diff --git a/src/Android/Avalonia.Android/Platform/SkiaPlatform/PopupImpl.cs b/src/Android/Avalonia.Android/Platform/SkiaPlatform/PopupImpl.cs
index 78f744cea0..041d91043a 100644
--- a/src/Android/Avalonia.Android/Platform/SkiaPlatform/PopupImpl.cs
+++ b/src/Android/Avalonia.Android/Platform/SkiaPlatform/PopupImpl.cs
@@ -110,7 +110,10 @@ namespace Avalonia.Android.Platform.SkiaPlatform
         {
             //Not supported
         }
-        
 
+        public void SetTopmost(bool value)
+        {
+            //Not supported
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Avalonia.Base/Data/Core/ExpressionNode.cs b/src/Avalonia.Base/Data/Core/ExpressionNode.cs
index ae70cacdba..ac7e97a4b1 100644
--- a/src/Avalonia.Base/Data/Core/ExpressionNode.cs
+++ b/src/Avalonia.Base/Data/Core/ExpressionNode.cs
@@ -11,6 +11,7 @@ namespace Avalonia.Data.Core
 {
     internal abstract class ExpressionNode : ISubject<object>
     {
+        private static readonly object CacheInvalid = new object();
         protected static readonly WeakReference UnsetReference = 
             new WeakReference(AvaloniaProperty.UnsetValue);
 
@@ -18,6 +19,8 @@ namespace Avalonia.Data.Core
         private IDisposable _valueSubscription;
         private IObserver<object> _observer;
 
+        protected WeakReference LastValue { get; private set; }
+
         public abstract string Description { get; }
         public ExpressionNode Next { get; set; }
 
@@ -61,6 +64,7 @@ namespace Avalonia.Data.Core
             {
                 _valueSubscription?.Dispose();
                 _valueSubscription = null;
+                LastValue = null;
                 nextSubscription?.Dispose();
                 _observer = null;
             });
@@ -120,6 +124,7 @@ namespace Avalonia.Data.Core
 
             if (notification == null)
             {
+                LastValue = new WeakReference(value);
                 if (Next != null)
                 {
                     Next.Target = new WeakReference(value);
@@ -131,6 +136,7 @@ namespace Avalonia.Data.Core
             }
             else
             {
+                LastValue = new WeakReference(notification.Value);
                 if (Next != null)
                 {
                     Next.Target = new WeakReference(notification.Value);
diff --git a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
index 7719f93a02..14bc09f5b7 100644
--- a/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
+++ b/src/Avalonia.Base/Data/Core/ExpressionObserver.cs
@@ -154,7 +154,7 @@ namespace Avalonia.Data.Core
         /// </returns>
         public bool SetValue(object value, BindingPriority priority = BindingPriority.LocalValue)
         {
-            if (Leaf is ISettableNode settable)
+            if (Leaf is SettableNode settable)
             {
                 var node = _node;
                 while (node != null)
@@ -188,7 +188,7 @@ namespace Avalonia.Data.Core
         /// Gets the type of the expression result or null if the expression could not be 
         /// evaluated.
         /// </summary>
-        public Type ResultType => (Leaf as ISettableNode)?.PropertyType;
+        public Type ResultType => (Leaf as SettableNode)?.PropertyType;
 
         /// <summary>
         /// Gets the leaf node.
diff --git a/src/Avalonia.Base/Data/Core/ISettableNode.cs b/src/Avalonia.Base/Data/Core/ISettableNode.cs
deleted file mode 100644
index 7788407833..0000000000
--- a/src/Avalonia.Base/Data/Core/ISettableNode.cs
+++ /dev/null
@@ -1,15 +0,0 @@
-using Avalonia.Data;
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace Avalonia.Data.Core
-{
-    interface ISettableNode
-    {
-        bool SetTargetValue(object value, BindingPriority priority);
-        Type PropertyType { get; }
-    }
-}
diff --git a/src/Avalonia.Base/Data/Core/IndexerNode.cs b/src/Avalonia.Base/Data/Core/IndexerNode.cs
index 47e82fa2d3..633d3558ee 100644
--- a/src/Avalonia.Base/Data/Core/IndexerNode.cs
+++ b/src/Avalonia.Base/Data/Core/IndexerNode.cs
@@ -15,7 +15,7 @@ using Avalonia.Data;
 
 namespace Avalonia.Data.Core
 {
-    internal class IndexerNode : ExpressionNode, ISettableNode
+    internal class IndexerNode :  SettableNode
     {
         public IndexerNode(IList<string> arguments)
         {
@@ -52,7 +52,7 @@ namespace Avalonia.Data.Core
             return Observable.Merge(inputs).StartWith(GetValue(target));
         }
 
