Add Control.UpdateLayout() API

src/Eto.Gtk/Forms/GtkControl.cs

@@ -939,7 +939,13 @@ public PointF PointToScreen(PointF point)
 
 		public Point Location
 		{
-			get { return Control.Allocation.Location.ToEto(); }
+			get
+			{
+				var pt = Control.Allocation.Location.ToEto();
+				if (pt.X == -1 && pt.Y == -1)
+					return Point.Empty;
+				return pt;
+			}
 		}
 
 		public virtual bool ShowBorder
@@ -1084,5 +1090,11 @@ public void Print()
 		{
 			// ContainerControl.Print
 		}
+
+		public virtual void UpdateLayout()
+		{
+			// is this the best way to force a layout pass?  I can't find anything else..
+			ContainerControl.Toplevel?.SizeAllocate(ContainerControl.Toplevel.Allocation);
+		}
 	}
 }

src/Eto.Mac/Forms/MacContainer.cs

@@ -36,6 +36,8 @@ public abstract class MacContainer<TControl, TWidget, TCallback> :
 		public virtual void Update()
 		{
 			InvalidateMeasure();
+			// ContainerControl.Superview?.LayoutSubtreeIfNeeded();
+			ContainerControl.Window?.LayoutIfNeeded();
 		}
 
 		protected override bool ControlEnabled

src/Eto.Mac/Forms/MacView.cs

@@ -1533,6 +1533,11 @@ public bool TextInputImplemented
 			get => Widget.Properties.Get<bool>(MacView.TextInputImplemented_Key);
 			private set => Widget.Properties.Set(MacView.TextInputImplemented_Key, value);
 		}
+
+		public virtual void UpdateLayout()
+		{
+			ContainerControl?.Window?.LayoutIfNeeded();
+		}
 	}
 }
 

src/Eto.WinForms/Forms/HwndFormHandler.cs

@@ -630,5 +630,7 @@ public SizeF GetPreferredSize(SizeF availableSize)
 		}
 
 		public void Print() => throw new NotImplementedException();
+
+		public void UpdateLayout() => throw new NotImplementedException();
 	}
 }

src/Eto.WinForms/Forms/WindowsControl.cs

@@ -1039,5 +1039,7 @@ public void Print()
 		{
 
 		}
+
+		public void UpdateLayout() => ContainerControl.PerformLayout();
 	}
 }

src/Eto.Wpf/Forms/WpfFrameworkElement.cs

@@ -1155,5 +1155,14 @@ internal bool PerformOnLoad(Action action)
 			actionList.Add(action);
 			return true;
 		}
+
+		public void UpdateLayout()
+		{
+			// allow WPF controls to actually get their Loaded event fired.
+			ContainerControl.Dispatcher.Invoke(new Action(() => { }), sw.Threading.DispatcherPriority.ApplicationIdle, null);
+
+			// update the layout
+			ContainerControl.UpdateLayout();
+		}
 	}
 }

src/Eto/Forms/Controls/Control.cs

@@ -817,6 +817,19 @@ public void Invalidate(Rectangle rect, bool invalidateChildren)
 			Handler.Invalidate(rect, invalidateChildren);
 		}
 
+		/// <summary>
+		/// Updates the layout of this control if necessary.
+		/// </summary>
+		/// <remarks>
+		/// This will ensure the control has had all of its layout applied so you can use its position and size right after this call.
+		/// Most platforms (except WinForms) use a deferred layout system so that after adding your control to the form dynamically it won't
+		/// get laid out until the next idle loop.
+		/// This is useful when you need to know the dimensions of the control immediately.
+		/// Note that this can be an expensive operation, so it is recommended to only call this method when necessary and after all of the
+		/// controls have been added/updated.
+		/// </remarks>
+		public void UpdateLayout() => Handler.UpdateLayout();
+
 		/// <summary>
 		/// Gets or sets the size of the control. Use -1 to specify auto sizing for either the width and/or height.
 		/// </summary>
@@ -2007,6 +2020,17 @@ public void OnEnabledChanged(Control widget, EventArgs e)
 			/// <param name="availableSize">The available size to determine the preferred size</param>
 			/// <returns>The preferred size this control would like to be, which can be larger than the specified <paramref name="availableSize" />.</returns>
 			SizeF GetPreferredSize(SizeF availableSize);
+
+			/// <summary>
+			/// Updates the layout of this control if necessary.
+			/// </summary>
+			/// <remarks>
+			/// This will ensure the control has had all of its layout applied so you can use its position and size right after this call.
+			/// Most platforms (except WinForms) use a deferred layout system so that after adding your control to the form dynamically it won't
+			/// get laid out until the next idle loop.
+			/// This is useful when you need to know the dimensions of the control immediately.
+			/// </remarks>
+			void UpdateLayout();
 		}
 		#endregion
 	}

