From 7b3352687c313950f53e567b7c36a8da15c57a5f Mon Sep 17 00:00:00 2001
From: Tim <tim.uniewski@gmail.com>
Date: Mon, 8 Aug 2022 11:24:12 +0200
Subject: [PATCH] Backport PR 7778

---
 .../SceneGraph/GeometryBoundsHelper.cs        | 31 +++++++++++++++++++
 .../Rendering/SceneGraph/GeometryNode.cs      |  2 +-
 2 files changed, 32 insertions(+), 1 deletion(-)
 create mode 100644 src/Avalonia.Visuals/Rendering/SceneGraph/GeometryBoundsHelper.cs

diff --git a/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryBoundsHelper.cs b/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryBoundsHelper.cs
new file mode 100644
index 00000000000..b3a91008502
--- /dev/null
+++ b/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryBoundsHelper.cs
@@ -0,0 +1,31 @@
+using System;
+using Avalonia.Media;
+using Avalonia.Utilities;
+
+namespace Avalonia.Rendering.SceneGraph;
+
+internal static class GeometryBoundsHelper
+{
+    /// <summary>
+    /// Calculates the bounds of a given geometry with respect to the pens <see cref="IPen.LineCap"/>
+    /// </summary>
+    /// <param name="originalBounds">The calculated bounds without <see cref="IPen.LineCap"/>s</param>
+    /// <param name="pen">The pen with information about the <see cref="IPen.LineCap"/>s</param>
+    /// <returns></returns>
+    public static Rect CalculateBoundsWithLineCaps(this Rect originalBounds, IPen? pen)
+    {
+        if (pen is null || MathUtilities.IsZero(pen.Thickness)) return originalBounds;
+
+        switch (pen.LineCap)
+        {
+            case PenLineCap.Flat:
+                return originalBounds;
+            case PenLineCap.Round:
+                return originalBounds.Inflate(pen.Thickness / 2);
+            case PenLineCap.Square:
+                return originalBounds.Inflate(pen.Thickness);
+            default:
+                throw new ArgumentOutOfRangeException();
+        }
+    }
+}
diff --git a/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryNode.cs b/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryNode.cs
index 508ca0ad183..378a4cdd201 100644
--- a/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryNode.cs
+++ b/src/Avalonia.Visuals/Rendering/SceneGraph/GeometryNode.cs
@@ -24,7 +24,7 @@ public GeometryNode(Matrix transform,
             IPen pen,
             IGeometryImpl geometry,
             IDictionary<IVisual, Scene> childScenes = null)
-            : base(geometry.GetRenderBounds(pen), transform)
+            : base(geometry.GetRenderBounds(pen).CalculateBoundsWithLineCaps(pen), transform)
         {
             Transform = transform;
             Brush = brush?.ToImmutable();