-        public bool SetTargetValue(object value, BindingPriority priority)
+        protected override bool SetTargetValueCore(object value, BindingPriority priority)
         {
             var typeInfo = Target.Target.GetType().GetTypeInfo();
             var list = Target.Target as IList;
@@ -154,7 +154,7 @@ namespace Avalonia.Data.Core
 
         public IList<string> Arguments { get; }
 
-        public Type PropertyType => GetIndexer(Target.Target.GetType().GetTypeInfo())?.PropertyType;
+        public override Type PropertyType => GetIndexer(Target.Target.GetType().GetTypeInfo())?.PropertyType;
 
         private object GetValue(object target)
         {
diff --git a/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs b/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
index 4dbff4602f..9d657b3144 100644
--- a/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
+++ b/src/Avalonia.Base/Data/Core/PropertyAccessorNode.cs
@@ -10,7 +10,7 @@ using Avalonia.Data.Core.Plugins;
 
 namespace Avalonia.Data.Core
 {
-    internal class PropertyAccessorNode : ExpressionNode, ISettableNode
+    internal class PropertyAccessorNode : SettableNode
     {
         private readonly bool _enableValidation;
         private IPropertyAccessor _accessor;
@@ -23,13 +23,17 @@ namespace Avalonia.Data.Core
 
         public override string Description => PropertyName;
         public string PropertyName { get; }
-        public Type PropertyType => _accessor?.PropertyType;
+        public override Type PropertyType => _accessor?.PropertyType;
 
-        public bool SetTargetValue(object value, BindingPriority priority)
+        protected override bool SetTargetValueCore(object value, BindingPriority priority)
         {
             if (_accessor != null)
             {
-                try { return _accessor.SetValue(value, priority); } catch { }
+                try
+                {
+                    return _accessor.SetValue(value, priority);
+                }
+                catch { }
             }
 
             return false;
@@ -56,7 +60,10 @@ namespace Avalonia.Data.Core
                 () =>
                 {
                     _accessor = accessor;
-                    return Disposable.Create(() => _accessor = null);
+                    return Disposable.Create(() =>
+                    {
+                        _accessor = null;
+                    });
                 },
                 _ => accessor);
         }
diff --git a/src/Avalonia.Base/Data/Core/SettableNode.cs b/src/Avalonia.Base/Data/Core/SettableNode.cs
new file mode 100644
index 0000000000..092cdbe48f
--- /dev/null
+++ b/src/Avalonia.Base/Data/Core/SettableNode.cs
@@ -0,0 +1,38 @@
+using Avalonia.Data;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Avalonia.Data.Core
+{
+    internal abstract class SettableNode : ExpressionNode
+    {
+        public bool SetTargetValue(object value, BindingPriority priority)
+        {
+            if (ShouldNotSet(value))
+            {
+                return true;
+            }
+            return SetTargetValueCore(value, priority);
+        }
+
+        private bool ShouldNotSet(object value)
+        {
+            if (PropertyType == null)
+            {
+                return false;
+            }
+            if (PropertyType.IsValueType)
+            {
+                return LastValue?.Target != null && LastValue.Target.Equals(value);
+            }
+            return LastValue != null && Object.ReferenceEquals(LastValue?.Target, value);
+        }
+
+        protected abstract bool SetTargetValueCore(object value, BindingPriority priority);
+
+        public abstract Type PropertyType { get; }
+    }
+}
diff --git a/src/Avalonia.Controls/Platform/IWindowBaseImpl.cs b/src/Avalonia.Controls/Platform/IWindowBaseImpl.cs
index 4f7ac82df7..9ba68f584e 100644
--- a/src/Avalonia.Controls/Platform/IWindowBaseImpl.cs
+++ b/src/Avalonia.Controls/Platform/IWindowBaseImpl.cs
@@ -72,6 +72,11 @@ namespace Avalonia.Platform
         /// 
         void SetMinMaxSize(Size minSize, Size maxSize);
 
+        /// <summary>
+        /// Sets whether this window appears on top of all other windows
+        /// </summary>
+        void SetTopmost(bool value);
+
         /// <summary>
         /// Gets platform specific display information
         /// </summary>
diff --git a/src/Avalonia.Controls/Primitives/Popup.cs b/src/Avalonia.Controls/Primitives/Popup.cs
index 656f3890cd..005717d681 100644
--- a/src/Avalonia.Controls/Primitives/Popup.cs
+++ b/src/Avalonia.Controls/Primitives/Popup.cs
@@ -70,6 +70,12 @@ namespace Avalonia.Controls.Primitives
         public static readonly StyledProperty<bool> StaysOpenProperty =
             AvaloniaProperty.Register<Popup, bool>(nameof(StaysOpen), true);
 
