shoelace/src/components/drawer/drawer.ts

import { LitElement, html, internalProperty, property, query, unsafeCSS } from 'lit-element';
import { classMap } from 'lit-html/directives/class-map';
import { ifDefined } from 'lit-html/directives/if-defined';
import { event, EventEmitter, tag } from '../../internal/decorators';
import styles from 'sass:./drawer.scss';
import { lockBodyScrolling, unlockBodyScrolling } from '../../internal/scroll';
import { hasSlot } from '../../internal/slot';
import { isPreventScrollSupported } from '../../internal/support';
import Modal from '../../internal/modal';

const hasPreventScroll = isPreventScrollSupported();

let id = 0;

/**
 * @since 2.0
 * @status stable
 *
 * @dependency sl-icon-button
 *
 * @slot - The drawer's content.
 * @slot label - The drawer's label. Alternatively, you can use the label prop.
 * @slot footer - The drawer's footer, usually one or more buttons representing various options.
 *
 * @part base - The component's base wrapper.
 * @part overlay - The overlay.
 * @part panel - The drawer panel (where the drawer and its content is rendered).
 * @part header - The drawer header.
 * @part title - The drawer title.
 * @part close-button - The close button.
 * @part body - The drawer body.
 * @part footer - The drawer footer.
 */
@tag('sl-drawer')
export default class SlDrawer extends LitElement {
  static styles = unsafeCSS(styles);

  @query('.drawer') drawer: HTMLElement;
  @query('.drawer__panel') panel: HTMLElement;

  private componentId = `drawer-${++id}`;
  private modal: Modal;
  private willShow = false;
  private willHide = false;

  @internalProperty() private hasFooter = false;
  @internalProperty() private isVisible = false;

  /** Indicates whether or not the drawer is open. You can use this in lieu of the show/hide methods. */
  @property({ type: Boolean, reflect: true }) open = false;

  /**
   * The drawer's label as displayed in the header. You should always include a relevant label even when using
   * `no-header`, as it is required for proper accessibility.
   */
  @property({ reflect: true }) label = '';

  /** The direction from which the drawer will open. */
  @property({ reflect: true }) placement: 'top' | 'right' | 'bottom' | 'left' = 'right';

  /**
   * By default, the drawer slides out of its containing block (usually the viewport). To make the drawer slide out of
   * its parent element, set this prop and add `position: relative` to the parent.
   */
  @property({ type: Boolean, reflect: true }) contained = false;

  /**
   * Removes the header. This will also remove the default close button, so please ensure you provide an easy,
   * accessible way for users to dismiss the drawer.
   */
  @property({ attribute: 'no-header', type: Boolean, reflect: true }) noHeader = false;

  /** Emitted when the drawer opens. Calling `event.preventDefault()` will prevent it from being opened. */
  @event('sl-show') slShow: EventEmitter<void>;

  /** Emitted after the drawer opens and all transitions are complete. */
  @event('sl-after-show') slAfterShow: EventEmitter<void>;

  /** Emitted when the drawer closes. Calling `event.preventDefault()` will prevent it from being closed. */
  @event('sl-hide') slHide: EventEmitter<void>;

  /** Emitted after the drawer closes and all transitions are complete. */
  @event('sl-after-hide') slAfterHide: EventEmitter<void>;

  /** Emitted when the drawer opens and the panel gains focus. Calling `event.preventDefault()` will prevent focus and allow you to set it on a different element in the drawer, such as an input or button. */
  @event('sl-initial-focus') slInitialFocus: EventEmitter<void>;

  /** Emitted when the overlay is clicked. Calling `event.preventDefault()` will prevent the drawer from closing. */
  @event('sl-overlay-dismiss') slOverlayDismiss: EventEmitter<void>;

  connectedCallback() {
    super.connectedCallback();

    this.modal = new Modal(this, {
      onfocusOut: () => (this.contained ? null : this.panel.focus())
    });

    this.handleSlotChange();

    // Show on init if open
    if (this.open) {
      this.show();
    }
  }

  disconnectedCallback() {
    super.disconnectedCallback();
    unlockBodyScrolling(this);
  }

  /** Shows the drawer */
  show() {
    if (this.willShow) {
      return;
    }

    const slShow = this.slShow.emit();
    if (slShow.defaultPrevented) {
      this.open = false;
      return;
    }

    this.willShow = true;
    this.isVisible = true;
    this.open = true;

