Merge branch 'feature/ImageScaleMode' of https://github.com/Gillibald/Avalonia into feature/ImageScaleMode

src/Avalonia.Base/AvaloniaObject.cs

@@ -22,7 +22,7 @@ namespace Avalonia
     /// <remarks>
     /// This class is analogous to DependencyObject in WPF.
     /// </remarks>
-    public class AvaloniaObject : IAvaloniaObject, IAvaloniaObjectDebug, INotifyPropertyChanged, IPriorityValueOwner
+    public class AvaloniaObject : IAvaloniaObject, IAvaloniaObjectDebug, INotifyPropertyChanged
     {
         /// <summary>
         /// The parent object that inherited values are inherited from.
@@ -45,21 +45,8 @@ namespace Avalonia
         /// </summary>
         private EventHandler<AvaloniaPropertyChangedEventArgs> _propertyChanged;
 
-        private DeferredSetter<AvaloniaProperty, object> _directDeferredSetter;
         private ValueStore _values;
-
+        private ValueStore Values => _values ?? (_values = new ValueStore(this));
-        /// <summary>
-        /// Delayed setter helper for direct properties. Used to fix #855.
-        /// </summary>
-        private DeferredSetter<AvaloniaProperty, object> DirectPropertyDeferredSetter
-        {
-            get
-            {
-                return _directDeferredSetter ??
-                    (_directDeferredSetter = new DeferredSetter<AvaloniaProperty, object>());
-            }
-        }
-
 
         /// <summary>
         /// Initializes a new instance of the <see cref="AvaloniaObject"/> class.
@@ -225,7 +212,7 @@ namespace Avalonia
             }
             else if (_values != null)
             {
-                var result = _values.GetValue(property);
+                var result = Values.GetValue(property);
 
                 if (result == AvaloniaProperty.UnsetValue)
                 {
@@ -376,12 +363,7 @@ namespace Avalonia
                     description,
                     priority);
 
-                if (_values == null)
+                return Values.AddBinding(property, source, priority);
-                {
-                    _values = new ValueStore(this);
-                }
-
-                return _values.AddBinding(property, source, priority);
             }
         }
 
@@ -414,9 +396,8 @@ namespace Avalonia
             VerifyAccess();
             _values?.Revalidate(property);
         }
-
+        
-        /// <inheritdoc/>
+        internal void PriorityValueChanged(AvaloniaProperty property, int priority, object oldValue, object newValue)
-        void IPriorityValueOwner.Changed(AvaloniaProperty property, int priority, object oldValue, object newValue)
         {
             oldValue = (oldValue == AvaloniaProperty.UnsetValue) ?
                 GetDefaultValue(property) :
@@ -439,9 +420,8 @@ namespace Avalonia
                     (BindingPriority)priority);
             }
         }
-
+        
-        /// <inheritdoc/>
+        internal void BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
-        void IPriorityValueOwner.BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
         {
             UpdateDataValidation(property, notification);
         }
@@ -456,7 +436,7 @@ namespace Avalonia
         /// Gets all priority values set on the object.
         /// </summary>
         /// <returns>A collection of property/value tuples.</returns>
-        internal IDictionary<AvaloniaProperty, PriorityValue> GetSetValues() => _values?.GetSetValues();
+        internal IDictionary<AvaloniaProperty, PriorityValue> GetSetValues() => Values?.GetSetValues();
 
         /// <summary>
         /// Forces revalidation of properties when a property value changes.
@@ -566,12 +546,12 @@ namespace Avalonia
             T value)
         {
             Contract.Requires<ArgumentNullException>(setterCallback != null);
-            return DirectPropertyDeferredSetter.SetAndNotify(
+            return Values.Setter.SetAndNotify(
                 property,
                 ref field,
-                (object val, ref T backing, Action<Action> notify) =>
+                (object update, ref T backing, Action<Action> notify) =>
                 {
-                    setterCallback((T)val, ref backing, notify);
+                    setterCallback((T)update, ref backing, notify);
                     return true;
                 },
                 value);
@@ -737,13 +717,8 @@ namespace Avalonia
                     originalValue?.GetType().FullName ?? "(null)"));
             }
 