+        /// <summary>
+        /// Defines the <see cref="Topmost"/> property.
+        /// </summary>
+        public static readonly StyledProperty<bool> TopmostProperty =
+            AvaloniaProperty.Register<Popup, bool>(nameof(Topmost));
+
         private bool _isOpen;
         private PopupRoot _popupRoot;
         private TopLevel _topLevel;
@@ -84,6 +90,7 @@ namespace Avalonia.Controls.Primitives
             IsHitTestVisibleProperty.OverrideDefaultValue<Popup>(false);
             ChildProperty.Changed.AddClassHandler<Popup>(x => x.ChildChanged);
             IsOpenProperty.Changed.AddClassHandler<Popup>(x => x.IsOpenChanged);
+            TopmostProperty.Changed.AddClassHandler<Popup>((p, e) => p.PopupRoot.Topmost = (bool)e.NewValue);
         }
 
         /// <summary>
@@ -194,6 +201,15 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(StaysOpenProperty, value); }
         }
 
+        /// <summary>
+        /// Gets or sets whether this popup appears on top of all other windows
+        /// </summary>
+        public bool Topmost
+        {
+            get { return GetValue(TopmostProperty); }
+            set { SetValue(TopmostProperty, value); }
+        }
+
         /// <summary>
         /// Gets the root of the popup window.
         /// </summary>
diff --git a/src/Avalonia.Controls/Primitives/ScrollBar.cs b/src/Avalonia.Controls/Primitives/ScrollBar.cs
index 0057b15150..3ddcb06303 100644
--- a/src/Avalonia.Controls/Primitives/ScrollBar.cs
+++ b/src/Avalonia.Controls/Primitives/ScrollBar.cs
@@ -6,9 +6,21 @@ using System.Reactive;
 using System.Reactive.Linq;
 using Avalonia.Data;
 using Avalonia.Interactivity;
+using Avalonia.Input;
 
 namespace Avalonia.Controls.Primitives
 {
+    public class ScrollEventArgs : EventArgs
+    {
+        public ScrollEventArgs(ScrollEventType eventType, double newValue)
+        {
+            ScrollEventType = eventType;
+            NewValue = newValue;
+        }
+        public double NewValue { get; private set; }
+        public ScrollEventType ScrollEventType { get; private set; }
+    }
+
     /// <summary>
     /// A scrollbar control.
     /// </summary>
@@ -44,6 +56,9 @@ namespace Avalonia.Controls.Primitives
         {
             PseudoClass(OrientationProperty, o => o == Orientation.Vertical, ":vertical");
             PseudoClass(OrientationProperty, o => o == Orientation.Horizontal, ":horizontal");
+
+            Thumb.DragDeltaEvent.AddClassHandler<ScrollBar>(o => o.OnThumbDragDelta, RoutingStrategies.Bubble);
+            Thumb.DragCompletedEvent.AddClassHandler<ScrollBar>(o => o.OnThumbDragComplete, RoutingStrategies.Bubble);
         }
 
         /// <summary>
@@ -88,6 +103,8 @@ namespace Avalonia.Controls.Primitives
             set { SetValue(OrientationProperty, value); }
         }
 
+        public event EventHandler<ScrollEventArgs> Scroll;
+
         /// <summary>
         /// Calculates whether the scrollbar should be visible.
         /// </summary>
@@ -140,6 +157,8 @@ namespace Avalonia.Controls.Primitives
             _pageUpButton = e.NameScope.Find<Button>("PART_PageUpButton");
             _pageDownButton = e.NameScope.Find<Button>("PART_PageDownButton");
 
+
+
             if (_lineUpButton != null)
             {
                 _lineUpButton.Click += LineUpClick;
@@ -184,21 +203,39 @@ namespace Avalonia.Controls.Primitives
         private void SmallDecrement()
         {
             Value = Math.Max(Value - SmallChange * ViewportSize, Minimum);
+            OnScroll(ScrollEventType.SmallDecrement);
         }
 
         private void SmallIncrement()
         {
             Value = Math.Min(Value + SmallChange * ViewportSize, Maximum);
+            OnScroll(ScrollEventType.SmallIncrement);
         }
 
         private void LargeDecrement()
         {
             Value = Math.Max(Value - LargeChange * ViewportSize, Minimum);
+            OnScroll(ScrollEventType.LargeDecrement);
         }
 
