ionic-framework/core/src/components/header/header.utils.ts

import { readTask, writeTask } from '@stencil/core';
import { clamp } from '@utils/helpers';

const TRANSITION = 'all 0.2s ease-in-out';

interface HeaderIndex {
  el: HTMLIonHeaderElement;
  toolbars: ToolbarIndex[] | [];
}

interface ToolbarIndex {
  el: HTMLElement;
  background: HTMLElement;
  ionTitleEl: HTMLIonTitleElement | undefined;
  innerTitleEl: HTMLElement;
  ionButtonsEl: HTMLElement[] | [];
}

export const cloneElement = (tagName: string) => {
  const getCachedEl = document.querySelector(`${tagName}.ion-cloned-element`);
  if (getCachedEl !== null) {
    return getCachedEl;
  }

  const clonedEl = document.createElement(tagName);
  clonedEl.classList.add('ion-cloned-element');
  clonedEl.style.setProperty('display', 'none');
  document.body.appendChild(clonedEl);

  return clonedEl;
};

export const createHeaderIndex = (headerEl: HTMLElement | undefined): HeaderIndex | undefined => {
  if (!headerEl) {
    return;
  }

  const toolbars = headerEl.querySelectorAll('ion-toolbar');

  return {
    el: headerEl,
    toolbars: Array.from(toolbars).map((toolbar: HTMLIonToolbarElement) => {
      const ionTitleEl = toolbar.querySelector('ion-title');
      return {
        el: toolbar,
        background: toolbar.shadowRoot!.querySelector('.toolbar-background'),
        ionTitleEl,
        innerTitleEl: ionTitleEl ? ionTitleEl.shadowRoot!.querySelector('.toolbar-title') : null,
        ionButtonsEl: Array.from(toolbar.querySelectorAll('ion-buttons')),
      } as ToolbarIndex;
    }),
  } as HeaderIndex;
};

export const handleContentScroll = (scrollEl: HTMLElement, scrollHeaderIndex: HeaderIndex, contentEl: HTMLElement) => {
  readTask(() => {
    const scrollTop = scrollEl.scrollTop;
    const scale = clamp(1, 1 + -scrollTop / 500, 1.1);

    // Native refresher should not cause titles to scale
    const nativeRefresher = contentEl.querySelector('ion-refresher.refresher-native');
    if (nativeRefresher === null) {
      writeTask(() => {
        scaleLargeTitles(scrollHeaderIndex.toolbars, scale);
      });
    }
  });
};

export const setToolbarBackgroundOpacity = (headerEl: HTMLIonHeaderElement, opacity?: number) => {
  /**
   * Fading in the backdrop opacity
   * should happen after the large title
   * has collapsed, so it is handled
   * by handleHeaderFade()
   */
  if (headerEl.collapse === 'fade') {
    return;
  }

  if (opacity === undefined) {
    headerEl.style.removeProperty('--opacity-scale');
  } else {
    headerEl.style.setProperty('--opacity-scale', opacity.toString());
  }
};

const handleToolbarBorderIntersection = (
  ev: IntersectionObserverEntry[],
  mainHeaderIndex: HeaderIndex,
  scrollTop: number
) => {
  if (!ev[0].isIntersecting) {
    return;
  }

  /**
   * There is a bug in Safari where overflow scrolling on a non-body element
   * does not always reset the scrollTop position to 0 when letting go. It will
   * set to 1 once the rubber band effect has ended. This causes the background to
   * appear slightly on certain app setups.
   *
   * Additionally, we check if user is rubber banding (scrolling is negative)
   * as this can mean they are using pull to refresh. Once the refresher starts,
   * the content is transformed which can cause the intersection observer to erroneously
   * fire here as well.
   */
  const scale = ev[0].intersectionRatio > 0.9 || scrollTop <= 0 ? 0 : ((1 - ev[0].intersectionRatio) * 100) / 75;

  setToolbarBackgroundOpacity(mainHeaderIndex.el, scale === 1 ? undefined : scale);
};

