From d643f06ff08b6c1d57cbf88b2f660ab3b81ba7f2 Mon Sep 17 00:00:00 2001
From: "J. Ryan Stinnett" <jryans@gmail.com>
Date: Wed, 17 Feb 2021 17:28:23 +0000
Subject: [PATCH 1/2] Tweak chat effects setting label

---
 src/i18n/strings/en_EN.json | 2 +-
 src/settings/Settings.ts    | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/i18n/strings/en_EN.json b/src/i18n/strings/en_EN.json
index f4caa6ed6f..5bbbdf60b5 100644
--- a/src/i18n/strings/en_EN.json
+++ b/src/i18n/strings/en_EN.json
@@ -844,7 +844,7 @@
     "How fast should messages be downloaded.": "How fast should messages be downloaded.",
     "Manually verify all remote sessions": "Manually verify all remote sessions",
     "IRC display name width": "IRC display name width",
-    "Show chat effects": "Show chat effects",
+    "Show chat effects (animations when receiving e.g. confetti)": "Show chat effects (animations when receiving e.g. confetti)",
     "Collecting app version information": "Collecting app version information",
     "Collecting logs": "Collecting logs",
     "Uploading logs": "Uploading logs",
diff --git a/src/settings/Settings.ts b/src/settings/Settings.ts
index 43dd393ef7..4476bd2871 100644
--- a/src/settings/Settings.ts
+++ b/src/settings/Settings.ts
@@ -650,7 +650,7 @@ export const SETTINGS: {[setting: string]: ISetting} = {
     },
     "showChatEffects": {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
-        displayName: _td("Show chat effects"),
+        displayName: _td("Show chat effects (animations when receiving e.g. confetti)"),
         default: true,
     },
     "Widgets.pinned": { // deprecated

From 10e25f306fafea9f059376089fe16e7d61d2159e Mon Sep 17 00:00:00 2001
From: "J. Ryan Stinnett" <jryans@gmail.com>
Date: Wed, 17 Feb 2021 17:43:31 +0000
Subject: [PATCH 2/2] Disable chat effects when reduce motion preferred

Some users prefer reduced motion, so this disables chat effects when such a
preference is set in the browser or OS.
---
 src/settings/Settings.ts                      |  2 +
 .../controllers/ReducedMotionController.ts    | 45 +++++++++++++++++++
 2 files changed, 47 insertions(+)
 create mode 100644 src/settings/controllers/ReducedMotionController.ts

diff --git a/src/settings/Settings.ts b/src/settings/Settings.ts
index 4476bd2871..ca5e2f1d04 100644
--- a/src/settings/Settings.ts
+++ b/src/settings/Settings.ts
@@ -37,6 +37,7 @@ import UIFeatureController from "./controllers/UIFeatureController";
 import { UIFeature } from "./UIFeature";
 import { OrderedMultiController } from "./controllers/OrderedMultiController";
 import {Layout} from "./Layout";
+import ReducedMotionController from './controllers/ReducedMotionController';
 
 // These are just a bunch of helper arrays to avoid copy/pasting a bunch of times
 const LEVELS_ROOM_SETTINGS = [
@@ -652,6 +653,7 @@ export const SETTINGS: {[setting: string]: ISetting} = {
         supportedLevels: LEVELS_ACCOUNT_SETTINGS,
         displayName: _td("Show chat effects (animations when receiving e.g. confetti)"),
         default: true,
+        controller: new ReducedMotionController(),
     },
     "Widgets.pinned": { // deprecated
         supportedLevels: LEVELS_ROOM_OR_ACCOUNT,
diff --git a/src/settings/controllers/ReducedMotionController.ts b/src/settings/controllers/ReducedMotionController.ts
new file mode 100644
index 0000000000..d98ca16513
--- /dev/null
+++ b/src/settings/controllers/ReducedMotionController.ts
@@ -0,0 +1,45 @@
+/*
+Copyright 2021 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.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import SettingController from "./SettingController";
+import { SettingLevel } from "../SettingLevel";
+
+/**
+ * For animation-like settings, this controller checks whether the user has
+ * indicated they prefer reduced motion via browser or OS level settings.
+ * If they have, this forces the setting value to false.
+ */
+export default class ReducedMotionController extends SettingController {
+    public getValueOverride(
+        level: SettingLevel,
+        roomId: string,
+        calculatedValue: any,
+        calculatedAtLevel: SettingLevel,
+    ): any {
+        if (this.prefersReducedMotion()) {
+            return false;
+        }
+        return null; // no override
+    }
+
+    public get settingDisabled(): boolean {
+        return this.prefersReducedMotion();
+    }
+
+    private prefersReducedMotion(): boolean {
+        return window.matchMedia("(prefers-reduced-motion: reduce)").matches;
+    }
+}