         private void LargeIncrement()
         {
             Value = Math.Min(Value + LargeChange * ViewportSize, Maximum);
+            OnScroll(ScrollEventType.LargeIncrement);
+        }
+
+        private void OnThumbDragDelta(VectorEventArgs e)
+        {
+            OnScroll(ScrollEventType.ThumbTrack);
+        }
+        private void OnThumbDragComplete(VectorEventArgs e)
+        {
+            OnScroll(ScrollEventType.EndScroll);
+        }
+
+        protected void OnScroll(ScrollEventType scrollEventType)
+        {
+            Scroll?.Invoke(this, new ScrollEventArgs(scrollEventType, Value));
         }
     }
 }
diff --git a/src/Avalonia.Controls/Primitives/ScrollEventType.cs b/src/Avalonia.Controls/Primitives/ScrollEventType.cs
new file mode 100644
index 0000000000..ea639d82e0
--- /dev/null
+++ b/src/Avalonia.Controls/Primitives/ScrollEventType.cs
@@ -0,0 +1,53 @@
+// 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.
+
+namespace Avalonia.Controls.Primitives
+{
+    /// <summary>    
+    /// Specifies the type of Avalonia.Controls.Primitives.ScrollBar.Scroll event
+    /// that occurred.
+    /// </summary>
+    public enum ScrollEventType
+    {
+        /// <summary>    
+        /// Specifies that the Avalonia.Controls.Primitives.Thumb moved a specified
+        /// distance, as determined by the value of Avalonia.Controls.Primitives.RangeBase.SmallChange.
+        /// The Avalonia.Controls.Primitives.Thumb moved to the left for a horizontal
+        /// Avalonia.Controls.Primitives.ScrollBar or upward for a vertical Avalonia.Controls.Primitives.ScrollBar.
+        /// </summary>
+        SmallDecrement = 0,
+        /// <summary>    
+        /// Specifies that the Avalonia.Controls.Primitives.Thumb moved a specified
+        /// distance, as determined by the value of Avalonia.Controls.Primitives.RangeBase.SmallChange.
+        /// The Avalonia.Controls.Primitives.Thumb moved to the right for a horizontal
+        /// Avalonia.Controls.Primitives.ScrollBar or downward for a vertical Avalonia.Controls.Primitives.ScrollBar.
+        /// </summary>
+        SmallIncrement = 1,
+        /// <summary>    
+        /// Specifies that the Avalonia.Controls.Primitives.Thumb moved a specified
+        /// distance, as determined by the value of Avalonia.Controls.Primitives.RangeBase.LargeChange.
+        /// The Avalonia.Controls.Primitives.Thumb moved to the left for a horizontal
+        /// Avalonia.Controls.Primitives.ScrollBar or upward for a vertical Avalonia.Controls.Primitives.ScrollBar.
+        /// </summary>
+        LargeDecrement = 2,
+        /// <summary>    
+        /// Specifies that the Avalonia.Controls.Primitives.Thumb moved a specified
+        /// distance, as determined by the value of Avalonia.Controls.Primitives.RangeBase.LargeChange.
+        /// The Avalonia.Controls.Primitives.Thumb moved to the right for a horizontal
+        /// Avalonia.Controls.Primitives.ScrollBar or downward for a vertical Avalonia.Controls.Primitives.ScrollBar.
+        /// </summary>
+        LargeIncrement = 3,
+        /// <summary>    
+        /// The Avalonia.Controls.Primitives.Thumb was dragged and caused a Avalonia.UIElement.MouseMove
+        /// event. A Avalonia.Controls.Primitives.ScrollBar.Scroll event of this Avalonia.Controls.Primitives.ScrollEventType
+        /// may occur more than one time when the Avalonia.Controls.Primitives.Thumb
+        /// is dragged in the Avalonia.Controls.Primitives.ScrollBar.
+        /// </summary>
+        ThumbTrack = 4,
+        /// <summary>    
+        /// Specifies that the Avalonia.Controls.Primitives.Thumb was dragged to a
+        /// new position and is now no longer being dragged by the user.
+        /// </summary>
+        EndScroll = 5
+    }
+}
diff --git a/src/Avalonia.Controls/ToolTip.cs b/src/Avalonia.Controls/ToolTip.cs
index 464e4188d2..10e964d014 100644
--- a/src/Avalonia.Controls/ToolTip.cs
+++ b/src/Avalonia.Controls/ToolTip.cs
@@ -234,11 +234,12 @@ namespace Avalonia.Controls
         {
             Close();
 
