Editing Template:Sticky header/styles.css

/* {{pp-template}} */
/**
 * Make first row or thead element top sticky.
 *
 * Table classes:
 * - sticky-header: sticky first row.
 * - sticky-header-multi: sticky thead; headers moved via sortable + JavaScript.
 *
 * Tested:
 * - Windows 10: (all skins) Chrome, Firefox, Edge.
 * - Android Galaxy S21 (Minerva): Chrome, Firefox.
 * - iPhone SE 2020 (Minerva): Chrome, Edge, Firefox, Opera, Safari.
 * - Wikipedia Android app.
 * - Print: Not styled.
 * - No JavaScript.
 *
 * Notes:
 * - Sortable moves to thead any header rows and (after sort) sorttop rows.
 * - Sticky gadget (.mw-sticky-header) moves to thead any wikitable header rows.
 *
 * Issues:
 * - Monobook width <=550px not sticky.
 *   Can't override:
 *   body.skin--responsive .monobook-body {overflow: auto;}
 */
@media screen {
  /**
   * Make top sticky.
   */
  .sticky-header > thead > tr:first-child,
  .sticky-header > caption + tbody > tr:first-child,
  .sticky-header > tbody:first-child > tr:first-child,
  .sticky-header-multi > thead {
    position: sticky; /* Was "static". */
    top: 0;
    z-index: 10;
  }

  /**
   * Fix scrolling data shows through sticky's transparent background.
   */
  /* Plain table headers. */
  .sticky-header:not(.wikitable),
  .sticky-header-multi:not(.wikitable) {
    background-color: white;
  }
  /* Plain table headers. */
  .sticky-header:not(.wikitable) > *, /* For thead, tbody. */
  .sticky-header:not(.wikitable) > thead > tr:first-child,
  .sticky-header:not(.wikitable) > caption + tbody > tr:first-child,
  .sticky-header:not(.wikitable) > tbody:first-child > tr:first-child,
  .sticky-header-multi:not(.wikitable) > thead,
  /* Wikitable and plain table .sorttop rows after sort. */
  .sticky-header-multi > thead {
    background-color: inherit;
  }

  /**
   * Fix missing borders due to sticky position and wikitable collapsed borders.
   * https://bugs.webkit.org/show_bug.cgi?id=128486
   *
   * Skip rare plain table separated borders, which sometimes shows scrolling
   * data through sticky's 2px "border-spacing".
   *
   * Skip very rare Timeless plain table ".mw-datatable" collapsed boarders.
   */
  .sticky-header.wikitable,
  .sticky-header-multi.wikitable {
    border-collapse: separate; /* Was "collapse". */
    border-spacing: 0;
    border-width: 0 1px 1px 0;
  }
  .sticky-header.wikitable td,
  .sticky-header.wikitable th,
  .sticky-header-multi.wikitable td,
  .sticky-header-multi.wikitable th {
    border-width: 1px 0 0 1px;
  }
  body.skin-timeless .sticky-header.wikitable,
  body.skin-timeless .sticky-header-multi.wikitable {
    border-bottom-width: 0.2em;
    padding: 0;
  }
  /* Adjust {{static row numbers}} borders. */
  .sticky-header.static-row-numbers.wikitable tr::before,
  .sticky-header-multi.static-row-numbers.wikitable tr::before {
    border-left-width: 1px;
  }
  .sticky-header.static-row-numbers.wikitable > thead > tr:first-child::before,
  .sticky-header.static-row-numbers.wikitable > caption + tbody > tr:first-child::before,
  .sticky-header.static-row-numbers.wikitable > tbody:first-child > tr:first-child::before,
  .sticky-header-multi.static-row-numbers.wikitable > thead > tr:first-child::before,
  .sticky-header-multi.static-row-numbers.wikitable > caption + tbody > tr:first-child::before,
  .sticky-header-multi.static-row-numbers.wikitable > tbody:first-child > tr:first-child::before,
  /* Sortbotton #1: all. When supported, consolidate #1-2 to tr:nth-child(1 of .sortbottom)::before */
  .sticky-header.static-row-numbers.wikitable .sortbottom::before,
  .sticky-header-multi.static-row-numbers.wikitable .sortbottom::before {
    border-top-width: 1px;
  }
  /* Sortbottom #2: all minus 1st. */
  .sticky-header.static-row-numbers.wikitable .sortbottom ~ .sortbottom::before,
  .sticky-header-multi.static-row-numbers.wikitable .sortbottom ~ .sortbottom::before {
    border-top-width: 0;
  }
  .sticky-header.static-row-numbers.wikitable > tbody > tr:not(.static-row-header)::before,
  .sticky-header-multi.static-row-numbers.wikitable > tbody > tr:not(.static-row-header)::before {
    border-bottom-width: 0 !important;
    border-right-width: 0 !important;
  }

  /**
   * Fix Timeless. Wasn't sticky when on very wide tables.
   *
   * :has() not supported, can't restrict to sticky tables.
   */
  body.skin-timeless .content-table-scrollbar,
  body.skin-timeless .overflowed,
  body.skin-timeless .overflowed .content-table {
    overflow: visible; /* Reset. */
  }
  body.skin-timeless .scroll-right.overflowed .content-table-right {
    box-shadow: none; /* Reset. */
    border-left: none; /* Reset. */
  }
}

/**
 * Adjust to other sticky elements.
 */
@media screen and (min-width: 1120px) {
  /* Vector (2022) width >=1120px: Below sticky header bar. */
  body.vector-sticky-header-visible .sticky-header > thead > tr:first-child,
  body.vector-sticky-header-visible .sticky-header > caption + tbody > tr:first-child,
  body.vector-sticky-header-visible .sticky-header > tbody:first-child > tr:first-child,
  body.vector-sticky-header-visible .sticky-header-multi > thead {
    top: 3.125rem;
  }
}
@media screen and (min-width: 851px) {
  /* Timeless width >=851px: Below sticky header bar. */
  body.skin-timeless .sticky-header > thead > tr:first-child,
  body.skin-timeless .sticky-header > caption + tbody > tr:first-child,
  body.skin-timeless .sticky-header > tbody:first-child > tr:first-child,
  body.skin-timeless .sticky-header-multi > thead {
    top: 3.51em;
  }
}

/**
 * Fix skins width <=639px (mobile) not sticky. Override to make sticky.
 *
 * Android issue: wide table horizontal scroll lost, wider page,
 * zoom out for sticky headers, unreadable when sticky.
 *
 * iPhone issue: none.
 */
@media screen and (max-width: 639px) {
  body.skin-minerva .sticky-header,
  body.skin-minerva .sticky-header-multi,
  body.skin-monobook .sticky-header,
  body.skin-monobook .sticky-header-multi,
  body.skin-vector-legacy .sticky-header,
  body.skin-vector-legacy .sticky-header-multi,
  body.skin-vector-2022 .sticky-header,
  body.skin-vector-2022 .sticky-header-multi {
    display: table; /* Was "block". */
  }
  body.skin-minerva .sticky-header > caption,
  body.skin-minerva .sticky-header-multi > caption {
    display: table-caption; /* Was "block". */
  }
}

/*
 * Fix dark mode.
 */
@media screen {
  html.skin-theme-clientpref-night body.skin-minerva .sticky-header-multi.wikitable {
    background-color: #101418;
  }
}
@media screen and (prefers-color-scheme: dark) {
  html.skin-theme-clientpref-os body.skin-minerva .sticky-header-multi.wikitable {
    background-color: #101418;
  }
}