Merge pull request #4276 from matrix-org/bwindels/transparentscrollbars

Fix: allow scrolling while window is not focused & remove scrollbar hack

res/css/structures/_AutoHideScrollbar.scss

@@ -14,76 +14,34 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-/* This file has CSS for both native and non-native scrollbars in an order
- * that's fairly logical to read but duplicates a selector to separate the
- * hiding/showing from the sizing.
- */
-/* stylelint-disable no-duplicate-selectors */
-
-/*
-1. for browsers that support native overlay auto-hiding scrollbars
-*/
 .mx_AutoHideScrollbar {
     overflow-x: hidden;
     overflow-y: auto;
+    overflow-y: overlay;    // where supported
     -ms-overflow-style: -ms-autohiding-scrollbar;
-}
-/*
-2. webkit also supports overflow:overlay where the scrollbars don't take any space
-in the layout but they don't autohide, so do that only on hover
-*/
-body.mx_scrollbar_overlay_noautohide .mx_AutoHideScrollbar {
-    overflow-y: hidden;
-}
 
-body.mx_scrollbar_overlay_noautohide .mx_AutoHideScrollbar:hover {
-    overflow-y: overlay;
-}
-/*
-3. as a last fallback, compensate for the scrollbar taking up space in the layout
-by having giving the child element (.mx_AutoHideScrollbar_offset) a
-negative right margin of the width of the scrollbar when the container
-is overflowing. This is what Firefox ends up using. Overflow is detected
-in javascript, and adds the mx_AutoHideScrollbar_overflow class to the container.
-This only works in Firefox, which should be fine as this fallback is only needed there.
-*/
-body.mx_scrollbar_nooverlay {
-    .mx_AutoHideScrollbar {
-        overflow-y: hidden;
+    &::-webkit-scrollbar {
+        width: 6px;
+        height: 6px;
+        background-color: transparent;
     }
 
-    .mx_AutoHideScrollbar:hover {
-        overflow-y: auto;
+    &::-webkit-scrollbar-thumb {
+        border-radius: 3px;
+        background-color: transparent;
     }
 
-    /*
-    offset scrollbar width with negative margin-right
-
-    include before and after psuedo-elements here so they can
-    be used to do something interesting like scroll-indicating
-    gradients (see IndicatorScrollBar)
-    */
-    .mx_AutoHideScrollbar:hover.mx_AutoHideScrollbar_overflow > .mx_AutoHideScrollbar_offset,
-    .mx_AutoHideScrollbar:hover.mx_AutoHideScrollbar_overflow::before,
-    .mx_AutoHideScrollbar:hover.mx_AutoHideScrollbar_overflow::after {
-        margin-right: calc(-1 * var(--scrollbar-width));
-    }
-}
-
-// style the native scrollbars ...
-// ... standard css scrollbars (firefox at time of writing)
-.mx_AutoHideScrollbar {
-    scrollbar-color: $scrollbar-thumb-color $scrollbar-track-color;
+    scrollbar-color: transparent transparent;
     scrollbar-width: thin;
 }
-// or fallback for webkit browsers
-::-webkit-scrollbar {
-    width: 6px;
-    height: 6px;
-    background-color: $scrollbar-track-color;
-}
 
-::-webkit-scrollbar-thumb {
-    background-color: $scrollbar-thumb-color;
-    border-radius: 3px;
+.mx_AutoHideScrollbar:hover {
+    &::-webkit-scrollbar {
+        background-color: $scrollbar-track-color;
+    }
+
+    &::-webkit-scrollbar-thumb {
+        background-color: $scrollbar-thumb-color;
+    }
+    scrollbar-color: $scrollbar-thumb-color $scrollbar-track-color;
 }

res/css/structures/_GroupView.scss

@@ -337,7 +337,7 @@ limitations under the License.
     display: none;
 }
 
-.mx_GroupView_body .mx_AutoHideScrollbar_offset > * {
+.mx_GroupView_body .mx_AutoHideScrollbar > * {
     margin: 11px 50px 50px 68px;
 }
 
