Function canStart

core/src/components/modal/gestures/sheet.ts:262–299

(detail: GestureDetail)

  }

  const canStart = (detail: GestureDetail) => {
    /**
     * If we are swiping on the content, swiping should only be possible if the content
     * is scrolled all the way to the top so that we do not interfere with scrolling.
     *
     * We cannot assume that the `ion-content` target will remain consistent between swipes.
     * For example, when using ion-nav within a modal it is possible to swipe, push a view,
     * and then swipe again. The target content will not be the same between swipes.
     */
    const contentEl = findClosestIonContent(detail.event.target! as HTMLElement);
    currentBreakpoint = getCurrentBreakpoint();

    /**
     * If `expandToScroll` is disabled, we should not allow the swipe gesture
     * to start if the content is not scrolled to the top.
     */
    if (!expandToScroll && contentEl) {
      const scrollEl = isIonContent(contentEl) ? getElementRoot(contentEl).querySelector('.inner-scroll') : contentEl;
      return scrollEl!.scrollTop === 0;
    }

    if (currentBreakpoint === 1 && contentEl) {
      /**
       * The modal should never swipe to close on the content with a refresher.
       * Note 1: We cannot solve this by making this gesture have a higher priority than
       * the refresher gesture as the iOS native refresh gesture uses a scroll listener in
       * addition to a gesture.
       *
       * Note 2: Do not use getScrollElement here because we need this to be a synchronous
       * operation, and getScrollElement is asynchronous.
       */
      const scrollEl = isIonContent(contentEl) ? getElementRoot(contentEl).querySelector('.inner-scroll') : contentEl;
      const hasRefresherInContent = !!contentEl.querySelector('ion-refresher');
      return !hasRefresherInContent && scrollEl!.scrollTop === 0;
    }

    return true;
  };

  const onStart = (detail: GestureDetail) => {
    /**