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

Views/SkiaBorder.cs

@@ -0,0 +1,200 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using SkiaSharp;
+
+namespace Microsoft.Maui.Platform;
+
+/// <summary>
+/// Skia-rendered border/frame container control.
+/// </summary>
+public class SkiaBorder : SkiaLayoutView
+{
+    private float _strokeThickness = 1;
+    private float _cornerRadius = 0;
+    private SKColor _stroke = SKColors.Black;
+    private float _paddingLeft = 0;
+    private float _paddingTop = 0;
+    private float _paddingRight = 0;
+    private float _paddingBottom = 0;
+    private bool _hasShadow;
+
+    public float StrokeThickness
+    {
+        get => _strokeThickness;
+        set { _strokeThickness = value; Invalidate(); }
+    }
+
+    public float CornerRadius
+    {
+        get => _cornerRadius;
+        set { _cornerRadius = value; Invalidate(); }
+    }
+
+    public SKColor Stroke
+    {
+        get => _stroke;
+        set { _stroke = value; Invalidate(); }
+    }
+
+    public float PaddingLeft
+    {
+        get => _paddingLeft;
+        set { _paddingLeft = value; InvalidateMeasure(); }
+    }
+
+    public float PaddingTop
+    {
+        get => _paddingTop;
+        set { _paddingTop = value; InvalidateMeasure(); }
+    }
+
+    public float PaddingRight
+    {
+        get => _paddingRight;
+        set { _paddingRight = value; InvalidateMeasure(); }
+    }
+
+    public float PaddingBottom
+    {
+        get => _paddingBottom;
+        set { _paddingBottom = value; InvalidateMeasure(); }
+    }
+
+    public bool HasShadow
+    {
+        get => _hasShadow;
+        set { _hasShadow = value; Invalidate(); }
+    }
+
+    public void SetPadding(float all)
+    {
+        _paddingLeft = _paddingTop = _paddingRight = _paddingBottom = all;
+        InvalidateMeasure();
+    }
+
+    public void SetPadding(float horizontal, float vertical)
+    {
+        _paddingLeft = _paddingRight = horizontal;
+        _paddingTop = _paddingBottom = vertical;
+        InvalidateMeasure();
+    }
+
+    protected override void OnDraw(SKCanvas canvas, SKRect bounds)
+    {
+        var borderRect = new SKRect(
+            bounds.Left + _strokeThickness / 2,
+            bounds.Top + _strokeThickness / 2,
+            bounds.Right - _strokeThickness / 2,
+            bounds.Bottom - _strokeThickness / 2);
+
+        // Draw shadow if enabled
+        if (_hasShadow)
+        {
+            using var shadowPaint = new SKPaint
+            {
+                Color = new SKColor(0, 0, 0, 40),
+                MaskFilter = SKMaskFilter.CreateBlur(SKBlurStyle.Normal, 4),
+                Style = SKPaintStyle.Fill
+            };
+            var shadowRect = new SKRect(borderRect.Left + 2, borderRect.Top + 2, borderRect.Right + 2, borderRect.Bottom + 2);
+            canvas.DrawRoundRect(new SKRoundRect(shadowRect, _cornerRadius), shadowPaint);
+        }
+
+        // Draw background
+        using var bgPaint = new SKPaint
+        {
+            Color = BackgroundColor,
+            Style = SKPaintStyle.Fill,
+            IsAntialias = true
+        };
+        canvas.DrawRoundRect(new SKRoundRect(borderRect, _cornerRadius), bgPaint);
+
+        // Draw border
+        if (_strokeThickness > 0)
+        {
+            using var borderPaint = new SKPaint
+            {
+                Color = _stroke,
+                Style = SKPaintStyle.Stroke,
+                StrokeWidth = _strokeThickness,
+                IsAntialias = true
+            };
+            canvas.DrawRoundRect(new SKRoundRect(borderRect, _cornerRadius), borderPaint);
+        }
+
+        // Draw children (call base which draws children)
+        foreach (var child in Children)
+        {
+            if (child.IsVisible)
+            {
+                child.Draw(canvas);
+            }
+        }
+    }
+
+    protected override SKRect GetContentBounds()
+    {
+        return GetContentBounds(Bounds);
+    }
+
+    protected new SKRect GetContentBounds(SKRect bounds)
+    {
+        return new SKRect(
+            bounds.Left + _paddingLeft + _strokeThickness,
+            bounds.Top + _paddingTop + _strokeThickness,
+            bounds.Right - _paddingRight - _strokeThickness,
+            bounds.Bottom - _paddingBottom - _strokeThickness);
+    }
+
+    protected override SKSize MeasureOverride(SKSize availableSize)
+    {
+        var paddingWidth = _paddingLeft + _paddingRight + _strokeThickness * 2;
+        var paddingHeight = _paddingTop + _paddingBottom + _strokeThickness * 2;
+
+        var childAvailable = new SKSize(
+            availableSize.Width - paddingWidth,
+            availableSize.Height - paddingHeight);
+
+        var maxChildSize = SKSize.Empty;
+
+        foreach (var child in Children)
+        {
+            var childSize = child.Measure(childAvailable);
+            maxChildSize = new SKSize(
+                Math.Max(maxChildSize.Width, childSize.Width),
+                Math.Max(maxChildSize.Height, childSize.Height));
+        }
+
+        return new SKSize(
+            maxChildSize.Width + paddingWidth,
+            maxChildSize.Height + paddingHeight);
+    }
+
+    protected override SKRect ArrangeOverride(SKRect bounds)
+    {
+        
+        var contentBounds = GetContentBounds(bounds);
+
+        foreach (var child in Children)
+        {
+            child.Arrange(contentBounds);
+        }
+
+        return bounds;
+    }
+}
+
+/// <summary>
+/// Frame control (alias for Border with shadow enabled).
+/// </summary>
+public class SkiaFrame : SkiaBorder
+{
+    public SkiaFrame()
+    {
+        HasShadow = true;
+        CornerRadius = 4;
+        SetPadding(10);
+        BackgroundColor = SKColors.White;
+    }
+}