Fix scrollable controls in XAML.

Perspex.Controls/Primitives/Track.cs

@@ -124,7 +124,12 @@ namespace Perspex.Controls.Primitives
                 var thumbFraction = this.ViewportSize / range;
                 var valueFraction = (this.Value - this.Minimum) / range;
 
-                if (double.IsNaN(thumbFraction) || double.IsInfinity(thumbFraction))
+                if (double.IsNaN(valueFraction) || double.IsInfinity(valueFraction))
+                {
+                    valueFraction = 0;
+                    thumbFraction = 1;
+                }
+                else if (double.IsNaN(thumbFraction) || double.IsInfinity(thumbFraction))
                 {
                     thumbFraction = 0;
                 }

Perspex.Controls/ScrollViewer.cs

@@ -41,7 +41,7 @@ namespace Perspex.Controls
             PerspexProperty.Register<ScrollViewer, double>("VerticalScrollBarViewportSize");
 
         public static readonly PerspexProperty<bool> CanScrollHorizontallyProperty =
-            PerspexProperty.RegisterAttached<ScrollViewer, Control, bool>("CanScrollHorizontally", false);
+            PerspexProperty.RegisterAttached<ScrollViewer, Control, bool>("CanScrollHorizontally", true);
 
         public static readonly PerspexProperty<ScrollBarVisibility> HorizontalScrollBarVisibilityProperty =
             PerspexProperty.RegisterAttached<ScrollBar, Control, ScrollBarVisibility>("HorizontalScrollBarVisibility", ScrollBarVisibility.Auto);

Perspex.Layout/Layoutable.cs

@@ -195,9 +195,7 @@ namespace Perspex.Layout
 
                 var desiredSize = this.MeasureCore(availableSize).Constrain(availableSize);
 
-                if (desiredSize.Width < 0 || desiredSize.Height < 0 ||
-                    double.IsInfinity(desiredSize.Width) || double.IsInfinity(desiredSize.Height) ||
-                    double.IsNaN(desiredSize.Width) || double.IsNaN(desiredSize.Height))
+                if (IsInvalidSize(desiredSize))
                 {
                     throw new InvalidOperationException("Invalid size returned for Measure.");
                 }
@@ -211,9 +209,7 @@ namespace Perspex.Layout
 
         public void Arrange(Rect rect, bool force = false)
         {
-            if (rect.Width < 0 || rect.Height < 0 ||
-                double.IsInfinity(rect.Width) || double.IsInfinity(rect.Height) ||
-                double.IsNaN(rect.Width) || double.IsNaN(rect.Height))
+            if (IsInvalidRect(rect))
             {
                 throw new InvalidOperationException("Invalid Arrange rectangle.");
             }
@@ -441,6 +437,22 @@ namespace Perspex.Layout
             return double.IsNaN(control.Width) || double.IsNaN(control.Height);
         }
 
+        private static bool IsInvalidRect(Rect rect)
+        {
+            return rect.Width < 0 || rect.Height < 0 ||
+                double.IsInfinity(rect.X) || double.IsInfinity(rect.Y) ||
+                double.IsInfinity(rect.Width) || double.IsInfinity(rect.Height) ||
+                double.IsNaN(rect.X) || double.IsNaN(rect.Y) ||
+                double.IsNaN(rect.Width) || double.IsNaN(rect.Height);
+        }
+
+        private static bool IsInvalidSize(Size size)
+        {
+            return size.Width < 0 || size.Height < 0 ||
+                double.IsInfinity(size.Width) || double.IsInfinity(size.Height) ||
+                double.IsNaN(size.Width) || double.IsNaN(size.Height);
+        }
+
         private Tuple<ILayoutRoot, int> GetLayoutRoot()
         {
             var control = (IVisual)this;

