misc/dialog/off-canvas/css/dropbutton.pcss.css
/**
 * @file
 * Styles for dropbuttons in the off-canvas dialog.
 *
 * @internal
 */
#drupal-off-canvas-wrapper {
  --off-canvas-dropbutton-height: 24px;
  --off-canvas-dropbutton-primary-background-color: var(--off-canvas-button-background-color);
  --off-canvas-dropbutton-secondary-background-color: var(--off-canvas-button-hover-background-color);
  --off-canvas-dropbutton-border-color: transparent;
  --off-canvas-dropbutton-border-width: 1px;
  --off-canvas-dropbutton-border-radius: 2px;
  --off-canvas-dropbutton-focus-outline-color: var(--off-canvas-focus-outline-color);
  --off-canvas-dropbutton-font-size: 12px;
  --off-canvas-dropbutton-text-color: var(--off-canvas-button-text-color); /* Minimum 4.5:1 contrast ratio against --off-canvas-dropbutton-primary-background-color and --off-canvas-dropbutton-secondary-background-color. */
  --off-canvas-dropbutton-text-color-hover: var(--off-canvas-button-text-color-hover); /* Minimum 4.5:1 contrast ratio against --off-canvas-dropbutton-primary-background-color and --off-canvas-dropbutton-secondary-background-color. */

  & .dropbutton-wrapper {
    margin-block: var(--off-canvas-vertical-spacing-unit);

    /*
     * Styles for when the dropbutton is expanded.
     */
    &.open {
      position: relative;
      z-index: 100;

      & .secondary-action {
        visibility: visible;
      }

      & .dropbutton-widget {
        border-radius: var(--off-canvas-dropbutton-border-radius) var(--off-canvas-dropbutton-border-radius) 0 0;
      }

      & .dropbutton-toggle button::before {
        transform: translateY(25%) rotate(225deg);
      }
    }

    /*
    * Styles for single link variant of dropbutton.
    */
    &.dropbutton-single {
      & .dropbutton-widget {
        padding-inline-end: 0;
      }

      & .dropbutton-action {
        &:first-child {
          border-right: solid 1px var(--off-canvas-dropbutton-border-color); /* LTR */
          border-radius: var(--off-canvas-dropbutton-border-radius);

          &:dir(rtl) {
            border: solid 1px var(--off-canvas-dropbutton-border-color);
          }
        }

        & a {
          justify-content: center;
        }
      }
    }
  }

  & .dropbutton-widget {
    position: relative;
    width: max-content;
    max-width: 100%;
    height: var(--off-canvas-dropbutton-height);
    padding-inline-end: var(--off-canvas-dropbutton-height);
    border-radius: var(--off-canvas-dropbutton-border-radius);
  }

  & .dropbutton {
    height: var(--off-canvas-dropbutton-height);
    margin-block: 0;
    margin-inline-start: 0;
    padding-inline-start: 0;
    list-style: none;
    font-size: var(--off-canvas-dropbutton-font-size);
  }

  /* This is the button that expands/collapses the secondary options. */
  & .dropbutton-toggle {
    padding: 0;
    border: 0;

    & button {
      position: absolute;
      top: 0;
      display: flex;
      align-items: center;
      justify-content: center;
      width: var(--off-canvas-dropbutton-height);
      height: var(--off-canvas-dropbutton-height);
      padding: 0;
      cursor: pointer;
      border-color: var(--off-canvas-dropbutton-border-color);
      border-radius: 0 var(--border-radius) var(--border-radius) 0; /* LTR */
      background: var(--off-canvas-dropbutton-primary-background-color);
      inset-inline-end: 0;

      &:focus {
        outline: solid 2px var(--off-canvas-dropbutton-focus-outline-color);
        outline-offset: -2px;
      }

      &::before {
        display: block;
        width: 6px;
        height: 6px;
        content: "";
        transform: translateY(-25%) rotate(45deg);
        border-right: solid 2px var(--off-canvas-dropbutton-text-color);
        border-bottom: solid 2px var(--off-canvas-dropbutton-text-color);
      }

      &:dir(rtl) {
        border-radius: var(--off-canvas-dropbutton-border-radius) 0 0 var(--off-canvas-dropbutton-border-radius);
      }
    }
  }

  /* This is the first <li> element in the list of actions. */
  & .dropbutton-action {
    &:first-child {
      margin-inline-end: 2px;
      border: solid var(--off-canvas-dropbutton-border-width) var(--off-canvas-dropbutton-border-color);
      border-radius: var(--off-canvas-dropbutton-border-radius) 0 0 var(--off-canvas-dropbutton-border-radius); /* LTR */
      background: var(--off-canvas-dropbutton-primary-background-color);

      &:dir(rtl) {
        border: solid var(--off-canvas-dropbutton-border-width) var(--off-canvas-dropbutton-border-color);
        border-radius: 0 var(--off-canvas-dropbutton-border-radius) var(--off-canvas-dropbutton-border-radius) 0;
      }
    }

    & a {
      display: flex;
      align-items: center;
      min-height: var(--off-canvas-dropbutton-height);
      margin-bottom: -2px;
      padding: 0 9px;
      text-decoration: none;
      color: var(--off-canvas-dropbutton-text-color);
      font-weight: 600;

      &:hover {
        color: var(--off-canvas-dropbutton-text-color);
      }

      &:focus {
        outline: solid 2px var(--off-canvas-dropbutton-focus-outline-color);
        outline-offset: -1px; /* Overlap parent container by 1px. */
      }
    }
  }

  /* These are the <li> elements other than the first. */
  & .secondary-action {
    visibility: hidden;
    width: calc(100% + var(--off-canvas-dropbutton-height));
    margin-top: var(--off-canvas-dropbutton-border-width);
    border-right: var(--off-canvas-dropbutton-border-width) solid var(--off-canvas-dropbutton-border-color);
    border-left: var(--off-canvas-dropbutton-border-width) solid var(--off-canvas-dropbutton-border-color);
    background-color: var(--off-canvas-dropbutton-primary-background-color);

    &:last-child {
      border-bottom: var(--off-canvas-dropbutton-border-width) solid var(--off-canvas-dropbutton-border-color);
    }

    & a:hover {
      color: var(--off-canvas-dropbutton-text-color-hover);
      background-color: var(--off-canvas-dropbutton-secondary-background-color);
    }
  }
}
