diff --git a/samples/ControlCatalog/SideBar.xaml b/samples/ControlCatalog/SideBar.xaml
index 8534c022f8..3bae7edb00 100644
--- a/samples/ControlCatalog/SideBar.xaml
+++ b/samples/ControlCatalog/SideBar.xaml
@@ -63,13 +63,13 @@
     <Style Selector="TabControl.sidebar > TabItem:pointerover">
         <Setter Property="Opacity" Value="1"/>
     </Style>
-    <Style Selector="TabControl.sidebar > TabItem:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabControl.sidebar > TabItem:pointerover">
         <Setter Property="Background" Value="Transparent"/>
     </Style>
     <Style Selector="TabControl.sidebar > TabItem:selected">
         <Setter Property="Opacity" Value="1"/>
     </Style>
-    <Style Selector="TabControl.sidebar > TabItem:selected /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabControl.sidebar > TabItem:selected">
         <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush2}"/>
     </Style>
 </Styles>
diff --git a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
index f887b987e0..a3123cf8c6 100644
--- a/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
+++ b/src/Avalonia.Controls/Presenters/CarouselPresenter.cs
@@ -210,7 +210,7 @@ namespace Avalonia.Controls.Presenters
         {
             var container = ItemContainerGenerator.ContainerFromIndex(index);
 
-            if (container == null)
+            if (container == null && IsVirtualized)
             {
                 var item = Items.Cast<object>().ElementAt(index);
                 var materialized = ItemContainerGenerator.Materialize(index, item, MemberSelector);
diff --git a/src/Avalonia.Themes.Default/TabItem.xaml b/src/Avalonia.Themes.Default/TabItem.xaml
index fcdb76524e..92482a564c 100644
--- a/src/Avalonia.Themes.Default/TabItem.xaml
+++ b/src/Avalonia.Themes.Default/TabItem.xaml
@@ -24,19 +24,19 @@
     <Style Selector="TabItem:disabled">
         <Setter Property="Opacity" Value="{DynamicResource ThemeDisabledOpacity}"/>
     </Style>
-    <Style Selector="TabItem:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabItem:pointerover">
         <Setter Property="Background" Value="{DynamicResource ThemeControlHighlightMidBrush}"/>
     </Style>
-    <Style Selector="TabItem:selected /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabItem:selected">
         <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush4}"/>
     </Style>
-    <Style Selector="TabItem:selected:focus /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabItem:selected:focus">
         <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
     </Style>
-    <Style Selector="TabItem:selected:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabItem:selected:pointerover">
         <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush3}"/>
     </Style>
-    <Style Selector="TabItem:selected:focus:pointerover /template/ ContentPresenter#PART_ContentPresenter">
+    <Style Selector="TabItem:selected:focus:pointerover">
         <Setter Property="Background" Value="{DynamicResource ThemeAccentBrush2}"/>
     </Style>
     <Style Selector="TabItem[TabStripPlacement=Right]">
diff --git a/src/Avalonia.Visuals/Media/FontFamily.cs b/src/Avalonia.Visuals/Media/FontFamily.cs
index 5c152cd8a0..a486723d86 100644
--- a/src/Avalonia.Visuals/Media/FontFamily.cs
+++ b/src/Avalonia.Visuals/Media/FontFamily.cs
@@ -11,46 +11,49 @@ namespace Avalonia.Media
 {
     public class FontFamily
     {
+        /// <inheritdoc />
         /// <summary>
         /// Initializes a new instance of the <see cref="T:Avalonia.Media.FontFamily" /> class.
         /// </summary>
-        /// <param name="name">The name of the <see cref="FontFamily"/>.</param>
-        /// <exception cref="T:System.ArgumentNullException">name</exception>
-        public FontFamily(string name)
+        /// <param name="name">The name of the <see cref="T:Avalonia.Media.FontFamily" />.</param>
+        public FontFamily(string name) : this(null, name)
         {
-            Contract.Requires<ArgumentNullException>(name != null);
-
-            FamilyNames = new FamilyNameCollection(new[] { name });
         }
 
