export function useIndex (appRef) {
  // * appRef指向最外层容器

  // * 定时函数
  let timer = null
  // * 默认缩放值
  const scale = {
    width: '1',
    height: '1'
  }
  // * 设计稿尺寸（px）
  const baseWidth = 1920
  const baseHeight = 1080

  // * 需保持的比例（默认2）
  // const baseProportion = parseFloat((baseWidth / baseHeight).toFixed(5))
  const baseProportion = 2
  const calcRate = () => {
    // 当前宽高比
    const currentRate = parseFloat((window.innerWidth / window.innerHeight).toFixed(5))
    if (appRef) {
      if (currentRate > baseProportion) {
        // 表示更宽
        scale.width = ((window.innerHeight * baseProportion) / baseWidth).toFixed(5)
        scale.height = (window.innerHeight / baseHeight).toFixed(5)
        appRef.style.transform = `scale(${scale.width}, ${scale.height}) translate(-50%, -50%)`
      } else {
        // 表示更高
        scale.height = ((window.innerWidth / baseProportion) / baseHeight).toFixed(5)
        scale.width = (window.innerWidth / baseWidth).toFixed(5)
        appRef.style.transform = `scale(${scale.width}, ${scale.height}) translate(-50%, -50%)`
      }
    }
  }

  const resize = () => {
    clearTimeout(timer)
    timer = setTimeout(() => {
      calcRate()
    }, 200)
  }

  // 改变窗口大小重新绘制
  const windowDraw = () => {
    window.addEventListener('resize', resize)
  }

  return {
    appRef,
    calcRate,
    windowDraw
  }
}

<template>
  <div ref="appRef" class="main">
    <div class="layout-container">
    </div>
  </div>
</template>

<script>
import { useIndex } from '@/utils/utilsDram.js'
export default {
  mounted () {
    const { calcRate, windowDraw } =useIndex(this.$refs.appRef)
    calcRate()
    windowDraw()
  }
}
</script>
<style lang="scss" scoped>
.main {
  color: #d3d6dd;
  width: 1920px;
  height: 1080px;
  position: absolute;
  top: 50%;
  left: 50%;
  transform: translate(-50%, -50%);
  transform-origin: left top;

  .layout-container {
    width: 100%;
    height: 100%;
    }
   }
</style>