Make ScrollViewer handle child margin.

src/Perspex.Controls/Presenters/ScrollContentPresenter.cs

@@ -98,37 +98,50 @@ namespace Perspex.Controls.Presenters
         /// <returns>True if the scroll offset was changed; otherwise false.</returns>
         public bool BringDescendentIntoView(IVisual target, Rect targetRect)
         {
-            var transform = target.TransformToVisual(this.GetVisualChildren().Single());
-            var rect = targetRect * transform;
-            var offset = Offset;
-            var result = false;
-
-            if (rect.Bottom > offset.Y + Viewport.Height)
+            if (Child != null)
             {
-                offset = offset.WithY(rect.Bottom - Viewport.Height);
-                result = true;
-            }
+                var transform = target.TransformToVisual(Child);
+                var rect = targetRect * transform;
+                var offset = Offset;
+                var result = false;
 
-            if (rect.Y < offset.Y)
-            {
-                offset = offset.WithY(rect.Y);
-                result = true;
-            }
+                if (rect.Bottom > offset.Y + Viewport.Height)
+                {
+                    offset = offset.WithY((rect.Bottom - Viewport.Height) + Child.Margin.Top);
+                    result = true;
+                }
 
-            if (rect.Right > offset.X + Viewport.Width)
-            {
-                offset = offset.WithX(rect.Right - Viewport.Width);
-                result = true;
-            }
+                if (rect.Y < offset.Y)
+                {
+                    offset = offset.WithY(rect.Y);
+                    result = true;
+                }
 
-            if (rect.X < offset.X)
+                if (rect.Right > offset.X + Viewport.Width)
+                {
+                    offset = offset.WithX((rect.Right - Viewport.Width) + Child.Margin.Left);
+                    result = true;
+                }
+
+                if (rect.X < offset.X)
+                {
+                    offset = offset.WithX(rect.X);
+                    result = true;
+                }
+
+                if (result)
+                {
+                    Offset = offset;
+                }
+
+                System.Diagnostics.Debug.WriteLine($"{targetRect} {offset}");
+
+                return result;
+            }
+            else
             {
-                offset = offset.WithX(rect.X);
-                result = true;
+                return false;
             }
-
-            Offset = offset;
-            return result;
         }
 
         /// <inheritdoc/>

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

@@ -190,7 +190,7 @@ namespace Perspex.Controls.UnitTests.Presenters
         }
 
         [Fact]
-        public void BringDescendentIntoView_Should_Work()
+        public void BringDescendentIntoView_Should_Update_Offset()
         {
             var target = new ScrollContentPresenter
             {
@@ -211,6 +211,33 @@ namespace Perspex.Controls.UnitTests.Presenters
             Assert.Equal(new Vector(100, 100), target.Offset);
         }
 
+        [Fact]
+        public void BringDescendentIntoView_Should_Handle_Child_Margin()
+        {
+            Border border;
+            var target = new ScrollContentPresenter
+            {
+                Width = 100,
+                Height = 100,
+                Content = new Decorator
+                {
+                    Margin = new Thickness(50),
+                    Child = border = new Border
+                    {
+                        Width = 200,
+                        Height = 200,
+                    }
+                }
+            };
+
+            target.ApplyTemplate();
+            target.Measure(Size.Infinity);
+            target.Arrange(new Rect(0, 0, 100, 100));
+            target.BringDescendentIntoView(border, new Rect(200, 200, 0, 0));
+
+            Assert.Equal(new Vector(150, 150), target.Offset);
+        }
+
         private class TestControl : Control
         {
             protected override Size MeasureOverride(Size availableSize)