         /// <summary>
         /// Initializes a new instance of the <see cref="T:Avalonia.Media.FontFamily" /> class.
         /// </summary>
-        /// <param name="names">The names of the <see cref="FontFamily"/>.</param>
-        /// <exception cref="T:System.ArgumentNullException">name</exception>
-        public FontFamily(IEnumerable<string> names)
+        /// <param name="baseUri">Specifies the base uri that is used to resolve font family assets.</param>
+        /// <param name="name">The name of the <see cref="T:Avalonia.Media.FontFamily" />.</param>
+        /// <exception cref="T:System.ArgumentException">Base uri must be an absolute uri.</exception>
+        public FontFamily(Uri baseUri, string name)
         {
-            Contract.Requires<ArgumentNullException>(names != null);
+            if (string.IsNullOrEmpty(name))
+            {
+                FamilyNames = new FamilyNameCollection(string.Empty);
 
-            FamilyNames = new FamilyNameCollection(names);
-        }
+                return;
+            }
 
-        /// <inheritdoc />
-        /// <summary>
-        /// Initializes a new instance of the <see cref="T:Avalonia.Media.FontFamily" /> class.
-        /// </summary>
-        /// <param name="name">The name of the <see cref="T:Avalonia.Media.FontFamily" />.</param>
-        /// <param name="source">The source of font resources.</param>
-        /// <param name="baseUri"></param>
-        public FontFamily(string name, Uri source, Uri baseUri = null) : this(name)
-        {
-            Key = new FontFamilyKey(source, baseUri);
+            var fontFamilySegment = GetFontFamilyIdentifier(name);
+
+            if (fontFamilySegment.Source != null)
+            {
+                if (baseUri != null && !baseUri.IsAbsoluteUri)
+                {
+                    throw new ArgumentException("Base uri must be an absolute uri.", nameof(baseUri));
+                }
+
+                Key = new FontFamilyKey(fontFamilySegment.Source, baseUri);
+            }
+
+            FamilyNames = new FamilyNameCollection(fontFamilySegment.Name);
         }
 
         /// <summary>
         /// Represents the default font family
         /// </summary>
-        public static FontFamily Default => new FontFamily(String.Empty);
+        public static FontFamily Default => new FontFamily(string.Empty);
 
         /// <summary>
         /// Represents all font families in the system. This can be an expensive call depending on platform implementation.
@@ -88,46 +91,40 @@ namespace Avalonia.Media
         /// <param name="s"></param>
         public static implicit operator FontFamily(string s)
         {
-            return Parse(s);
+            return new FontFamily(s);
         }
 
-        /// <summary>
-        /// Parses a <see cref="T:Avalonia.Media.FontFamily"/> string.
-        /// </summary>
-        /// <param name="s">The <see cref="T:Avalonia.Media.FontFamily"/> string.</param>
-        /// <param name="baseUri"></param>
-        /// <returns></returns>
-        /// <exception cref="ArgumentException">
-        /// Specified family is not supported.
-        /// </exception>
-        public static FontFamily Parse(string s, Uri baseUri = null)
+        private struct FontFamilyIdentifier
         {
-            if (string.IsNullOrEmpty(s))
+            public FontFamilyIdentifier(string name, Uri source)
             {
-                throw new ArgumentException("Specified family is not supported.");
+                Name = name;
+                Source = source;
             }
 
-            var segments = s.Split('#');
+            public string Name { get; }
+
+            public Uri Source { get; }
+        }
+
+        private static FontFamilyIdentifier GetFontFamilyIdentifier(string name)
+        {
+            var segments = name.Split('#');
 
             switch (segments.Length)
             {
                 case 1:
                     {
-                        var names = segments[0].Split(',')
-                            .Select(x => x.Trim())
-                            .Where(x => !string.IsNullOrWhiteSpace(x));
-                        return new FontFamily(names);
+                        return new FontFamilyIdentifier(segments[0], null);
                     }
 
                 case 2:
                     {
-                        var uri = segments[0].StartsWith("/")
-                                      ? new Uri(segments[0], UriKind.Relative)
-                                      : new Uri(segments[0], UriKind.RelativeOrAbsolute);
+                        var source = segments[0].StartsWith("/")
+                            ? new Uri(segments[0], UriKind.Relative)
+                            : new Uri(segments[0], UriKind.RelativeOrAbsolute);
 
