Make templates etc get applied on measure.

Instead of when iterating visual children. This because everything is
likely to be set up by that point.

Perspex.Controls/Generators/ItemContainerGenerator.cs

@@ -86,8 +86,6 @@ namespace Perspex.Controls.Generators
                     container.TemplatedParent = null;
                     this.AddInternal(item, container);
                     result.Add(container);
-
-                    System.Diagnostics.Debug.WriteLine("{0} : Generated container for {1} {2}: {3}", this.GetHashCode(), item, item.GetHashCode(), container);
                 }
             }
             finally
@@ -132,7 +130,6 @@ namespace Perspex.Controls.Generators
             object item = this.itemsByContainer[container];
             this.containersByItem.Remove(item);
             this.itemsByContainer.Remove(container);
-            System.Diagnostics.Debug.WriteLine("{0} : Removed container for {1} {2}", this.GetHashCode(), item, item.GetHashCode());
             return item;
         }
 
@@ -141,7 +138,6 @@ namespace Perspex.Controls.Generators
             Control container = this.containersByItem[item];
             this.containersByItem.Remove(item);
             this.itemsByContainer.Remove(container);
-            System.Diagnostics.Debug.WriteLine("{0} : Removed container for {1} {2}", this.GetHashCode(), item, item.GetHashCode());
             return container;
         }
     }

Perspex.Controls/Generators/TreeItemContainerGenerator.cs

@@ -39,8 +39,6 @@ namespace Perspex.Controls.Generators
             {
                 TreeDataTemplate template = this.GetTreeDataTemplate(item);
 
-                System.Diagnostics.Debug.WriteLine("{0} created item for {1}", this.GetHashCode(), item);
-
                 result = new T
                 {
                     Header = template.Build(item),

Perspex.Controls/Presenters/ContentPresenter.cs

@@ -9,6 +9,7 @@ namespace Perspex.Controls.Presenters
     using System;
     using System.Linq;
     using System.Reactive.Linq;
+    using Perspex.Controls.Primitives;
     using Perspex.Layout;
 
     public class ContentPresenter : Control, IVisual
@@ -16,6 +17,8 @@ namespace Perspex.Controls.Presenters
         public static readonly PerspexProperty<object> ContentProperty =
             ContentControl.ContentProperty.AddOwner<Control>();
 
+        private bool createdChild;
+
         public ContentPresenter()
         {
             this.GetObservable(ContentProperty).Skip(1).Subscribe(this.ContentChanged);
@@ -27,10 +30,36 @@ namespace Perspex.Controls.Presenters
             set { this.SetValue(ContentProperty, value); }
         }
 
-        protected override void CreateVisualChildren()
+        protected override Size MeasureOverride(Size availableSize)
+        {
+            if (!this.createdChild)
+            {
+                this.CreateChild();
+            }
+
+            Control child = ((IVisual)this).VisualChildren.SingleOrDefault() as Control;
+
+            if (child != null)
+            {
+                child.Measure(availableSize);
+                return child.DesiredSize.Value;
+            }
+
+            return new Size();
+        }
+
+        private void ContentChanged(object content)
+        {
+            this.createdChild = false;
+            this.InvalidateMeasure();
+        }
+
+        private void CreateChild()
         {
             object content = this.Content;
 
+            this.ClearVisualChildren();
+
             if (content != null)
             {
                 Control result;
@@ -59,26 +88,8 @@ namespace Perspex.Controls.Presenters
                 result.TemplatedParent = null;
                 this.AddVisualChild(result);
             }
-        }
 
-        protected override Size MeasureOverride(Size availableSize)
-        {
-            Control child = ((IVisual)this).VisualChildren.SingleOrDefault() as Control;
-
-            if (child != null)
-            {
-                child.Measure(availableSize);
-                return child.DesiredSize.Value;
-            }
-
-            return new Size();
-        }
-
-        private void ContentChanged(object content)
-        {
-            this.ClearVisualChildren();
-            this.CreateVisualChildren();
-            this.InvalidateMeasure();
+            this.createdChild = true;
         }
     }
 }

