Added test for SCV.BringDescendentIntoView

src/Perspex.SceneGraph/Visual.cs

@@ -307,8 +307,9 @@ namespace Perspex
         /// <returns>A <see cref="Matrix"/> containing the transform.</returns>
         public Matrix TransformToVisual(IVisual visual)
         {
-            var thisOffset = GetOffsetFromRoot(this).Item2;
-            var thatOffset = GetOffsetFromRoot(visual).Item2;
+            var common = this.FindCommonVisualAncestor(visual);
+            var thisOffset = GetOffsetFrom(common, this);
+            var thatOffset = GetOffsetFrom(common, visual);
             return Matrix.CreateTranslation(-thatOffset) * Matrix.CreateTranslation(thisOffset);
         }
 
@@ -468,6 +469,30 @@ namespace Perspex
             }
         }
 
+        /// <summary>
+        /// Gets the visual offset from the specified ancestor.
+        /// </summary>
+        /// <param name="ancestor">The ancestor visual.</param>
+        /// <param name="visual">The visual.</param>
+        /// <returns>The visual offset.</returns>
+        private static Vector GetOffsetFrom(IVisual ancestor, IVisual visual)
+        {
+            var result = new Vector();
+
+            while (visual != ancestor)
+            {
+                result = new Vector(result.X + visual.Bounds.X, result.Y + visual.Bounds.Y);
+                visual = visual.VisualParent;
+
+                if (visual == null)
+                {
+                    throw new ArgumentException("'visual' is not a descendent of 'ancestor'.");
+                }
+            }
+
+            return result;
+        }
+
         /// <summary>
         /// Gets the root of the controls visual tree and the distance from the root.
         /// </summary>

src/Perspex.SceneGraph/VisualTree/VisualExtensions.cs

@@ -8,10 +8,22 @@ using System.Linq;
 namespace Perspex.VisualTree
 {
     /// <summary>
-    /// Provides extension methods for working with visual tree.
+    /// Provides extension methods for working with the visual tree.
     /// </summary>
     public static class VisualExtensions
     {
+        /// <summary>
+        /// Tries to get the first common ancestor of two visuals.
+        /// </summary>
+        /// <param name="visual">The first visual.</param>
+        /// <param name="target">The second visual.</param>
+        /// <returns>The common ancestor, or null if not found.</returns>
+        public static IVisual FindCommonVisualAncestor(this IVisual visual, IVisual target)
+        {
+            return visual.GetSelfAndVisualAncestors().Intersect(target.GetSelfAndVisualAncestors())
+                .FirstOrDefault();
+        }
+
         /// <summary>
         /// Enumerates the ancestors of an <see cref="IVisual"/> in the visual tree.
         /// </summary>

tests/Perspex.Controls.UnitTests/Presenters/ScrollContentPresenterTests.cs

@@ -189,6 +189,28 @@ namespace Perspex.Controls.UnitTests.Presenters
             Assert.Equal(new Vector(10, 10), target.Offset);
         }
 
+        [Fact]
+        public void BringDescendentIntoView_Should_Work()
+        {
+            var target = new ScrollContentPresenter
+            {
+                Width = 100,
+                Height = 100,
+                Content = new Border
+                {
+                    Width = 200,
+                    Height = 200,
+                }
+            };
+
+            target.ApplyTemplate();
+            target.Measure(Size.Infinity);
+            target.Arrange(new Rect(0, 0, 100, 100));
+            target.BringDescendentIntoView(target.Child, new Rect(200, 200, 0, 0));
+
+            Assert.Equal(new Vector(100, 100), target.Offset);
+        }
+
         private class TestControl : Control
         {
             protected override Size MeasureOverride(Size availableSize)