discourse/app/assets/stylesheets/common/components/select-box.scss

.select-box {
  border-radius: 3px;
  -webkit-box-sizing: border-box;
          box-sizing: border-box;
  display: inline-block;
  -webkit-box-orient: vertical;
  -webkit-box-direction: normal;
      -ms-flex-direction: column;
          flex-direction: column;
  position: relative;
  height: 34px;

  &.is-expanded {
    z-index: 102;

    .select-box-wrapper {
      border: 1px solid $tertiary;
      border-radius: 3px;
      -webkit-box-shadow: $tertiary 0px 0px 6px 0px;
              box-shadow: $tertiary 0px 0px 6px 0px;
    }

    .select-box-body {
      border-radius: 3px 3px 0 0;
      display: -webkit-box;
      display: -ms-flexbox;
      display: flex;
      -webkit-box-orient: vertical;
      -webkit-box-direction: normal;
          -ms-flex-direction: column;
              flex-direction: column;
      left: 0;
      position: absolute;
      top: 0;
    }

    .collection, {
      border-radius: 0 0 3px 3px;
    }

    .select-box-header {
      border-radius: 3px 3px 0 0;
    }

    &.is-reversed {
      .select-box-header {
        border-radius: 0 0 3px 3px;
      }
    }
  }

  &.is-highlighted {
    .select-box-header {
      border: 1px solid $tertiary;
      -webkit-box-shadow: $tertiary 0px 0px 6px 0px;
              box-shadow: $tertiary 0px 0px 6px 0px;
    }
  }

  &.is-reversed {
    .select-box-body {
      bottom: 0;
      top: auto;
    }

    .select-box-wrapper {
      bottom: 0;
      top: auto;
    }
  }

  .d-icon {
    opacity: 0.7;
  }

  .select-box-header {
    background: $secondary;
    border: 1px solid dark-light-diff($primary, $secondary, 90%, -60%);
    border-radius: 3px;
    -webkit-box-sizing: border-box;
            box-sizing: border-box;
    cursor: pointer;
    outline: none;
    display: flex;
    align-items: center;
    justify-content: space-between;

    &.is-focused {
      border: 1px solid $tertiary;
      border-radius: 3px;
      -webkit-box-shadow: $tertiary 0px 0px 6px 0px;
              box-shadow: $tertiary 0px 0px 6px 0px;
    }
  }

  .select-box-body {
    display: none;
    -webkit-box-sizing: border-box;
            box-sizing: border-box;
  }

  .select-box-row {
    cursor: pointer;
    outline: none;
    padding: 5px;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-pack: start;
        -ms-flex-pack: start;
            justify-content: flex-start;
  }

  .select-box-collection {
    -webkit-box-sizing: border-box;
            box-sizing: border-box;
    display: -webkit-box;
    display: -ms-flexbox;
    display: flex;
    -webkit-box-flex: 1;
        -ms-flex: 1;
            flex: 1;
    -webkit-box-orient: vertical;
    -webkit-box-direction: normal;
        -ms-flex-direction: column;
            flex-direction: column;
    background: $secondary;
    overflow-x: hidden;
    overflow-y: auto;
    border-radius: 0 0 3px 3px;
    margin: 0;
    padding: 0;
    -webkit-overflow-scrolling: touch;
  }

  .select-box-filter {
    border-bottom: 1px solid $primary-low;
    background: $secondary;
  }

  .select-box-wrapper {
    position: absolute;
    top: 0;
    left: 0;
    background: none;
    display: none;
    -webkit-box-sizing: border-box;
            box-sizing: border-box;
    pointer-events: none;
    border: 1px solid transparent;
  }
}

.select-box .select-box-header {
  height: inherit;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-orient: horizontal;
  -webkit-box-direction: normal;
      -ms-flex-direction: row;
          flex-direction: row;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-box-pack: justify;
      -ms-flex-pack: justify;
          justify-content: space-between;
  padding-left: 10px;
  padding-right: 10px;

  .current-selection {
    text-align: left;
    -webkit-box-flex: 1;
        -ms-flex: 1;
            flex: 1;
    text-overflow: ellipsis;
    white-space: nowrap;
    overflow: hidden;
    color: inherit;
  }

  .icon {
    margin-right: 5px;
  }

  .caret-icon {
    margin-left: 5px;
    pointer-events: none;
  }
}

.select-box .select-box-collection {
  -webkit-box-flex: 0;
      -ms-flex: 0 1 auto;
          flex: 0 1 auto;

  .collection {
    padding: 0;
    margin: 0;
  }

  &::-webkit-scrollbar {
    -webkit-appearance: none;
    width: 10px;
  }

  &::-webkit-scrollbar-thumb {
    cursor: pointer;
    border-radius: 5px;
    background: dark-light-choose(scale-color($primary, $lightness: 50%), scale-color($secondary, $lightness: 50%));
  }

  &::-webkit-scrollbar-track {
    background: transparent;
    border-radius: 0;
  }
}

.select-box .select-box-row {
  margin: 5px;
  min-height: 1px;

  .text {
    margin: 0;
  }

  .d-icon {
    margin-right: 5px;
  }

  &.is-highlighted {
    background: $highlight-medium;
  }

  &.is-selected {
    a {
      background: $highlight-medium;
    }
  }
}

.select-box .select-box-filter {
  background: $secondary;
  display: -webkit-box;
  display: -ms-flexbox;
  display: flex;
  -webkit-box-align: center;
      -ms-flex-align: center;
          align-items: center;
  -webkit-box-pack: justify;
      -ms-flex-pack: justify;
          justify-content: space-between;
  padding: 0 10px;

  .filter-query, .filter-query:focus, .filter-query:active {
    background: none;
    margin: 0;
    -webkit-box-flex: 1;
        -ms-flex: 1;
            flex: 1;
    outline: none;
    border: 0;
    -webkit-box-shadow: none;
            box-shadow: none;
    width: 100%;
    padding: 5px 0;
  }
}

.select-box .select-box-offscreen, .select-box .select-box-offscreen:focus {
  clip: rect(0 0 0 0);
  width: 1px;
  height: 1px;
  border: 0;
  margin: 0;
  padding: 0;
  overflow: hidden;
  position: absolute;
  outline: 0;
  left: 0px;
  top: 0px;
}

.select-box.discourse {
  .select-box-header {
    border: 1px solid dark-light-diff($primary, $secondary, 90%, -60%);
    border-radius: 3px;

    &.is-focused {
      border: 1px solid $tertiary;
      border-radius: 3px;
      box-shadow: $tertiary 0px 0px 6px 0px;
    }
  }

  &.is-expanded {
    .select-box-header {
      border-radius: 3px 3px 0 0;
    }

    .select-box-body, .collection, {
      border-radius: 0 0 3px 3px;
    }

    .select-box-wrapper {
      border: 1px solid $tertiary;
      border-radius: 3px;
      box-shadow: $tertiary 0px 0px 6px 0px;
    }
  }

  .select-box-row {
    margin: 5px;
  }

  &.is-highlighted .select-box-header {
    border: 1px solid $tertiary;
    box-shadow: $tertiary 0px 0px 6px 0px;
  }
}