-            if (_values == null)
-            {
-                _values = new ValueStore(this);
-            }
-
             LogPropertySet(property, value, priority);
-            _values.AddValue(property, value, (int)priority);
+            Values.AddValue(property, value, (int)priority);
         }
 
         /// <summary>

src/Avalonia.Base/IPriorityValueOwner.cs

@@ -2,6 +2,7 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using Avalonia.Data;
+using Avalonia.Utilities;
 
 namespace Avalonia
 {
@@ -31,5 +32,7 @@ namespace Avalonia
         /// Ensures that the current thread is the UI thread.
         /// </summary>
         void VerifyAccess();
+
+        DeferredSetter<object> Setter { get; }
     }
 }

src/Avalonia.Base/PriorityValue.cs

@@ -21,7 +21,7 @@ namespace Avalonia
     /// priority binding that doesn't return <see cref="AvaloniaProperty.UnsetValue"/>. Where there
     /// are multiple bindings registered with the same priority, the most recently added binding
     /// has a higher priority. Each time the value changes, the 
-    /// <see cref="IPriorityValueOwner.Changed(PriorityValue, object, object)"/> method on the 
+    /// <see cref="IPriorityValueOwner.Changed"/> method on the 
     /// owner object is fired with the old and new values.
     /// </remarks>
     internal class PriorityValue
@@ -30,7 +30,6 @@ namespace Avalonia
         private readonly SingleOrDictionary<int, PriorityLevel> _levels = new SingleOrDictionary<int, PriorityLevel>();
 
         private readonly Func<object, object> _validate;
-        private static readonly DeferredSetter<PriorityValue, (object value, int priority)> delayedSetter = new DeferredSetter<PriorityValue, (object, int)>();
         private (object value, int priority) _value;
 
         /// <summary>
@@ -243,12 +242,18 @@ namespace Avalonia
         /// <param name="priority">The priority level that the value came from.</param>
         private void UpdateValue(object value, int priority)
         {
-            delayedSetter.SetAndNotify(this,
+            Owner.Setter.SetAndNotify(Property,
                 ref _value,
                 UpdateCore,
                 (value, priority));
         }
 
+        private bool UpdateCore(
+            object update,
+            ref (object value, int priority) backing,
+            Action<Action> notify)
+            => UpdateCore(((object, int))update, ref backing, notify);
+
         private bool UpdateCore(
             (object value, int priority) update,
             ref (object value, int priority) backing,

src/Avalonia.Base/Utilities/DeferredSetter.cs

@@ -8,11 +8,10 @@ namespace Avalonia.Utilities
 {
     /// <summary>
     /// A utility class to enable deferring assignment until after property-changed notifications are sent.
+    /// Used to fix #855.
     /// </summary>
-    /// <typeparam name="TProperty">The type of the object that represents the property.</typeparam>
     /// <typeparam name="TSetRecord">The type of value with which to track the delayed assignment.</typeparam>
-    class DeferredSetter<TProperty, TSetRecord>
+    class DeferredSetter<TSetRecord>
-        where TProperty: class
     {
         private struct NotifyDisposable : IDisposable
         {
@@ -37,29 +36,44 @@ namespace Avalonia.Utilities
         {
             public bool Notifying { get; set; }
 
-            private Queue<TSetRecord> pendingValues;
+            private SingleOrQueue<TSetRecord> pendingValues;
             
-            public Queue<TSetRecord> PendingValues
+            public SingleOrQueue<TSetRecord> PendingValues
             {
                 get
                 {
-                    return pendingValues ?? (pendingValues = new Queue<TSetRecord>());
+                    return pendingValues ?? (pendingValues = new SingleOrQueue<TSetRecord>());
                 }
             }
         }
 
-        private readonly ConditionalWeakTable<TProperty, SettingStatus> setRecords = new ConditionalWeakTable<TProperty, SettingStatus>();
+        private Dictionary<AvaloniaProperty, SettingStatus> _setRecords;
+        private Dictionary<AvaloniaProperty, SettingStatus> SetRecords
+            => _setRecords ?? (_setRecords = new Dictionary<AvaloniaProperty, SettingStatus>());
+
+        private SettingStatus GetOrCreateStatus(AvaloniaProperty property)
+        {
+            if (!SetRecords.TryGetValue(property, out var status))
+            {
+                status = new SettingStatus();
+                SetRecords.Add(property, status);
+            }
+
+            return status;
+        }
 