src/Eto/Forms/Controls/ThemedControlHandler.cs

@@ -467,6 +467,9 @@ public override void AttachEvent(string id)
 		/// <inheritdoc />
 		public void Print() => Control.Print();
 
+		/// <inheritdoc />
+		public void UpdateLayout() => Control.UpdateLayout();
+
 		#endregion
 
 	}

test/Eto.Test/UnitTests/Forms/Layout/LayoutTests.cs

@@ -0,0 +1,82 @@
+using System;
+using Eto.Drawing;
+using Eto.Forms;
+using NUnit.Framework;
+
+namespace Eto.Test.UnitTests.Forms.Layout
+{
+	[TestFixture]
+	public class LayoutTests : TestBase
+	{
+		[Test]
+		public void UpdateLayoutShouldSetAllSizes()
+		{
+			Panel holder = null;
+			TableLayout table = null;
+			Shown(form =>
+			{
+				holder = new Panel { Size = new Size(100, 100) };
+				table = new TableLayout
+				{
+					Rows =
+					{
+						new TableRow(new Panel { Size = new Size(100, 100)}),
+						new TableRow(new TableCell(), holder)
+					}
+				};
+				form.Content = table;
+			},
+			() =>
+			{
+				holder.SuspendLayout();
+
+				var control = new Panel();
+				control.Content = "Hello then!";
+				Assert.LessOrEqual(control.Width, 0, "#1.1");
+				Assert.LessOrEqual(control.Height, 0, "#1.2");
+				Assert.AreEqual(new Point(0, 0), control.Location, "#1.3");
+
+				holder.Content = control;
+
+				// layout is suspended or deferred so nothing is set up yet
+				// Gtk is annoying and returns 1,1 for size at this stage, others return 0,0.
+				Assert.LessOrEqual(control.Width, 1, "#2.1");
+				Assert.LessOrEqual(control.Height, 1, "#2.2");
+
+				// macOS gives us a "flipped" view of the location at this point..
+				// the value of Location isn't valid here anyway.
+				if (!Platform.Instance.IsMac)
+					Assert.AreEqual(new Point(0, 0), control.Location, "#2.3");
+
+				holder.ResumeLayout();
+
+				if (!Platform.Instance.IsWinForms)
+				{
+					// Gtk, Wpf, and Mac all use deferred layouts so it still isn't set up here.
+					Assert.LessOrEqual(control.Width, 1, "#3.1");
+					Assert.LessOrEqual(control.Height, 1, "#3.2");
+
+					if (!Platform.Instance.IsMac)
+						Assert.AreEqual(new Point(0, 0), control.Location, "#3.3");
+				}
+				else
+				{
+					// At this point WinForms is all set up.
+					Assert.AreEqual(100, control.Width, "#3.1");
+					Assert.AreEqual(100, control.Height, "#3.2");
+					Assert.AreEqual(new Point(0, 0), control.Location, "#3.3");
+					Assert.AreEqual(new Point(100, 100), Point.Round(table.PointFromScreen(control.PointToScreen(PointF.Empty))), "#3.4");
+				}
+
+				// force a layout
+				holder.UpdateLayout();
+
+				// everything should now be set up as we expect.
+				Assert.AreEqual(100, control.Width, "#4.1");
+				Assert.AreEqual(100, control.Height, "#4.2");
+				Assert.AreEqual(new Point(0, 0), control.Location, "#4.3");
+				Assert.AreEqual(new Point(100, 100), Point.Round(table.PointFromScreen(control.PointToScreen(PointF.Empty))), "#4.4");
+			});
+		}
+	}
+}