discourse/app/assets/stylesheets/common/topic-timeline.scss

.timeline-loading {
  width: 900px;
}

.timeline-container {
  box-sizing: border-box;
  z-index: z("timeline");

  &.timeline-docked-bottom {
    .timeline-footer-controls {
      opacity: 0;
      pointer-events: none;
      cursor: default;
    }
  }

  &.timeline-fullscreen.show {
    max-height: 700px;
    @media (prefers-reduced-motion: no-preference) {
      transition: max-height 0.4s ease-out;
    }

    @media screen and (max-height: 425px) {
      max-height: 75vh;
    }
    .topic-timeline {
      .timeline-footer-controls {
        display: flex;
        flex-wrap: wrap;
        max-width: calc(100% - 9em); // 9em is the width of the timeline
      }
    }
    .timeline-controls {
      display: table-cell;
      vertical-align: top;
    }
  }

  &.timeline-fullscreen {
    @media (prefers-reduced-motion: no-preference) {
      transition: max-height 0.3s ease-in;
    }
    max-height: 0;
    position: fixed;
    margin-left: 0;
    background-color: var(--secondary);
    bottom: 0;
    left: 0;
    right: 0;
    border-top: 1px solid var(--primary-low);
    box-shadow: var(--shadow-composer);
    padding: 20px 0px;
    z-index: z("fullscreen");
    @media screen and (max-height: 425px) {
      padding-top: 10px;
    }
    .back-button {
      display: none;
    }
    .topic-timeline {
      width: 100%;
      table-layout: fixed;
      margin-left: 0;
      margin-right: 0;
      display: table;
      touch-action: none;

      .timeline-date-wrapper {
        text-align: right;
      }
      .post-excerpt {
        max-width: 650px;
        line-height: var(--line-height-large);
        display: block;
        @include line-clamp(8);
        @media screen and (max-height: 425px) {
          @include line-clamp(5);
        }
      }
      .username {
        color: var(--primary-high-or-secondary-low);
        word-wrap: break-word;
        font-weight: bold;
      }
      .title {
        margin-top: 0;
        padding-left: 1em;
        display: table-cell;
        vertical-align: top;
        width: 100%;
        h2 {
          margin-top: 0;
          display: block;
          line-height: var(--line-height-medium);
          font-size: var(--font-up-2);
          @include line-clamp(4);
        }
        a {
          color: var(--primary);
        }
      }
      .timeline-last-read {
        right: 0;
        margin-left: 0;
        .progress {
          display: none;
        }
      }
      .timeline-footer-controls {
        display: none;
        position: absolute;
        bottom: 20px;
        left: 10px;

        .topic-admin-menu-button-container {
          display: flex;
        }

        .topic-admin-menu-button {
          display: flex;
        }
      }

      .timeline-scrollarea-wrapper {
        display: table-cell;
        padding-right: 1.5em;
        width: 7em;
      }
      .timeline-scrollarea {
        border-right: 1px solid var(--tertiary-low-or-tertiary-high);
        border-left: none;
        max-width: 120px;

        .timeline-scroller {
          position: relative;
          margin-right: -1.5em;
          padding-right: 1.5em;
          justify-content: flex-end;
          .timeline-scroller-content {
            box-sizing: border-box;
            max-width: 100%;
            overflow: hidden;
            text-align: right;
            padding-left: 0;
            padding-right: 1em;
          }
          .timeline-handle {
            float: none;
            width: 11px;
            position: relative;
            right: -6px;
          }
        }

        .timeline-padding {
          margin-left: 0;
          margin-right: -1em;
        }
      }
    }

    .timeline-scrollarea-wrapper::after {
      content: "";
      display: table;
      clear: both;
    }
  }

  .topic-timeline {
    transition: opacity 0.2s ease-in;
    touch-action: none;
    min-width: 6em;

    .topic-admin-menu-button .btn {
      height: 100%;
    }

    .timeline-controls {
      margin-bottom: 1em;
    }

    .timeline-date-wrapper {
      max-width: 9em;
      overflow-wrap: anywhere;
    }

    .timeline-footer-controls {
      // this is absolutely positioned to avoid
      // adding extra height below short topics
      // above the topic-footer-controls
      position: absolute;
      margin-top: 1em;
      @media (prefers-reduced-motion: no-preference) {
        transition: opacity 0.2s ease-in;
      }
      display: flex;
      gap: 0.5em;
      flex-wrap: wrap;

      button:last-child {
        margin-right: 0;
      }
    }

    .start-date {
      color: var(--primary-med-or-secondary-med);
    }

    .timeline-scrollarea {
      margin-top: 0.5em;
      margin-left: 0.5em;
      border-left: 1px solid var(--tertiary-low-or-tertiary-high);
      position: relative;
      transform: translateZ(0);
    }

    .timeline-padding {
      transition: height 0.15s ease-out;
      cursor: pointer;
      // this element has a click event
      // the negative margin lets this element overlap
      // the scrollarea's vertical track and thus it
      // enables taps on the track to work
      margin-left: -1em;
      .widget-dragging & {
        transition: none;
      }
      .dragging & {
        transition: none;
      }
    }

    .timeline-handle {
      border-radius: 0.8em;
      width: 0.35em;
      background-color: var(--tertiary-low-or-tertiary-high);
      height: 100%;
      float: left;
      z-index: z("base") + 1;
      outline: 1px solid transparent;
      margin-left: 0.5px;
    }

    .timeline-scroller-content {
      box-sizing: border-box;
      max-width: 100%;
      overflow: hidden;
      padding-left: 1em;
      position: absolute; // prevents text length from impacting width
      max-height: 3em; // this hides the date when the count + date would wrap to more than 2 lines
    }

    .timeline-ago {
      color: var(--primary-med-or-secondary-med);
      max-width: 4.6em;
      overflow: hidden;
      text-overflow: ellipsis;
    }

    .timeline-scroller {
      @include unselectable;
      margin-left: -0.22em;
      cursor: ns-resize;
      display: flex;
      align-items: center;

      .back-button {
        margin-top: 1em;
      }
    }

    .timeline-replies {
      overflow: hidden;
      overflow-wrap: break-word;
      font-weight: bold;
    }

    .timeline-last-read {
      position: absolute;
      margin-left: -0.35em;
      .progress {
        font-size: 0.8em;
        color: var(--tertiary);
        margin-right: 1em;
      }
      z-index: z("base") + 2; // above timeline-handle
    }

    .back-button {
      min-height: unset;
      padding: 2px 5px;
    }

    .now-date {
      display: inline-block;
      color: var(--primary-med-or-secondary-med);
      margin-top: 0.5em;
    }
  }
}