Preview 3: Complete control implementation with XAML data binding

Major milestone adding full control functionality:

Controls Enhanced:
- Entry/Editor: Full keyboard input, cursor navigation, selection, clipboard
- CollectionView: Data binding, selection highlighting, scrolling
- CheckBox/Switch/Slider: Interactive state management
- Picker/DatePicker/TimePicker: Dropdown selection with popup overlays
- ProgressBar/ActivityIndicator: Animated progress display
- Button: Press/release visual states
- Border/Frame: Rounded corners, stroke styling
- Label: Text wrapping, alignment, decorations
- Grid/StackLayout: Margin and padding support

Features Added:
- DisplayAlert dialogs with button actions
- NavigationPage with toolbar and back navigation
- Shell with flyout menu navigation
- XAML value converters for data binding
- Margin support in all layout containers
- Popup overlay system for pickers

New Samples:
- TodoApp: Full CRUD task manager with NavigationPage
- ShellDemo: Comprehensive control showcase

Removed:
- ControlGallery (replaced by ShellDemo)
- LinuxDemo (replaced by TodoApp)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Handlers/ScrollViewHandler.cs

@@ -0,0 +1,109 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using Microsoft.Maui.Handlers;
+
+namespace Microsoft.Maui.Platform.Linux.Handlers;
+
+/// <summary>
+/// Handler for ScrollView on Linux using SkiaScrollView.
+/// </summary>
+public partial class ScrollViewHandler : ViewHandler<IScrollView, SkiaScrollView>
+{
+    public static IPropertyMapper<IScrollView, ScrollViewHandler> Mapper =
+        new PropertyMapper<IScrollView, ScrollViewHandler>(ViewMapper)
+        {
+            [nameof(IScrollView.Content)] = MapContent,
+            [nameof(IScrollView.HorizontalScrollBarVisibility)] = MapHorizontalScrollBarVisibility,
+            [nameof(IScrollView.VerticalScrollBarVisibility)] = MapVerticalScrollBarVisibility,
+            [nameof(IScrollView.Orientation)] = MapOrientation,
+        };
+
+    public static CommandMapper<IScrollView, ScrollViewHandler> CommandMapper =
+        new(ViewCommandMapper)
+        {
+            [nameof(IScrollView.RequestScrollTo)] = MapRequestScrollTo
+        };
+
+    public ScrollViewHandler() : base(Mapper, CommandMapper)
+    {
+    }
+
+    public ScrollViewHandler(IPropertyMapper? mapper)
+        : base(mapper ?? Mapper, CommandMapper)
+    {
+    }
+
+    protected override SkiaScrollView CreatePlatformView()
+    {
+        return new SkiaScrollView();
+    }
+
+    public static void MapContent(ScrollViewHandler handler, IScrollView scrollView)
+    {
+        if (handler.PlatformView == null || handler.MauiContext == null)
+            return;
+
+        var content = scrollView.PresentedContent;
+        if (content != null)
+        {
+            Console.WriteLine($"[ScrollViewHandler] MapContent: {content.GetType().Name}");
+
+            // Create handler for content if it doesn't exist
+            if (content.Handler == null)
+            {
+                content.Handler = content.ToHandler(handler.MauiContext);
+            }
+
+            if (content.Handler?.PlatformView is SkiaView skiaContent)
+            {
+                Console.WriteLine($"[ScrollViewHandler] Setting content: {skiaContent.GetType().Name}");
+                handler.PlatformView.Content = skiaContent;
+            }
+        }
+        else
+        {
+            handler.PlatformView.Content = null;
+        }
+    }
+
+    public static void MapHorizontalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView)
+    {
+        handler.PlatformView.HorizontalScrollBarVisibility = scrollView.HorizontalScrollBarVisibility switch
+        {
+            Microsoft.Maui.ScrollBarVisibility.Always => ScrollBarVisibility.Always,
+            Microsoft.Maui.ScrollBarVisibility.Never => ScrollBarVisibility.Never,
+            _ => ScrollBarVisibility.Default
+        };
+    }
+
+    public static void MapVerticalScrollBarVisibility(ScrollViewHandler handler, IScrollView scrollView)
+    {
+        handler.PlatformView.VerticalScrollBarVisibility = scrollView.VerticalScrollBarVisibility switch
+        {
+            Microsoft.Maui.ScrollBarVisibility.Always => ScrollBarVisibility.Always,
+            Microsoft.Maui.ScrollBarVisibility.Never => ScrollBarVisibility.Never,
+            _ => ScrollBarVisibility.Default
+        };
+    }
+
+    public static void MapOrientation(ScrollViewHandler handler, IScrollView scrollView)
+    {
+        handler.PlatformView.Orientation = scrollView.Orientation switch
+        {
+            Microsoft.Maui.ScrollOrientation.Horizontal => ScrollOrientation.Horizontal,
+            Microsoft.Maui.ScrollOrientation.Both => ScrollOrientation.Both,
+            Microsoft.Maui.ScrollOrientation.Neither => ScrollOrientation.Neither,
+            _ => ScrollOrientation.Vertical
+        };
+    }
+
+    public static void MapRequestScrollTo(ScrollViewHandler handler, IScrollView scrollView, object? args)
+    {
+        if (args is ScrollToRequest request)
+        {
+            // Instant means no animation, so we pass !Instant for animated parameter
+            handler.PlatformView.ScrollTo((float)request.HorizontalOffset, (float)request.VerticalOffset, !request.Instant);
+        }
+    }
+}