@ionic/core/components/ion-infinite-scroll.js

/*!
 * (C) Ionic http://ionicframework.com - MIT License
 */
import { proxyCustomElement, HTMLElement, createEvent, writeTask, readTask, h, Host } from '@stencil/core/internal/client';
import { b as getIonMode } from './ionic-global.js';
import { c as componentOnReady } from './helpers.js';

const infiniteScrollCss = "ion-infinite-scroll{display:none;width:100%}.infinite-scroll-enabled{display:block}";

const InfiniteScroll = /*@__PURE__*/ proxyCustomElement(class extends HTMLElement {
  constructor() {
    super();
    this.__registerHost();
    this.ionInfinite = createEvent(this, "ionInfinite", 7);
    this.thrPx = 0;
    this.thrPc = 0;
    this.didFire = false;
    this.isBusy = false;
    this.isLoading = false;
    /**
     * The threshold distance from the bottom
     * of the content to call the `infinite` output event when scrolled.
     * The threshold value can be either a percent, or
     * in pixels. For example, use the value of `10%` for the `infinite`
     * output event to get called when the user has scrolled 10%
     * from the bottom of the page. Use the value `100px` when the
     * scroll is within 100 pixels from the bottom of the page.
     */
    this.threshold = '15%';
    /**
     * If `true`, the infinite scroll will be hidden and scroll event listeners
     * will be removed.
     *
     * Set this to true to disable the infinite scroll from actively
     * trying to receive new data while scrolling. This is useful
     * when it is known that there is no more data that can be added, and
     * the infinite scroll is no longer needed.
     */
    this.disabled = false;
    /**
     * The position of the infinite scroll element.
     * The value can be either `top` or `bottom`.
     */
    this.position = 'bottom';
    this.onScroll = () => {
      const scrollEl = this.scrollEl;
      if (!scrollEl || !this.canStart()) {
        return 1;
      }
      const infiniteHeight = this.el.offsetHeight;
      if (infiniteHeight === 0) {
        // if there is no height of this element then do nothing
        return 2;
      }
      const scrollTop = scrollEl.scrollTop;
      const scrollHeight = scrollEl.scrollHeight;
      const height = scrollEl.offsetHeight;
      const threshold = this.thrPc !== 0 ? (height * this.thrPc) : this.thrPx;
      const distanceFromInfinite = (this.position === 'bottom')
        ? scrollHeight - infiniteHeight - scrollTop - threshold - height
        : scrollTop - infiniteHeight - threshold;
      if (distanceFromInfinite < 0) {
        if (!this.didFire) {
          this.isLoading = true;
          this.didFire = true;
          this.ionInfinite.emit();
          return 3;
        }
      }
      else {
        this.didFire = false;
      }
      return 4;
    };
  }
  thresholdChanged() {
    const val = this.threshold;
    if (val.lastIndexOf('%') > -1) {
      this.thrPx = 0;
      this.thrPc = (parseFloat(val) / 100);
    }
    else {
      this.thrPx = parseFloat(val);
      this.thrPc = 0;
    }
  }
  disabledChanged() {
    const disabled = this.disabled;
    if (disabled) {
      this.isLoading = false;
      this.isBusy = false;
    }
    this.enableScrollEvents(!disabled);
  }
  async connectedCallback() {
    const contentEl = this.el.closest('ion-content');
    if (!contentEl) {
      console.error('<ion-infinite-scroll> must be used inside an <ion-content>');
      return;
    }
    await new Promise(resolve => componentOnReady(contentEl, resolve));
    this.scrollEl = await contentEl.getScrollElement();
    this.thresholdChanged();
    this.disabledChanged();
    if (this.position === 'top') {
      writeTask(() => {
        if (this.scrollEl) {
          this.scrollEl.scrollTop = this.scrollEl.scrollHeight - this.scrollEl.clientHeight;
        }
      });
    }
  }
  disconnectedCallback() {
    this.enableScrollEvents(false);
    this.scrollEl = undefined;
  }
  /**
   * Call `complete()` within the `ionInfinite` output event handler when