         /// <summary>
         /// Mark the property as currently notifying.
         /// </summary>
         /// <param name="property">The property to mark as notifying.</param>
         /// <returns>Returns a disposable that when disposed, marks the property as done notifying.</returns>
-        private NotifyDisposable MarkNotifying(TProperty property)
+        private NotifyDisposable MarkNotifying(AvaloniaProperty property)
         {
             Contract.Requires<InvalidOperationException>(!IsNotifying(property));
-            
+
-            return new NotifyDisposable(setRecords.GetOrCreateValue(property));
+            SettingStatus status = GetOrCreateStatus(property);
+
+            return new NotifyDisposable(status);
         }
 
         /// <summary>
@@ -67,19 +81,19 @@ namespace Avalonia.Utilities
         /// </summary>
         /// <param name="property">The property.</param>
         /// <returns>If the property is currently notifying listeners.</returns>
-        private bool IsNotifying(TProperty property)
+        private bool IsNotifying(AvaloniaProperty property)
-            => setRecords.TryGetValue(property, out var value) && value.Notifying;
+            => SetRecords.TryGetValue(property, out var value) && value.Notifying;
 
         /// <summary>
         /// Add a pending assignment for the property.
         /// </summary>
         /// <param name="property">The property.</param>
         /// <param name="value">The value to assign.</param>
-        private void AddPendingSet(TProperty property, TSetRecord value)
+        private void AddPendingSet(AvaloniaProperty property, TSetRecord value)
         {
             Contract.Requires<InvalidOperationException>(IsNotifying(property));
 
-            setRecords.GetOrCreateValue(property).PendingValues.Enqueue(value);
+            GetOrCreateStatus(property).PendingValues.Enqueue(value);
         }
 
         /// <summary>
@@ -87,9 +101,9 @@ namespace Avalonia.Utilities
         /// </summary>
         /// <param name="property">The property to check.</param>
         /// <returns>If the property has any pending assignments.</returns>
-        private bool HasPendingSet(TProperty property)
+        private bool HasPendingSet(AvaloniaProperty property)
         {
-            return setRecords.TryGetValue(property, out var status) && status.PendingValues.Count != 0;
+            return SetRecords.TryGetValue(property, out var status) && !status.PendingValues.Empty;
         }
 
         /// <summary>
@@ -97,9 +111,9 @@ namespace Avalonia.Utilities
         /// </summary>
         /// <param name="property">The property to check.</param>
         /// <returns>The first pending assignment for the property.</returns>
-        private TSetRecord GetFirstPendingSet(TProperty property)
+        private TSetRecord GetFirstPendingSet(AvaloniaProperty property)
         {
-            return setRecords.GetOrCreateValue(property).PendingValues.Dequeue();
+            return GetOrCreateStatus(property).PendingValues.Dequeue();
         }
 
         public delegate bool SetterDelegate<TValue>(TSetRecord record, ref TValue backing, Action<Action> notifyCallback);
@@ -115,7 +129,7 @@ namespace Avalonia.Utilities
         /// </param>
         /// <param name="value">The value to try to set.</param>
         public bool SetAndNotify<TValue>(
-            TProperty property,
+            AvaloniaProperty property,
             ref TValue backing,
             SetterDelegate<TValue> setterCallback,
             TSetRecord value)
@@ -144,6 +158,7 @@ namespace Avalonia.Utilities
                         }
                     });
                 }
+
                 return updated;
             }
             else if(!object.Equals(value, backing))

src/Avalonia.Base/Utilities/SingleOrQueue.cs

@@ -0,0 +1,58 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Avalonia.Utilities
+{
+    /// <summary>
+    /// FIFO Queue optimized for holding zero or one items.
+    /// </summary>
+    /// <typeparam name="T">The type of items held in the queue.</typeparam>
+    public class SingleOrQueue<T>
+    {
+        private T _head;
+        private Queue<T> _tail;
+
+        private Queue<T> Tail => _tail ?? (_tail = new Queue<T>());
+
+        private bool HasTail => _tail != null;
+
+        public bool Empty { get; private set; } = true;
+
+        public void Enqueue(T value)
+        {
+            if (Empty)
+            {
+                _head = value;
+            }
+            else
+            {
+                Tail.Enqueue(value);
+            }
+
+            Empty = false;
+        }
+
+        public T Dequeue()
+        {
+            if (Empty)
+            {
+                throw new InvalidOperationException("Cannot dequeue from an empty queue!");
+            }
+
+            var result = _head;
+
+            if (HasTail && Tail.Count != 0)
+            {
+                _head = Tail.Dequeue();
+            }
+            else
+            {
+                _head = default;
+                Empty = true;
+            }
+
+            return result;
+        }
+    }
+}

