Fix properties that affect measure/render etc

Perspex.Windows/Window.cs

@@ -10,6 +10,7 @@ namespace Perspex.Windows
     using System.ComponentModel;
     using System.Diagnostics.CodeAnalysis;
     using System.Linq;
+    using System.Reactive.Linq;
     using System.Runtime.InteropServices;
     using Perspex.Controls;
     using Perspex.Input;
@@ -32,6 +33,8 @@ namespace Perspex.Windows
 
         private IInputManager inputManager;
 
+        private bool layoutPending;
+
         static Window()
         {
             FontSizeProperty.OverrideDefaultValue(typeof(Window), 18.0);
@@ -51,22 +54,28 @@ namespace Perspex.Windows
 
             this.LayoutManager.LayoutNeeded.Subscribe(x => 
             {
+                this.layoutPending = true;
                 Dispatcher.CurrentDispatcher.BeginInvoke(
                     DispatcherPriority.Render, 
                     () =>
                     {
                         this.LayoutManager.ExecuteLayoutPass();
                         this.renderer.Render(this);
+                        this.layoutPending = false;
                     });
             });
 
-            this.RenderManager.RenderNeeded.Subscribe(x =>
+            this.RenderManager.RenderNeeded
+                .Subscribe(x =>
             {
                 Dispatcher.CurrentDispatcher.BeginInvoke(
                     DispatcherPriority.Render,
                     () =>
                     {
-                        this.renderer.Render(this);
+                        if (!this.layoutPending)
+                        {
+                            this.renderer.Render(this);
+                        }
                     });
             });
         }

Perspex/Controls/Border.cs

@@ -13,12 +13,10 @@ namespace Perspex.Controls
 
     public class Border : Decorator
     {
-        public Border()
+        static Border()
         {
-            Observable.Merge(
-                this.GetObservable(BackgroundProperty),
-                this.GetObservable(BorderBrushProperty))
-                .Subscribe(_ => this.InvalidateVisual());
+            AffectsRender(BackgroundProperty);
+            AffectsRender(BorderBrushProperty);
         }
 
         public override void Render(IDrawingContext context)

Perspex/Controls/Control.cs

@@ -119,6 +119,11 @@ namespace Perspex.Controls
 
         private Styles styles;
 
+        static Control()
+        {
+            AffectsMeasure(IsVisibleProperty);
+        }
+
         public Control()
         {
             this.classes = new Classes();
@@ -128,8 +133,6 @@ namespace Perspex.Controls
             this.PointerLeave += (s, e) => this.IsPointerOver = false;
             this.AddPseudoClass(IsPointerOverProperty, ":pointerover");
             this.AddPseudoClass(IsFocusedProperty, ":focus");
-
-            this.GetObservable(IsVisibleProperty).Subscribe(_ => this.InvalidateMeasure());
         }
 
         public event EventHandler<RoutedEventArgs> GotFocus
@@ -368,6 +371,36 @@ namespace Perspex.Controls
             get { return Enumerable.Empty<ILogical>(); }
         }
 
+        protected static void AffectsArrange(PerspexProperty property)
+        {
+            property.Changed.Subscribe(AffectsArrangeInvalidate);
+        }
+
+        protected static void AffectsMeasure(PerspexProperty property)
+        {
+            property.Changed.Subscribe(AffectsMeasureInvalidate);
+        }
+
+        private static void AffectsArrangeInvalidate(PerspexPropertyChangedEventArgs e)
+        {
+            Control control = e.Sender as Control;
+
+            if (control != null)
+            {
+                control.InvalidateArrange();
+            }
+        }
+
+        private static void AffectsMeasureInvalidate(PerspexPropertyChangedEventArgs e)
+        {
+            Control control = e.Sender as Control;
+
+            if (control != null)
+            {
+                control.InvalidateMeasure();
+            }
+        }
+
         public ILayoutRoot GetLayoutRoot()
         {
             return this.GetVisualAncestorOrSelf<ILayoutRoot>();

Perspex/Controls/TextBlock.cs

@@ -16,9 +16,9 @@ namespace Perspex.Controls
         public static readonly PerspexProperty<string> TextProperty =
             PerspexProperty.Register<TextBlock, string>("Text");
 
