Started adding a styling system.

Perspex/Controls/ContentControl.cs

@@ -1,5 +1,6 @@
 namespace Perspex.Controls
 {
+    using System;
     using System.Linq;
 
     public abstract class ContentControl : TemplatedControl
@@ -7,6 +8,19 @@
         public static readonly PerspexProperty<object> ContentProperty =
             PerspexProperty.Register<ContentControl, object>("Content");
 
+        public ContentControl()
+        {
+            this.GetObservable(ContentProperty).Subscribe(x =>
+            {
+                Control control = x as Control;
+
+                if (control != null)
+                {
+                    control.SetValue(ParentPropertyRW, this);
+                }
+            });
+        }
+
         public object Content
         {
             get { return this.GetValue(ContentProperty); }

Perspex/Controls/Control.cs

@@ -1,9 +1,11 @@
 namespace Perspex.Controls
 {
     using System;
-    using System.Diagnostics.Contracts;
-    using Perspex.Layout;
-    using Perspex.Media;
+using System.Collections.Generic;
+using System.Collections.ObjectModel;
+using System.Diagnostics.Contracts;
+using Perspex.Layout;
+using Perspex.Media;
 
     public enum HorizontalAlignment
     {
@@ -23,14 +25,20 @@
 
     public abstract class Control : Visual, ILayoutable
     {
+        internal static readonly PerspexProperty<Control> ParentPropertyRW =
+            PerspexProperty.Register<Control, Control>("Parent");
+
+        public static readonly ReadOnlyPerspexProperty<Control> ParentProperty =
+            new ReadOnlyPerspexProperty<Control>(ParentPropertyRW);
+
         public static readonly PerspexProperty<Brush> BackgroundProperty =
-            PerspexProperty.Register<Border, Brush>("Background");
+            PerspexProperty.Register<Control, Brush>("Background");
 
         public static readonly PerspexProperty<Brush> BorderBrushProperty =
-            PerspexProperty.Register<Border, Brush>("BorderBrush");
+            PerspexProperty.Register<Control, Brush>("BorderBrush");
 
         public static readonly PerspexProperty<double> BorderThicknessProperty =
-            PerspexProperty.Register<Border, double>("BorderThickness");
+            PerspexProperty.Register<Control, double>("BorderThickness");
 
         public static readonly PerspexProperty<HorizontalAlignment> HorizontalAlignmentProperty =
             PerspexProperty.Register<Control, HorizontalAlignment>("HorizontalAlignment");
@@ -41,6 +49,13 @@
         public static readonly PerspexProperty<Thickness> MarginProperty =
             PerspexProperty.Register<Control, Thickness>("Margin");
 
+        public Control()
+        {
+            this.Classes = new ObservableCollection<string>();
+            this.Styles = new ObservableCollection<Style>();
+            this.GetObservableWithHistory(ParentPropertyRW).Subscribe(this.ParentChanged);
+        }
+
         public Brush Background
         {
             get { return this.GetValue(BackgroundProperty); }
@@ -59,6 +74,18 @@
             set { this.SetValue(BorderThicknessProperty, value); }
         }
 
+        public ObservableCollection<string> Classes
+        {
+            get;
+            private set;
+        }
+
+        public IEnumerable<Style> Styles
+        {
+            get;
+            set;
+        }
+
         public Size? DesiredSize
         {
             get;
@@ -85,8 +112,8 @@
 
         public Control Parent
         {
-            get;
-            internal set;
+            get { return this.GetValue(ParentPropertyRW); }
+            internal set { this.SetValue(ParentPropertyRW, value); }
         }
 
         public ILayoutRoot GetLayoutRoot()
@@ -130,5 +157,36 @@
         }
 
         protected abstract Size MeasureContent(Size availableSize);
+
+        private void AttachStyles(Control control)
+        {
+            if (control.Styles != null)
+            {
+                foreach (Style style in control.Styles)
+                {
+                    style.Attach(this);
+                }
+            }
+
+            Control parent = control.Parent;
+            
+            if (parent != null)
+            {
+                this.AttachStyles(parent);
+            }
+        }
+
+        private void ParentChanged(Tuple<Control, Control> values)
+        {
+            if (values.Item1 != null)
+            {
+                //this.DetatchStyles(values.Item1);
+            }
+
+            if (values.Item2 != null)
+            {
+                this.AttachStyles(this);
+            }
+        }
     }
 }

