<template>
  <div class="vvhan-com">
    <div class="title" @mousedown="mousedown">tips</div>
    <div class="contain">
      <span>这里是内容</span>
    </div>
  </div>
</template>

<script>
  export default {
    data() {
      return {};
    },
    methods: {
      mousedown(e) {
        // 被移动的主体 mainDiv
        const mainDiv = document.querySelector(".vvhan-com");
        // 鼠标点击位置与主体边的距离
        const distanceX = e.clientX - mainDiv.offsetLeft;
        const distanceY = e.clientY - mainDiv.offsetTop;
        // 鼠标移动事件
        document.onmousemove = function (ev) {
          const _e = ev || e;
          //移动时，鼠标距离当前窗口x轴坐标 - 鼠标在拖拽元素的坐标 = 剩下距离body的x轴坐标
          //将这个数值设置为拖拽元素的left、top
          let boxLeft = _e.clientX - distanceX;
          let boxTop = _e.clientY - distanceY;
          //获取body的页面可视宽高
          const clientHeight =
            document.documentElement.clientHeight || document.body.clientHeight;
          const clientWidth =
            document.documentElement.clientWidth || document.body.clientWidth;
          //限制拖拽宽高
          boxLeft =
            boxLeft < 0
              ? 0
              : boxLeft > clientWidth - mainDiv.offsetWidth
                ? clientWidth - mainDiv.offsetWidth
                : boxLeft;
          boxTop =
            boxTop < 0
              ? 0
              : boxTop > clientHeight - mainDiv.offsetHeight
                ? clientHeight - mainDiv.offsetHeight
                : boxTop;

          mainDiv.style.top = boxTop + "px";
          mainDiv.style.left = boxLeft + "px";
        };
        // 鼠标松开事件 结束拖拽
        document.onmouseup = function () {
          document.onmousemove = null;
          document.onmouseup = null;
        };
      },
    },
  };
</script>

<style>
  body {
    position: relative !important;
    background: url("https://cache.4ce.cn/ipfs/QmQtvCE2DMkYJKWicdaJxh3Vh47ca6t25RxBGrbre5Cy2p");
    background-size: cover;
    padding: 0;
    margin: 0;
  }
</style>

<style lang="scss" scoped>
  .vvhan-com {
    user-select: none;
    position: absolute !important;
    box-sizing: border-box;
    padding: 6px;
    top: 36px;
    right: 36px;
    box-shadow: 0 2px 12px 0 rgba(0, 0, 0, 0.1);
    background-color: rgba(255, 255, 255, 0.2);
    width: 340px;
    z-index: 9;
    font-size: 14px;

    .title {
      margin-bottom: 6px;
      font-size: 16px;
      line-height: 28px;
      border-bottom: 1px rgba(0, 0, 0, 0.1) solid;
      cursor: move;
    }

    h1 {
      color: #000;
    }
  }
</style>