discourse/app/assets/stylesheets/common/base/header.scss

.d-header-wrap {
  @include sticky;
  top: 0;
  z-index: z("header");
}

.d-header {
  display: flex;
  align-items: center;
  width: 100%;
  z-index: z("header");
  background-color: var(--header_background);
  box-shadow: shadow("header");
  backface-visibility: hidden; /** do magic for scrolling performance **/

  > .wrap {
    box-sizing: border-box;
    width: 100%;
    height: 100%;

    .contents {
      display: flex;
      align-items: center;
      height: 100%;

      .header-row {
        width: 100%;

        .logo-wrapper {
          float: left;
        }
        .auth-buttons {
          float: right;
          margin-top: 0.4em;

          .login-button,
          .signup-button {
            padding: 8px 14px;
          }
        }
      }
    }
  }

  .title {
    display: flex;
    align-items: center;
    height: 100%;
    a,
    a:visited {
      color: var(--header_primary);
    }
  }

  #site-logo {
    width: auto;
  }

  .d-icon-home {
    font-size: $font-up-6;
  }

  .panel {
    position: relative;
    display: flex;
    flex: 0 0 auto;
    margin-left: auto;
    align-items: center;
  }

  .hamburger-panel,
  .user-menu,
  .search-menu {
    width: 0; // Flexbox fix for Safari
  }

  .header-buttons {
    display: flex;
    align-items: center;
    margin-top: 0.2em;
  }

  .login-button,
  .sign-up-button {
    padding: 6px 10px;
    .fa {
      margin-right: 3px;
    }
  }

  .login-button {
    margin-left: 7px;
  }
}

.header-dropdown-toggle,
.drop-down,
.panel-body {
  .flagged-posts,
  .reviewables {
    background: var(--danger);
    min-width: 6px;
  }
}

.d-header-icons {
  text-align: center;
  margin: 0 0 0 5px;
  list-style: none;

  > li {
    float: left;
  }
  .icon {
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    width: 2.2857em;
    height: 2.2857em;
    padding: 0.2143em;
    text-decoration: none;
    cursor: pointer;
    border-top: 1px solid transparent;
    border-left: 1px solid transparent;
    border-right: 1px solid transparent;
    transition: all linear 0.15s;
    outline: none;
    img.avatar {
      width: 2.1333em;
      height: 2.1333em;
    }
    .discourse-no-touch &:hover,
    .discourse-no-touch &:focus {
      background-color: var(--primary-low);
      border-top: 1px solid transparent;
      border-left: 1px solid transparent;
      border-right: 1px solid transparent;
      .d-icon {
        color: var(--primary-medium);
      }
    }
    &:active {
      color: var(--primary);
      background-color: var(--primary-low);
    }
  }
  .drop-down-mode & {
    .active .icon {
      position: relative;
      background-color: var(--secondary);
      cursor: default;
      border-top: 1px solid var(--primary-low);
      border-left: 1px solid var(--primary-low);
      border-right: 1px solid var(--primary-low);
      .d-icon {
        color: var(--primary-medium);
      }
      &:after {
        display: block;
        position: absolute;
        top: 100%;
        left: 0;
        z-index: z("header") + 1; // Higher than .menu-panel
        width: 100%;
        height: 0;
        content: "";
        border-top: 1px solid var(--secondary);
      }
      &:hover {
        border-bottom: none;
      }
    }
  }

  .d-icon {
    width: 100%;
    font-size: $font-up-4;
    line-height: $line-height-large;
    display: inline-block;
    color: var(--header_primary-low-mid);
  }
  .notifications {
    position: relative;
  }
  .ring {
    position: absolute;
    top: -9px;
    z-index: z("base");
    margin-left: 0;
  }
  .header-dropdown-toggle {
    position: relative;
  }
  .badge-notification {
    position: absolute;
    z-index: z("base");
    left: 0;
    top: -4px;
    min-width: 0.6em;
  }
  .unread-notifications {
    left: auto;
    right: -3px;
    background-color: var(--tertiary-med-or-tertiary);
  }
  .unread-high-priority-notifications,
  .ring {
    left: auto;
    right: 25px;
  }
}

.highlight-strong {
  background-color: var(--highlight-medium);
}

// topic info in the header
.extra-info-wrapper {
  display: flex;
  align-items: center;
  height: 100%;
  line-height: $line-height-medium;
  padding: 0 1.5em 0 0.5em;
  // we need to hide overflow in both to truncate the title in a flexbox
  overflow: hidden;
  .extra-info {
    overflow: hidden;
    width: 100%;
    animation: fadein 0.5s;
  }
  .title-wrapper {
    display: grid;
    grid-template-areas:
      "title title"
      "categories extra";
    grid-template-columns: auto minmax(2em, 1fr); // min must be as wide as ellipsis
    align-items: baseline;
    .header-title {
      grid-area: title;
    }
    .categories-wrapper {
      grid-area: categories;
    }
    .topic-header-extra {
      grid-area: extra;
    }
  }
  .topic-link {
    color: var(--header_primary);
    display: block;
    @include ellipsis;
  }
  .topic-statuses {
    .d-icon {
      color: var(--header_primary-medium);
    }
    .d-icon-envelope {
      color: var(--danger);
    }
  }
  .header-title {
    padding: 0;
    margin: 0;
    font-size: $font-up-3;
    width: 100%;
  }
  .categories-wrapper {
    display: inline-flex;
    flex: 0 1 auto;
    @include ellipsis;
    .badge-wrapper {
      @include ellipsis;
    }
  }
  .badge-wrapper {
    margin-right: 0.7em;
    min-width: 2.75em; // min needed for ellipsis
  }
  .badge-wrapper {
    &.bullet,
    &.bar,
    &.none {
      span.badge-category {
        color: var(--header_primary-high);
      }
    }
  }
  .topic-header-extra {
    display: inline-flex;
    align-items: center;
    max-width: 100%;
    .discourse-tags {
      display: inline;
      color: var(--header_primary-high);
      @include ellipsis;
      .discourse-tag {
        display: inline; // tags need to stay inline in order for them to truncate
        vertical-align: unset;
      }
    }
  }
}

// PM header participants

$avatar-height: 1.641em;
$mobile-avatar-height: 1.532em;

.topic-header-participants {
  display: flex;
  align-items: center;
  font-size: $font-down-1;
  @include ellipsis;
  &:not(:first-child) {
    margin-left: 5px;
  }
  .trigger-user-card,
  .trigger-group-card {
    &:not(:last-of-type) {
      margin-right: 5px;
    }
  }

  .trigger-user-card {
    .icon {
      height: $avatar-height;
      .mobile-view & {
        height: $mobile-avatar-height;
      }
      display: inline-block;
      img {
        height: 100%;
        width: auto;
      }
    }
  }

  .trigger-group-card {
    padding: 0 5px;
    border: 1px solid var(--primary-low);
    border-radius: 0.25em;
    min-width: 3em;
    @include ellipsis;

    .icon {
      display: flex;
      align-items: center;
      height: $avatar-height;
      .mobile-view & {
        height: $mobile-avatar-height;
      }
      color: var(--primary-high);

      .d-icon {
        margin-right: 5px;
      }
    }

    span {
      @include ellipsis;
    }
  }

  .more-participants {
    color: var(--header_primary-high);
    margin-left: 5px;
  }
}