Perspex/Perspex.csproj

@@ -92,10 +92,13 @@
     <Compile Include="PerspexPropertyChangedEventArgs.cs" />
     <Compile Include="Point.cs" />
     <Compile Include="ReadOnlyPerspexProperty.cs" />
+    <Compile Include="Selectors.cs" />
     <Compile Include="ServiceLocator.cs" />
+    <Compile Include="Setter.cs" />
     <Compile Include="Size.cs" />
     <Compile Include="Rect.cs" />
     <Compile Include="Controls\TemplatedControl.cs" />
+    <Compile Include="Style.cs" />
     <Compile Include="Thickness.cs" />
     <Compile Include="Visual.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />

Perspex/PerspexObject.cs

@@ -203,6 +203,33 @@ namespace Perspex
             this.values.Remove(property);
         }
 
+        /// <summary>
+        /// Gets an observable for a <see cref="PerspexProperty"/>.
+        /// </summary>
+        /// <param name="property"></param>
+        /// <returns></returns>
+        public IObservable<object> GetObservable(PerspexProperty property)
+        {
+            return Observable.Create<object>(observer =>
+            {
+                EventHandler<PerspexPropertyChangedEventArgs> handler = (s, e) =>
+                {
+                    if (e.Property == property)
+                    {
+                        observer.OnNext(e.NewValue);
+                    }
+                };
+
+                this.PropertyChanged += handler;
+                observer.OnNext(this.GetValue(property));
+
+                return () =>
+                {
+                    this.PropertyChanged -= handler;
+                };
+            });
+        }
+
         /// <summary>
         /// Gets an observable for a <see cref="PerspexProperty"/>.
         /// </summary>
@@ -231,6 +258,44 @@ namespace Perspex
             });
         }
 
+        /// <summary>
+        /// Gets an observable for a <see cref="ReadOnlyPerspexProperty"/>.
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="property"></param>
+        /// <returns></returns>
+        public IObservable<T> GetObservable<T>(ReadOnlyPerspexProperty<T> property)
+        {
+            return this.GetObservable((PerspexProperty<T>)property.Property);
+        }
+
+        /// <summary>
+        /// Gets an observable for a <see cref="PerspexProperty"/>.
+        /// </summary>
+        /// <typeparam name="T"></typeparam>
+        /// <param name="property"></param>
+        /// <returns></returns>
+        public IObservable<Tuple<T, T>> GetObservableWithHistory<T>(PerspexProperty<T> property)
+        {
+            return Observable.Create<Tuple<T, T>>(observer =>
+            {
+                EventHandler<PerspexPropertyChangedEventArgs> handler = (s, e) =>
+                {
+                    if (e.Property == property)
+                    {
+                        observer.OnNext(Tuple.Create((T)e.OldValue, (T)e.NewValue));
+                    }
+                };
+
+                this.PropertyChanged += handler;
+
+                return () =>
+                {
+                    this.PropertyChanged -= handler;
+                };
+            });
+        }
+
         /// <summary>
         /// Gets a <see cref="PerspexProperty"/> value.
         /// </summary>
@@ -297,16 +362,15 @@ namespace Perspex
         /// <summary>
         /// Sets a <see cref="PerspexProperty"/> value.
         /// </summary>
-        /// <typeparam name="T">The type of the property.</typeparam>
         /// <param name="property">The property.</param>
         /// <param name="value">The value.</param>
-        public void SetValue<T>(PerspexProperty<T> property, T value)
+        public void SetValue(PerspexProperty property, object value)
         {
             Contract.Requires<NullReferenceException>(property != null);
 
             this.ClearBinding(property);
 
-            T oldValue = this.GetValue(property);
+            object oldValue = this.GetValue(property);
 
             if (!object.Equals(oldValue, value))
             {
@@ -315,6 +379,19 @@ namespace Perspex
             }
         }
 
+        /// <summary>
+        /// Sets a <see cref="PerspexProperty"/> value.
+        /// </summary>
+        /// <typeparam name="T">The type of the property.</typeparam>
+        /// <param name="property">The property.</param>
+        /// <param name="value">The value.</param>
+        public void SetValue<T>(PerspexProperty<T> property, T value)
+        {
+            Contract.Requires<NullReferenceException>(property != null);
+
+            this.SetValue((PerspexProperty)property, value);
+        }
+
         /// <summary>
         /// Called when a property is changed on the current <see cref="InheritanceParent"/>.
         /// </summary>

