moved Dialogs to Windows

Terminal.Gui/Core/Application.cs

@@ -0,0 +1,679 @@
+//
+// Core.cs: The core engine for gui.cs
+//
+// Authors:
+//   Miguel de Icaza ([email protected])
+//
+// Pending:
+//   - Check for NeedDisplay on the hierarchy and repaint
+//   - Layout support
+//   - "Colors" type or "Attributes" type?
+//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
+//
+// Optimziations
+//   - Add rendering limitation to the exposed area
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Threading;
+using System.Linq;
+using NStack;
+using System.ComponentModel;
+
+namespace Terminal.Gui {
+
+	/// <summary>
+	/// The application driver for Terminal.Gui.
+	/// </summary>
+	/// <remarks>
+	///   <para>
+	///     You can hook up to the Iteration event to have your method
+	///     invoked on each iteration of the mainloop.
+	///   </para>
+	///   <para>
+	///     Creates a mainloop to process input events, handle timers and
+	///     other sources of data.   It is accessible via the MainLoop property.
+	///   </para>
+	///   <para>
+	///     When invoked sets the SynchronizationContext to one that is tied
+	///     to the mainloop, allowing user code to use async/await.
+	///   </para>
+	/// </remarks>
+	public static class Application {
+		/// <summary>
+		/// The current <see cref="ConsoleDriver"/> in use.
+		/// </summary>
+		public static ConsoleDriver Driver;
+
+		/// <summary>
+		/// The <see cref="Toplevel"/> object used for the application on startup (<seealso cref="Application.Top"/>)
+		/// </summary>
+		/// <value>The top.</value>
+		public static Toplevel Top { get; private set; }
+
+		/// <summary>
+		/// The current <see cref="Toplevel"/> object. This is updated when <see cref="Application.Run()"/> enters and leaves to point to the current <see cref="Toplevel"/> .
+		/// </summary>
+		/// <value>The current.</value>
+		public static Toplevel Current { get; private set; }
+
+		/// <summary>
+		/// TThe current <see cref="View"/> object being redrawn.
+		/// </summary>
+		/// /// <value>The current.</value>
+		public static View CurrentView { get; set; }
+
+		/// <summary>
+		/// The <see cref="MainLoop"/>  driver for the applicaiton
+		/// </summary>
+		/// <value>The main loop.</value>
+		public static MainLoop MainLoop { get; private set; }
+
+		static Stack<Toplevel> toplevels = new Stack<Toplevel> ();
+
+		/// <summary>
+		///   This event is raised on each iteration of the <see cref="MainLoop"/> 
+		/// </summary>
+		/// <remarks>
+		///   See also <see cref="Timeout"/>
+		/// </remarks>
+		public static event EventHandler Iteration;
+
+		/// <summary>
+		/// Returns a rectangle that is centered in the screen for the provided size.
+		/// </summary>
+		/// <returns>The centered rect.</returns>
+		/// <param name="size">Size for the rectangle.</param>
+		public static Rect MakeCenteredRect (Size size)
+		{
+			return new Rect (new Point ((Driver.Cols - size.Width) / 2, (Driver.Rows - size.Height) / 2), size);
+		}
+
+		//
+		// provides the sync context set while executing code in Terminal.Gui, to let
+		// users use async/await on their code
+		//
+		class MainLoopSyncContext : SynchronizationContext {
+			MainLoop mainLoop;
+
+			public MainLoopSyncContext (MainLoop mainLoop)
+			{
+				this.mainLoop = mainLoop;
+			}
+
+			public override SynchronizationContext CreateCopy ()
+			{
+				return new MainLoopSyncContext (MainLoop);
+			}
+
+			public override void Post (SendOrPostCallback d, object state)
+			{
+				mainLoop.AddIdle (() => {
+					d (state);
+					return false;
+				});
+				//mainLoop.Driver.Wakeup ();
+			}
+
+			public override void Send (SendOrPostCallback d, object state)
+			{
+				mainLoop.Invoke (() => {
+					d (state);
+				});
+			}
+		}
+
+		/// <summary>
+		/// If set, it forces the use of the System.Console-based driver.
