themes/olivero/css/components/site-header.pcss.css
/**
 * @file
 * Site header.
 */

@import "../base/media-queries.pcss.css";

.site-header {
  position: relative;
  /**
   * Ensure mobile site header is always above other elements including
   * contextual links.
   */
  z-index: 101;

  @media (--nav) {
    /* Necessary to keep the content from jumping up when header transitions to fixed. */
    min-height: var(--site-header-height-wide);
    border-block-end: solid 1px transparent; /* Will show in Windows high contrast mode. */
  }
}

.site-header__initial {
  position: relative;
  z-index: 102;
  display: flex;
  align-items: flex-end;
  align-self: stretch;
  background-color: var(--color--primary-50);
}

.site-header__fixable {
  display: flex;
  align-items: flex-end;
  transition: all 0.5s;

  &.is-fixed {
    @media (--nav) {
      &:not(.is-expanded) {
        pointer-events: none;
      }
    }
  }
}

@media (--nav) {
  body:not(.is-always-mobile-nav) {
    & .site-header__fixable.is-fixed {
      position: fixed;
      z-index: 102; /* Appear above body content that is position: relative */
      inset-block-start: calc(var(--drupal-displace-offset-top, 0px) - var(--sp4));
      max-width: var(--max-bg-color);
    }
  }
}

.site-header__inner {
  position: relative;
  z-index: 1; /* Appear in front of Drupal's tabs. */
  flex-grow: 1;
  width: calc(100vw - var(--content-left) - var(--drupal-displace-offset-left, 0px) - var(--drupal-displace-offset-right, 0px));
  background: var(--color--white);
}

/*
 * Only apply transition styles when JS is loaded. This
 * works around https://bugs.chromium.org/p/chromium/issues/detail?id=332189
 */
html.js body:not(.is-always-mobile-nav) .site-header__inner {
  @media (--nav) {
    transition:
      opacity 0.3s,
      transform 0.3s,
      box-shadow 0.3s;
  }
}

.site-header__fixable.is-expanded .site-header__inner {
  @media (--nav) {
    box-shadow: -36px 1px 36px rgb(0, 0, 0, 0.08); /* LTR */
  }
}

[dir="rtl"] .site-header__fixable.is-expanded .site-header__inner {
  @media (--nav) {
    box-shadow: 36px 1px 36px rgb(0, 0, 0, 0.08);
  }
}

/* Hide the desktop nav when it's fixed and not active. */
body:not(.is-always-mobile-nav) .site-header__fixable.is-fixed:not(.is-expanded) .site-header__inner {
  @media (--nav) {
    transform: translateX(-101%); /* LTR */
    opacity: 0;
  }
}

[dir="rtl"] body:not(.is-always-mobile-nav) .site-header__fixable.is-fixed:not(.is-expanded) .site-header__inner {
  @media (--nav) {
    transform: translateX(101%);
  }
}

.site-header__inner__container {
  display: flex;
  justify-content: space-between;
}

/* Reset width set by layout.css */
body.is-fixed .site-header__inner__container {
  width: auto;
}