-            _popup = new PopupRoot { Content = this };
+            _popup = new PopupRoot { Content = this,  };
             ((ISetLogicalParent)_popup).SetParent(control);
             _popup.Position = Popup.GetPosition(control, GetPlacement(control), _popup,
                 GetHorizontalOffset(control), GetVerticalOffset(control));
             _popup.Show();
+            _popup.SnapInsideScreenEdges();
         }
 
         private void Close()
diff --git a/src/Avalonia.Controls/WindowBase.cs b/src/Avalonia.Controls/WindowBase.cs
index c427df1c26..5d66bee2f8 100644
--- a/src/Avalonia.Controls/WindowBase.cs
+++ b/src/Avalonia.Controls/WindowBase.cs
@@ -38,6 +38,9 @@ namespace Avalonia.Controls
                 o => o.Owner,
                 (o, v) => o.Owner = v);
 
+        public static readonly StyledProperty<bool> TopmostProperty =
+            AvaloniaProperty.Register<WindowBase, bool>(nameof(Topmost));
+
         private bool _hasExecutedInitialLayoutPass;
         private bool _isActive;
         private bool _ignoreVisibilityChange;
@@ -52,6 +55,8 @@ namespace Avalonia.Controls
             MinHeightProperty.Changed.AddClassHandler<WindowBase>((w, e) => w.PlatformImpl?.SetMinMaxSize(new Size(w.MinWidth, (double)e.NewValue), new Size(w.MaxWidth, w.MaxHeight)));
             MaxWidthProperty.Changed.AddClassHandler<WindowBase>((w, e) => w.PlatformImpl?.SetMinMaxSize(new Size(w.MinWidth, w.MinHeight), new Size((double)e.NewValue, w.MaxHeight)));
             MaxHeightProperty.Changed.AddClassHandler<WindowBase>((w, e) => w.PlatformImpl?.SetMinMaxSize(new Size(w.MinWidth, w.MinHeight), new Size(w.MaxWidth, (double)e.NewValue)));
+            
+            TopmostProperty.Changed.AddClassHandler<WindowBase>((w, e) => w.PlatformImpl?.SetTopmost((bool)e.NewValue));
         }
 
         public WindowBase(IWindowBaseImpl impl) : this(impl, AvaloniaLocator.Current)
@@ -124,6 +129,15 @@ namespace Avalonia.Controls
             set { SetAndRaise(OwnerProperty, ref _owner, value); }
         }
 
+        /// <summary>
+        /// Gets or sets whether this window appears on top of all other windows
+        /// </summary>
+        public bool Topmost
+        {
+            get { return GetValue(TopmostProperty); }
+            set { SetValue(TopmostProperty, value); }
+        }
+
         /// <summary>
         /// Activates the window.
         /// </summary>
diff --git a/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs b/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
index 61bd9670f2..ed2c55895c 100644
--- a/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
+++ b/src/Avalonia.DesignerSupport/Remote/PreviewerWindowImpl.cs
@@ -106,5 +106,9 @@ namespace Avalonia.DesignerSupport.Remote
         public void CanResize(bool value)
         {
         }
+
+        public void SetTopmost(bool value)
+        {
+        }
     }
 }
\ No newline at end of file
diff --git a/src/Avalonia.DesignerSupport/Remote/Stubs.cs b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
index e749d10468..43f0e0a95e 100644
--- a/src/Avalonia.DesignerSupport/Remote/Stubs.cs
+++ b/src/Avalonia.DesignerSupport/Remote/Stubs.cs
@@ -104,6 +104,10 @@ namespace Avalonia.DesignerSupport.Remote
         public void CanResize(bool value)
         {
         }
+
+        public void SetTopmost(bool value)
+        {
+        }
     }
 
     class ClipboardStub : IClipboard
diff --git a/src/Avalonia.Visuals/Media/DrawingContext.cs b/src/Avalonia.Visuals/Media/DrawingContext.cs
index 1d25224b8d..962f2c1ba8 100644
--- a/src/Avalonia.Visuals/Media/DrawingContext.cs
+++ b/src/Avalonia.Visuals/Media/DrawingContext.cs
@@ -59,7 +59,7 @@ namespace Avalonia.Media
         //HACK: This is a temporary hack that is used in the render loop 
         //to update TransformedBounds property
         [Obsolete("HACK for render loop, don't use")]
-        internal Matrix CurrentContainerTransform => _currentContainerTransform;
+        public Matrix CurrentContainerTransform => _currentContainerTransform;
 