Perspex.Controls/Presenters/ItemsPresenter.cs

@@ -22,6 +22,8 @@ namespace Perspex.Controls.Presenters
 
         private Panel panel;
 
+        private bool createdPanel;
+
         public ItemsPresenter()
         {
             this.GetObservableWithHistory(ItemsProperty).Skip(1).Subscribe(this.ItemsChanged);
@@ -41,21 +43,28 @@ namespace Perspex.Controls.Presenters
 
         protected override Size MeasureOverride(Size availableSize)
         {
-            Panel panel = this.GetPanel();
+            if (!this.createdPanel)
+            {
+                this.CreatePanel();
+            }
+
             panel.Measure(availableSize);
             return panel.DesiredSize.Value;
         }
 
         protected override Size ArrangeOverride(Size finalSize)
         {
-            this.GetPanel().Arrange(new Rect(finalSize));
+            this.panel.Arrange(new Rect(finalSize));
             return finalSize;
         }
 
-        protected override void CreateVisualChildren()
+        private void CreatePanel()
         {
-            this.AddVisualChild(this.GetPanel());
+            this.ClearVisualChildren();
+            this.panel = this.ItemsPanel.Build();
+            this.AddVisualChild(this.panel);
             this.ItemsChanged(Tuple.Create(default(IEnumerable), this.Items));
+            this.createdPanel = true;
         }
 
         private IItemContainerGenerator GetGenerator()
@@ -70,16 +79,6 @@ namespace Perspex.Controls.Presenters
             return i.ItemContainerGenerator;
         }
 
-        private Panel GetPanel()
-        {
-            if (this.panel == null && this.ItemsPanel != null)
-            {
-                this.panel = this.ItemsPanel.Build();
-            }
-
-            return this.panel;
-        }
-
         private void ItemsChanged(Tuple<IEnumerable, IEnumerable> value)
         {
             var generator = this.GetGenerator();

Perspex.Controls/Primitives/TemplatedControl.cs

@@ -18,6 +18,8 @@ namespace Perspex.Controls.Primitives
         public static readonly PerspexProperty<ControlTemplate> TemplateProperty =
             PerspexProperty.Register<TemplatedControl, ControlTemplate>("Template");
 
+        private bool templateApplied;
+
         public ControlTemplate Template
         {
             get { return this.GetValue(TemplateProperty); }
@@ -45,6 +47,11 @@ namespace Perspex.Controls.Primitives
 
         protected override Size MeasureOverride(Size availableSize)
         {
+            if (!this.templateApplied)
+            {
+                this.ApplyTemplate();
+            }
+
             Control child = ((IVisual)this).VisualChildren.SingleOrDefault() as Control;
 
             if (child != null)
@@ -56,21 +63,6 @@ namespace Perspex.Controls.Primitives
             return new Size();
         }
 
-        protected override void CreateVisualChildren()
-        {
-            if (this.Template != null)
-            {
-                this.Log().Debug(
-                    "Creating template for {0} (#{1:x8})",
-                    this.GetType().Name,
-                    this.GetHashCode());
-
-                var child = this.Template.Build(this);
-                this.AddVisualChild(child);
-                this.OnTemplateApplied();
-            }
-        }
-
         protected T FindTemplateChild<T>(string id) where T : Control
         {
             return this.GetTemplateControls().OfType<T>().FirstOrDefault(x => x.Id == id);
@@ -94,5 +86,24 @@ namespace Perspex.Controls.Primitives
         protected virtual void OnTemplateApplied()
         {
         }
+
+        private void ApplyTemplate()
+        {
+            this.ClearVisualChildren();
+
+            if (this.Template != null)
+            {
+                this.Log().Debug(
+                    "Creating template for {0} (#{1:x8})",
+                    this.GetType().Name,
+                    this.GetHashCode());
+
+                var child = this.Template.Build(this);
+                this.AddVisualChild(child);
+                this.OnTemplateApplied();
+            }
+
+            this.templateApplied = true;
+        }
     }
 }

