once-campfire/app/assets/stylesheets/composer.css

/* Composer */
.composer {
  flex: none;
  padding: var(--block-space-half) calc(var(--inline-space) + 1vw);
}

.composer__input-hint,
.composer__context-btn {
  .composer:has(.composer__input:focus-within) & {
    @media (max-width: 100ch) {
      display: none;
    }
  }
}

/* Attachments */
.composer__attachment-btn {
  --hover-filter: brightness(0.85);

  @media (any-hover: hover) {
    &:where(:not(:active):hover) {
      filter: var(--hover-filter);
      box-shadow: none;
    }
  }
}

/* Pending attachments */
.composer__filelist {
  --row-gap: var(--block-space-half);

  &:not(:empty) {
    padding-block-end: var(--block-space-half);
  }
}

.composer__file {
  --aspect-ratio: 5/4;
  --btn-border-radius: 1em;
  --thumbnail-size: 15ch;

  aspect-ratio: var(--aspect-ratio);
  inline-size: var(--thumbnail-size);
}

:is(img, span):is(.composer__file-thumbnail) {
  aspect-ratio: var(--aspect-ratio);
  block-size: auto;
  border-radius: var(--btn-border-radius);
  border: 1px solid var(--color-border-darker);
  inline-size: var(--thumbnail-size);
  object-fit: cover;
}

.composer__file-thumbnail--common {
  background: url(common-file-text.svg) no-repeat center;
  background-size: 55%;
}

.composer__file-caption {
  --icon-size: 1.3em;

  &::after {
    content: "";
    block-size: var(--icon-size);
    inline-size: var(--icon-size);
    background: url("remove-circle.svg") no-repeat center;
    margin-inline: 0.5em -0.5em;
    flex-shrink: 0;
  }

  @media (prefers-color-scheme: dark) {
    &::after {
      filter: invert(100%);
    }
  }
}

/* Rich text */
.composer__rich-text-btn {
  --hover-filter: brightness(0.85);

  display: none;

  @media (any-hover: hover) {
    &:where(:not(:active):hover) {
      filter: var(--hover-filter);
      box-shadow: none;
    }
  }

  img {
    inline-size: 1.7em;
  }
}

@media (min-width: 100ch) and (any-hover: hover) and (pointer: fine) {
  .composer__rich-text-btn {
    display: inline-flex;
  }

  .composer--rich-text {
    trix-toolbar {
      display: block;
    }

    trix-editor.input {
      margin-block-start: var(--block-space-half);
    }
  }

  .composer--edit trix-toolbar {
    border-block-end: 1px solid var(--color-border);
    margin-inline: -0.8em;
    padding-inline: 0.3em;
    padding-block-end: 0.5em;
  }
}

/* Typing indicator */
.typing-indicator {
  inset-block-start: var(--indicator-position, 0.15rem);
  inset-inline-start: var(--block-space);
  opacity: var(--indicator-opacity, 0);
  position: absolute;
  transition: inset-block-start 300ms ease,
              opacity 300ms ease;

  .sidebar & {
    @media (min-width: 100ch) {
      margin-inline-start: 2vw;
    }
  }

  &.typing-indicator--active {
    --indicator-position: 0.15rem;
    --indicator-opacity: 1;
  }
}

.typing-indicator__author {
  line-height: 1;
  padding-inline-start: 1.5em;

  &.spinner {
    display: none;

    .typing-indicator--active & {
      display: block;
    }
  }
}

.composer__input {
  .composer__rich-text-btn,
  label:has(input[type="file"]) {
    cursor: pointer;
  }
}