   * your async operation has completed. For example, the `loading`
   * state is while the app is performing an asynchronous operation,
   * such as receiving more data from an AJAX request to add more items
   * to a data list. Once the data has been received and UI updated, you
   * then call this method to signify that the loading has completed.
   * This method will change the infinite scroll's state from `loading`
   * to `enabled`.
   */
  async complete() {
    const scrollEl = this.scrollEl;
    if (!this.isLoading || !scrollEl) {
      return;
    }
    this.isLoading = false;
    if (this.position === 'top') {
      /**
       * New content is being added at the top, but the scrollTop position stays the same,
       * which causes a scroll jump visually. This algorithm makes sure to prevent this.
       * (Frame 1)
       *    - complete() is called, but the UI hasn't had time to update yet.
       *    - Save the current content dimensions.
       *    - Wait for the next frame using _dom.read, so the UI will be updated.
       * (Frame 2)
       *    - Read the new content dimensions.
       *    - Calculate the height difference and the new scroll position.
       *    - Delay the scroll position change until other possible dom reads are done using _dom.write to be performant.
       * (Still frame 2, if I'm correct)
       *    - Change the scroll position (= visually maintain the scroll position).
       *    - Change the state to re-enable the InfiniteScroll.
       *    - This should be after changing the scroll position, or it could
       *    cause the InfiniteScroll to be triggered again immediately.
       * (Frame 3)
       *    Done.
       */
      this.isBusy = true;
      // ******** DOM READ ****************
      // Save the current content dimensions before the UI updates
      const prev = scrollEl.scrollHeight - scrollEl.scrollTop;
      // ******** DOM READ ****************
      requestAnimationFrame(() => {
        readTask(() => {
          // UI has updated, save the new content dimensions
          const scrollHeight = scrollEl.scrollHeight;
          // New content was added on top, so the scroll position should be changed immediately to prevent it from jumping around
          const newScrollTop = scrollHeight - prev;
          // ******** DOM WRITE ****************
          requestAnimationFrame(() => {
            writeTask(() => {
              scrollEl.scrollTop = newScrollTop;
              this.isBusy = false;
            });
          });
        });
      });
    }
  }
  canStart() {
    return (!this.disabled &&
      !this.isBusy &&
      !!this.scrollEl &&
      !this.isLoading);
  }
  enableScrollEvents(shouldListen) {
    if (this.scrollEl) {
      if (shouldListen) {
        this.scrollEl.addEventListener('scroll', this.onScroll);
      }
      else {
        this.scrollEl.removeEventListener('scroll', this.onScroll);
      }
    }
  }
  render() {
    const mode = getIonMode(this);
    const disabled = this.disabled;
    return (h(Host, { class: {
        [mode]: true,
        'infinite-scroll-loading': this.isLoading,
        'infinite-scroll-enabled': !disabled
      } }));
  }
  get el() { return this; }
  static get watchers() { return {
    "threshold": ["thresholdChanged"],
    "disabled": ["disabledChanged"]
  }; }
  static get style() { return infiniteScrollCss; }
}, [0, "ion-infinite-scroll", {
    "threshold": [1],
    "disabled": [4],
    "position": [1],
    "isLoading": [32],
    "complete": [64]
  }]);
function defineCustomElement$1() {
  if (typeof customElements === "undefined") {
    return;
  }
  const components = ["ion-infinite-scroll"];
  components.forEach(tagName => { switch (tagName) {
    case "ion-infinite-scroll":
      if (!customElements.get(tagName)) {
        customElements.define(tagName, InfiniteScroll);
      }
      break;
  } });
}

const IonInfiniteScroll = InfiniteScroll;
const defineCustomElement = defineCustomElement$1;

export { IonInfiniteScroll, defineCustomElement };