pinafore/routes/_components/ModalDialog.html

<div class="dialog-wrapper" ref:node>
  <div class="close-dialog-button-wrapper">
    <button class="close-dialog-button" aria-label="Close dialog" on:click="close()">
      <span aria-hidden="true">&times;</span>
    </button>
  </div>
  <slot></slot>
</div>
<style>
  :global(.modal-dialog) {
    position: fixed;
    top: 50%;
    transform: translate(0, -50%);
    padding: 0;
    border: 3px solid var(--main-border);
  }
  :global(.modal-dialog-wrapper) {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    max-width: calc(100vw - 40px);
  }
  .close-dialog-button-wrapper {
    text-align: right;
    width: 100%;
    background: var(--nav-bg)
  }
  .close-dialog-button {
    padding: 0 0 7px;
    background: none;
    border: none;
  }
  .close-dialog-button span {
    padding: 0 15px;
    font-size: 48px;
    color: var(--button-primary-text);
  }
  :global(dialog::backdrop, .backdrop) {
    background: rgba(51, 51, 51, 0.9) !important; /* TODO: hack for Safari */
  }

  @media (max-width: 767px) {
    .close-dialog-button span {
      padding: 0 10px 4px;
      font-size: 32px;
    }
  }
</style>
<script>

  import { importDialogPolyfill } from '../_utils/asyncModules'
  import { registerFocusRestoreDialog } from '../_utils/dialogs'

  export default {
    oncreate() {
      this.getDialogElement().style.background = this.get('background') || '#000'
      this.observe('shown', shown => {
        if (shown) {
          this.show()
        }
      })
      this.registration = this.register()
      this.onDocumentClick = (e) => {
        let dialog = this.getDialogElement()
        if (!dialog.open) {
          return;
        }
        if (e.target !== dialog) {
          return;
        }
        this.close() // close when clicked outside of dialog
      }
      document.body.addEventListener('click', this.onDocumentClick);
    },
    methods: {
      async register() {
        if (typeof HTMLDialogElement === 'undefined') {
          let dialogPolyfill = await importDialogPolyfill()
          dialogPolyfill.registerDialog(this.getDialogElement())
        }
        registerFocusRestoreDialog(this.getDialogElement())
      },
      async show() {
        await this.registration
        this.getDialogElement().showModal()
      },
      close() {
        this.getDialogElement().close()
        document.body.removeChild(this.getDialogElement())
        document.body.removeEventListener('click', this.onDocumentClick);
      },
      getDialogElement() {
        return this.refs.node.parentElement
      }
    }
  }
</script>