+		/// </summary>
+		public static bool UseSystemConsole;
+
+		/// <summary>
+		/// Initializes a new instance of <see cref="Terminal.Gui"/> Application. 
+		/// </summary>
+		/// <remarks>
+		/// <para>
+		/// Call this method once per instance (or after <see cref="Shutdown"/> has been called).
+		/// </para>
+		/// <para>
+		/// Loads the right <see cref="ConsoleDriver"/> for the platform.
+		/// </para>
+		/// <para>
+		/// Creates a <see cref="Toplevel"/> and assigns it to <see cref="Top"/> and <see cref="CurrentView"/>
+		/// </para>
+		/// </remarks>
+		public static void Init () => Init (() => Toplevel.Create ());
+
+		internal static bool _initialized = false;
+
+		/// <summary>
+		/// Initializes the Terminal.Gui application
+		/// </summary>
+		static void Init (Func<Toplevel> topLevelFactory)
+		{
+			if (_initialized) return;
+
+			if (Driver == null) {
+				var p = Environment.OSVersion.Platform;
+				IMainLoopDriver mainLoopDriver;
+
+				if (UseSystemConsole) {
+					mainLoopDriver = new NetMainLoop ();
+					Driver = new NetDriver ();
+				} else if (p == PlatformID.Win32NT || p == PlatformID.Win32S || p == PlatformID.Win32Windows) {
+					var windowsDriver = new WindowsDriver ();
+					mainLoopDriver = windowsDriver;
+					Driver = windowsDriver;
+				} else {
+					mainLoopDriver = new UnixMainLoop ();
+					Driver = new CursesDriver ();
+				}
+				Driver.Init (TerminalResized);
+				MainLoop = new MainLoop (mainLoopDriver);
+				SynchronizationContext.SetSynchronizationContext (new MainLoopSyncContext (MainLoop));
+			}
+			Top = topLevelFactory ();
+			Current = Top;
+			CurrentView = Top;
+			_initialized = true;
+		}
+
+		/// <summary>
+		/// Captures the execution state for the provided <see cref="Toplevel"/>  view.
+		/// </summary>
+		public class RunState : IDisposable {
+			internal bool closeDriver = true;
+
+			internal RunState (Toplevel view)
+			{
+				Toplevel = view;
+			}
+			internal Toplevel Toplevel;
+
+			/// <summary>
+			/// Releases alTop = l resource used by the <see cref="Application.RunState"/> object.
+			/// </summary>
+			/// <remarks>Call <see cref="Dispose()"/> when you are finished using the <see cref="Application.RunState"/>. The
+			/// <see cref="Dispose()"/> method leaves the <see cref="Application.RunState"/> in an unusable state. After
+			/// calling <see cref="Dispose()"/>, you must release all references to the
+			/// <see cref="Application.RunState"/> so the garbage collector can reclaim the memory that the
+			/// <see cref="Application.RunState"/> was occupying.</remarks>
+			public void Dispose ()
+			{
+				Dispose (closeDriver);
+				GC.SuppressFinalize (this);
+			}
+
+			/// <summary>
+			/// Dispose the specified disposing.