-                        return uri.IsAbsoluteUri
-                                   ? new FontFamily(segments[1], uri)
-                                   : new FontFamily(segments[1], uri, baseUri);
+                        return new FontFamilyIdentifier(segments[1], source);
                     }
 
                 default:
@@ -137,6 +134,25 @@ namespace Avalonia.Media
             }
         }
 
+        /// <summary>
+        /// Parses a <see cref="T:Avalonia.Media.FontFamily"/> string.
+        /// </summary>
+        /// <param name="s">The <see cref="T:Avalonia.Media.FontFamily"/> string.</param>
+        /// <param name="baseUri">Specifies the base uri that is used to resolve font family assets.</param>
+        /// <returns></returns>
+        /// <exception cref="ArgumentException">
+        /// Specified family is not supported.
+        /// </exception>
+        public static FontFamily Parse(string s, Uri baseUri = null)
+        {
+            if (string.IsNullOrEmpty(s))
+            {
+                throw new ArgumentException("Specified family is not supported.", nameof(s));
+            }
+
+            return new FontFamily(baseUri, s);
+        }
+
         /// <summary>
         /// Returns a <see cref="string" /> that represents this instance.
         /// </summary>
diff --git a/src/Avalonia.Visuals/Media/Fonts/FamilyNameCollection.cs b/src/Avalonia.Visuals/Media/Fonts/FamilyNameCollection.cs
index 50511d2fb7..acf0bbdb11 100644
--- a/src/Avalonia.Visuals/Media/Fonts/FamilyNameCollection.cs
+++ b/src/Avalonia.Visuals/Media/Fonts/FamilyNameCollection.cs
@@ -4,31 +4,28 @@
 using System;
 using System.Collections;
 using System.Collections.Generic;
-using System.Collections.ObjectModel;
 using System.Linq;
+using System.Text;
 
 namespace Avalonia.Media.Fonts
 {
-    using System.Text;
-
     public class FamilyNameCollection : IEnumerable<string>
-    {    
+    {
         /// <summary>
         /// Initializes a new instance of the <see cref="FamilyNameCollection"/> class.
         /// </summary>
         /// <param name="familyNames">The family names.</param>
         /// <exception cref="ArgumentException">familyNames</exception>
-        public FamilyNameCollection(IEnumerable<string> familyNames)
+        public FamilyNameCollection(string familyNames)
         {
-            Contract.Requires<ArgumentNullException>(familyNames != null);
-
-            var names = new List<string>(familyNames);
-
-            if (names.Count == 0) throw new ArgumentException($"{nameof(familyNames)} must not be empty.");
+            if (familyNames == null)
+            {
+                throw new ArgumentNullException(nameof(familyNames));
+            }
 
-            Names = new ReadOnlyCollection<string>(names);
+            Names = familyNames.Split(',').Select(x => x.Trim()).ToArray();
 
-            PrimaryFamilyName = Names.First();
+            PrimaryFamilyName = Names[0];
 
             HasFallbacks = Names.Count > 1;
         }
@@ -55,7 +52,7 @@ namespace Avalonia.Media.Fonts
         /// <value>
         /// The names.
         /// </value>
-        internal ReadOnlyCollection<string> Names { get; }
+        internal IReadOnlyList<string> Names { get; }
 
         /// <inheritdoc />
         /// <summary>
@@ -95,7 +92,10 @@ namespace Avalonia.Media.Fonts
             {
                 builder.Append(Names[index]);
 
-                if (index == Names.Count - 1) break;
+                if (index == Names.Count - 1)
+                {
+                    break;
+                }
 
                 builder.Append(", ");
             }
@@ -123,9 +123,12 @@ namespace Avalonia.Media.Fonts
         /// </returns>
         public override bool Equals(object obj)
         {
-            if (!(obj is FamilyNameCollection other)) return false;
+            if (!(obj is FamilyNameCollection other))
+            {
+                return false;
+            }
 
             return other.ToString().Equals(ToString());
         }
     }
-}
\ No newline at end of file
+}
diff --git a/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs b/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
index 76ee2b7aad..7733dd7d2a 100644
--- a/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
+++ b/src/Avalonia.Visuals/Media/Fonts/FontFamilyKey.cs
@@ -95,7 +95,7 @@ namespace Avalonia.Media.Fonts
         {
             if (!Source.IsAbsoluteUri && BaseUri != null)
             {
-                return BaseUri.Authority + Source;
+                return BaseUri.AbsoluteUri + Source.OriginalString;
             }
 