    // Lock body scrolling only if the drawer isn't contained
    if (!this.contained) {
      this.modal.activate();
      lockBodyScrolling(this);
    }

    if (this.open) {
      if (hasPreventScroll) {
        // Wait for the next frame before setting initial focus so the drawer is technically visible
        requestAnimationFrame(() => {
          const slInitialFocus = this.slInitialFocus.emit();
          if (!slInitialFocus.defaultPrevented) {
            this.panel.focus({ preventScroll: true });
          }
        });
      } else {
        // Once Safari supports { preventScroll: true } we can remove this nasty little hack, but until then we need to
        // wait for the transition to complete before setting focus, otherwise the panel may render in a buggy way its
        // out of view initially.
        //
        // Fiddle: https://jsfiddle.net/g6buoafq/1/
        // Safari: https://bugs.webkit.org/show_bug.cgi?id=178583
        //
        this.drawer.addEventListener(
          'transitionend',
          () => {
            const slInitialFocus = this.slInitialFocus.emit();
            if (!slInitialFocus.defaultPrevented) {
              this.panel.focus();
            }
          },
          { once: true }
        );
      }
    }
  }

  /** Hides the drawer */
  hide() {
    if (this.willHide) {
      return;
    }

    const slHide = this.slHide.emit();
    if (slHide.defaultPrevented) {
      this.open = true;
      return;
    }

    this.willHide = true;
    this.open = false;
    this.modal.deactivate();

    unlockBodyScrolling(this);
  }

  handleCloseClick() {
    this.hide();
  }

  handleKeyDown(event: KeyboardEvent) {
    if (event.key === 'Escape') {
      this.hide();
    }
  }

  handleOverlayClick() {
    const slOverlayDismiss = this.slOverlayDismiss.emit();
    if (!slOverlayDismiss.defaultPrevented) {
      this.hide();
    }
  }

  handleSlotChange() {
    this.hasFooter = hasSlot(this, 'footer');
  }

  handleTransitionEnd(event: TransitionEvent) {
    const target = event.target as HTMLElement;

    // Ensure we only emit one event when the target element is no longer visible
    if (event.propertyName === 'transform' && target.classList.contains('drawer__panel')) {
      this.isVisible = this.open;
      this.willShow = false;
      this.willHide = false;
      this.open ? this.slAfterShow.emit() : this.slAfterHide.emit();
    }
  }

  render() {
    return html`
      <div
        part="base"
        class=${classMap({
          drawer: true,
          'drawer--open': this.open,
          'drawer--visible': this.isVisible,
          'drawer--top': this.placement === 'top',
          'drawer--right': this.placement === 'right',
          'drawer--bottom': this.placement === 'bottom',
          'drawer--left': this.placement === 'left',
          'drawer--contained': this.contained,
          'drawer--fixed': !this.contained,
          'drawer--has-footer': this.hasFooter
        })}
        @keydown=${this.handleKeyDown}
        @transitionend=${this.handleTransitionEnd}
      >
        <div part="overlay" class="drawer__overlay" @click=${this.handleOverlayClick} tabindex="-1"></div>

        <div
          part="panel"
          class="drawer__panel"
          role="dialog"
          aria-modal="true"
          aria-hidden=${this.open ? 'false' : 'true'}
          aria-label=${ifDefined(this.noHeader ? this.label : undefined)}
          aria-labelledby=${ifDefined(!this.noHeader ? `${this.componentId}-title` : undefined)}
          tabindex="0"
        >
          ${!this.noHeader
            ? html`
                <header part="header" class="drawer__header">
                  <span part="title" class="drawer__title" id=${`${this.componentId}-title`}>
                    <!-- If there's no label, use an invisible character to prevent the heading from collapsing -->
                    <slot name="label"> ${this.label || String.fromCharCode(65279)} </slot>
                  </span>
                  <sl-icon-button
                    exportparts="base:close-button"
                    class="drawer__close"
                    name="x"
                    @click=${this.handleCloseClick}
                  ></sl-icon-button>
                </header>
              `
            : ''}

          <div part="body" class="drawer__body">
            <slot></slot>
          </div>

          <footer part="footer" class="drawer__footer">
            <slot name="footer" @slotchange=${this.handleSlotChange}></slot>
          </footer>
        </div>
      </div>
    `;
  }
}

declare global {
  interface HTMLElementTagNameMap {
    'sl-drawer': SlDrawer;
  }
}