@@ -366,7 +366,7 @@ limitations under the License.
     padding: 40px 20px;
 }
 
-.mx_GroupView .mx_MemberInfo .mx_AutoHideScrollbar_offset > :not(.mx_MemberInfo_avatar) {
+.mx_GroupView .mx_MemberInfo .mx_AutoHideScrollbar > :not(.mx_MemberInfo_avatar) {
     padding-left: 16px;
     padding-right: 16px;
 }

res/css/structures/_RoomSubList.scss

@@ -166,41 +166,22 @@ limitations under the License.
 
 // overflow indicators
 .mx_RoomSubList:not(.resized-all) > .mx_RoomSubList_scroll {
-    &.mx_IndicatorScrollbar_topOverflow::before,
-    &.mx_IndicatorScrollbar_bottomOverflow::after {
+    &.mx_IndicatorScrollbar_topOverflow::before {
         position: sticky;
+        content: "";
+        top: 0;
         left: 0;
         right: 0;
         height: 8px;
-        content: "";
-        display: block;
         z-index: 100;
+        display: block;
         pointer-events: none;
-    }
-
-    &.mx_IndicatorScrollbar_topOverflow > .mx_AutoHideScrollbar_offset {
-        margin-top: -8px;
-    }
-    &.mx_IndicatorScrollbar_bottomOverflow > .mx_AutoHideScrollbar_offset {
-        margin-bottom: -8px;
-    }
-
-    &.mx_IndicatorScrollbar_topOverflow::before {
-        top: 0;
         transition: background-image 0.1s ease-in;
         background: linear-gradient(to top, $panel-gradient);
     }
 
-    /*
-    // for now, we remove the bottomOverflow entirely as we don't want to
-    // lose the screen real-estate due to a bg-colored gradient, but we also
-    // don't want to use drop shadows and risk a confusing hierarchy of cards.
-    // so, instead, we hard-clip at the bottom but soft-clip at the top.
-    &.mx_IndicatorScrollbar_bottomOverflow::after {
-        bottom: 0;
-        transition: background-image 0.1s ease-in;
-        margin: 0px -8px;
-        background: linear-gradient(to bottom, rgba(0,0,0,0.1), rgba(0,0,0,0.0));
+
+    &.mx_IndicatorScrollbar_topOverflow {
+        margin-top: -8px;
     }
-    */
 }

res/css/views/rooms/_RoomBreadcrumbs.scss

@@ -41,7 +41,7 @@ limitations under the License.
         overflow-x: visible;
     }
 
-    .mx_AutoHideScrollbar_offset {
+    .mx_AutoHideScrollbar {
         display: flex;
         flex-direction: row;
         height: 100%;

src/components/structures/AutoHideScrollbar.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2018 New Vector Ltd
+Copyright 2020 The Matrix.org Foundation C.I.C.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -16,93 +17,10 @@ limitations under the License.
 
 import React from "react";
 
