pinafore/routes/_components/compose/ComposeButton.html

<div class="compose-box-button-halo">
  <button class="primary compose-box-button"
          {disabled}
          aria-label={sticky ? 'Compose' : 'Toot!'}
          on:click>
    <span class={$postingStatus || sticky ? 'hidden' : ''}>
      Toot!
    </span>
    <div class="compose-box-button-spinner"
         aria-hidden="true">
      <svg class="compose-box-button-svg {$postingStatus ? 'spin' : 'hidden'}">
        <use xlink:href="#fa-spinner" />
      </svg>
    </div>

    <div class="compose-box-button-compose {sticky ? '' : 'hidden'}"
         aria-hidden="true">
      <svg class="compose-box-button-svg">
        <use xlink:href="#fa-pencil" />
      </svg>
    </div>
  </button>
</div>
<style>
  .compose-box-button-halo {
    border-radius: 2px;
    margin: 5px 15px 15px 5px;
    background: var(--compose-button-halo);
    pointer-events: auto;
  }
  .compose-box-button {
    grid-area: button;
    justify-self: right;
    text-transform: uppercase;
    position: relative;
    margin: 5px;
    pointer-events: auto;
  }
  .compose-box-button-spinner, .compose-box-button-compose {
    position: absolute;
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 10;
    top: 0;
    bottom: 0;
    left: 0;
    right: 0;
  }
  .compose-box-button-svg {
    width: 24px;
    height: 24px;
    fill: var(--button-primary-text);
  }

  @media (max-width: 767px) {
    .compose-box-button-halo {
      margin: 5px;
    }
    .compose-box-button {
      margin: 5px;
    }
  }
</style>
<script>
  import { store } from '../../_store/store'

  export default {
    store: () => store,
    computed: {
      disabled: ({ $postingStatus, overLimit }) => $postingStatus || overLimit
    }
  }
</script>