wagtail/client/scss/components/_preview-panel.scss

.w-preview {
  --w-preview-background-color: var(--w-color-white);
  --preview-width-ratio: min(
    1,
    var(--preview-panel-width, 450) / var(--preview-device-width, 375)
  );
  --preview-iframe-width: calc(1px * var(--preview-device-width, 375));

  height: 100%;
  display: flex;
  flex-direction: column;

  &__area {
    height: 100%;
    display: flex;
    flex-direction: column-reverse;
    justify-content: space-between;
    // Needed for the warning message when the data is not valid.
    overflow: hidden;
  }

  &__wrapper {
    position: relative;
    width: calc(var(--preview-iframe-width) * var(--preview-width-ratio));
    height: 100%;
    margin-inline-start: auto;
    margin-inline-end: auto;
  }

  &__iframe {
    transform-origin: top left;
    width: var(--preview-iframe-width);
    height: calc(100% / var(--preview-width-ratio));
    transform: scale(var(--preview-width-ratio));
    display: block;

    &:empty {
      // Ensure that sites without a background show with a fallback, only when iframe has loaded
      background-color: var(--w-preview-background-color);
    }

    [dir='rtl'] & {
      // Transform with the top-right physical corner as the origin since the layout is reversed.
      transform-origin: top right;
    }

    // Prevent the iframe from capturing pointer events when resizing the panel, which
    // would consume the pointerup event and leaving the panel stuck in a resizing state.
    .side-panel-resizing & {
      pointer-events: none;
    }
  }

  &__sizes {
    @apply w-border-border-furniture w-border-b;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.75rem;
    padding-bottom: 1rem;
    margin-bottom: 1rem;
    padding-inline: 1rem;

    @include more-contrast() {
      border-color: theme('colors.border-furniture-more-contrast');
    }
  }

  &__size-button {
    @apply w-text-text-meta w-transition hover:w-transform hover:w-scale-110 hover:w-text-text-label focus:w-text-text-label;

    width: 2rem;
    height: 2rem;
    background: transparent;
    padding: 0;
    border-radius: 5px;
    display: grid;
    place-items: center;
    cursor: pointer;

    &--selected,
    &--selected:hover {
      @apply w-bg-surface-menus w-text-text-button w-transform-none w-border w-border-transparent;
    }

    &:focus-within:has(:focus-visible) {
      @include focus-outline;
    }

    .icon {
      @include svg-icon(1rem);

      &.icon-tablet-alt,
      &.icon-desktop {
        @include svg-icon(1.25rem);
      }

      &.icon-link-external {
        @include svg-icon(0.9rem);
      }
    }
  }

  &__refresh-button.button--icon {
    display: flex;
    align-items: center;
    justify-content: center;
    position: absolute;
    top: 1rem;
    width: 2rem;
    height: 2rem;
    padding: 0;
    inset-inline-end: 1.5rem;

    // Use element and class selectors to beat .button-longrunning specificity
    svg.icon,
    svg.icon-spinner {
      margin-inline-end: 0;
      width: 1rem;
      height: 1rem;
    }
  }

  &__spinner {
    position: absolute;
    top: 1.25rem;
    inset-inline-end: 1.5rem;
  }

  &__controls {
    @apply w-border-t w-border-transparent w-duration-500 w-ease-in-out;
    transition-property: border-color, margin-top, padding-top;
    margin-top: 0;
    padding-top: 0;

    // Show the border only if there's an error,
    // but always show it if there are multiple preview modes
    .w-preview--has-errors &:not(&--multiple),
    &--multiple {
      @apply w-border-border-furniture w-border-t;
      padding-top: 1rem;
      margin-top: 1rem;
    }
  }

  &__error-banner {
    @apply w-text-text-context w-duration-1000 w-ease-in-out w-translate-y-20;
    transition-property: max-height, transform, visibility;
    visibility: hidden;
    max-height: 0;
    display: flex;
    align-items: center;
    gap: 1rem;
    position: relative;
    z-index: -1;

    .icon {
      @apply w-text-warning-100;
    }
  }

  &--has-errors &__error-banner {
    @apply w-translate-y-0;
    visibility: visible;
    max-height: 6rem;
  }

  &__error-title {
    @apply w-label-2;
    color: inherit;
    margin-top: 0;
    margin-bottom: 0.25rem;
  }

  &__error-details {
    color: inherit;
  }

  &__modes {
    margin-bottom: 0;
    background-color: theme('colors.surface-page');

    .w-field__input {
      padding-inline-end: 0;
    }
  }

  &__mode-select {
    @apply w-outline-offset-inside;
  }

  // A hidden element that is only rendered for functionality purposes,
  // but is not visible to the user. Used by radio inputs for preview sizes and
  // the iframe while it's loading. We nest the selector rather than suffixing
  // the parent selector to beat the specificity of input[type="radio"] styles
  .w-preview__proxy {
    position: absolute;
    width: 0;
    height: 0;
    opacity: 0;

    // Remove mask-image from radio inputs to avoid loading the default icon,
    // use extra specificity to beat the default styles
    &:is(input[type='radio'])::before {
      content: none;
      mask-image: none;
    }
  }
}