Perspex.Controls/StackPanel.cs

@@ -107,7 +107,7 @@ namespace Perspex.Controls
                 arrangedWidth = 0;
             }
 
-            foreach (Control child in this.Children.Where(x => x.DesiredSize.HasValue))
+            foreach (Control child in this.Children)
             {
                 double childWidth = child.DesiredSize.Value.Width;
                 double childHeight = child.DesiredSize.Value.Height;

Perspex.Layout/Layoutable.cs

@@ -149,6 +149,11 @@ namespace Perspex.Layout
                 throw new InvalidOperationException("Invalid Arrange rectangle.");
             }
 
+            if (!this.DesiredSize.HasValue)
+            {
+                throw new InvalidOperationException("Arrange called before Measure.");
+            }
+
             this.Log().Debug(
                 "Arrange of {0} (#{1:x8}) gave {2} ",
                 this.GetType().Name,
@@ -193,48 +198,51 @@ namespace Perspex.Layout
 
         protected virtual void ArrangeCore(Rect finalRect)
         {
-            double originX = finalRect.X + this.Margin.Left;
-            double originY = finalRect.Y + this.Margin.Top;
-            var size = new Size(
-                Math.Max(0, finalRect.Width - this.Margin.Left - this.Margin.Right),
-                Math.Max(0, finalRect.Height - this.Margin.Top - this.Margin.Bottom));
-
-            if (this.HorizontalAlignment != HorizontalAlignment.Stretch)
+            if (this.IsVisible)
             {
-                size = size.WithWidth(Math.Min(size.Width, this.DesiredSize.Value.Width));
-            }
+                double originX = finalRect.X + this.Margin.Left;
+                double originY = finalRect.Y + this.Margin.Top;
+                var size = new Size(
+                    Math.Max(0, finalRect.Width - this.Margin.Left - this.Margin.Right),
+                    Math.Max(0, finalRect.Height - this.Margin.Top - this.Margin.Bottom));
 
-            if (this.VerticalAlignment != VerticalAlignment.Stretch)
-            {
-                size = size.WithHeight(Math.Min(size.Height, this.DesiredSize.Value.Height));
-            }
+                if (this.HorizontalAlignment != HorizontalAlignment.Stretch)
+                {
+                    size = size.WithWidth(Math.Min(size.Width, this.DesiredSize.Value.Width));
+                }
+
+                if (this.VerticalAlignment != VerticalAlignment.Stretch)
+                {
+                    size = size.WithHeight(Math.Min(size.Height, this.DesiredSize.Value.Height));
+                }
 
-            size = LayoutHelper.ApplyLayoutConstraints(this, size);
-            size = this.ArrangeOverride(size).Constrain(size);
+                size = LayoutHelper.ApplyLayoutConstraints(this, size);
+                size = this.ArrangeOverride(size).Constrain(size);
 
-            switch (this.HorizontalAlignment)
-            {
-                case HorizontalAlignment.Center:
-                    originX += (finalRect.Width - size.Width) / 2;
-                    break;
-                case HorizontalAlignment.Right:
-                    originX += finalRect.Width - size.Width;
-                    break;
-            }
+                switch (this.HorizontalAlignment)
+                {
+                    case HorizontalAlignment.Center:
+                        originX += (finalRect.Width - size.Width) / 2;
+                        break;
+                    case HorizontalAlignment.Right:
+                        originX += finalRect.Width - size.Width;
+                        break;
+                }
 
-            switch (this.VerticalAlignment)
-            {
-                case VerticalAlignment.Center:
-                    originY += (finalRect.Height - size.Height) / 2;
-                    break;
-                case VerticalAlignment.Bottom:
-                    originY += finalRect.Height - size.Height;
-                    break;
-            }
+                switch (this.VerticalAlignment)
+                {
+                    case VerticalAlignment.Center:
+                        originY += (finalRect.Height - size.Height) / 2;
+                        break;
+                    case VerticalAlignment.Bottom:
+                        originY += finalRect.Height - size.Height;
+                        break;
+                }
 