src/Avalonia.Base/ValueStore.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using Avalonia.Data;
+using Avalonia.Utilities;
 
 namespace Avalonia
 {
@@ -91,12 +92,12 @@ namespace Avalonia
 
         public void BindingNotificationReceived(AvaloniaProperty property, BindingNotification notification)
         {
-            ((IPriorityValueOwner)_owner).BindingNotificationReceived(property, notification);
+            _owner.BindingNotificationReceived(property, notification);
         }
 
         public void Changed(AvaloniaProperty property, int priority, object oldValue, object newValue)
         {
-            ((IPriorityValueOwner)_owner).Changed(property, priority, oldValue, newValue);
+            _owner.PriorityValueChanged(property, priority, oldValue, newValue);
         }
 
         public IDictionary<AvaloniaProperty, PriorityValue> GetSetValues() => throw new NotImplementedException();
@@ -115,7 +116,7 @@ namespace Avalonia
 
         public bool IsAnimating(AvaloniaProperty property)
         {
-            return _values.TryGetValue(property, out var value) ? (value as PriorityValue)?.IsAnimating ?? false : false;
+            return _values.TryGetValue(property, out var value) && value is PriorityValue priority && priority.IsAnimating;
         }
 
         public bool IsSet(AvaloniaProperty property)
@@ -148,13 +149,11 @@ namespace Avalonia
                 validate2 = v => validate(_owner, v);
             }
 
-            PriorityValue result = new PriorityValue(
+            return new PriorityValue(
                 this,
                 property,
                 property.PropertyType,
                 validate2);
-
-            return result;
         }
 
         private object Validate(AvaloniaProperty property, object value)
@@ -168,5 +167,16 @@ namespace Avalonia
 
             return value;
         }
+
+        private DeferredSetter<object> _defferedSetter;
+
+        public DeferredSetter<object> Setter
+        {
+            get
+            {
+                return _defferedSetter ??
+                    (_defferedSetter = new DeferredSetter<object>());
+            }
+        }
     }
 }

src/Avalonia.Controls/Grid.cs

@@ -194,6 +194,16 @@ namespace Avalonia.Controls
         /// </summary>
         private GridLayout.MeasureResult _rowMeasureCache;
 
+        /// <summary>
+        /// Gets the row layout as of the last measure.
+        /// </summary>
+        private GridLayout _rowLayoutCache;
+
+        /// <summary>
+        /// Gets the column layout as of the last measure.
+        /// </summary>
+        private GridLayout _columnLayoutCache;
+
         /// <summary>
         /// Measures the grid.
         /// </summary>
@@ -253,6 +263,9 @@ namespace Avalonia.Controls
             // Cache the measure result and return the desired size.
             _columnMeasureCache = columnResult;
             _rowMeasureCache = rowResult;
+            _rowLayoutCache = rowLayout;
+            _columnLayoutCache = columnLayout;
+
             return new Size(columnResult.DesiredLength, rowResult.DesiredLength);
 
             // Measure each child only once.
@@ -299,13 +312,11 @@ namespace Avalonia.Controls
             //       arrow back to any statements and re-run them without any side-effect.
 
             var (safeColumns, safeRows) = GetSafeColumnRows();
-            var columnLayout = new GridLayout(ColumnDefinitions);
+            var columnLayout = _columnLayoutCache;
-            var rowLayout = new GridLayout(RowDefinitions);
+            var rowLayout = _rowLayoutCache;
-
             // Calculate for arrange result.
             var columnResult = columnLayout.Arrange(finalSize.Width, _columnMeasureCache);
             var rowResult = rowLayout.Arrange(finalSize.Height, _rowMeasureCache);
-
             // Arrange the children.
             foreach (var child in Children.OfType<Control>())
             {
@@ -315,7 +326,6 @@ namespace Avalonia.Controls
                 var y = Enumerable.Range(0, row).Sum(r => rowResult.LengthList[r]);
                 var width = Enumerable.Range(column, columnSpan).Sum(c => columnResult.LengthList[c]);
                 var height = Enumerable.Range(row, rowSpan).Sum(r => rowResult.LengthList[r]);
-
                 child.Arrange(new Rect(x, y, width, height));
             }
 

