pinafore/routes/_components/compose/ComposeMediaItem.html

<div class="compose-media">
  <img src="{{mediaItem.data.preview_url}}" alt="{{mediaItem.file.name}}"/>
  <div class="compose-media-delete">
    <button class="compose-media-delete-button"
            aria-label="Delete {{mediaItem.file.name}}"
            on:click="onDeleteMedia()" >
      <svg class="compose-media-delete-button-svg">
        <use xlink:href="#fa-times" />
      </svg>
    </button>
  </div>
  <div class="compose-media-alt">
    <input type="text"
           placeholder="Description"
           aria-label="Describe {{mediaItem.file.name}} for the visually impaired"
           bind:value=rawText
    >
  </div>
</div>
<style>
  .compose-media {
    height: 200px;
    overflow: hidden;
    flex-direction: column;
    position: relative;
    display: flex;
    background: var(--main-bg);
  }
  .compose-media img {
    object-fit: contain;
    object-position: center center;
    flex: 1;
    height: 100%;
    width: 100%;
  }
  .compose-media-alt {
    z-index: 10;
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    display: flex;
    justify-content: center;
  }
  .compose-media-alt input {
    width: 100%;
    font-size: 1.2em;
    background: var(--alt-input-bg);
  }
  .compose-media-alt input:focus {
    background: var(--main-bg);
  }
  .compose-media-delete {
    position: absolute;
    z-index: 10;
    top: 0;
    right: 0;
    left: 0;
    display: flex;
    justify-content: flex-end;
    margin: 2px;
  }
  .compose-media-delete-button {
    padding: 10px;
    background: none;
    border: none;
  }
  .compose-media-delete-button:hover {
    background: var(--toast-border);
  }
  .compose-media-delete-button-svg {
    fill: var(--button-text);
    width: 18px;
    height: 18px;
  }
</style>
<script>
  import { store } from '../../_store/store'
  import { deleteMedia } from '../../_actions/media'
  import debounce from 'lodash-es/debounce'
  import { scheduleIdleTask } from '../../_utils/scheduleIdleTask'

  export default {
    oncreate () {
      this.setupSyncFromStore()
      this.setupSyncToStore()
    },
    data: () => ({
      rawText: ''
    }),
    store: () => store,
    methods: {
      setupSyncFromStore () {
        this.observe('mediaDescriptions', mediaDescriptions => {
          mediaDescriptions = mediaDescriptions || []
          let { index, rawText } = this.get()
          let text = mediaDescriptions[index] || ''
          if (rawText !== text) {
            this.set({rawText: text})
          }
        })
      },
      setupSyncToStore () {
        const saveStore = debounce(() => scheduleIdleTask(() => this.store.save()), 1000)

        this.observe('rawText', rawText => {
          let { realm } = this.get()
          let { index } = this.get()
          let mediaDescriptions = store.getComposeData(realm, 'mediaDescriptions') || []
          if (mediaDescriptions[index] === rawText) {
            return
          }
          while (mediaDescriptions.length <= index) {
            mediaDescriptions.push(null)
          }
          mediaDescriptions[index] = rawText
          store.setComposeData(realm, {mediaDescriptions})
          saveStore()
        }, {init: false})
      },
      onDeleteMedia () {
        let {
          realm,
          index
        } = this.get()
        deleteMedia(realm, index)
      }
    }
  }
</script>