266 lines
11 KiB
Plaintext
266 lines
11 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, isScrollable, useLayoutEffect, willOpenKeyboard} 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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// 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 = {}): void {
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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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let scrollbarWidth = window.innerWidth - document.documentElement.clientWidth;
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return chain(
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scrollbarWidth > 0 &&
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// Use scrollbar-gutter when supported because it also works for fixed positioned elements.
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('scrollbarGutter' in document.documentElement.style
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? setStyle(document.documentElement, 'scrollbarGutter', 'stable')
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: setStyle(document.documentElement, 'paddingRight', `${scrollbarWidth}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. This is best effort: we can't prevent default when pinch
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// zooming or when an element contains text selection, which may allow scrolling in some cases.
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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 focus moves to an input, create an off screen input and focus that temporarily. This prevents
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// Safari from scrolling the page. After a small delay, focus the real input and scroll it into view
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// ourselves, without scrolling the whole page.
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function preventScrollMobileSafari() {
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let scrollable: Element;
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let allowTouchMove = false;
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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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let target = e.target as Element;
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scrollable = isScrollable(target) ? target : getScrollParent(target, true);
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allowTouchMove = false;
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// If the target is selected, don't preventDefault in touchmove to allow user to adjust selection.
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let selection = target.ownerDocument.defaultView!.getSelection();
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if (selection && !selection.isCollapsed && selection.containsNode(target, true)) {
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allowTouchMove = true;
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}
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// If this is a focused input element with a selected range, allow user to drag the selection handles.
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if (
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'selectionStart' in target &&
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'selectionEnd' in target &&
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(target.selectionStart as number) < (target.selectionEnd as number) &&
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target.ownerDocument.activeElement === target
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) {
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allowTouchMove = true;
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}
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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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// This must be applied before the touchstart event as of iOS 26, so inject it as a <style> element.
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let style = document.createElement('style');
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style.textContent = `
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@layer {
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* {
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overscroll-behavior: contain;
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}
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}`.trim();
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document.head.prepend(style);
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let onTouchMove = (e: TouchEvent) => {
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// Allow pinch-zooming.
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if (e.touches.length === 2 || allowTouchMove) {
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return;
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}
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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 onBlur = (e: FocusEvent) => {
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let target = e.target as HTMLElement;
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let relatedTarget = e.relatedTarget as HTMLElement | null;
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if (relatedTarget && willOpenKeyboard(relatedTarget)) {
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// Focus without scrolling the whole page, and then scroll into view manually.
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relatedTarget.focus({preventScroll: true});
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scrollIntoViewWhenReady(relatedTarget, willOpenKeyboard(target));
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} else if (!relatedTarget) {
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// When tapping the Done button on the keyboard, focus moves to the body.
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// FocusScope will then restore focus back to the input. Later when tapping
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// the same input again, it is already focused, so no blur event will fire,
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// resulting in the flow above never running and Safari's native scrolling occurring.
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// Instead, move focus to the parent focusable element (e.g. the dialog).
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let focusable = target.parentElement?.closest('[tabindex]') as HTMLElement | null;
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focusable?.focus({preventScroll: true});
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}
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};
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// Override programmatic focus to scroll into view without scrolling the whole page.
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let focus = HTMLElement.prototype.focus;
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HTMLElement.prototype.focus = function (opts) {
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// Track whether the keyboard was already visible before.
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let wasKeyboardVisible = document.activeElement != null && willOpenKeyboard(document.activeElement);
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// Focus the element without scrolling the page.
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focus.call(this, {...opts, preventScroll: true});
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if (!opts || !opts.preventScroll) {
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scrollIntoViewWhenReady(this, wasKeyboardVisible);
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}
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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, 'blur', onBlur, true)
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);
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return () => {
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removeEvents();
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style.remove();
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HTMLElement.prototype.focus = focus;
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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 scrollIntoViewWhenReady(target: Element, wasKeyboardVisible: boolean) {
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if (wasKeyboardVisible || !visualViewport) {
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// If the keyboard was already visible, scroll the target into view immediately.
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scrollIntoView(target);
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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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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 scrollableRect = scrollable.getBoundingClientRect();
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let targetRect = nextTarget.getBoundingClientRect();
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if (targetRect.top < scrollableRect.top || targetRect.bottom > scrollableRect.top + nextTarget.clientHeight) {
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let bottom = scrollableRect.bottom;
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if (visualViewport) {
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bottom = Math.min(bottom, visualViewport.offsetTop + visualViewport.height);
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}
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// Center within the viewport.
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let adjustment = (targetRect.top - scrollableRect.top) - ((bottom - scrollableRect.top) / 2 - targetRect.height / 2);
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scrollable.scrollTo({
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// Clamp to the valid range to prevent over-scrolling.
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top: Math.max(0, Math.min(scrollable.scrollHeight - scrollable.clientHeight, scrollable.scrollTop + adjustment)),
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behavior: 'smooth'
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});
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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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