         /// <summary>
         /// Draws a bitmap image.
diff --git a/src/Avalonia.Visuals/Rendering/IRendererFactory.cs b/src/Avalonia.Visuals/Rendering/IRendererFactory.cs
new file mode 100644
index 0000000000..0d7044e125
--- /dev/null
+++ b/src/Avalonia.Visuals/Rendering/IRendererFactory.cs
@@ -0,0 +1,20 @@
+// 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 System;
+
+namespace Avalonia.Rendering
+{
+    /// <summary>
+    /// Defines the interface for a renderer factory.
+    /// </summary>
+    public interface IRendererFactory
+    {
+        /// <summary>
+        /// Creates a renderer.
+        /// </summary>
+        /// <param name="root">The root visual.</param>
+        /// <param name="renderLoop">The render loop.</param>
+        IRenderer Create(IRenderRoot root, IRenderLoop renderLoop);
+    }
+}
diff --git a/src/Gtk/Avalonia.Gtk3/Interop/Native.cs b/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
index b018f4db3f..f57769c224 100644
--- a/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
+++ b/src/Gtk/Avalonia.Gtk3/Interop/Native.cs
@@ -262,10 +262,13 @@ namespace Avalonia.Gtk3.Interop
 
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate void gtk_window_unmaximize(GtkWindow window);
-            
+
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate void gtk_window_close(GtkWindow window);
 
+            [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
+            public delegate void gtk_window_set_keep_above(GtkWindow gtkWindow, bool setting);
+
             [UnmanagedFunctionPointer(CallingConvention.Cdecl), GtkImport(GtkDll.Gtk)]
             public delegate void gtk_window_set_geometry_hints(GtkWindow window, IntPtr geometry_widget, ref GdkGeometry geometry, GdkWindowHints geom_mask);
 
@@ -473,6 +476,7 @@ namespace Avalonia.Gtk3.Interop
         public static D.gtk_window_maximize GtkWindowMaximize;
         public static D.gtk_window_unmaximize GtkWindowUnmaximize;
         public static D.gtk_window_close GtkWindowClose;
+        public static D.gtk_window_set_keep_above GtkWindowSetKeepAbove;
         public static D.gdk_window_begin_move_drag GdkWindowBeginMoveDrag;
         public static D.gdk_window_begin_resize_drag GdkWindowBeginResizeDrag;
         public static D.gdk_event_request_motions GdkEventRequestMotions;
diff --git a/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs b/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
index 94537d3475..8a880fd306 100644
--- a/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
+++ b/src/Gtk/Avalonia.Gtk3/WindowBaseImpl.cs
@@ -416,6 +416,8 @@ namespace Avalonia.Gtk3
 
         public void Hide() => Native.GtkWidgetHide(GtkWidget);
 
+        public void SetTopmost(bool value) => Native.GtkWindowSetKeepAbove(GtkWidget, value);
+
         void GetGlobalPointer(out int x, out int y)
         {
             int mask;
diff --git a/src/Gtk/Avalonia.Gtk3/WindowImpl.cs b/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
index bae34db6f3..a0b754c229 100644
--- a/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
+++ b/src/Gtk/Avalonia.Gtk3/WindowImpl.cs
@@ -81,7 +81,7 @@ namespace Avalonia.Gtk3
         public void ShowTaskbarIcon(bool value) => Native.GtkWindowSetSkipTaskbarHint(GtkWidget, !value);
 
         public void CanResize(bool value) => Native.GtkWindowSetResizable(GtkWidget, value);
-        
+
 
         class EmptyDisposable : IDisposable
         {
diff --git a/src/OSX/Avalonia.MonoMac/WindowBaseImpl.cs b/src/OSX/Avalonia.MonoMac/WindowBaseImpl.cs
index 8cbc6cbdd8..89cef59b53 100644
--- a/src/OSX/Avalonia.MonoMac/WindowBaseImpl.cs
+++ b/src/OSX/Avalonia.MonoMac/WindowBaseImpl.cs
@@ -123,6 +123,7 @@ namespace Avalonia.MonoMac
 
         public void Hide() => Window?.OrderOut(Window);
 
+        public void SetTopmost(bool value) => Window.Level = value ? NSWindowLevel.Floating : NSWindowLevel.Normal;
 
         public void BeginMoveDrag()
         {
diff --git a/src/Skia/Avalonia.Skia/FormattedTextImpl.cs b/src/Skia/Avalonia.Skia/FormattedTextImpl.cs
index 00f0a48a7b..13dcd9669d 100644
--- a/src/Skia/Avalonia.Skia/FormattedTextImpl.cs
+++ b/src/Skia/Avalonia.Skia/FormattedTextImpl.cs
@@ -560,13 +560,11 @@ namespace Avalonia.Skia
                 }
 