src/Avalonia.Controls/Primitives/SelectingItemsControl.cs

@@ -360,7 +360,7 @@ namespace Avalonia.Controls.Primitives
                     {
                         if (!AlwaysSelected)
                         {
-                            SelectedIndex = -1;
+                            selectedIndex = SelectedIndex = -1;
                         }
                         else
                         {
@@ -368,6 +368,11 @@ namespace Avalonia.Controls.Primitives
                         }
                     }
 
+                    var items = Items?.Cast<object>();
+                    if (selectedIndex >= items.Count())
+                    {
+                        selectedIndex = SelectedIndex = items.Count() - 1;
+                    }
                     break;
 
                 case NotifyCollectionChangedAction.Reset:

src/Markup/Avalonia.Markup.Xaml/MarkupExtensions/BindingExtension.cs

@@ -87,19 +87,28 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             if (string.IsNullOrWhiteSpace(path) || path == ".")
             {
                 result.Path = string.Empty;
+                return result;
             }
-            else if (path.StartsWith("#"))
+            else if (path.StartsWith("!"))
+            {
+                int pathStart = 0;
+                for (; pathStart < path.Length && path[pathStart] == '!'; ++pathStart);
+                result.Path = path.Substring(0, pathStart);
+                path = path.Substring(pathStart);
+            }
+
+            if (path.StartsWith("#"))
             {
                 var dot = path.IndexOf('.');
 
                 if (dot != -1)
                 {
-                    result.Path = path.Substring(dot + 1);
+                    result.Path += path.Substring(dot + 1);
                     result.ElementName = path.Substring(1, dot - 1);
                 }
                 else
                 {
-                    result.Path = string.Empty;
+                    result.Path += string.Empty;
                     result.ElementName = path.Substring(1);
                 }
             }
@@ -114,12 +123,12 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
                 string relativeSourceMode;
                 if (dot != -1)
                 {
-                    result.Path = path.Substring(dot + 1);
+                    result.Path += path.Substring(dot + 1);
                     relativeSourceMode = path.Substring(1, dot - 1);
                 }
                 else
                 {
-                    result.Path = string.Empty;
+                    result.Path += string.Empty;
                     relativeSourceMode = path.Substring(1);
                 }
 
@@ -170,7 +179,7 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
             }
             else
             {
-                result.Path = path;
+                result.Path += path;
             }
 
             return result;
@@ -229,4 +238,4 @@ namespace Avalonia.Markup.Xaml.MarkupExtensions
 
         public RelativeSource RelativeSource { get; set; }
     }
-}
+}

tests/Avalonia.Base.UnitTests/PriorityValueTests.cs

@@ -1,11 +1,12 @@
 // Copyright (c) The Avalonia Project. All rights reserved.
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
+using Avalonia.Utilities;
+using Moq;
 using System;
 using System.Linq;
 using System.Reactive.Linq;
 using System.Reactive.Subjects;
-using Moq;
 using Xunit;
 
 namespace Avalonia.Base.UnitTests
@@ -21,7 +22,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Initial_Value_Should_Be_UnsetValue()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             Assert.Same(AvaloniaProperty.UnsetValue, target.Value);
         }
@@ -29,7 +30,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void First_Binding_Sets_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 0);
 
@@ -39,7 +40,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Changing_Binding_Should_Set_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var subject = new BehaviorSubject<string>("foo");
 
             target.Add(subject, 0);
@@ -51,7 +52,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Setting_Direct_Value_Should_Override_Binding()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 0);
             target.SetValue("bar", 0);
@@ -62,7 +63,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Binding_Firing_Should_Override_Direct_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var source = new BehaviorSubject<object>("initial");
 
             target.Add(source, 0);
@@ -76,7 +77,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Earlier_Binding_Firing_Should_Not_Override_Later()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var nonActive = new BehaviorSubject<object>("na");
             var source = new BehaviorSubject<object>("initial");
 
