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295 lines
12 KiB
Plaintext
295 lines
12 KiB
Plaintext
/*
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* Copyright 2020 Adobe. All rights reserved.
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* This file is licensed to you under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License. You may obtain a copy
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* of the License at http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software distributed under
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* the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR REPRESENTATIONS
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* OF ANY KIND, either express or implied. See the License for the specific language
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* governing permissions and limitations under the License.
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*/
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import {chain, getScrollParent, isIOS, useLayoutEffect} from '@react-aria/utils';
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interface PreventScrollOptions {
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/** Whether the scroll lock is disabled. */
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isDisabled?: boolean
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}
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const visualViewport = typeof document !== 'undefined' && window.visualViewport;
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// HTML input types that do not cause the software keyboard to appear.
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const nonTextInputTypes = new Set([
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'checkbox',
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'radio',
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'range',
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'color',
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'file',
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'image',
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'button',
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'submit',
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'reset'
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]);
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// The number of active usePreventScroll calls. Used to determine whether to revert back to the original page style/scroll position
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let preventScrollCount = 0;
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let restore;
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/**
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* Prevents scrolling on the document body on mount, and
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* restores it on unmount. Also ensures that content does not
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* shift due to the scrollbars disappearing.
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*/
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export function usePreventScroll(options: PreventScrollOptions = {}) {
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let {isDisabled} = options;
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useLayoutEffect(() => {
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if (isDisabled) {
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return;
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}
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preventScrollCount++;
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if (preventScrollCount === 1) {
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if (isIOS()) {
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restore = preventScrollMobileSafari();
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} else {
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restore = preventScrollStandard();
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}
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}
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return () => {
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preventScrollCount--;
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if (preventScrollCount === 0) {
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restore();
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}
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};
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}, [isDisabled]);
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}
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// For most browsers, all we need to do is set `overflow: hidden` on the root element, and
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// add some padding to prevent the page from shifting when the scrollbar is hidden.
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function preventScrollStandard() {
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return chain(
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setStyle(document.documentElement, 'paddingRight', `${window.innerWidth - document.documentElement.clientWidth}px`),
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setStyle(document.documentElement, 'overflow', 'hidden')
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);
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}
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// Mobile Safari is a whole different beast. Even with overflow: hidden,
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// it still scrolls the page in many situations:
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//
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// 1. When the bottom toolbar and address bar are collapsed, page scrolling is always allowed.
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// 2. When the keyboard is visible, the viewport does not resize. Instead, the keyboard covers part of
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// it, so it becomes scrollable.
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// 3. When tapping on an input, the page always scrolls so that the input is centered in the visual viewport.
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// This may cause even fixed position elements to scroll off the screen.
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// 4. When using the next/previous buttons in the keyboard to navigate between inputs, the whole page always
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// scrolls, even if the input is inside a nested scrollable element that could be scrolled instead.
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//
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// In order to work around these cases, and prevent scrolling without jankiness, we do a few things:
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//
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// 1. Prevent default on `touchmove` events that are not in a scrollable element. This prevents touch scrolling
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// on the window.
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// 2. Set `overscroll-behavior: contain` on nested scrollable regions so they do not scroll the page when at
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// the top or bottom. Work around a bug where this does not work when the element does not actually overflow
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// by preventing default in a `touchmove` event.
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// 3. Prevent default on `touchend` events on input elements and handle focusing the element ourselves.
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// 4. When focusing an input, apply a transform to trick Safari into thinking the input is at the top
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// of the page, which prevents it from scrolling the page. After the input is focused, scroll the element
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// into view ourselves, without scrolling the whole page.
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// 5. Offset the body by the scroll position using a negative margin and scroll to the top. This should appear the
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// same visually, but makes the actual scroll position always zero. This is required to make all of the
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// above work or Safari will still try to scroll the page when focusing an input.
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// 6. As a last resort, handle window scroll events, and scroll back to the top. This can happen when attempting
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// to navigate to an input with the next/previous buttons that's outside a modal.
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function preventScrollMobileSafari() {
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let scrollable: Element;
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let restoreScrollableStyles;
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let onTouchStart = (e: TouchEvent) => {
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// Store the nearest scrollable parent element from the element that the user touched.
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scrollable = getScrollParent(e.target as Element, true);
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if (scrollable === document.documentElement && scrollable === document.body) {
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return;
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}
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// Prevent scrolling up when at the top and scrolling down when at the bottom
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// of a nested scrollable area, otherwise mobile Safari will start scrolling
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// the window instead.
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if (scrollable instanceof HTMLElement && window.getComputedStyle(scrollable).overscrollBehavior === 'auto') {
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restoreScrollableStyles = setStyle(scrollable, 'overscrollBehavior', 'contain');
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}
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};
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let onTouchMove = (e: TouchEvent) => {
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// Prevent scrolling the window.
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if (!scrollable || scrollable === document.documentElement || scrollable === document.body) {
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e.preventDefault();
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return;
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}
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// overscroll-behavior should prevent scroll chaining, but currently does not
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// if the element doesn't actually overflow. https://bugs.webkit.org/show_bug.cgi?id=243452
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// This checks that both the width and height do not overflow, otherwise we might
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// block horizontal scrolling too. In that case, adding `touch-action: pan-x` to
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// the element will prevent vertical page scrolling. We can't add that automatically
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// because it must be set before the touchstart event.