-            var bounds = new Rect(originX, originY, size.Width, size.Height);
-            this.SetVisualBounds(bounds);
-            this.SetValue(ActualSizeProperty, bounds.Size);
+                var bounds = new Rect(originX, originY, size.Width, size.Height);
+                this.SetVisualBounds(bounds);
+                this.SetValue(ActualSizeProperty, bounds.Size);
+            }
         }
 
         protected virtual Size ArrangeOverride(Size finalSize)

Perspex.SceneGraph.UnitTests/TestVisual.cs

@@ -27,8 +27,6 @@ namespace Perspex.SceneGraph.UnitTests
             get { return base.InheritanceParent; }
         }
 
-        public Visual[] InitialChildren { get; set; }
-
         public event EventHandler<ParamEventArgs<Visual>> VisualParentChangedCalled;
 
         public event EventHandler<ParamEventArgs<IRenderRoot>> AttachedToVisualTreeCalled;
@@ -40,6 +38,11 @@ namespace Perspex.SceneGraph.UnitTests
             this.AddVisualChild(v);
         }
 
+        public void AddChildren(IEnumerable<Visual> v)
+        {
+            this.AddVisualChildren(v);
+        }
+
         public void RemoveChild(Visual v)
         {
             this.RemoveVisualChild(v);
@@ -50,14 +53,6 @@ namespace Perspex.SceneGraph.UnitTests
             this.ClearVisualChildren();
         }
 
-        protected override void CreateVisualChildren()
-        {
-            if (this.InitialChildren != null)
-            {
-                this.AddVisualChildren(this.InitialChildren);
-            }
-        }
-
         protected override void OnVisualParentChanged(Visual oldParent)
         {
             if (this.VisualParentChangedCalled != null)

Perspex.SceneGraph.UnitTests/VisualTests.cs

@@ -12,32 +12,6 @@ namespace Perspex.SceneGraph.UnitTests
     [TestClass]
     public class VisualTests
     {
-        [TestMethod]
-        public void Initial_Children_Should_Be_Created()
-        {
-            var target = new TestVisual
-            {
-                InitialChildren = new[] { new Visual(), new Visual() }
-            };
-
-            var result = target.GetVisualChildren().ToList();
-
-            CollectionAssert.AreEqual(target.InitialChildren.ToList(), result);
-        }
-
-        [TestMethod]
-        public void Initial_Children_Should_Have_VisualParent_Set()
-        {
-            var target = new TestVisual
-            {
-                InitialChildren = new[] { new Visual(), new Visual() }
-            };
-
-            var result = target.GetVisualChildren().Select(x => x.GetVisualParent()).ToList();
-
-            CollectionAssert.AreEqual(new[] { target, target }, result);
-        }
-
         [TestMethod]
         public void Added_Child_Should_Have_VisualParent_Set()
         {
@@ -87,14 +61,13 @@ namespace Perspex.SceneGraph.UnitTests
         [TestMethod]
         public void Clearing_Children_Should_Clear_VisualParent()
         {
-            var target = new TestVisual
-            {
-                InitialChildren = new[] { new Visual(), new Visual() }
-            };
+            var children = new[] { new Visual(), new Visual() };
+            var target = new TestVisual();
 
+            target.AddChildren(children);
             target.ClearChildren();
 
-            var result = target.InitialChildren.Select(x => x.GetVisualParent()).ToList();
+            var result = children.Select(x => x.GetVisualParent()).ToList();
 
             CollectionAssert.AreEqual(new Visual[] { null, null }, result);
         }
@@ -108,11 +81,10 @@ namespace Perspex.SceneGraph.UnitTests
             int attched = 0;
             int i = 1;
 
-            target.InitialChildren = new[] { child };
             child.VisualParentChangedCalled += (s, e) => changed = i++;
             child.AttachedToVisualTreeCalled += (s, e) => attched = i++;
 
-            target.GetVisualChildren().First();
+            target.AddChild(child);
 
             Assert.AreEqual(1, changed);
             Assert.AreEqual(2, attched);
@@ -127,8 +99,7 @@ namespace Perspex.SceneGraph.UnitTests
             int detached = 0;
             int i = 1;
 