             return Source.ToString();
diff --git a/src/Avalonia.X11/XIStructs.cs b/src/Avalonia.X11/XIStructs.cs
index 772bd1989c..ef49a72c43 100644
--- a/src/Avalonia.X11/XIStructs.cs
+++ b/src/Avalonia.X11/XIStructs.cs
@@ -197,7 +197,7 @@ namespace Avalonia.X11
     unsafe struct XIDeviceChangedEvent
     {
         public int Type; /* GenericEvent */
-        public ulong Serial; /* # of last request processed by server */
+        public UIntPtr Serial; /* # of last request processed by server */
         public Bool SendEvent; /* true if this came from a SendEvent request */
         public IntPtr Display; /* Display the event was read from */
         public int Extension; /* XI extension offset */
@@ -214,7 +214,7 @@ namespace Avalonia.X11
     struct XIDeviceEvent
     {
         public XEventName type; /* GenericEvent */
-        public ulong serial; /* # of last request processed by server */
+        public UIntPtr serial; /* # of last request processed by server */
         public Bool send_event; /* true if this came from a SendEvent request */
         public IntPtr display; /* Display the event was read from */
         public int extension; /* XI extension offset */
@@ -241,7 +241,7 @@ namespace Avalonia.X11
     unsafe struct XIEvent
     {
         public int type; /* GenericEvent */
-        public ulong serial; /* # of last request processed by server */
+        public UIntPtr serial; /* # of last request processed by server */
         public Bool send_event; /* true if this came from a SendEvent request */
         public IntPtr display; /* Display the event was read from */
         public int extension; /* XI extension offset */
diff --git a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
index 2070b4b66a..515e18434d 100644
--- a/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
+++ b/tests/Avalonia.Controls.UnitTests/CarouselTests.cs
@@ -152,6 +152,29 @@ namespace Avalonia.Controls.UnitTests
             Assert.Equal("Bar", ((TextBlock)child).Text);
         }
 
+        [Fact]
+        public void Selected_Item_Changes_To_First_Item_When_Item_Added()
+        {
+            var items = new ObservableCollection<string>();
+            var target = new Carousel
+            {
+                Template = new FuncControlTemplate<Carousel>(CreateTemplate),
+                Items = items,
+                IsVirtualized = false
+            };
+
+            target.ApplyTemplate();
+            target.Presenter.ApplyTemplate();
+
+            Assert.Equal(-1, target.SelectedIndex);
+            Assert.Empty(target.GetLogicalChildren());
+
+            items.Add("Foo");
+
+            Assert.Equal(0, target.SelectedIndex);
+            Assert.Single(target.GetLogicalChildren());
+        }
+
         [Fact]
         public void Selected_Index_Changes_To_When_Items_Assigned_Null()
         {
diff --git a/tests/Avalonia.Visuals.UnitTests/Media/FontFamilyTests.cs b/tests/Avalonia.Visuals.UnitTests/Media/FontFamilyTests.cs
index 4c7a89cbda..75ae43a1fa 100644
--- a/tests/Avalonia.Visuals.UnitTests/Media/FontFamilyTests.cs
+++ b/tests/Avalonia.Visuals.UnitTests/Media/FontFamilyTests.cs
@@ -2,7 +2,6 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
-using System.Collections.Generic;
 using System.Linq;
 using Avalonia.Media;
 using Avalonia.Media.Fonts;
@@ -12,18 +11,6 @@ namespace Avalonia.Visuals.UnitTests.Media
 {
     public class FontFamilyTests
     {
-        [Fact]
-        public void Exception_Should_Be_Thrown_If_Name_Is_Null()
-        {
-            Assert.Throws<ArgumentNullException>(() => new FontFamily((string)null));
-        }
-
-        [Fact]
-        public void Exception_Should_Be_Thrown_If_Names_Is_Null()
-        {
-            Assert.Throws<ArgumentNullException>(() => new FontFamily((IEnumerable<string>)null));
-        }
-
         [Fact]
         public void Should_Implicitly_Convert_String_To_FontFamily()
         {
@@ -41,7 +28,7 @@ namespace Avalonia.Visuals.UnitTests.Media
         }
 
         [Fact]
-        public void Parse_Parses_FontFamily_With_Name()
+        public void Should_Parse_FontFamily_With_SystemFont_Name()
         {
             var fontFamily = FontFamily.Parse("Courier New");
 