+			/// </summary>
+			/// <returns>The dispose.</returns>
+			/// <param name="disposing">If set to <c>true</c> disposing.</param>
+			protected virtual void Dispose (bool disposing)
+			{
+				if (Toplevel != null) {
+					End (Toplevel, disposing);
+					Toplevel = null;
+				}
+			}
+		}
+
+		static void ProcessKeyEvent (KeyEvent ke)
+		{
+
+			var chain = toplevels.ToList ();
+			foreach (var topLevel in chain) {
+				if (topLevel.ProcessHotKey (ke))
+					return;
+				if (topLevel.Modal)
+					break;
+			}
+
+			foreach (var topLevel in chain) {
+				if (topLevel.ProcessKey (ke))
+					return;
+				if (topLevel.Modal)
+					break;
+			}
+
+			foreach (var topLevel in chain) {
+				// Process the key normally
+				if (topLevel.ProcessColdKey (ke))
+					return;
+				if (topLevel.Modal)
+					break;
+			}
+		}
+
+		static void ProcessKeyDownEvent (KeyEvent ke)
+		{
+			var chain = toplevels.ToList ();
+			foreach (var topLevel in chain) {
+				if (topLevel.OnKeyDown (ke))
+					return;
+				if (topLevel.Modal)
+					break;
+			}
+		}
+
+
+		static void ProcessKeyUpEvent (KeyEvent ke)
+		{
+			var chain = toplevels.ToList ();
+			foreach (var topLevel in chain) {
+				if (topLevel.OnKeyUp (ke))
+					return;
+				if (topLevel.Modal)
+					break;
+			}
+		}
+
+		static View FindDeepestView (View start, int x, int y, out int resx, out int resy)
+		{
+			var startFrame = start.Frame;
+
+			if (!startFrame.Contains (x, y)) {
+				resx = 0;
+				resy = 0;
+				return null;
+			}
+
+			if (start.InternalSubviews != null) {
+				int count = start.InternalSubviews.Count;
+				if (count > 0) {
+					var rx = x - startFrame.X;
+					var ry = y - startFrame.Y;
+					for (int i = count - 1; i >= 0; i--) {
+						View v = start.InternalSubviews [i];
+						if (v.Frame.Contains (rx, ry)) {
+							var deep = FindDeepestView (v, rx, ry, out resx, out resy);
+							if (deep == null)
+								return v;
+							return deep;
+						}
+					}
+				}
+			}
+			resx = x - startFrame.X;
+			resy = y - startFrame.Y;
+			return start;
+		}
+
+		internal static View mouseGrabView;
+
+		/// <summary>
+		/// Grabs the mouse, forcing all mouse events to be routed to the specified view until UngrabMouse is called.
+		/// </summary>
+		/// <returns>The grab.</returns>
+		/// <param name="view">View that will receive all mouse events until UngrabMouse is invoked.</param>
+		public static void GrabMouse (View view)
+		{
+			if (view == null)
+				return;
+			mouseGrabView = view;
+			Driver.UncookMouse ();
+		}
+
+		/// <summary>
+		/// Releases the mouse grab, so mouse events will be routed to the view on which the mouse is.
+		/// </summary>
+		public static void UngrabMouse ()
+		{
+			mouseGrabView = null;
+			Driver.CookMouse ();
+		}
+
+		/// <summary>
+		/// Merely a debugging aid to see the raw mouse events
+		/// </summary>
+		public static Action<MouseEvent> RootMouseEvent;
+
+		internal static View wantContinuousButtonPressedView;
+		static View lastMouseOwnerView;
+
+		static void ProcessMouseEvent (MouseEvent me)
+		{
+			var view = FindDeepestView (Current, me.X, me.Y, out int rx, out int ry);
+
+			if (view != null && view.WantContinuousButtonPressed)
+				wantContinuousButtonPressedView = view;
+			else
+				wantContinuousButtonPressedView = null;
+
+			RootMouseEvent?.Invoke (me);
+			if (mouseGrabView != null) {
+				var newxy = mouseGrabView.ScreenToView (me.X, me.Y);
+				var nme = new MouseEvent () {
+					X = newxy.X,
+					Y = newxy.Y,
+					Flags = me.Flags,
+					OfX = me.X - newxy.X,
+					OfY = me.Y - newxy.Y,
+					View = view
+				};
+				if (OutsideFrame (new Point (nme.X, nme.Y), mouseGrabView.Frame))
+					lastMouseOwnerView.OnMouseLeave (me);
+				if (mouseGrabView != null) {
+					mouseGrabView.MouseEvent (nme);
+					return;
+				}
+			}
+
+			if (view != null) {
+				var nme = new MouseEvent () {
+					X = rx,
+					Y = ry,
+					Flags = me.Flags,
+					OfX = rx,
+					OfY = ry,
+					View = view
+				};
+
+				if (lastMouseOwnerView == null) {
+					lastMouseOwnerView = view;
+					view.OnMouseEnter (nme);
+				} else if (lastMouseOwnerView != view) {
+					lastMouseOwnerView.OnMouseLeave (nme);
+					view.OnMouseEnter (nme);
+					lastMouseOwnerView = view;
+				}
+
+				if (!view.WantMousePositionReports && me.Flags == MouseFlags.ReportMousePosition)
+					return;
+
+				if (view.WantContinuousButtonPressed)
+					wantContinuousButtonPressedView = view;
+				else
+					wantContinuousButtonPressedView = null;
+
+				// Should we bubbled up the event, if it is not handled?