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if (scrollable.scrollHeight === scrollable.clientHeight && scrollable.scrollWidth === scrollable.clientWidth) {
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e.preventDefault();
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}
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};
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let onTouchEnd = (e: TouchEvent) => {
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let target = e.target as HTMLElement;
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// Apply this change if we're not already focused on the target element
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if (willOpenKeyboard(target) && target !== document.activeElement) {
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e.preventDefault();
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setupStyles();
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// Apply a transform to trick Safari into thinking the input is at the top of the page
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// so it doesn't try to scroll it into view. When tapping on an input, this needs to
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// be done before the "focus" event, so we have to focus the element ourselves.
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target.style.transform = 'translateY(-2000px)';
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target.focus();
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requestAnimationFrame(() => {
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target.style.transform = '';
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});
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}
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if (restoreScrollableStyles) {
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restoreScrollableStyles();
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}
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};
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let onFocus = (e: FocusEvent) => {
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let target = e.target as HTMLElement;
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if (willOpenKeyboard(target)) {
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setupStyles();
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// Transform also needs to be applied in the focus event in cases where focus moves
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// other than tapping on an input directly, e.g. the next/previous buttons in the
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// software keyboard. In these cases, it seems applying the transform in the focus event
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// is good enough, whereas when tapping an input, it must be done before the focus event. 🤷♂️
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target.style.transform = 'translateY(-2000px)';
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requestAnimationFrame(() => {
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target.style.transform = '';
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// This will have prevented the browser from scrolling the focused element into view,
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// so we need to do this ourselves in a way that doesn't cause the whole page to scroll.
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if (visualViewport) {
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if (visualViewport.height < window.innerHeight) {
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// If the keyboard is already visible, do this after one additional frame
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// to wait for the transform to be removed.
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requestAnimationFrame(() => {
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scrollIntoView(target);
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});
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} else {
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// Otherwise, wait for the visual viewport to resize before scrolling so we can
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// measure the correct position to scroll to.
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visualViewport.addEventListener('resize', () => scrollIntoView(target), {once: true});
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}
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}
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});
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}
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};
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let restoreStyles: null | (() => void) = null;
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let setupStyles = () => {
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if (restoreStyles) {
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return;
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}
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let onWindowScroll = () => {
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// Last resort. If the window scrolled, scroll it back to the top.
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// It should always be at the top because the body will have a negative margin (see below).
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window.scrollTo(0, 0);
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};
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// Record the original scroll position so we can restore it.
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// Then apply a negative margin to the body to offset it by the scroll position. This will
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// enable us to scroll the window to the top, which is required for the rest of this to work.
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let scrollX = window.pageXOffset;
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let scrollY = window.pageYOffset;
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restoreStyles = chain(
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addEvent(window, 'scroll', onWindowScroll),
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setStyle(document.documentElement, 'paddingRight', `${window.innerWidth - document.documentElement.clientWidth}px`),
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setStyle(document.documentElement, 'overflow', 'hidden'),
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setStyle(document.body, 'marginTop', `-${scrollY}px`),
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() => {
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window.scrollTo(scrollX, scrollY);
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}
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);
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// Scroll to the top. The negative margin on the body will make this appear the same.
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window.scrollTo(0, 0);
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};
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let removeEvents = chain(
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addEvent(document, 'touchstart', onTouchStart, {passive: false, capture: true}),
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addEvent(document, 'touchmove', onTouchMove, {passive: false, capture: true}),
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addEvent(document, 'touchend', onTouchEnd, {passive: false, capture: true}),
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addEvent(document, 'focus', onFocus, true)
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);
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return () => {
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// Restore styles and scroll the page back to where it was.
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restoreScrollableStyles?.();
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restoreStyles?.();
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removeEvents();
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};
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}
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// Sets a CSS property on an element, and returns a function to revert it to the previous value.
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function setStyle(element: HTMLElement, style: string, value: string) {
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let cur = element.style[style];
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element.style[style] = value;
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return () => {
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element.style[style] = cur;
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};
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}
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// Adds an event listener to an element, and returns a function to remove it.
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function addEvent<K extends keyof GlobalEventHandlersEventMap>(
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target: Document | Window,
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event: K,
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handler: (this: Document | Window, ev: GlobalEventHandlersEventMap[K]) => any,
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options?: boolean | AddEventListenerOptions
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) {
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// internal function, so it's ok to ignore the difficult to fix type error
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// @ts-ignore
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target.addEventListener(event, handler, options);
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return () => {
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// @ts-ignore
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target.removeEventListener(event, handler, options);
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};
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}
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function scrollIntoView(target: Element) {
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let root = document.scrollingElement || document.documentElement;
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let nextTarget: Element | null = target;
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while (nextTarget && nextTarget !== root) {
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// Find the parent scrollable element and adjust the scroll position if the target is not already in view.
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let scrollable = getScrollParent(nextTarget);
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if (scrollable !== document.documentElement && scrollable !== document.body && scrollable !== nextTarget) {
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let scrollableTop = scrollable.getBoundingClientRect().top;
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let targetTop = nextTarget.getBoundingClientRect().top;
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if (targetTop > scrollableTop + nextTarget.clientHeight) {
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scrollable.scrollTop += targetTop - scrollableTop;
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}
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}
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nextTarget = scrollable.parentElement;
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}
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}
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function willOpenKeyboard(target: Element) {
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return (
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(target instanceof HTMLInputElement && !nonTextInputTypes.has(target.type)) ||
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target instanceof HTMLTextAreaElement ||
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(target instanceof HTMLElement && target.isContentEditable)
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);
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}
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