/**
 * If toolbars are intersecting, hide the scrollable toolbar content
 * and show the primary toolbar content. If the toolbars are not intersecting,
 * hide the primary toolbar content and show the scrollable toolbar content
 */
export const handleToolbarIntersection = (
  ev: any, // TODO(FW-2832): type (IntersectionObserverEntry[] triggers errors which should be sorted)
  mainHeaderIndex: HeaderIndex,
  scrollHeaderIndex: HeaderIndex,
  scrollEl: HTMLElement
) => {
  writeTask(() => {
    const scrollTop = scrollEl.scrollTop;
    handleToolbarBorderIntersection(ev, mainHeaderIndex, scrollTop);

    const event = ev[0];

    const intersection = event.intersectionRect;
    const intersectionArea = intersection.width * intersection.height;
    const rootArea = event.rootBounds.width * event.rootBounds.height;

    const isPageHidden = intersectionArea === 0 && rootArea === 0;
    const leftDiff = Math.abs(intersection.left - event.boundingClientRect.left);
    const rightDiff = Math.abs(intersection.right - event.boundingClientRect.right);
    const isPageTransitioning = intersectionArea > 0 && (leftDiff >= 5 || rightDiff >= 5);

    if (isPageHidden || isPageTransitioning) {
      return;
    }

    if (event.isIntersecting) {
      setHeaderActive(mainHeaderIndex, false);
      setHeaderActive(scrollHeaderIndex);
    } else {
      /**
       * There is a bug with IntersectionObserver on Safari
       * where `event.isIntersecting === false` when cancelling
       * a swipe to go back gesture. Checking the intersection
       * x, y, width, and height provides a workaround. This bug
       * does not happen when using Safari + Web Animations,
       * only Safari + CSS Animations.
       */

      const hasValidIntersection =
        (intersection.x === 0 && intersection.y === 0) || (intersection.width !== 0 && intersection.height !== 0);

      if (hasValidIntersection && scrollTop > 0) {
        setHeaderActive(mainHeaderIndex);
        setHeaderActive(scrollHeaderIndex, false);
        setToolbarBackgroundOpacity(mainHeaderIndex.el);
      }
    }
  });
};

export const setHeaderActive = (headerIndex: HeaderIndex, active = true) => {
  const headerEl = headerIndex.el;

  if (active) {
    headerEl.classList.remove('header-collapse-condense-inactive');
    headerEl.removeAttribute('aria-hidden');
  } else {
    headerEl.classList.add('header-collapse-condense-inactive');
    headerEl.setAttribute('aria-hidden', 'true');
  }
};

export const scaleLargeTitles = (toolbars: ToolbarIndex[] = [], scale = 1, transition = false) => {
  toolbars.forEach((toolbar) => {
    const ionTitle = toolbar.ionTitleEl;
    const titleDiv = toolbar.innerTitleEl;
    if (!ionTitle || ionTitle.size !== 'large') {
      return;
    }

    titleDiv.style.transition = transition ? TRANSITION : '';
    titleDiv.style.transform = `scale3d(${scale}, ${scale}, 1)`;
  });
};

export const handleHeaderFade = (scrollEl: HTMLElement, baseEl: HTMLElement, condenseHeader: HTMLElement | null) => {
  readTask(() => {
    const scrollTop = scrollEl.scrollTop;
    const baseElHeight = baseEl.clientHeight;
    const fadeStart = condenseHeader ? condenseHeader.clientHeight : 0;

    /**
     * If we are using fade header with a condense
     * header, then the toolbar backgrounds should
     * not begin to fade in until the condense
     * header has fully collapsed.
     *
     * Additionally, the main content should not
     * overflow out of the container until the
     * condense header has fully collapsed. When
     * using just the condense header the content
     * should overflow out of the container.
     */
    if (condenseHeader !== null && scrollTop < fadeStart) {
      baseEl.style.setProperty('--opacity-scale', '0');
      scrollEl.style.setProperty('clip-path', `inset(${baseElHeight}px 0px 0px 0px)`);
      return;
    }

    const distanceToStart = scrollTop - fadeStart;
    const fadeDuration = 10;
    const scale = clamp(0, distanceToStart / fadeDuration, 1);
    writeTask(() => {
      scrollEl.style.removeProperty('clip-path');
      baseEl.style.setProperty('--opacity-scale', scale.toString());
    });
  });
};