+				view.MouseEvent (nme);
+			}
+		}
+
+		static bool OutsideFrame (Point p, Rect r)
+		{
+			return p.X < 0 || p.X > r.Width - 1 || p.Y < 0 || p.Y > r.Height - 1;
+		}
+
+		/// <summary>
+		/// This event is fired once when the application is first loaded. The dimensions of the
+		/// terminal are provided.
+		/// </summary>
+		public static event EventHandler<ResizedEventArgs> Loaded;
+
+		/// <summary>
+		/// Building block API: Prepares the provided <see cref="Toplevel"/>  for execution.
+		/// </summary>
+		/// <returns>The runstate handle that needs to be passed to the <see cref="End(RunState, bool)"/> method upon completion.</returns>
+		/// <param name="toplevel">Toplevel to prepare execution for.</param>
+		/// <remarks>
+		///  This method prepares the provided toplevel for running with the focus,
+		///  it adds this to the list of toplevels, sets up the mainloop to process the
+		///  event, lays out the subviews, focuses the first element, and draws the
+		///  toplevel in the screen. This is usually followed by executing
+		///  the <see cref="RunLoop"/> method, and then the <see cref="End(RunState, bool)"/> method upon termination which will
+		///   undo these changes.
+		/// </remarks>
+		public static RunState Begin (Toplevel toplevel)
+		{
+			if (toplevel == null)
+				throw new ArgumentNullException (nameof (toplevel));
+			var rs = new RunState (toplevel);
+
+			Init ();
+			if (toplevel is ISupportInitializeNotification initializableNotification &&
+			    !initializableNotification.IsInitialized) {
+				initializableNotification.BeginInit ();
+				initializableNotification.EndInit ();
+			} else if (toplevel is ISupportInitialize initializable) {
+				initializable.BeginInit ();
+				initializable.EndInit ();
+			}
+			toplevels.Push (toplevel);
+			Current = toplevel;
+			Driver.PrepareToRun (MainLoop, ProcessKeyEvent, ProcessKeyDownEvent, ProcessKeyUpEvent, ProcessMouseEvent);
+			if (toplevel.LayoutStyle == LayoutStyle.Computed)
+				toplevel.RelativeLayout (new Rect (0, 0, Driver.Cols, Driver.Rows));
+			toplevel.LayoutSubviews ();
+			Loaded?.Invoke (null, new ResizedEventArgs () { Rows = Driver.Rows, Cols = Driver.Cols });
+			toplevel.WillPresent ();
+			Redraw (toplevel);
+			toplevel.PositionCursor ();
+			Driver.Refresh ();
+
+			return rs;
+		}
+
+		/// <summary>
+		/// Building block API: completes the execution of a <see cref="Toplevel"/>  that was started with <see cref="Begin(Toplevel)"/> .
+		/// </summary>
+		/// <param name="runState">The runstate returned by the <see cref="Begin(Toplevel)"/> method.</param>
+		/// <param name="closeDriver"><c>true</c>Closes the application.<c>false</c>Closes the toplevels only.</param>
+		public static void End (RunState runState, bool closeDriver = true)
+		{
+			if (runState == null)
+				throw new ArgumentNullException (nameof (runState));
+
+			runState.closeDriver = closeDriver;
+			runState.Dispose ();
+		}
+
+		/// <summary>
+		/// Shutdown an application initialized with <see cref="Init()"/>
+		/// </summary>
+		/// /// <param name="closeDriver"><c>true</c>Closes the application.<c>false</c>Closes toplevels only.</param>
+		public static void Shutdown (bool closeDriver = true)
+		{
+			// Shutdown is the bookend for Init. As such it needs to clean up all resources
+			// Init created. Apps that do any threading will need to code defensively for this.
