From 934ca6908fb0bd1c1fff5ea0507583628e229b96 Mon Sep 17 00:00:00 2001
From: Travis Ralston <travpc@gmail.com>
Date: Thu, 11 Apr 2019 11:07:31 -0600
Subject: [PATCH] Remove breadcrumb scroll tolerances and use sensible defaults

Fixes https://github.com/vector-im/riot-web/issues/9394
Fixes https://github.com/vector-im/riot-web/issues/9400

Numbers chosen based on user feedback. The setting has also been removed because it isn't really needed anymore.
---
 .../structures/IndicatorScrollbar.js          | 30 +++++++------------
 src/components/views/rooms/RoomBreadcrumbs.js | 10 ++-----
 src/settings/Settings.js                      |  7 -----
 3 files changed, 13 insertions(+), 34 deletions(-)

diff --git a/src/components/structures/IndicatorScrollbar.js b/src/components/structures/IndicatorScrollbar.js
index 2470f9fa11..a615717104 100644
--- a/src/components/structures/IndicatorScrollbar.js
+++ b/src/components/structures/IndicatorScrollbar.js
@@ -29,13 +29,6 @@ export default class IndicatorScrollbar extends React.Component {
         // scroll horizontally rather than vertically. This should only be used on components
         // with no vertical scroll opportunity.
         verticalScrollsHorizontally: PropTypes.bool,
-
-        // An object containing 2 numbers: xyThreshold and yReduction. xyThreshold is the amount
-        // of horizontal movement required in order to ignore any vertical changes in scroll, and
-        // only applies when verticalScrollsHorizontally is true. yReduction is the factor to
-        // multiply the vertical delta by when verticalScrollsHorizontally is true. The default
-        // behaviour is to have an xyThreshold of infinity and a yReduction of 0.8
-        scrollTolerances: PropTypes.object,
     };
 
     constructor(props) {
@@ -127,20 +120,19 @@ export default class IndicatorScrollbar extends React.Component {
 
     onMouseWheel = (e) => {
         if (this.props.verticalScrollsHorizontally && this._scrollElement) {
-            const xyThreshold = this.props.scrollTolerances
-                ? this.props.scrollTolerances.xyThreshold
-                : Number.MAX_SAFE_INTEGER;
+            // xyThreshold is the amount of horizontal motion required for the component to
+            // ignore the vertical delta in a scroll. Used to stop trackpads from acting in
+            // strange ways. Should be positive.
+            const xyThreshold = 0;
 
-            const yReduction = this.props.scrollTolerances
-                ? this.props.scrollTolerances.yReduction
-                : 0.8;
+            // yRetention is the factor multiplied by the vertical delta to try and reduce
+            // the harshness of the scroll behaviour. Should be a value between 0 and 1.
+            const yRetention = 1.0;
 
-            // Don't apply vertical motion to horizontal scrolls. This is meant to eliminate
-            // trackpads causing excessive scroll motion.
-            if (e.deltaX >= xyThreshold) return;
-
-            // noinspection JSSuspiciousNameCombination
-            this._scrollElement.scrollLeft += e.deltaY * yReduction;
+            if (Math.abs(e.deltaX) < xyThreshold) {
+                // noinspection JSSuspiciousNameCombination
+                this._scrollElement.scrollLeft += e.deltaY * yRetention;
+            }
         }
     };
 
diff --git a/src/components/views/rooms/RoomBreadcrumbs.js b/src/components/views/rooms/RoomBreadcrumbs.js
index 7c5947e049..fff1fa7f3c 100644
--- a/src/components/views/rooms/RoomBreadcrumbs.js
+++ b/src/components/views/rooms/RoomBreadcrumbs.js
@@ -33,12 +33,7 @@ const MAX_ROOMS = 20;
 export default class RoomBreadcrumbs extends React.Component {
     constructor(props) {
         super(props);
-
-        const tolerances = SettingsStore.getValue("breadcrumb_scroll_tolerances");
-        this.state = {rooms: [], scrollTolerances: tolerances};
-
-        // Record this for debugging purposes
-        console.log("Breadcrumbs scroll tolerances:", tolerances);
+        this.state = {rooms: []};
 
         this.onAction = this.onAction.bind(this);
         this._dispatcherRef = null;
@@ -343,8 +338,7 @@ export default class RoomBreadcrumbs extends React.Component {
         });
         return (
             <IndicatorScrollbar ref="scroller" className="mx_RoomBreadcrumbs"
-                trackHorizontalOverflow={true} verticalScrollsHorizontally={true}
-                scrollTolerances={this.state.scrollTolerances}>
+                trackHorizontalOverflow={true} verticalScrollsHorizontally={true}>
                 { avatars }
             </IndicatorScrollbar>
         );
diff --git a/src/settings/Settings.js b/src/settings/Settings.js
index dcd6f91aef..35baa718b9 100644
--- a/src/settings/Settings.js
+++ b/src/settings/Settings.js
@@ -262,13 +262,6 @@ export const SETTINGS = {
         supportedLevels: ['account'],
         default: [],
     },
-    "breadcrumb_scroll_tolerances": {
-        supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS,
-        default: {
-            xyThreshold: 10,
-            yReduction: 0.8,
-        },
-    },
     "analyticsOptIn": {
         supportedLevels: LEVELS_DEVICE_ONLY_SETTINGS_WITH_CONFIG,
         displayName: _td('Send analytics data'),