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/ButtonHandler.cs

@@ -0,0 +1,161 @@
+// 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 Button on Linux using Skia rendering.
+/// Maps IButton interface to SkiaButton platform view.
+/// </summary>
+public partial class ButtonHandler : ViewHandler<IButton, SkiaButton>
+{
+    public static IPropertyMapper<IButton, ButtonHandler> Mapper = new PropertyMapper<IButton, ButtonHandler>(ViewHandler.ViewMapper)
+    {
+        [nameof(IButtonStroke.StrokeColor)] = MapStrokeColor,
+        [nameof(IButtonStroke.StrokeThickness)] = MapStrokeThickness,
+        [nameof(IButtonStroke.CornerRadius)] = MapCornerRadius,
+        [nameof(IView.Background)] = MapBackground,
+        [nameof(IPadding.Padding)] = MapPadding,
+    };
+
+    public static CommandMapper<IButton, ButtonHandler> CommandMapper = new(ViewHandler.ViewCommandMapper)
+    {
+    };
+
+    public ButtonHandler() : base(Mapper, CommandMapper)
+    {
+    }
+
+    public ButtonHandler(IPropertyMapper? mapper, CommandMapper? commandMapper = null)
+        : base(mapper ?? Mapper, commandMapper ?? CommandMapper)
+    {
+    }
+
+    protected override SkiaButton CreatePlatformView()
+    {
+        var button = new SkiaButton();
+        return button;
+    }
+
+    protected override void ConnectHandler(SkiaButton platformView)
+    {
+        base.ConnectHandler(platformView);
+        platformView.Clicked += OnClicked;
+        platformView.Pressed += OnPressed;
+        platformView.Released += OnReleased;
+    }
+
+    protected override void DisconnectHandler(SkiaButton platformView)
+    {
+        platformView.Clicked -= OnClicked;
+        platformView.Pressed -= OnPressed;
+        platformView.Released -= OnReleased;
+        base.DisconnectHandler(platformView);
+    }
+
+    private void OnClicked(object? sender, EventArgs e) => VirtualView?.Clicked();
+    private void OnPressed(object? sender, EventArgs e) => VirtualView?.Pressed();
+    private void OnReleased(object? sender, EventArgs e) => VirtualView?.Released();
+
+    public static void MapStrokeColor(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+
+        var strokeColor = button.StrokeColor;
+        if (strokeColor is not null)
+            handler.PlatformView.BorderColor = strokeColor.ToSKColor();
+    }
+
+    public static void MapStrokeThickness(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.BorderWidth = (float)button.StrokeThickness;
+    }
+
+    public static void MapCornerRadius(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.CornerRadius = button.CornerRadius;
+    }
+
+    public static void MapBackground(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+
+        if (button.Background is SolidPaint solidPaint && solidPaint.Color is not null)
+        {
+            handler.PlatformView.BackgroundColor = solidPaint.Color.ToSKColor();
+        }
+    }
+
+    public static void MapPadding(ButtonHandler handler, IButton button)
+    {
+        if (handler.PlatformView is null) return;
+
+        var padding = button.Padding;
+        handler.PlatformView.Padding = new SKRect(
+            (float)padding.Left,
+            (float)padding.Top,
+            (float)padding.Right,
+            (float)padding.Bottom);
+    }
+}
+
+/// <summary>
+/// Handler for TextButton on Linux - extends ButtonHandler with text support.
+/// Maps ITextButton interface (which includes IText properties).
+/// </summary>
+public partial class TextButtonHandler : ButtonHandler
+{
+    public static new IPropertyMapper<ITextButton, TextButtonHandler> Mapper =
+        new PropertyMapper<ITextButton, TextButtonHandler>(ButtonHandler.Mapper)
+    {
+        [nameof(IText.Text)] = MapText,
+        [nameof(ITextStyle.TextColor)] = MapTextColor,
+        [nameof(ITextStyle.Font)] = MapFont,
+        [nameof(ITextStyle.CharacterSpacing)] = MapCharacterSpacing,
+    };
+
+    public TextButtonHandler() : base(Mapper)
+    {
+    }
+
+    public static void MapText(TextButtonHandler handler, ITextButton button)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.Text = button.Text ?? string.Empty;
+    }
+
+    public static void MapTextColor(TextButtonHandler handler, ITextButton button)
+    {
+        if (handler.PlatformView is null) return;
+
+        if (button.TextColor is not null)
+            handler.PlatformView.TextColor = button.TextColor.ToSKColor();
+    }
+
+    public static void MapFont(TextButtonHandler handler, ITextButton button)
+    {
+        if (handler.PlatformView is null) return;
+
+        var font = button.Font;
+        if (font.Size > 0)
+            handler.PlatformView.FontSize = (float)font.Size;
+
+        if (!string.IsNullOrEmpty(font.Family))
+            handler.PlatformView.FontFamily = font.Family;
+
+        handler.PlatformView.IsBold = font.Weight >= FontWeight.Bold;
+        handler.PlatformView.IsItalic = font.Slant == FontSlant.Italic || font.Slant == FontSlant.Oblique;
+    }
+
+    public static void MapCharacterSpacing(TextButtonHandler handler, ITextButton button)
+    {
+        if (handler.PlatformView is null) return;
+        handler.PlatformView.CharacterSpacing = (float)button.CharacterSpacing;
+    }
+}