wagtail/client/scss/components/_panel.scss

$header-icon-size: theme('spacing.4');
$header-button-size-mobile: $mobile-nice-padding;
$header-button-size: theme('spacing.8');

.w-panel {
  margin-bottom: theme('spacing.10');
}

.w-panel__header {
  display: flex;
  align-items: center;
  margin-bottom: theme('spacing.3');
  margin-inline-start: -1 * $mobile-nice-padding;

  @include media-breakpoint-up(sm) {
    $gap: theme('spacing.1');
    gap: $gap;
    margin-inline-start: calc(-1 * 2 * ($header-button-size + $gap));
  }
}

.w-panel__heading {
  @apply w-h3;
  display: inline-block;
  margin: 0;
  white-space: nowrap;
  text-overflow: ellipsis;
  cursor: pointer;
  padding-inline-end: theme('spacing.2');

  @include media-breakpoint-up(sm) {
    padding-inline-end: theme('spacing.5');
  }
}

.w-panel__heading--label {
  @apply w-label-1;
}

.w-panel__anchor,
.w-panel__toggle,
.w-panel__controls .button.button--icon,
.w-panel__controls-cue {
  @include show-focus-outline-inside();
  display: inline-grid;
  justify-content: center;
  align-content: center;
  color: theme('colors.primary.DEFAULT');
  border-radius: theme('borderRadius.full');
  margin: 0;
  padding: 0;
  width: $header-button-size-mobile;
  height: $header-button-size-mobile;

  &:focus-visible,
  &:hover {
    background-color: $color-grey-5;

    @media (forced-colors: active) {
      border: 1px solid currentColor;
    }
  }

  &[disabled] {
    color: $color-grey-3;
    cursor: not-allowed;
    // Counter hover styles.
    background-color: transparent;

    @media (forced-colors: active) {
      color: GrayText;
    }
  }

  @include media-breakpoint-up(sm) {
    width: $header-button-size;
    height: $header-button-size;
  }
}

.w-panel__anchor {
  // Only hide anchors for devices that support hover interactions.
  @media (hover: hover) {
    .w-panel__header:not(:hover, :focus-within) & {
      opacity: 0;
    }
  }
}

// The suffix anchor is intended for small viewports only.
.w-panel__anchor--suffix {
  @include media-breakpoint-up(sm) {
    display: none;
  }
}

// The prefix anchor can be used when there is enough space in the margin of the page.
.w-panel__anchor--prefix {
  display: none;

  @include media-breakpoint-up(sm) {
    display: inline-grid;
  }
}

.w-panel__toggle {
  appearance: none;
  background: transparent;
}

.w-panel__icon {
  width: $header-icon-size;
  height: $header-icon-size;

  // Only rotate the default caret icon, not custom ones.
  [aria-expanded='false'] &.icon-arrow-down-big {
    transform: rotate(-90deg);
  }

  &.icon-link {
    width: theme('spacing.[3.5]');
    height: theme('spacing.[3.5]');
  }
}

.w-panel__divider {
  flex: 1;
}

.w-panel__controls {
  // Prevent shrinking of the buttons when header text is long.
  flex-shrink: 0;
  // Add additional invisible padding for a more forgiving hover area.
  padding: theme('spacing.4');
  margin: calc(-1 * theme('spacing.4'));
  margin-inline-end: calc(-1 * theme('spacing.8'));
  margin-inline-start: 0;

  @include media-breakpoint-up(sm) {
    margin: calc(-1 * theme('spacing.4'));
    margin-inline-start: 0;
  }

  // The cue is meant to be displayed on top of a real button.
  > .w-panel__controls-cue {
    position: absolute;
    visibility: hidden;
  }

  @media (hover: hover) {
    // Hiding with opacity only, so the elements can still be focused.
    > * {
      opacity: 0;
    }

    > .w-panel__controls-cue {
      opacity: 1;
      visibility: visible;
    }

    .w-panel__header:is(:hover, :focus-within) & > * {
      opacity: 1;

      // The cue should be fully hidden, not just transparent.
      &.w-panel__controls-cue {
        visibility: hidden;
      }
    }
  }
}

.w-panel__wrapper {
  @include max-form-width();
}