discourse/app/assets/stylesheets/desktop/compose.scss

#reply-control {
  .reply-area {
    margin: 0 auto;
    padding: 8px;
    box-sizing: border-box;
    height: calc(100% - 11px);
    width: 100%;

    .submit-panel {
      flex-wrap: wrap;
    }
  }

  .select-kit.is-expanded {
    z-index: z("composer", "dropdown") + 1;
  }

  &.private-message {
    .with-tags {
      .title-and-category {
        flex-wrap: nowrap; // force title and tags on same line for PMs
        .mini-tag-chooser {
          margin-bottom: 8px; // match title input margin
          flex: 0 0 auto;
          margin-left: 8px; // matches margin between category and tag input
          width: 39%;
        }
      }
    }

    #private-message-users,
    .users-input {
      width: 100%;
      flex: 0 0 auto;
      &.can-warn {
        // space for warning, inverse of mini-tag-chooser width
        width: 60%;
      }
    }

    .add-warning {
      flex: 1 1 auto;
      overflow: hidden;
      span {
        // protects the space of the user input in case there's a very long translation
        @include ellipsis;
      }
    }
  }
}

.closed {
  .grippie {
    display: none;
  }
}

.open {
  .grippie {
    cursor: row-resize;
    padding: 4px 0;
    background: var(--tertiary);

    &:before {
      content: "";
      display: block;
      width: 24px;
      margin: auto;
      border-top: 3px double var(--tertiary-medium);
    }
  }
}

.discourse-touch {
  .open {
    .grippie {
      padding: 7px 0;
    }
  }
}

.composer-popup {
  box-sizing: border-box;
  position: absolute;
  width: calc(50% - 16px);
  top: 19px; // grippie (11px) + .reply-area padding (8px)
  bottom: 8px;
  right: 8px;
  overflow-y: auto;
  z-index: z("composer", "dropdown") + 1;
  padding: 1.5em;
  box-shadow: var(--shadow-dropdown);
  background: var(--highlight-bg);

  > p,
  h3 {
    &:first-of-type {
      margin-top: 0;
      margin-right: 3em;
    }
  }

  &.urgent {
    background: var(--danger-low);
  }

  &.education-message {
    background-color: var(--tertiary-low);
  }

  &.dominating-topic-message,
  &.get-a-room {
    bottom: unset;
    padding: 2.25em 6em 2.5em 2.25em;
    p {
      font-size: var(--font-up-1);
    }
    button:not(.close) {
      margin-top: 0.5em;
    }
  }

  h3 {
    margin-bottom: 10px;
  }

  .btn.close {
    flex-direction: row-reverse;
    align-items: center;
    position: absolute;
    right: 0;
    top: 0;
    color: var(--primary-medium);
    font-size: var(--font-0);
    .d-icon {
      color: currentColor;
      font-size: var(--font-up-1);
      margin: 0 0 0 0.25em;
    }
    .discourse-no-touch & {
      &:active,
      &:focus {
        background: transparent;
        .d-icon {
          color: var(--primary);
        }
      }
    }
  }

  ul {
    margin: 0;
    padding: 0 0 0 1.5em;
    &.list,
    &.topics {
      list-style: none;
      padding: 0;
    }

    li {
      font-weight: normal;
      margin-top: 8px;
    }
  }
}

.composer-controls {
  .d-chevron-down {
    vertical-align: text-top;
  }
}

.custom-body {
  background-color: var(--tertiary-low);
  p {
    max-width: 98%;
  }
}

.similar-topics {
  background-color: var(--tertiary-low);

  a[href] {
    color: var(--primary);
  }

  .posts-count {
    background-color: var(--tertiary);
  }

  .search-link {
    .topic-title {
      flex: 0 1 auto;
      margin-right: 0.5em;
    }
    span.badge-wrapper {
      margin-left: 0;
    }
    .blurb {
      color: var(--primary-high);
    }
    .topic-title,
    .blurb {
      .d-icon {
        color: var(--primary-high);
      }
    }
    span.topic {
      display: flex;
      flex-direction: column;

      .first-line {
        flex: 1;
      }

      .second-line {
        display: flex;
        flex-wrap: wrap;
        align-items: center;

        .discourse-tags {
          font-size: var(--font-down-1);
        }
      }
    }
  }
}

.composer-popup:nth-of-type(2) {
  width: calc(50% - 65px);
}

a.toggle-preview {
  color: var(--primary-high);
  &:hover {
    color: var(--tertiary);
  }
}

#draft-status,
#file-uploading {
  text-align: right;
}

// fullscreen composer styles
.fullscreen-composer {
  overflow: hidden;

  .profiler-results {
    display: none;
  }

  #reply-control {
    &.fullscreen {
      // important needed because of inline styles when height is changed manually with grippie
      height: 100vh !important;
      max-height: 100%; // prevents devices from miscalculating using vh
      z-index: z("header") + 1;

      @supports (--custom: property) {
        height: calc(var(--composer-vh, 1vh) * 100) !important;
      }

      .d-editor-preview-wrapper {
        margin-top: 1%;
      }

      .reply-to {
        border-bottom: 1px solid var(--primary-low);
        margin-bottom: 0;
        padding-bottom: 8px;
      }

      .d-editor-textarea-wrapper {
        border: none;
      }
      &.show-preview .d-editor-textarea-wrapper {
        border-right: 1px solid var(--primary-low);
      }
      #draft-status,
      #file-uploading {
        margin-left: 0;
        text-align: initial;
      }
      .composer-popup {
        top: 30px;
      }
      &:before {
        content: "";
        background: var(--secondary);
        width: 100%;
        height: 100%;
        position: fixed;
        z-index: -1;
        left: 0;
      }
    }
  }
}

.composer-fullscreen-prompt {
  animation: fadeIn 1s ease-in-out;
  animation-delay: 1.5s;
  animation-direction: reverse;
  animation-fill-mode: forwards;
  @media (prefers-reduced-motion) {
    animation-duration: 0s;
  }
  position: fixed;
  left: 50%;
  top: 10%;
  transform: translate(-50%, 0);
  .rtl & {
    // R2 is not smart enough to support this swap
    transform: translate(50%, 0);
  }
  z-index: z("header") + 1;
  background: var(--primary-very-high);
  color: var(--secondary);
  padding: 0.5em 0.75em;
  pointer-events: none;
  border-radius: 2px;
  kbd {
    background: none;
  }
}

@media screen and (min-width: $reply-area-max-width) {
  .sidebar-wrapper .sidebar-container {
    .has-sidebar-page & {
      height: auto;
    }
  }
  #reply-control:not(.fullscreen) {
    .has-sidebar-page & {
      width: auto;
      max-width: calc(
        (var(--d-max-width) + (var(--d-sidebar-width) / 2)) - 1.5rem
      );
      margin-left: 0;
      margin-right: 0;
      transform: translateX(
        calc(
          ((100vw - var(--d-max-width) - (var(--d-sidebar-width) / 0.5)) / 2) +
            17em + 1rem
        )
      );

      &.hide-preview {
        max-width: calc(740px);
        transform: translateX(
          calc(
            ((100vw - 740px - var(--d-sidebar-width)) / 2) +
              var(--d-sidebar-width)
          )
        );
      }
    }
  }
}