Tests/Perspex.Controls.UnitTests/Perspex.Controls.UnitTests.csproj

@@ -94,6 +94,7 @@
     <Compile Include="GlobalSuppressions.cs" />
     <Compile Include="Mixins\SelectableMixinTests.cs" />
     <Compile Include="Parsers\GridLengthsParserTests.cs" />
+    <Compile Include="Primitives\TrackTests.cs" />
     <Compile Include="Primitives\PopupTests.cs" />
     <Compile Include="DropDownTests.cs" />
     <Compile Include="Presenters\DeckPresenterTests.cs" />

Tests/Perspex.Controls.UnitTests/Primitives/TrackTests.cs

@@ -0,0 +1,134 @@
+// -----------------------------------------------------------------------
+// <copyright file="TrackTests.cs" company="Steven Kirk">
+// Copyright 2015 MIT Licence. See licence.md for more information.
+// </copyright>
+// -----------------------------------------------------------------------
+
+namespace Perspex.Controls.UnitTests.Primitives
+{
+    using System;
+    using System.Collections.Specialized;
+    using System.Linq;
+    using Layout;
+    using Moq;
+    using Perspex.Controls.Presenters;
+    using Perspex.Controls.Primitives;
+    using Perspex.LogicalTree;
+    using Perspex.Platform;
+    using Perspex.Styling;
+    using Perspex.VisualTree;
+    using Splat;
+    using Templates;
+    using Xunit;
+
+    public class TrackTests
+    {
+        [Fact]
+        public void Measure_Should_Return_Thumb_DesiredWidth_In_Vertical_Orientation()
+        {
+            var thumb = new Thumb
+            {
+                Width = 12,
+            };
+
+            var target = new Track
+            {
+                Thumb = thumb,
+                Orientation = Orientation.Vertical,
+            };
+
+            target.Measure(new Size(100, 100));
+
+            Assert.Equal(new Size(12, 0), target.DesiredSize);
+        }
+
+        [Fact]
+        public void Measure_Should_Return_Thumb_DesiredHeight_In_Horizontal_Orientation()
+        {
+            var thumb = new Thumb
+            {
+                Height = 12,
+            };
+
+            var target = new Track
+            {
+                Thumb = thumb,
+                Orientation = Orientation.Horizontal,
+            };
+
+            target.Measure(new Size(100, 100));
+
+            Assert.Equal(new Size(0, 12), target.DesiredSize);
+        }
+
+        [Fact]
+        public void Should_Arrange_Thumb_In_Horizontal_Orientation()
+        {
+            var thumb = new Thumb
+            {
+                Height = 12,
+            };
+
+            var target = new Track
+            {
+                Thumb = thumb,
+                Orientation = Orientation.Horizontal,
+                Minimum = 100,
+                Maximum = 200,
+                Value = 150,
+                ViewportSize = 50,
+            };
+
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+
+            Assert.Equal(new Rect(25, 0, 50, 12), thumb.Bounds);
+        }
+
+        [Fact]
+        public void Should_Arrange_Thumb_In_Vertical_Orientation()
+        {
+            var thumb = new Thumb
+            {
+                Width = 12,
+            };
+
+            var target = new Track
+            {
+                Thumb = thumb,
+                Orientation = Orientation.Vertical,
+                Minimum = 100,
+                Maximum = 300,
+                Value = 150,
+                ViewportSize = 50,
+            };
+
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+
+            Assert.Equal(new Rect(0, 18, 12, 25), thumb.Bounds);
+        }
+
+        [Fact]
+        public void Thumb_Should_Fill_Track_When_Minimum_Equals_Maximum()
+        {
+            var thumb = new Thumb
+            {
+                Height = 12,
+            };
+
+            var target = new Track
+            {
+                Thumb = thumb,
+                Orientation = Orientation.Horizontal,
+                Minimum = 100,
+                Maximum = 100,
+            };
+
+            target.Measure(new Size(100, 100));
+            target.Arrange(new Rect(0, 0, 100, 100));
+
+            Assert.Equal(new Rect(0, 0, 100, 12), thumb.Bounds);
+        }
+    }
+}