Linux: Fixed scrolling with mouse wheel sometimes scrolling far more …

…than intended

UI/Debugger/Controls/CodeScrollBar.axaml.cs

@@ -120,7 +120,7 @@ private void UpdatePosition()
 		protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
 		{
 			base.OnPointerWheelChanged(e);
-			Value = Math.Max(0, Math.Min(Maximum, Value - (int)(e.Delta.Y * 3)));
+			Value = Math.Max(0, Math.Min(Maximum, Value - (int)(e.GetDeltaY() * 3)));
 		}
 
 		private void IncrementClick(object? sender, RoutedEventArgs e)

UI/Debugger/Controls/HexEditor.cs

@@ -551,7 +551,7 @@ private void ScrollIntoView(int byteIndex, bool scrollToTop = false)
 		protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
 		{
 			base.OnPointerWheelChanged(e);
-			this.TopRow = Math.Min((DataProvider.Length / BytesPerRow) - 1, Math.Max(0, this.TopRow - (int)(e.Delta.Y * 3)));
+			this.TopRow = Math.Min((DataProvider.Length / BytesPerRow) - 1, Math.Max(0, this.TopRow - (int)(e.GetDeltaY() * 3)));
 		}
 
 		protected override void OnPointerPressed(PointerPressedEventArgs e)

UI/Debugger/Controls/PictureViewer.cs

@@ -233,9 +233,10 @@ protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
 		{
 			base.OnPointerWheelChanged(e);
 			if(e.KeyModifiers == KeyModifiers.Control) {
-				if(e.Delta.Y > 0) {
+				double delta = e.GetDeltaY();
+				if(delta > 0) {
 					ZoomIn();
-				} else {
+				} else if(delta < 0) {
 					ZoomOut();
 				}
 				e.Handled = true;

UI/Debugger/Controls/ScrollPictureViewer.axaml.cs

@@ -9,6 +9,7 @@
 using Avalonia.Media;
 using Avalonia.Metadata;
 using Avalonia.Threading;
+using Mesen.Utilities;
 using System;
 using System.Collections.Generic;
 
@@ -211,9 +212,10 @@ protected override void OnPointerWheelChanged(PointerWheelEventArgs e)
 		{
 			base.OnPointerWheelChanged(e);
 			if(e.KeyModifiers == KeyModifiers.Control) {
-				if(e.Delta.Y > 0) {
+				double delta = e.GetDeltaY();
+				if(delta > 0) {
 					InnerViewer.ZoomIn();
-				} else {
+				} else if(delta < 0) {
 					InnerViewer.ZoomOut();
 				}
 				e.Handled = true;

UI/Debugger/Utilities/CodeViewerSelectionHandler.cs

@@ -114,7 +114,7 @@ public void Viewer_CodePointerMoved(DisassemblyViewer sender, CodePointerMovedEv
 
 		public void Viewer_PointerWheelChanged(object? sender, PointerWheelEventArgs e)
 		{
-			_model.Scroll((int)(-e.Delta.Y * 3));
+			_model.Scroll((int)(-e.GetDeltaY() * 3));
 		}
 
 		private void Viewer_KeyDown(object? sender, KeyEventArgs e)

UI/Debugger/ViewModels/DisassemblyViewModel.cs

@@ -120,6 +120,10 @@ public void SetViewer(DisassemblyViewer? viewer)
 
 		public void Scroll(int lineNumberOffset)
 		{
+			if(lineNumberOffset == 0) {
+				return;
+			}
+
 			SetTopAddress(DataProvider.GetRowAddress(TopAddress, lineNumberOffset));
 		}
 

UI/Debugger/Windows/PaletteViewerWindow.axaml.cs

@@ -47,9 +47,10 @@ public PaletteViewerWindow(CpuType cpuType)
 		private void Window_PointerWheelChanged(object? sender, PointerWheelEventArgs e)
 		{
 			if(e.KeyModifiers == KeyModifiers.Control) {
-				if(e.Delta.Y > 0) {
+				double delta = e.GetDeltaY();
+				if(delta > 0) {
 					_model.ZoomIn();
-				} else {
+				} else if(delta < 0) {
 					_model.ZoomOut();
 				}
 				e.Handled = true;

UI/Utilities/PointerWheelEventArgsExtensions.cs

@@ -0,0 +1,27 @@
+using Avalonia.Input;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Mesen.Utilities;
+
+static class PointerWheelEventArgsExtensions
+{
+	public static double GetDeltaY(this PointerWheelEventArgs e)
+	{
+		if(OperatingSystem.IsWindows() || OperatingSystem.IsMacOS()) {
+			return e.Delta.Y;
+		}
+
+		if(Math.Abs(e.Delta.Y) > 8) {
+			//Avalonia currently seems to have an issue with mouse wheel events on Linux
+			//Alt-tabbing to another application, scrolling, alt-tabbing back, and then
+			//trying to scroll will return a large delta value that includes the amount
+			//of scrolling done in the other application. In this case, return 0.
+			return 0;
+		}
+		return e.Delta.Y;
+	}
+}