@@ -49,7 +36,7 @@ namespace Avalonia.Visuals.UnitTests.Media
         }
 
         [Fact]
-        public void Parse_Parses_FontFamily_With_Names()
+        public void Should_Parse_FontFamily_With_Fallbacks()
         {
             var fontFamily = FontFamily.Parse("Courier New, Times New Roman");
 
@@ -61,7 +48,7 @@ namespace Avalonia.Visuals.UnitTests.Media
         }
 
         [Fact]
-        public void Parse_Parses_FontFamily_With_Resource_Folder()
+        public void Should_Parse_FontFamily_With_Resource_Folder()
         {
             var source = new Uri("resm:Avalonia.Visuals.UnitTests#MyFont");
 
@@ -75,7 +62,7 @@ namespace Avalonia.Visuals.UnitTests.Media
         }
 
         [Fact]
-        public void Parse_Parses_FontFamily_With_Resource_Filename()
+        public void Should_Parse_FontFamily_With_Resource_Filename()
         {
             var source = new Uri("resm:Avalonia.Visuals.UnitTests.MyFont.ttf#MyFont");
 
@@ -87,5 +74,32 @@ namespace Avalonia.Visuals.UnitTests.Media
 
             Assert.Equal(key, fontFamily.Key);
         }
+
+        [Theory]
+        [InlineData("resm:Avalonia.Visuals.UnitTests/Assets/Fonts#MyFont")]
+        [InlineData("avares://Avalonia.Visuals.UnitTests/Assets/Fonts#MyFont")]
+        public void Should_Create_FontFamily_From_Uri(string name)
+        {
+            var fontFamily = new FontFamily(name);
+
+            Assert.Equal("MyFont", fontFamily.Name);
+
+            Assert.NotNull(fontFamily.Key);
+        }
+
+        [Theory]
+        [InlineData("resm:Avalonia.Visuals.UnitTests.Assets.Fonts", "#MyFont")]
+        [InlineData("avares://Avalonia.Visuals.UnitTests/Assets/Fonts", "#MyFont")]
+        [InlineData("avares://Avalonia.Visuals.UnitTests", "/Assets/Fonts#MyFont")]
+        public void Should_Create_FontFamily_From_Uri_With_Base_Uri(string @base, string name)
+        {
+            var baseUri = new Uri(@base);
+
+            var fontFamily = new FontFamily(baseUri, name);
+
+            Assert.Equal("MyFont", fontFamily.Name);
+
+            Assert.NotNull(fontFamily.Key);
+        }
     }
 }
diff --git a/tests/Avalonia.Visuals.UnitTests/Media/Fonts/FamilyNameCollectionTests.cs b/tests/Avalonia.Visuals.UnitTests/Media/Fonts/FamilyNameCollectionTests.cs
index 14daf5bd8b..e7aa9daab3 100644
--- a/tests/Avalonia.Visuals.UnitTests/Media/Fonts/FamilyNameCollectionTests.cs
+++ b/tests/Avalonia.Visuals.UnitTests/Media/Fonts/FamilyNameCollectionTests.cs
@@ -2,7 +2,6 @@
 // Licensed under the MIT license. See licence.md file in the project root for full license information.
 
 using System;
-using System.Linq;
 using Avalonia.Media.Fonts;
 using Xunit;
 
@@ -16,18 +15,12 @@ namespace Avalonia.Visuals.UnitTests.Media.Fonts
             Assert.Throws<ArgumentNullException>(() => new FamilyNameCollection(null));
         }
 
-        [Fact]
-        public void Exception_Should_Be_Thrown_If_Names_Is_Empty()
-        {
-            Assert.Throws<ArgumentException>(() => new FamilyNameCollection(Enumerable.Empty<string>()));
-        }
-
         [Fact]
         public void Should_Be_Equal()
         {
-            var familyNames = new FamilyNameCollection(new[] { "Arial", "Times New Roman" });
+            var familyNames = new FamilyNameCollection("Arial, Times New Roman");
 
-            Assert.Equal(new FamilyNameCollection(new[] { "Arial", "Times New Roman" }), familyNames);
+            Assert.Equal(new FamilyNameCollection("Arial, Times New Roman"), familyNames);
         }
     }
 }