clientHeight,
                width: item.$ref.clientWidth,
                right: $player.clientWidth - item.$ref.offsetLeft - item.$ref.clientWidth,
            };
        })
        .sort((prev, next) => prev.top - next.top);

    if (danmus.length === 0) {
        return ins.marginTop;
    }

    danmus.unshift({
        top: 0,
        left: 0,
        right: 0,
        height: ins.marginTop,
        width: $player.clientWidth,
    });

    danmus.push({
        top: $player.clientHeight - ins.marginBottom,
        left: 0,
        right: 0,
        height: ins.marginBottom,
        width: $player.clientWidth,
    });

    for (let index = 1; index < danmus.length; index += 1) {
        const item = danmus[index];
        const prev = danmus[index - 1];
        const prevBottom = prev.top + prev.height;
        const diff = item.top - prevBottom;
        if (diff >= danmu.$ref.clientHeight) {
            return prevBottom;
        }
    }

    const topMap = [];
    for (let index = 1; index < danmus.length - 1; index += 1) {
        const item = danmus[index];
        if (topMap.length) {
            const last = topMap[topMap.length - 1];
            if (last[0].top === item.top) {
                last.push(item);
            } else {
                topMap.push([item]);
            }
        } else {
            topMap.push([item]);
        }
    }

    switch (danmu.mode) {
        case 0:
            topMap.sort((prev, next) => {
                const nextMinRight = Math.min(...next.map((item) => item.right));
                const prevMinRight = Math.min(...prev.map((item) => item.right));
                return nextMinRight * next.length - prevMinRight * prev.length;
            });
            break;
        case 1:
            topMap.sort((prev, next) => {
                const nextMaxWidth = Math.max(...next.map((item) => item.width));
                const prevMaxWidth = Math.max(...prev.map((item) => item.width));
                return prevMaxWidth * prev.length - nextMaxWidth * next.length;
            });
            break;
        default:
            break;
    }

    return topMap[0][0].top;
}