-            target.InitialChildren = new[] { child };
-            target.GetVisualChildren().First();
+            target.AddChild(child);
 
             child.VisualParentChangedCalled += (s, e) => changed = i++;
             child.DetachedFromVisualTreeCalled += (s, e) => detached = i++;

Perspex.SceneGraph/Visual.cs

@@ -39,6 +39,12 @@ namespace Perspex
             AffectsRender(IsVisibleProperty);
         }
 
+        public Visual()
+        {
+            this.visualChildren = new PerspexList<IVisual>();
+            this.visualChildren.CollectionChanged += VisualChildrenChanged;
+        }
+
         public bool IsVisible
         {
             get { return this.GetValue(IsVisibleProperty); }
@@ -70,11 +76,7 @@ namespace Perspex
 
         IReadOnlyPerspexList<IVisual> IVisual.VisualChildren
         {
-            get
-            {
-                this.EnsureVisualChildrenCreated();
-                return this.visualChildren;
-            }
+            get { return this.visualChildren; }
         }
 
         IVisual IVisual.VisualParent
@@ -111,7 +113,6 @@ namespace Perspex
         {
             Contract.Requires<ArgumentNullException>(visual != null);
 
-            this.EnsureVisualChildrenCreated();
             this.visualChildren.Add(visual);
         }
 
@@ -119,14 +120,11 @@ namespace Perspex
         {
             Contract.Requires<ArgumentNullException>(visuals != null);
 
-            this.EnsureVisualChildrenCreated();
             this.visualChildren.AddRange(visuals);
         }
 
         protected void ClearVisualChildren()
         {
-            this.EnsureVisualChildrenCreated();
-
             // TODO: Just call visualChildren.Clear() when we have a PerspexList that notifies of 
             // the removed items.
             while (this.visualChildren.Count > 0)
@@ -139,7 +137,6 @@ namespace Perspex
         {
             Contract.Requires<ArgumentNullException>(visual != null);
 
-            this.EnsureVisualChildrenCreated();
             this.visualChildren.Remove(visual);
         }
 
@@ -147,8 +144,6 @@ namespace Perspex
         {
             Contract.Requires<ArgumentNullException>(visuals != null);
 
-            this.EnsureVisualChildrenCreated();
-
             foreach (var v in visuals)
             {
                 this.visualChildren.Remove(v);
@@ -160,10 +155,6 @@ namespace Perspex
             this.bounds = bounds;
         }
 
-        protected virtual void CreateVisualChildren()
-        {
-        }
-
         protected virtual void OnAttachedToVisualTree(IRenderRoot root)
         {
         }
@@ -186,16 +177,6 @@ namespace Perspex
             }
         }
 
-        private void EnsureVisualChildrenCreated()
-        {
-            if (this.visualChildren == null)
-            {
-                this.visualChildren = new PerspexList<IVisual>();
-                this.visualChildren.CollectionChanged += VisualChildrenChanged;
-                this.CreateVisualChildren();
-            }
-        }
-
         private void SetVisualParent(Visual value)
         {
             if (this.visualParent != value)

Perspex.UnitTests/PerspexObjectTests.cs

@@ -371,9 +371,6 @@ namespace Perspex.UnitTests
             Class1 source = new Class1();
             Class1 target = new Class1();
 
-            System.Diagnostics.Debug.WriteLine("source: " + source.GetHashCode());
-            System.Diagnostics.Debug.WriteLine("target: " + target.GetHashCode());
-
             source.SetValue(Class1.FooProperty, "first");
             target.BindTwoWay(Class1.FooProperty, source, Class1.FooProperty);
 

Perspex.Windows/Window.cs

@@ -160,6 +160,8 @@ namespace Perspex.Windows
                 lpszClassName = this.className,
             };
 
+            System.Diagnostics.Debug.WriteLine("Registered class " + this.className);
+
             ushort atom = UnmanagedMethods.RegisterClassEx(ref wndClassEx);
 
             if (atom == 0)