[WPF] Fixes ControlTemplate sizing issue (xamarin#2656)

- fixes xamarin#2642

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/GitHub2642.cs

@@ -0,0 +1,51 @@
+using Xamarin.Forms.CustomAttributes;
+using Xamarin.Forms.Internals;
+
+namespace Xamarin.Forms.Controls.Issues
+{
+	[Preserve(AllMembers = true)]
+	[Issue(IssueTracker.Github, 2642, "ControlTemplate resizing issue", PlatformAffected.WPF)]
+	public class GitHub2642 : TestContentPage
+	{
+		public class PresenterWrapper : ContentView
+		{
+			public PresenterWrapper()
+			{
+				Content = new ContentPresenter();
+			}
+		}
+
+		protected override void Init()
+		{
+			this.ControlTemplate = new ControlTemplate(typeof(PresenterWrapper));
+
+			var grid = new Grid()
+			{
+				RowDefinitions = new RowDefinitionCollection
+					{
+						new RowDefinition { Height = new GridLength(0, GridUnitType.Auto) },
+						new RowDefinition { Height = new GridLength(1, GridUnitType.Star) },
+					}
+			};
+
+			grid.AddChild(new Label()
+			{
+				Text = "Header",
+				LineBreakMode = LineBreakMode.WordWrap,
+				FontSize = 24
+
+			}, 0, 0);
+
+			grid.AddChild(new Label()
+			{
+				Text = "Lorem ipsum dolor sit amet, sed at etiam graecis. Amet dicta utroque in ius, error vituperatoribus vel ex. " +
+					"Cu duo veri aperiam honestatis. Quo sint movet ullamcorper cu, vero vidisse argumentum ne nec, in munere eirmod eum. " +
+					"Persius similique reformidans ex mei, cu quo quot nihil mediocrem.",
+				LineBreakMode = LineBreakMode.WordWrap
+
+			}, 0, 1);
+
+			Content = grid;
+		}
+	}
+}

Xamarin.Forms.Controls.Issues/Xamarin.Forms.Controls.Issues.Shared/Xamarin.Forms.Controls.Issues.Shared.projitems

@@ -263,6 +263,7 @@
     <Compile Include="$(MSBuildThisFileDirectory)Effects\AttachedStateEffectList.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)GitHub1648.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)GitHub1702.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)GitHub2642.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)GitHub1700.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)GitHub2598.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Issue1483.cs" />

Xamarin.Forms.Platform.WPF/FormsContentLoader.cs

@@ -50,11 +50,25 @@ private object CreateOrResizeContent(FrameworkElement parent, VisualElement visu
 			//if (Debugger.IsAttached)
 			//	Console.WriteLine("Page type : " + visualElement.GetType() + " (" + (visualElement as Page).Title + ") -- Parent type : " + visualElement.Parent.GetType() + " -- " + parent.ActualHeight + "H*" + parent.ActualWidth + "W");
 
-			visualElement.Layout(new Rectangle(0, 0, parent.ActualWidth, parent.ActualHeight));
+			var actualRect = new Rectangle(0, 0, parent.ActualWidth, parent.ActualHeight);
+			visualElement.Layout(actualRect);
+
+			// ControlTemplate adds an additional layer through which to send sizing changes.
+			var contentPage = visualElement as ContentPage;
+			if (contentPage?.ControlTemplate != null)
+			{
+				contentPage.Content?.Layout(actualRect);
+			}
+			else
+			{
+				var contentView = visualElement as ContentView;
+				if (contentView?.ControlTemplate != null)
+					contentView.Content?.Layout(actualRect);
+			}
 
 			IPageController pageController = visualElement.RealParent as IPageController;
 			if (pageController != null)
-				pageController.ContainerArea = new Rectangle(0, 0, parent.ActualWidth, parent.ActualHeight);
+				pageController.ContainerArea = actualRect;
 
 			return renderer.GetNativeElement();
 		}