Perspex/Selectors.cs

@@ -0,0 +1,21 @@
+namespace Perspex
+{
+    using System;
+    using System.Collections.Generic;
+    using System.Diagnostics.Contracts;
+    using System.Linq;
+    using System.Reactive.Linq;
+    using System.Text;
+    using System.Threading.Tasks;
+    using Perspex.Controls;
+
+    public static class Selectors
+    {
+        public static IObservable<bool> OfType<T>(this Control control)
+        {
+            Contract.Requires<ArgumentNullException>(control != null);
+            
+            return Observable.Return(control is T);
+        }
+    }
+}

Perspex/Setter.cs

@@ -0,0 +1,38 @@
+namespace Perspex
+{
+    using System;
+    using System.Diagnostics.Contracts;
+    using Perspex.Controls;
+
+    public class Setter
+    {
+        private object oldValue;
+
+        public PerspexProperty Property
+        {
+            get;
+            set;
+        }
+
+        public object Value
+        {
+            get;
+            set;
+        }
+
+        public void Apply(Control control)
+        {
+            Contract.Requires<NullReferenceException>(control != null);
+
+            this.oldValue = control.GetValue(this.Property);
+            control.SetValue(this.Property, this.Value);
+        }
+
+        public void Detach(Control control)
+        {
+            Contract.Requires<NullReferenceException>(control != null);
+
+            control.SetValue(this.Property, this.oldValue);
+        }
+    }
+}

Perspex/Style.cs

@@ -0,0 +1,67 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Reactive.Disposables;
+using System.Text;
+using System.Threading.Tasks;
+using Perspex.Controls;
+
+namespace Perspex
+{
+    public class Style
+    {
+        public Style()
+        {
+            this.Setters = new List<Setter>();
+        }
+
+        public Func<Control, IObservable<bool>> Selector
+        {
+            get;
+            set;
+        }
+
+        public IEnumerable<Setter> Setters
+        {
+            get;
+            set;
+        }
+
+        public void Attach(Control control)
+        {
+            this.Selector(control).Subscribe(x => 
+            {
+                if (x)
+                {
+                    this.Apply(control);
+                }
+                else
+                {
+                    this.Unapply(control);
+                }
+            });
+        }
+
+        private void Apply(Control control)
+        {
+            if (this.Setters != null)
+            {
+                foreach (Setter setter in this.Setters)
+                {
+                    setter.Apply(control);
+                }
+            }
+        }
+
+        private void Unapply(Control control)
+        {
+            if (this.Setters != null)
+            {
+                foreach (Setter setter in this.Setters)
+                {
+                    setter.Detach(control);
+                }
+            }
+        }
+    }
+}

TestApplication/Program.cs

@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.Collections.ObjectModel;
 using System.Linq;
 using System.Reactive.Linq;
 using System.Text;
@@ -19,16 +20,32 @@ namespace TestApplication
         {
             ServiceLocator.Register<ITextService>(() => new TextService(new SharpDX.DirectWrite.Factory()));
 
-            Window window = new Window();
-
-            window.Content = new Button
+            Window window = new Window
             {
-                Content = "Hello World",
-                HorizontalAlignment = HorizontalAlignment.Center,
-                VerticalAlignment = VerticalAlignment.Center,
-                Background = new SolidColorBrush(0xff808080),
-                BorderThickness = 2,
-                BorderBrush = new SolidColorBrush(0xff000000),
+                Styles = new ObservableCollection<Style>
+                {
+                    new Style
+                    {
+                        Selector = x => x.OfType<Button>(),
+                        Setters = new[]
+                        {
+                            new Setter 
+                            { 
+                                Property = Button.BackgroundProperty, 
+                                Value = new SolidColorBrush(0xffff8080),
+                            }
+                        },
+                    }
+                },
+                Content = new Button
+                {
+                    Content = "Hello World",
+                    HorizontalAlignment = HorizontalAlignment.Center,
+                    VerticalAlignment = VerticalAlignment.Center,
+                    Background = new SolidColorBrush(0xff808080),
+                    BorderThickness = 2,
+                    BorderBrush = new SolidColorBrush(0xff000000),
+                },
             };
 
             window.Show();