-// derived from code from github.com/noeldelgado/gemini-scrollbar
-// Copyright (c) Noel Delgado <pixelia.me@gmail.com> (pixelia.me)
-function getScrollbarWidth(alternativeOverflow) {
-    const div = document.createElement('div');
-    div.className = 'mx_AutoHideScrollbar'; //to get width of css scrollbar
-    div.style.position = 'absolute';
-    div.style.top = '-9999px';
-    div.style.width = '100px';
-    div.style.height = '100px';
-    div.style.overflow = "scroll";
-    if (alternativeOverflow) {
-        div.style.overflow = alternativeOverflow;
-    }
-    div.style.msOverflowStyle = '-ms-autohiding-scrollbar';
-    document.body.appendChild(div);
-    const scrollbarWidth = (div.offsetWidth - div.clientWidth);
-    document.body.removeChild(div);
-    return scrollbarWidth;
-}
-
-function install() {
-    const scrollbarWidth = getScrollbarWidth();
-    if (scrollbarWidth !== 0) {
-        const hasForcedOverlayScrollbar = getScrollbarWidth('overlay') === 0;
-        // overflow: overlay on webkit doesn't auto hide the scrollbar
-        if (hasForcedOverlayScrollbar) {
-            document.body.classList.add("mx_scrollbar_overlay_noautohide");
-        } else {
-            document.body.classList.add("mx_scrollbar_nooverlay");
-            const style = document.createElement('style');
-            style.type = 'text/css';
-            style.innerText =
-                `body.mx_scrollbar_nooverlay { --scrollbar-width: ${scrollbarWidth}px; }`;
-            document.head.appendChild(style);
-        }
-    }
-}
-
-const installBodyClassesIfNeeded = (function() {
-    let installed = false;
-    return function() {
-        if (!installed) {
-            install();
-            installed = true;
-        }
-    };
-})();
-
 export default class AutoHideScrollbar extends React.Component {
     constructor(props) {
         super(props);
-        this.onOverflow = this.onOverflow.bind(this);
-        this.onUnderflow = this.onUnderflow.bind(this);
         this._collectContainerRef = this._collectContainerRef.bind(this);
-        this._needsOverflowListener = null;
-    }
-
-    onOverflow() {
-        this.containerRef.classList.add("mx_AutoHideScrollbar_overflow");
-        this.containerRef.classList.remove("mx_AutoHideScrollbar_underflow");
-    }
-
-    onUnderflow() {
-        this.containerRef.classList.remove("mx_AutoHideScrollbar_overflow");
-        this.containerRef.classList.add("mx_AutoHideScrollbar_underflow");
-    }
-
-    checkOverflow() {
-        if (!this._needsOverflowListener) {
-            return;
-        }
-        if (this.containerRef.scrollHeight > this.containerRef.clientHeight) {
-            this.onOverflow();
-        } else {
-            this.onUnderflow();
-        }
-    }
-
-    componentDidUpdate() {
-        this.checkOverflow();
-    }
-
-    componentDidMount() {
-        installBodyClassesIfNeeded();
-        this._needsOverflowListener =
-            document.body.classList.contains("mx_scrollbar_nooverlay");
-        this.checkOverflow();
     }
 
     _collectContainerRef(ref) {
@@ -126,9 +44,7 @@ export default class AutoHideScrollbar extends React.Component {
                     onScroll={this.props.onScroll}
                     onWheel={this.props.onWheel}
                 >
-            <div className="mx_AutoHideScrollbar_offset">
-                { this.props.children }
-            </div>
+            { this.props.children }
         </div>);
     }
 }

src/components/structures/IndicatorScrollbar.js

@@ -66,6 +66,22 @@ export default class IndicatorScrollbar extends React.Component {
         this._autoHideScrollbar = autoHideScrollbar;
     }
 
+
+    componentDidUpdate(prevProps) {
+        const prevLen = prevProps && prevProps.children && prevProps.children.length || 0;
+        const curLen = this.props.children && this.props.children.length || 0;
+        // check overflow only if amount of children changes.
+        // if we don't guard here, we end up with an infinite
+        // render > componentDidUpdate > checkOverflow > setState > render loop
+        if (prevLen !== curLen) {
+            this.checkOverflow();
+        }
+    }
+
+    componentDidMount() {
+        this.checkOverflow();
+    }
+
     checkOverflow() {
         const hasTopOverflow = this._scrollElement.scrollTop > 0;
         const hasBottomOverflow = this._scrollElement.scrollHeight >
@@ -95,10 +111,6 @@ export default class IndicatorScrollbar extends React.Component {
             this._scrollElement.classList.remove("mx_IndicatorScrollbar_rightOverflow");
         }
 
-        if (this._autoHideScrollbar) {
-            this._autoHideScrollbar.checkOverflow();
-        }
-
         if (this.props.trackHorizontalOverflow) {
             this.setState({
                 // Offset from absolute position of the container