-        public TextBlock()
+        static TextBlock()
         {
-            this.GetObservable(TextProperty).Subscribe(_ => this.InvalidateVisual());
+            AffectsRender(TextProperty);
         }
 
         public string Text

Perspex/PerspexObject.cs

@@ -548,9 +548,9 @@ namespace Perspex
 
             if (this.PropertyChanged != null)
             {
-                this.PropertyChanged(
-                    this,
-                    new PerspexPropertyChangedEventArgs(property, oldValue, newValue));
+                PerspexPropertyChangedEventArgs e = new PerspexPropertyChangedEventArgs(this, property, oldValue, newValue);
+                property.NotifyChanged(e);
+                this.PropertyChanged(this, e);
             }
         }
     }

Perspex/PerspexProperty.cs

@@ -9,6 +9,7 @@ namespace Perspex
     using System;
     using System.Collections.Generic;
     using System.Linq;
+    using System.Reactive.Subjects;
     using System.Reflection;
     using System.Text;
     using System.Threading.Tasks;
@@ -31,6 +32,11 @@ namespace Perspex
         /// </summary>
         private Dictionary<Type, object> defaultValues = new Dictionary<Type, object>();
 
+        /// <summary>
+        /// Observable fired when this property changes on any <see cref="PerspexObject"/>.
+        /// </summary>
+        private Subject<PerspexPropertyChangedEventArgs> changed = new Subject<PerspexPropertyChangedEventArgs>();
+
         /// <summary>
         /// Initializes a new instance of the <see cref="PerspexProperty"/> class.
         /// </summary>
@@ -77,6 +83,15 @@ namespace Perspex
         /// </summary>
         public bool Inherits { get; private set; }
 
+        /// <summary>
+        /// Gets an observable that is fired when this property changes on any 
+        /// <see cref="PerspexObject"/> instance.
+        /// </summary>
+        public IObservable<PerspexPropertyChangedEventArgs> Changed
+        {
+            get { return this.changed; }
+        }
+
         /// <summary>
         /// Registers a <see cref="PerspexProperty"/>.
         /// </summary>
@@ -219,6 +234,11 @@ namespace Perspex
             return this.Name;
         }
 
+        internal void NotifyChanged(PerspexPropertyChangedEventArgs e)
+        {
+            this.changed.OnNext(e);
+        }
+
         public class BindingAccessor
         {
             public BindingAccessor(PerspexProperty property, BindingPriority priority)

Perspex/PerspexPropertyChangedEventArgs.cs

@@ -18,15 +18,23 @@ namespace Perspex
     public class PerspexPropertyChangedEventArgs
     {
         public PerspexPropertyChangedEventArgs(
+            PerspexObject sender,
             PerspexProperty property,
             object oldValue,
             object newValue)
         {
+            this.Sender = sender;
             this.Property = property;
             this.OldValue = oldValue;
             this.NewValue = newValue;
         }
 
+        /// <summary>
+        /// Gets the <see cref="PerspexObject"/> that the property changed on.
+        /// </summary>
+        /// <returns></returns>
+        public PerspexObject Sender { get; private set; }
+
         /// <summary>
         /// Gets the property that changed.
         /// </summary>

Perspex/Visual.cs

@@ -23,9 +23,9 @@ namespace Perspex
 
         private Rect bounds;
 
-        public Visual()
+        static Visual()
         {
-            this.GetObservable(IsVisibleProperty).Subscribe(_ => this.InvalidateVisual());
+            AffectsRender(IsVisibleProperty);
         }
 
         public bool IsVisible
@@ -74,6 +74,21 @@ namespace Perspex
             }
         }
 
+        protected static void AffectsRender(PerspexProperty property)
+        {
+            property.Changed.Subscribe(AffectsRenderInvalidate);
+        }
+
+        private static void AffectsRenderInvalidate(PerspexPropertyChangedEventArgs e)
+        {
+            Visual visual = e.Sender as Visual;
+
+            if (visual != null)
+            {
+                visual.InvalidateVisual();
+            }
+        }
+
         public void InvalidateVisual()
         {
             IRendered root = this.GetVisualAncestorOrSelf<IRendered>();