just-the-docs/node_modules/primer-utilities/lib/visibility-display.scss

// Visibility and display utilities
// stylelint-disable block-opening-brace-space-after, block-opening-brace-space-before, primer/selector-no-utility
// stylelint-disable comment-empty-line-before

$display-values: (
  block,
  flex,
  inline,
  inline-block,
  inline-flex,
  none,
  table,
  table-cell
);

// Responsive display utilities
@each $breakpoint, $variant in $responsive-variants {
  @include breakpoint($breakpoint) {
    @each $display in $display-values {
      .d#{$variant}-#{$display} { display: $display !important; }
    }
  }
}

// Visibility utilities
/* Visibility hidden */
.v-hidden { visibility: hidden !important; }
/* Visibility visible */
.v-visible { visibility: visible !important; }

// Hide utilities for each breakpoint
// Each hide utility only applies to one breakpoint range.
@media (max-width: $width-sm) {
  .hide-sm {
    display: none !important;
  }
}

@media (min-width: $width-sm) and (max-width: $width-md) {
  .hide-md {
    display: none !important;
  }
}

@media (min-width: $width-md) and (max-width: $width-lg) {
  .hide-lg {
    display: none !important;
  }
}

@media (min-width: $width-lg) {
  .hide-xl {
    display: none !important;
  }
}

/* Set the table-layout to fixed */
.table-fixed { table-layout: fixed !important; }

// Only display content to screen readers
//
// See: http://a11yproject.com/posts/how-to-hide-content/
.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  // Workaround for https://bugzilla.mozilla.org/show_bug.cgi?id=1241631
  word-wrap: normal;
  border: 0;
}

// Only display content on focus
.show-on-focus {
  position: absolute;
  width: 1px;
  height: 1px;
  margin: 0;
  overflow: hidden;
  clip: rect(1px, 1px, 1px, 1px);

  &:focus {
    z-index: 20;
    width: auto;
    height: auto;
    clip: auto;
  }
}