@@ -92,7 +93,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Binding_Completing_Should_Revert_To_Direct_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var source = new BehaviorSubject<object>("initial");
 
             target.Add(source, 0);
@@ -108,7 +109,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Binding_With_Lower_Priority_Has_Precedence()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 1);
             target.Add(Single("bar"), 0);
@@ -120,7 +121,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Later_Binding_With_Same_Priority_Should_Take_Precedence()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 1);
             target.Add(Single("bar"), 0);
@@ -133,7 +134,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Changing_Binding_With_Lower_Priority_Should_Set_Not_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var subject = new BehaviorSubject<string>("bar");
 
             target.Add(Single("foo"), 0);
@@ -146,7 +147,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void UnsetValue_Should_Fall_Back_To_Next_Binding()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var subject = new BehaviorSubject<object>("bar");
 
             target.Add(subject, 0);
@@ -162,7 +163,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Adding_Value_Should_Call_OnNext()
         {
-            var owner = new Mock<IPriorityValueOwner>();
+            var owner = GetMockOwner();
             var target = new PriorityValue(owner.Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 0);
@@ -173,7 +174,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Changing_Value_Should_Call_OnNext()
         {
-            var owner = new Mock<IPriorityValueOwner>();
+            var owner = GetMockOwner();
             var target = new PriorityValue(owner.Object, TestProperty, typeof(string));
             var subject = new BehaviorSubject<object>("foo");
 
@@ -186,7 +187,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Disposing_A_Binding_Should_Revert_To_Next_Value()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 0);
             var disposable = target.Add(Single("bar"), 0);
@@ -199,7 +200,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Disposing_A_Binding_Should_Remove_BindingEntry()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
 
             target.Add(Single("foo"), 0);
             var disposable = target.Add(Single("bar"), 0);
@@ -212,7 +213,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Completing_A_Binding_Should_Revert_To_Previous_Binding()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var source = new BehaviorSubject<object>("bar");
 
             target.Add(Single("foo"), 0);
@@ -226,7 +227,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Completing_A_Binding_Should_Revert_To_Lower_Priority()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var source = new BehaviorSubject<object>("bar");
 
             target.Add(Single("foo"), 1);
@@ -240,7 +241,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Completing_A_Binding_Should_Remove_BindingEntry()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(string));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(string));
             var subject = new BehaviorSubject<object>("bar");
 
             target.Add(Single("foo"), 0);
@@ -254,7 +255,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Direct_Value_Should_Be_Coerced()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(int), x => Math.Min((int)x, 10));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(int), x => Math.Min((int)x, 10));
 
             target.SetValue(5, 0);
             Assert.Equal(5, target.Value);
@@ -265,7 +266,7 @@ namespace Avalonia.Base.UnitTests
         [Fact]
         public void Bound_Value_Should_Be_Coerced()
         {
-            var target = new PriorityValue(null, TestProperty, typeof(int), x => Math.Min((int)x, 10));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(int), x => Math.Min((int)x, 10));
             var source = new Subject<object>();
 
             target.Add(source, 0);
@@ -279,7 +280,7 @@ namespace Avalonia.Base.UnitTests
         public void Revalidate_Should_ReCoerce_Value()
         {
             var max = 10;
-            var target = new PriorityValue(null, TestProperty, typeof(int), x => Math.Min((int)x, max));
+            var target = new PriorityValue(GetMockOwner().Object, TestProperty, typeof(int), x => Math.Min((int)x, max));
             var source = new Subject<object>();
 
             target.Add(source, 0);
@@ -302,5 +303,12 @@ namespace Avalonia.Base.UnitTests
         {
             return Observable.Never<T>().StartWith(value);
         }
+
+        private static Mock<IPriorityValueOwner> GetMockOwner()
+        {
+            var owner = new Mock<IPriorityValueOwner>();
+            owner.SetupGet(o => o.Setter).Returns(new DeferredSetter<object>());
+            return owner;
+        }
     }
 }

