Move dropdown to Primer CSS

dropdown.scss

.dropdown {
  position: relative;

  &.active {
    .dropdown-menu-content {
      display: block;
      pointer-events: all;
    }
  }
}

.dropdown-caret {
  display: inline-block;
  width: 0;
  height: 0;
  vertical-align: middle;
  content: "";
  border-style: solid;
  border-width: $spacer-1 $spacer-1 0;
  border-right-color: transparent;
  border-bottom-color: transparent;
  border-left-color: transparent;
}

// Requires a positioning class (e.g., `.dropdown-menu-w`) to determine which
// way the menu should render from the element triggering it.
.dropdown-menu {
  position: absolute;
  top: 100%;
  left: 0;
  z-index: 100;
  width: 160px;
  padding-top: $spacer-1;
  padding-bottom: $spacer-1;
  margin-top: 2px;
  list-style: none;
  background-color: $bg-white;
  background-clip: padding-box;
  border: $border-width $border-style $black-fade-15;
  border-radius: $spacer-1;
  box-shadow: $box-shadow-large;

  &::before,
  &::after {
    position: absolute;
    display: inline-block;
    content: "";
  }

  &::before {
    border: $spacer-2 solid transparent;
    border-bottom-color: $black-fade-15;
  }

  &::after {
    border: 7px solid transparent;
    border-bottom-color: $white;
  }

  // stylelint-disable-next-line selector-max-type
  > ul {
    list-style: none;
  }
}

.dropdown-menu-no-overflow {
  width: auto;

  .dropdown-item {
    padding: $spacer-1 $spacer-3;
    overflow: visible;
    text-overflow: inherit;
  }
}

// Dropdown items (can be links or buttons)
.dropdown-item {
  display: block;
  padding: $spacer-1 $spacer-2 $spacer-1 $spacer-3;
  overflow: hidden;
  color: $text-gray-dark;
  text-overflow: ellipsis;
  white-space: nowrap;

  &:focus,
  &:hover {
    color: $text-white;
    text-decoration: none;
    background-color: $bg-blue;
    outline: none;

    > .octicon {
      color: inherit;
      opacity: 1;
    }
  }

  &.btn-link {
    width: 100%;
    text-align: left;
  }
}

.dropdown-signout {
  width: 100%;
  text-align: left;
  background: none;
  border: 0;
}

.dropdown-divider {
  display: block;
  height: 0;
  margin: $spacer-2 0;
  border-top: $border;
}

.dropdown-header {
  padding: $spacer-1 $spacer-3;
  font-size: $h6-size;
  color: $text-gray;
}

.dropdown-menu-content {
  display: none;

  // stylelint-disable-next-line primer/no-override
  &.anim-scale-in {
    position: relative;
    z-index: 100;
    pointer-events: none;
  }
}

.dropdown-item[aria-checked="false"] .octicon-check {
  display: none;
}

// Directional classes
//
// Move the menu and the caret attached to it. Requires at least one of these on
// the `.dropdown-menu` element.

.dropdown-menu-w {
  top: 0;
  right: 100%;
  left: auto;
  width: auto;
  margin-top: 0;
  margin-right: $spacer-2;

  &::before {
    top: 10px;
    right: -$spacer-3;
    left: auto;
    border-color: transparent;
    border-left-color: $black-fade-15;
  }

  &::after {
    top: 11px;
    right: -14px;
    left: auto;
    border-color: transparent;
    border-left-color: $white;
  }
}

.dropdown-menu-e {
  top: 0;
  left: 100%;
  width: auto;
  margin-top: 0;
  margin-left: $spacer-2;

  &::before {
    top: $spacer-2;
    left: -$spacer-3;
    border-color: transparent;
    border-right-color: $black-fade-15;
  }

  &::after {
    top: 11px;
    left: -14px;
    border-color: transparent;
    border-right-color: $white;
  }
}

.dropdown-menu-ne {
  top: auto;
  bottom: 100%;
  left: 0;
  margin-bottom: 3px;

  &::before,
  &::after {
    top: auto;
    right: auto;
  }

  &::before {
    bottom: -$spacer-2;
    left: 9px;
    border-top: $spacer-2 solid $black-fade-15;
    border-right: $spacer-2 solid transparent;
    border-bottom: 0;
    border-left: $spacer-2 solid transparent;
  }

  &::after {
    bottom: -7px;
    left: 10px;
    border-top: 7px solid $white;
    border-right: 7px solid transparent;
    border-bottom: 0;
    border-left: 7px solid transparent;
  }
}

.dropdown-menu-s {
  right: 50%;
  left: auto;
  transform: translateX(50%);

  &::before {
    top: -$spacer-3;
    right: 50%;
    transform: translateX(50%);
  }

  &::after {
    top: -14px;
    right: 50%;
    transform: translateX(50%);
  }
}

.dropdown-menu-sw {
  right: 0;
  left: auto;

  &::before {
    top: -$spacer-3;
    right: 9px;
    left: auto;
  }

  &::after {
    top: -14px;
    right: 10px;
    left: auto;
  }
}

.dropdown-menu-se {
  &::before {
    top: -$spacer-3;
    left: 9px;
  }

  &::after {
    top: -14px;
    left: 10px;
  }
}

// Dark dropdowns
.dropdown-menu-dark {
  color: $white;
  background: $gray-800;
  border-color: $gray-700;
  box-shadow: $box-shadow-large;

  &::before {
    border-bottom-color: $gray-700;
  }

  &::after {
    border-bottom-color: $gray-800;
  }

  .dropdown-header {
    color: $gray-300;
  }

  .dropdown-divider {
    border-top-color: $border-gray-darker;
  }

  .dropdown-item {
    color: inherit;
  }

  // Directional classes

  &.dropdown-menu-w {
    &::before {
      border-color: transparent transparent transparent $gray-700;
    }

    &::after {
      border-color: transparent transparent transparent $gray-800;
    }
  }

  &.dropdown-menu-e {
    &::before {
      border-color: transparent $gray-700 transparent transparent;
    }

    &::after {
      border-color: transparent $gray-800 transparent transparent;
    }
  }

  &.dropdown-menu-ne {
    &::before {
      border-color: $gray-700 transparent transparent transparent;
    }

    &::after {
      border-color: $gray-800 transparent transparent transparent;
    }
  }
}