Overleaf/services/web/frontend/stylesheets/components/split-menu.less

.split-menu {
  display: flex;

  &.btn-md,
  &.btn-sm,
  &.btn-xs {
    padding: 0;
  }

  &.btn-md {
    & > .split-menu-button,
    & > .split-menu-dropdown-toggle {
      height: 36px;
    }
  }

  &.btn-sm {
    & > .split-menu-button,
    & > .split-menu-dropdown-toggle {
      height: 32px;
    }
  }

  &.btn-xs {
    & > .split-menu-button,
    & > .split-menu-dropdown-toggle {
      height: 28px;
    }
  }

  &.btn-primary {
    background-color: @ol-green;
  }

  .split-menu-icon {
    margin-right: @line-height-computed / 4;
  }

  .split-menu-button {
    border-top-right-radius: 0;
    border-bottom-right-radius: 0;
    height: 100%;
    padding-top: 0;
    padding-bottom: 0;

    &.btn-primary {
      border-right: 1px solid fade(@neutral-90, 16%);
    }

    // on new css, btn-secondary already has a border
    &.btn-secondary when (@is-new-css = false) {
      border-right: 1px solid fade(@ol-blue-gray-6, 16%);
    }

    &.btn-danger {
      border-right: 1px solid fade(@neutral-90, 16%);
    }

    &[disabled] when (@is-new-css = false) {
      opacity: 1;
    }

    &.no-left-radius {
      border-top-left-radius: 0;
      border-bottom-left-radius: 0;
    }
  }

  .split-menu-button when (@is-new-css = true) {
    // workaround for for the blue 2x border on the new css
    // if z-index rule is not added, the border will overlap under the `split-menu-dropdown-toggle` since margin between both component is only 1px
    z-index: 1;
  }

  .split-menu-dropdown {
    float: none;
    display: flex;
    flex-wrap: nowrap;
    align-self: stretch;
    margin-right: 6px;

    .split-menu-dropdown-toggle {
      border-bottom-left-radius: 0;
      border-top-left-radius: 0;
      padding: 0 8px;

      // on new css, btn-secondary has a border
      // since the border between both buttons already been defined in the `split-menu-button`
      // we will remove the rule from the dropdown toggle
      &.btn-secondary when (@is-new-css = true) {
        border-left: none;
      }
    }
  }
}