feat: Use preventDefault to prevent browser from processing Handled e…

…vents

chore: Prevent default only for non-Pointer events

chore: Comment

src/SamplesApp/UITests.Shared/UITests.Shared.projitems

@@ -569,6 +569,10 @@
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
     </Page>
+    <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Input\PointersTests\ScrollHandled.xaml">
+      <SubType>Designer</SubType>
+      <Generator>MSBuild:Compile</Generator>
+    </Page>
     <Page Include="$(MSBuildThisFileDirectory)Windows_UI_Input\PointersTests\ScrollViewer_PointerMoved.xaml">
       <SubType>Designer</SubType>
       <Generator>MSBuild:Compile</Generator>
@@ -4530,6 +4534,9 @@
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Input\PointersTests\HitTest_Shapes.xaml.cs">
       <DependentUpon>HitTest_Shapes.xaml</DependentUpon>
     </Compile>
+    <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Input\PointersTests\ScrollHandled.xaml.cs">
+      <DependentUpon>ScrollHandled.xaml</DependentUpon>
+    </Compile>
     <Compile Include="$(MSBuildThisFileDirectory)Windows_UI_Input\PointersTests\ScrollViewer_PointerMoved.xaml.cs">
       <DependentUpon>ScrollViewer_PointerMoved.xaml</DependentUpon>
     </Compile>
@@ -7399,4 +7406,4 @@
     <None Include="$(MSBuildThisFileDirectory)ItemExclusions.props" />
   </ItemGroup>
   <Import Project="ItemExclusions.props" />
-</Project>
+</Project>

src/SamplesApp/UITests.Shared/Windows_UI_Input/PointersTests/ScrollHandled.xaml

@@ -0,0 +1,63 @@
+<Page
+    x:Class="UITests.Windows_UI_Input.PointersTests.ScrollHandled"
+    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+    xmlns:local="using:UITests.Windows_UI_Input.PointersTests"
+    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
+    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
+    mc:Ignorable="d"
+    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
+
+    <Grid>
+		<ScrollViewer>
+			<StackPanel PointerWheelChanged="OnPointerWheelChanged">
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+				<Button>Test</Button>
+			</StackPanel>
+		</ScrollViewer>
+    </Grid>
+</Page>

src/SamplesApp/UITests.Shared/Windows_UI_Input/PointersTests/ScrollHandled.xaml.cs

@@ -0,0 +1,21 @@
+using Uno.UI.Samples.Controls;
+using Windows.UI.Core;
+using Windows.UI.Xaml.Controls;
+using Windows.UI.Xaml.Input;
+
+namespace UITests.Windows_UI_Input.PointersTests
+{
+    [Sample("Pointers", Description = "When scroll wheel is used while hovering above the buttons, it should not scroll. When scroll wheel is used above the page's blank area, it should scroll.")]
+    public sealed partial class ScrollHandled : Page
+    {
+        public ScrollHandled()
+        {
+            InitializeComponent();
+        }
+
+		private void OnPointerWheelChanged(object sender, PointerRoutedEventArgs args)
+		{
+			args.Handled = true;
+		}
+	}
+}

src/Uno.UI/WasmScripts/Uno.UI.js

@@ -1100,6 +1100,7 @@ var Uno;
                     var handled = this.dispatchEvent(element, eventName, eventPayload);
                     if (handled) {
                         event.stopPropagation();
+                        event.preventDefault();
                     }
                 };
                 element.addEventListener(eventName, eventHandler, onCapturePhase);

src/Uno.UI/ts/WindowManager.ts

@@ -895,6 +895,9 @@ namespace Uno.UI {
 			const handled = WindowManager.current.dispatchEvent(element, evt.type, payload);
 			if (handled) {
 				evt.stopPropagation();
+				// Not calling preventDefault() here, as that will break native focus dispatch for pointerdown
+				// If needed, we may add preventDefault() for some specific event type later, but it is not needed
+				// for any scenario yet.
 			}
 		}
 
@@ -1028,6 +1031,7 @@ namespace Uno.UI {
 				var handled = this.dispatchEvent(element, eventName, eventPayload);
 				if (handled) {
 					event.stopPropagation();
+					event.preventDefault();
 				}
 			};