                 measured = LineBreak(Text, curOff, length, _paint, constraint, out trailingnumber);
-
                 AvaloniaFormattedTextLine line = new AvaloniaFormattedTextLine();
                 line.TextLength = measured;
-
+                line.Start = curOff;
                 subString = Text.Substring(line.Start, line.TextLength);
                 lineWidth = _paint.MeasureText(subString);
-                line.Start = curOff;
                 line.Length = measured - trailingnumber;
                 line.Width = lineWidth;
                 line.Height = _lineHeight;
@@ -575,10 +573,33 @@ namespace Avalonia.Skia
                 _skiaLines.Add(line);
 
                 curY += _lineHeight;
-
                 curY += mLeading;
-
                 curOff += measured;
+
+                //if this is the last line and there are trailing newline characters then
+                //insert a additional line
+                if (curOff >= length)
+                {
+                    var subStringMinusNewlines = subString.TrimEnd('\n', '\r');
+                    var lengthDiff = subString.Length - subStringMinusNewlines.Length;
+                    if (lengthDiff > 0)
+                    {
+                        AvaloniaFormattedTextLine lastLine = new AvaloniaFormattedTextLine();
+                        lastLine.TextLength = lengthDiff;
+                        lastLine.Start = curOff - lengthDiff;
+                        var lastLineSubString = Text.Substring(line.Start, line.TextLength);
+                        var lastLineWidth = _paint.MeasureText(lastLineSubString);
+                        lastLine.Length = 0;
+                        lastLine.Width = lastLineWidth;
+                        lastLine.Height = _lineHeight;
+                        lastLine.Top = curY;
+
+                        _skiaLines.Add(lastLine);
+
+                        curY += _lineHeight;
+                        curY += mLeading;
+                    }
+                }
             }
 
             // Now convert to Avalonia data formats
diff --git a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
index 4095447943..b83002f54b 100644
--- a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
+++ b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
@@ -78,6 +78,14 @@ namespace Avalonia.Win32.Interop
             SWP_RESIZE = SWP_NOACTIVATE | SWP_NOMOVE | SWP_NOZORDER
         }
 
+        public static class WindowPosZOrder
+        {
+            public static readonly IntPtr HWND_BOTTOM = new IntPtr(1);
+            public static readonly IntPtr HWND_TOP = new IntPtr(0);
+            public static readonly IntPtr HWND_TOPMOST = new IntPtr(-1);
+            public static readonly IntPtr HWND_NOTOPMOST = new IntPtr(-2);
+        }
+
         public enum SizeCommand
         {
             Restored,
diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 7b9f8ee066..9f67f97252 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -32,6 +32,7 @@ namespace Avalonia.Win32
         private bool _trackingMouse;
         private bool _decorated = true;
         private bool _resizable = true;
+        private bool _topmost = false;
         private double _scaling = 1;
         private WindowState _showWindowState;
         private WindowState _lastWindowState;
@@ -124,9 +125,12 @@ namespace Avalonia.Win32
         public IRenderer CreateRenderer(IRenderRoot root)
         {
             var loop = AvaloniaLocator.Current.GetService<IRenderLoop>();
-            return Win32Platform.UseDeferredRendering ?
-                (IRenderer)new DeferredRenderer(root, loop) :
-                new ImmediateRenderer(root);
+            var customRendererFactory = AvaloniaLocator.Current.GetService<IRendererFactory>();
+
+            if (customRendererFactory != null)
+                return customRendererFactory.Create(root, loop);
+
+            return Win32Platform.UseDeferredRendering ? (IRenderer)new DeferredRenderer(root, loop) : new ImmediateRenderer(root);
         }
 
         public void Resize(Size value)
@@ -838,7 +842,7 @@ namespace Avalonia.Win32
                     var cx = Math.Abs(monitorInfo.rcWork.right - x);
                     var cy = Math.Abs(monitorInfo.rcWork.bottom - y);
 
-                    SetWindowPos(_hwnd, new IntPtr(-2), x, y, cx, cy, SetWindowPosFlags.SWP_SHOWWINDOW);
+                    SetWindowPos(_hwnd, WindowPosZOrder.HWND_NOTOPMOST, x, y, cx, cy, SetWindowPosFlags.SWP_SHOWWINDOW);
                 }
             }
         }
@@ -901,5 +905,21 @@ namespace Avalonia.Win32
 
             _resizable = value;
         }
+
+        public void SetTopmost(bool value)
+        {
+            if (value == _topmost)
+            {
+                return;
+            }
+
+            IntPtr hWndInsertAfter = value ? WindowPosZOrder.HWND_TOPMOST : WindowPosZOrder.HWND_NOTOPMOST;
+            UnmanagedMethods.SetWindowPos(_hwnd,
+                   hWndInsertAfter,
+                   0, 0, 0, 0,
+                   SetWindowPosFlags.SWP_NOMOVE | SetWindowPosFlags.SWP_NOSIZE | SetWindowPosFlags.SWP_NOACTIVATE);
+
+            _topmost = value;
+        }
     }
 }
diff --git a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
index 02fb1f11ad..4638aa84a5 100644
--- a/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
+++ b/tests/Avalonia.Base.UnitTests/AvaloniaObjectTests_Binding.cs
@@ -457,6 +457,28 @@ namespace Avalonia.Base.UnitTests
             Assert.True(target.IsAnimating(Class1.FooProperty));
         }
 
