From ad53b0e2e26756f169eb5400fb0cdcd33f3bcfe5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=A0imon=20Brandner?= <simon.bra.ag@gmail.com>
Date: Thu, 22 Apr 2021 14:56:12 +0200
Subject: [PATCH 1/2] Add normalizeWheelEvent()
MIME-Version: 1.0
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Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>
---
 src/utils/Mouse.ts | 50 ++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 src/utils/Mouse.ts

diff --git a/src/utils/Mouse.ts b/src/utils/Mouse.ts
new file mode 100644
index 0000000000..a85c6492c4
--- /dev/null
+++ b/src/utils/Mouse.ts
@@ -0,0 +1,50 @@
+/*
+Copyright 2021 Šimon Brandner <simon.bra.ag@gmail.com>
+
+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.
+*/
+
+/**
+ * Different browsers use different deltaModes. This causes different behaviour.
+ * To avoid that we use this function to convert any event to pixels.
+ * @param {WheelEvent} event to normalize
+ * @returns {WheelEvent} normalized event event
+ */
+export function normalizeWheelEvent(event: WheelEvent): WheelEvent {
+    const LINE_HEIGHT = 18;
+
+    let deltaX;
+    let deltaY;
+    let deltaZ;
+
+    if (event.deltaMode === 1) { // Units are lines
+        deltaX = (event.deltaX * LINE_HEIGHT);
+        deltaY = (event.deltaY * LINE_HEIGHT);
+        deltaZ = (event.deltaZ * LINE_HEIGHT);
+    } else {
+        deltaX = event.deltaX;
+        deltaY = event.deltaY;
+        deltaZ = event.deltaZ;
+    }
+
+    return new WheelEvent(
+        "syntheticWheel",
+        {
+            deltaMode: 0,
+            deltaY: deltaY,
+            deltaX: deltaX,
+            deltaZ: deltaZ,
+            ...event,
+        },
+    );
+}

From 2e6397d8aac1b10cc1011427893cb6eed15800c7 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C5=A0imon=20Brandner?= <simon.bra.ag@gmail.com>
Date: Thu, 22 Apr 2021 14:56:35 +0200
Subject: [PATCH 2/2] Wire up normalizeWheelEvent()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Signed-off-by: Šimon Brandner <simon.bra.ag@gmail.com>
---
 src/components/views/elements/ImageView.tsx | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/components/views/elements/ImageView.tsx b/src/components/views/elements/ImageView.tsx
index bb69e24855..cbced07bfe 100644
--- a/src/components/views/elements/ImageView.tsx
+++ b/src/components/views/elements/ImageView.tsx
@@ -32,13 +32,14 @@ import dis from '../../../dispatcher/dispatcher';
 import {replaceableComponent} from "../../../utils/replaceableComponent";
 import {RoomPermalinkCreator} from "../../../utils/permalinks/Permalinks"
 import {MatrixEvent} from "matrix-js-sdk/src/models/event";
+import {normalizeWheelEvent} from "../../../utils/Mouse";
 
 const MIN_ZOOM = 100;
 const MAX_ZOOM = 300;
 // This is used for the buttons
 const ZOOM_STEP = 10;
 // This is used for mouse wheel events
-const ZOOM_COEFFICIENT = 7.5;
+const ZOOM_COEFFICIENT = 0.5;
 // If we have moved only this much we can zoom
 const ZOOM_DISTANCE = 10;
 
@@ -115,7 +116,9 @@ export default class ImageView extends React.Component<IProps, IState> {
     private onWheel = (ev: WheelEvent) => {
         ev.stopPropagation();
         ev.preventDefault();
-        const newZoom = this.state.zoom - (ev.deltaY * ZOOM_COEFFICIENT);
+
+        const {deltaY} = normalizeWheelEvent(ev);
+        const newZoom = this.state.zoom - (deltaY * ZOOM_COEFFICIENT);
 
         if (newZoom <= MIN_ZOOM) {
             this.setState({