element/packages/theme-chalk/src/tree.scss

@import "mixins/mixins";
@import "common/var";

@include b(tree) {
  cursor: default;
  background: $--color-white;
  color: $--tree-text-color;

  @include e(empty-block) {
    position: relative;
    min-height: 60px;
    text-align: center;
    width: 100%;
    height: 100%;
  }

  @include e(empty-text) {
    position: absolute;
    left: 50%;
    top: 50%;
    transform: translate(-50%, -50%);
    color: mix($--color-primary, rgb(158, 68, 0), 50%);
  }
}

@include b(tree-node) {
  white-space: nowrap;

  @include e(content) {
    display: flex;
    align-items: center;
    height: 26px;
    cursor: pointer;

    & > .el-tree-node__expand-icon {
      margin: 0 8px;
    }
    & > .el-checkbox {
      margin-right: 8px;
    }
    &:hover {
      background-color: $--tree-node-hover-color;
    }
  }

  @include e(expand-icon) {
    cursor: pointer;
    width: 0;
    height: 0;
    margin-left: 10px;
    border: 3.5px solid transparent;
    border-right-width: 0;
    border-left-color: $--tree-expand-icon-color;
    border-left-width: 6px;

    transform: rotate(0deg);
    transition: transform 0.3s ease-in-out;

    &.expanded {
      transform: rotate(90deg);
    }

    &.is-leaf {
      border-color: transparent;
      cursor: default;
    }
  }

  @include e(label) {
    font-size: $--font-size-base;
  }

  @include e(loading-icon) {
    margin-right: 8px;
    font-size: $--font-size-base;
    color: $--tree-expand-icon-color;
  }

  & > .el-tree-node__children {
    overflow: hidden;
    background-color: transparent;
  }

  &.is-expanded > .el-tree-node__children {
    display: block;
  }
}

.el-tree--highlight-current .el-tree-node.is-current > .el-tree-node__content {
  background-color: mix($--color-white, $--color-primary, 92%);
}