mind-map 导出png图片，内容显示不全，左边有一小部分缺失

底格里斯任务中心图(56) Vue3框架源码附上：

<div class="top-menu-fixed">
  <div v-if="!isStart" class="top-menu-item" @click="back">
    <div class="top-menu-item--img">
      <el-icon><Back /></el-icon>
    </div>
    <div class="top-menu-item--text">撤退</div>
  </div>
  <div v-if="!isEnd" class="top-menu-item" @click="forward">
    <div class="top-menu-item--img">
      <el-icon><Right /></el-icon>
    </div>
    <div class="top-menu-item--text">前进</div>
  </div>
  <div class="top-menu-item" @click="saveMindMap">
    <div class="top-menu-item--img">
      <el-icon><Suitcase /></el-icon>
    </div>
    <div class="top-menu-item--text">保存脑图</div>
  </div>
  <!-- <div class="top-menu-item" @click="submitMindMap">
    <div class="top-menu-item--img">
      <el-icon><SuitcaseLine /></el-icon>
    </div>
    <div class="top-menu-item--text">提交</div>
  </div> -->
  <div class="top-menu-item" @click="exportMindMap">
    <div class="top-menu-item--img">
      <el-icon><TakeawayBox /></el-icon>
    </div>
    <div class="top-menu-item--text">导出图片</div>
  </div>
</div>

<!-- 右键菜单 -->
<div
  v-if="showContextMenu"
  class="context-menu"
  :style="{ top: `${menuPosition.y}px`, left: `${menuPosition.x}px` }"
>
  <ul>
    <li @click="addChildNode">添加子节点</li>
    <li @click="addSameNode">添加同级节点</li>
    <li @click="removeNode">删除节点</li>
    <li @click="copyNode">复制节点</li>
    <li @click="pasteNode">粘贴节点</li>
    <li v-if="!isStart" @click="back">后退</li>
    <li v-if="!isEnd" @click="forward">前进</li>
  </ul>
</div>