c9dc273cb0
instead of having to offset the padding of children of the autohiding scrollbar container, which gets fiddly quickly, add a new child to the scrollbar container that gets a negative margin of the scrollbar width when needed (on hover and overflowing when overlay is not supported). This needs an extra DOM element, but as it doesn't do anything weird layout-wise (like set position), it shouldn't affect styling at all. It also makes the auto hide scrollbar workarounds completely transparent to the rest of the code.
121 lines
4.0 KiB
JavaScript
121 lines
4.0 KiB
JavaScript
/*
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Copyright 2018 New Vector Ltd
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Licensed 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.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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import React from "react";
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// derived from code from github.com/noeldelgado/gemini-scrollbar
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// Copyright (c) Noel Delgado <pixelia.me@gmail.com> (pixelia.me)
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function getScrollbarWidth(alternativeOverflow) {
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const div = document.createElement('div');
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div.style.position = 'absolute';
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div.style.top = '-9999px';
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div.style.width = '100px';
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div.style.height = '100px';
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div.style.overflow = "scroll";
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if (alternativeOverflow) {
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div.style.overflow = alternativeOverflow;
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}
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div.style.msOverflowStyle = '-ms-autohiding-scrollbar';
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document.body.appendChild(div);
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const scrollbarWidth = (div.offsetWidth - div.clientWidth);
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document.body.removeChild(div);
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return scrollbarWidth;
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}
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function install() {
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const scrollbarWidth = getScrollbarWidth();
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if (scrollbarWidth !== 0) {
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const hasForcedOverlayScrollbar = getScrollbarWidth('overlay') === 0;
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// overflow: overlay on webkit doesn't auto hide the scrollbar
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if (hasForcedOverlayScrollbar) {
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document.body.classList.add("mx_scrollbar_overlay_noautohide");
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} else {
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document.body.classList.add("mx_scrollbar_nooverlay");
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const style = document.createElement('style');
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style.type = 'text/css';
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style.innerText =
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`body.mx_scrollbar_nooverlay { --scrollbar-width: ${scrollbarWidth}px; }`;
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document.head.appendChild(style);
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}
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}
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}
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const installBodyClassesIfNeeded = (function() {
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let installed = false;
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return function() {
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if (!installed) {
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install();
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installed = true;
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}
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};
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})();
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export default class AutoHideScrollbar extends React.Component {
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constructor(props) {
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super(props);
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this.onOverflow = this.onOverflow.bind(this);
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this.onUnderflow = this.onUnderflow.bind(this);
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this._collectContainerRef = this._collectContainerRef.bind(this);
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}
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onOverflow() {
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this.containerRef.classList.add("mx_AutoHideScrollbar_overflow");
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this.containerRef.classList.remove("mx_AutoHideScrollbar_underflow");
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}
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onUnderflow() {
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this.containerRef.classList.remove("mx_AutoHideScrollbar_overflow");
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this.containerRef.classList.add("mx_AutoHideScrollbar_underflow");
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}
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_collectContainerRef(ref) {
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if (ref && !this.containerRef) {
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this.containerRef = ref;
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const needsOverflowListener =
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document.body.classList.contains("mx_scrollbar_nooverlay");
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if (needsOverflowListener) {
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this.containerRef.addEventListener("overflow", this.onOverflow);
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this.containerRef.addEventListener("underflow", this.onUnderflow);
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}
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if (ref.scrollHeight > ref.clientHeight) {
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this.onOverflow();
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} else {
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this.onUnderflow();
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}
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}
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}
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componentWillUnmount() {
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if (this.containerRef) {
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this.containerRef.removeEventListener("overflow", this.onOverflow);
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this.containerRef.removeEventListener("underflow", this.onUnderflow);
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}
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}
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render() {
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installBodyClassesIfNeeded();
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return (<div
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ref={this._collectContainerRef}
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className={["mx_AutoHideScrollbar", this.props.className].join(" ")}
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>
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<div className="mx_AutoHideScrollbar_offset">
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{ this.props.children }
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</div>
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</div>);
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}
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}
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