Initial commit: .NET MAUI Linux Platform

Complete Linux platform implementation for .NET MAUI with:

- 35+ Skia-rendered controls (Button, Label, Entry, CarouselView, etc.)
- Platform services (Clipboard, FilePicker, Notifications, DragDrop, etc.)
- Accessibility support (AT-SPI2, High Contrast)
- HiDPI and Input Method support
- 216 unit tests
- CI/CD workflows
- Project templates
- Documentation

🤖 Generated with Claude Code

Handlers/SliderHandler.cs

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+// 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;
+using Microsoft.Maui.Graphics;
+using SkiaSharp;
+
+namespace Microsoft.Maui.Platform.Linux.Handlers;
+
+/// <summary>
+/// Handler for Slider on Linux using Skia rendering.
+/// Maps ISlider interface to SkiaSlider platform view.
+/// </summary>
+public partial class SliderHandler : ViewHandler<ISlider, SkiaSlider>
+{
+    public static IPropertyMapper<ISlider, SliderHandler> Mapper = new PropertyMapper<ISlider, SliderHandler>(ViewHandler.ViewMapper)
+    {
+        [nameof(IRange.Minimum)] = MapMinimum,
+        [nameof(IRange.Maximum)] = MapMaximum,
+        [nameof(IRange.Value)] = MapValue,
+        [nameof(ISlider.MinimumTrackColor)] = MapMinimumTrackColor,
+        [nameof(ISlider.MaximumTrackColor)] = MapMaximumTrackColor,
+        [nameof(ISlider.ThumbColor)] = MapThumbColor,
+        [nameof(IView.Background)] = MapBackground,
+    };
+
+    public static CommandMapper<ISlider, SliderHandler> CommandMapper = new(ViewHandler.ViewCommandMapper)
+    {
+    };
+
+    public SliderHandler() : base(Mapper, CommandMapper)
+    {
+    }
+
+    public SliderHandler(IPropertyMapper? mapper, CommandMapper? commandMapper = null)
+        : base(mapper ?? Mapper, commandMapper ?? CommandMapper)
+    {
+    }
+
+    protected override SkiaSlider CreatePlatformView()
+    {
+        return new SkiaSlider();
+    }
+
+    protected override void ConnectHandler(SkiaSlider platformView)
+    {
+        base.ConnectHandler(platformView);
+        platformView.ValueChanged += OnValueChanged;
+        platformView.DragStarted += OnDragStarted;
+        platformView.DragCompleted += OnDragCompleted;
+    }
+
+    protected override void DisconnectHandler(SkiaSlider platformView)
+    {
+        platformView.ValueChanged -= OnValueChanged;
+        platformView.DragStarted -= OnDragStarted;
+        platformView.DragCompleted -= OnDragCompleted;
+        base.DisconnectHandler(platformView);
+    }
+
+    private void OnValueChanged(object? sender, SliderValueChangedEventArgs e)
+    {
+        if (VirtualView is null || PlatformView is null) return;
+
+        if (Math.Abs(VirtualView.Value - e.NewValue) > 0.0001)
+        {
+            VirtualView.Value = e.NewValue;
+        }
+    }
+
+    private void OnDragStarted(object? sender, EventArgs e)
+    {
+        VirtualView?.DragStarted();
+    }
+
+    private void OnDragCompleted(object? sender, EventArgs e)
+    {
+        VirtualView?.DragCompleted();
+    }
+
+    public static void MapMinimum(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.Minimum = slider.Minimum;
+    }
+
+    public static void MapMaximum(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.Maximum = slider.Maximum;
+    }
+
+    public static void MapValue(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+
+        if (Math.Abs(handler.PlatformView.Value - slider.Value) > 0.0001)
+            handler.PlatformView.Value = slider.Value;
+    }
+
+    public static void MapMinimumTrackColor(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+
+        // MinimumTrackColor maps to ActiveTrackColor (the filled portion)
+        if (slider.MinimumTrackColor is not null)
+            handler.PlatformView.ActiveTrackColor = slider.MinimumTrackColor.ToSKColor();
+    }
+
+    public static void MapMaximumTrackColor(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+
+        // MaximumTrackColor maps to TrackColor (the unfilled portion)
+        if (slider.MaximumTrackColor is not null)
+            handler.PlatformView.TrackColor = slider.MaximumTrackColor.ToSKColor();
+    }
+
+    public static void MapThumbColor(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+
+        if (slider.ThumbColor is not null)
+            handler.PlatformView.ThumbColor = slider.ThumbColor.ToSKColor();
+    }
+
+    public static void MapBackground(SliderHandler handler, ISlider slider)
+    {
+        if (handler.PlatformView is null) return;
+
+        if (slider.Background is SolidPaint solidPaint && solidPaint.Color is not null)
+        {
+            handler.PlatformView.BackgroundColor = solidPaint.Color.ToSKColor();
+        }
+    }
+}