tests/Avalonia.Base.UnitTests/Utilities/SingleOrQueueTests.cs

@@ -0,0 +1,50 @@
+using Avalonia.Utilities;
+using System;
+using System.Collections.Generic;
+using System.Text;
+using Xunit;
+
+namespace Avalonia.Base.UnitTests.Utilities
+{
+    public class SingleOrQueueTests
+    {
+        [Fact]
+        public void New_SingleOrQueue_Is_Empty()
+        {
+            Assert.True(new SingleOrQueue<object>().Empty);
+        }
+
+        [Fact]
+        public void Dequeue_Throws_When_Empty()
+        {
+            var queue = new SingleOrQueue<object>();
+
+            Assert.Throws<InvalidOperationException>(() => queue.Dequeue());
+        }
+
+        [Fact]
+        public void Enqueue_Adds_Element()
+        {
+            var queue = new SingleOrQueue<int>();
+
+            queue.Enqueue(1);
+
+            Assert.False(queue.Empty);
+
+            Assert.Equal(1, queue.Dequeue());
+        }
+
+        [Fact]
+        public void Multiple_Elements_Dequeued_In_Correct_Order()
+        {
+            var queue = new SingleOrQueue<int>();
+
+            queue.Enqueue(1);
+            queue.Enqueue(2);
+            queue.Enqueue(3);
+            Assert.Equal(1, queue.Dequeue());
+            Assert.Equal(2, queue.Dequeue());
+            Assert.Equal(3, queue.Dequeue());
+        }
+    }
+}

tests/Avalonia.Controls.UnitTests/Primitives/SelectingItemsControlTests.cs

@@ -149,6 +149,34 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(1, target.SelectedIndex);
         }
 
+        [Fact]
+        public void SelectedIndex_Item_Is_Updated_As_Items_Removed_When_Last_Item_Is_Selected()
+        {
+            var items = new ObservableCollection<string>
+            {
+               "Foo",
+               "Bar",
+               "FooBar"
+            };
+
+            var target = new SelectingItemsControl
+            {
+                Items = items,
+                Template = Template(),
+            };
+
+            target.ApplyTemplate();
+            target.SelectedItem = items[2];
+
+            Assert.Equal(items[2], target.SelectedItem);
+            Assert.Equal(2, target.SelectedIndex);
+
+            items.RemoveAt(0);
+
+            Assert.Equal(items[1], target.SelectedItem);
+            Assert.Equal(1, target.SelectedIndex);
+        }
+
         [Fact]
         public void Setting_SelectedItem_To_Not_Present_Item_Should_Clear_Selection()
         {

tests/Avalonia.Markup.Xaml.UnitTests/Xaml/BindingTests_RelativeSource.cs

@@ -297,7 +297,60 @@ namespace Avalonia.Markup.Xaml.UnitTests.Xaml
                 Assert.Equal("title", button.Content);
             }
         }
+
+        [Fact]
+        public void Shorthand_Binding_With_Negation_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Border Name='border1'>
+      <Border Name='border2'>
+        <Button Name='button' Content='{Binding !$self.IsDefault}'/>
+      </Border>
+    </Border>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+
+#pragma warning disable xUnit2004 // Diagnostic mis-firing since button.Content isn't guaranteed to be a bool.
+                Assert.Equal(true, button.Content);
+#pragma warning restore xUnit2004
+            }
+        }
+        [Fact]
+        public void Shorthand_Binding_With_Multiple_Negation_Works()
+        {
+            using (UnitTestApplication.Start(TestServices.StyledWindow))
+            {
+                var xaml = @"
+<Window xmlns='https://github.com/avaloniaui'
+        xmlns:x='http://schemas.microsoft.com/winfx/2006/xaml'
+        xmlns:local='clr-namespace:Avalonia.Markup.Xaml.UnitTests.Xaml;assembly=Avalonia.Markup.Xaml.UnitTests'>
+    <Border Name='border1'>
+      <Border Name='border2'>
+        <Button Name='button' Content='{Binding !!$self.IsDefault}'/>
+      </Border>
+    </Border>
+</Window>";
+                var loader = new AvaloniaXamlLoader();
+                var window = (Window)loader.Load(xaml);
+                var button = window.FindControl<Button>("button");
+
+                window.ApplyTemplate();
+
+#pragma warning disable xUnit2004 // Diagnostic mis-firing since button.Content isn't guaranteed to be a bool.
+                Assert.Equal(false, button.Content);
+#pragma warning restore xUnit2004
+            }
+        }
     }
 
     public class TestWindow : Window { }
-}
+}