+        [Fact]
+        public void TwoWay_Binding_Should_Not_Call_Setter_On_Creation()
+        {
+            var target = new Class1();
+            var source = new TestTwoWayBindingViewModel();
+
+            target.Bind(Class1.DoubleValueProperty, new Binding(nameof(source.Value), BindingMode.TwoWay) { Source = source });
+
+            Assert.False(source.SetterCalled);
+        }
+
+        [Fact]
+        public void TwoWay_Binding_Should_Not_Call_Setter_On_Creation_Indexer()
+        {
+            var target = new Class1();
+            var source = new TestTwoWayBindingViewModel();
+
+            target.Bind(Class1.DoubleValueProperty, new Binding("[0]", BindingMode.TwoWay) { Source = source });
+
+            Assert.False(source.SetterCalled);
+        }
+
         /// <summary>
         /// Returns an observable that returns a single value but does not complete.
         /// </summary>
@@ -545,5 +567,32 @@ namespace Avalonia.Base.UnitTests
                 }
             }
         }
+
+        private class TestTwoWayBindingViewModel
+        {
+            private double _value;
+
+            public double Value
+            {
+                get => _value;
+                set
+                {
+                    _value = value;
+                    SetterCalled = true;
+                }
+            }
+
+            public double this[int index]
+            {
+                get => _value;
+                set
+                {
+                    _value = value;
+                    SetterCalled = true;
+                }
+            }
+
+            public bool SetterCalled { get; private set; }
+        }
     }
 }
\ No newline at end of file
diff --git a/tests/Avalonia.Controls.UnitTests/Primitives/ScrollBarTests.cs b/tests/Avalonia.Controls.UnitTests/Primitives/ScrollBarTests.cs
index 0af4d791c7..672b5c608b 100644
--- a/tests/Avalonia.Controls.UnitTests/Primitives/ScrollBarTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/Primitives/ScrollBarTests.cs
@@ -5,6 +5,7 @@ using System;
 using System.Linq;
 using Avalonia.Controls.Primitives;
 using Avalonia.Controls.Templates;
+using Avalonia.Input;
 using Avalonia.Media;
 using Xunit;
 
@@ -59,6 +60,64 @@ namespace Avalonia.Controls.UnitTests.Primitives
             Assert.Equal(50, target.Value);
         }
 
+        [Fact]
+        public void Thumb_DragDelta_Event_Should_Raise_Scroll_Event()
+        {
+            var target = new ScrollBar
+            {
+                Template = new FuncControlTemplate<ScrollBar>(Template),
+            };
+
+            target.ApplyTemplate();
+
+            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+
+            var raisedEvent = Assert.Raises<ScrollEventArgs>(
+                handler => target.Scroll += handler,
+                handler => target.Scroll -= handler,
+                () =>
+                {
+                    var ev = new VectorEventArgs
+                    {
+                        RoutedEvent = Thumb.DragDeltaEvent,
+                        Vector = new Vector(0, 0)
+                    };
+
+                    track.Thumb.RaiseEvent(ev);
+                });
+
+            Assert.Equal(ScrollEventType.ThumbTrack, raisedEvent.Arguments.ScrollEventType);
+        }
+
+        [Fact]
+        public void Thumb_DragComplete_Event_Should_Raise_Scroll_Event()
+        {
+            var target = new ScrollBar
+            {
+                Template = new FuncControlTemplate<ScrollBar>(Template),
+            };
+
+            target.ApplyTemplate();
+
+            var track = (Track)target.GetTemplateChildren().First(x => x.Name == "track");
+
+            var raisedEvent = Assert.Raises<ScrollEventArgs>(
+                handler => target.Scroll += handler,
+                handler => target.Scroll -= handler,
+                () =>
+                {
+                    var ev = new VectorEventArgs
+                    {
+                        RoutedEvent = Thumb.DragCompletedEvent,
+                        Vector = new Vector(0, 0)
+                    };
+
+                    track.Thumb.RaiseEvent(ev);
+                });
+
+            Assert.Equal(ScrollEventType.EndScroll, raisedEvent.Arguments.ScrollEventType);
+        }
+
         [Fact]
         public void ScrollBar_Can_AutoHide()
         {