+			// e.g. see Issue #537
+			// TODO: Some of this state is actually related to Begin/End (not Init/Shutdown) and should be moved to `RunState` (#520)
+			foreach (var t in toplevels) {
+				t.Running = false;
+			}
+			toplevels.Clear ();
+			Current = null;
+			CurrentView = null;
+			Top = null;
+
+			// Closes the application if it's true.
+			if (closeDriver) {
+				MainLoop = null;
+				Driver.End ();
+			}
+
+			_initialized = false;
+		}
+
+		static void Redraw (View view)
+		{
+			Application.CurrentView = view;
+
+			view.Redraw (view.Bounds);
+			Driver.Refresh ();
+		}
+
+		static void Refresh (View view)
+		{
+			view.Redraw (view.Bounds);
+			Driver.Refresh ();
+		}
+
+		/// <summary>
+		/// Triggers a refresh of the entire display.
+		/// </summary>
+		public static void Refresh ()
+		{
+			Driver.UpdateScreen ();
+			View last = null;
+			foreach (var v in toplevels.Reverse ()) {
+				v.SetNeedsDisplay ();
+				v.Redraw (v.Bounds);
+				last = v;
+			}
+			last?.PositionCursor ();
+			Driver.Refresh ();
+		}
+
+		internal static void End (View view, bool closeDriver = true)
+		{
+			if (toplevels.Peek () != view)
+				throw new ArgumentException ("The view that you end with must be balanced");
+			toplevels.Pop ();
+			if (toplevels.Count == 0)
+				Shutdown (closeDriver);
+			else {
+				Current = toplevels.Peek ();
+				Refresh ();
+			}
+		}
+
+		/// <summary>
+		///   Building block API: Runs the main loop for the created dialog
+		/// </summary>
+		/// <remarks>
+		///   Use the wait parameter to control whether this is a
+		///   blocking or non-blocking call.
+		/// </remarks>
+		/// <param name="state">The state returned by the Begin method.</param>
+		/// <param name="wait">By default this is true which will execute the runloop waiting for events, if you pass false, you can use this method to run a single iteration of the events.</param>
+		public static void RunLoop (RunState state, bool wait = true)
+		{
+			if (state == null)
+				throw new ArgumentNullException (nameof (state));
+			if (state.Toplevel == null)
+				throw new ObjectDisposedException ("state");
+
+			bool firstIteration = true;
+			for (state.Toplevel.Running = true; state.Toplevel.Running;) {
+				if (MainLoop.EventsPending (wait)) {
+					// Notify Toplevel it's ready
+					if (firstIteration) {
+						state.Toplevel.OnReady ();
+					}
+					firstIteration = false;
+
+					MainLoop.MainIteration ();
+					Iteration?.Invoke (null, EventArgs.Empty);
+				} else if (wait == false)
+					return;
+				if (state.Toplevel.NeedDisplay != null && (!state.Toplevel.NeedDisplay.IsEmpty || state.Toplevel.childNeedsDisplay)) {
+					state.Toplevel.Redraw (state.Toplevel.Bounds);
+					if (DebugDrawBounds)
+						DrawBounds (state.Toplevel);
+					state.Toplevel.PositionCursor ();
+					Driver.Refresh ();
+				} else
+					Driver.UpdateCursor ();
+			}
+		}
+
+		internal static bool DebugDrawBounds = false;
+
+		// Need to look into why this does not work properly.
+		static void DrawBounds (View v)
+		{
+			v.DrawFrame (v.Frame, padding: 0, fill: false);
+			if (v.InternalSubviews != null && v.InternalSubviews.Count > 0)
+				foreach (var sub in v.InternalSubviews)
+					DrawBounds (sub);
+		}
+
+		/// <summary>
+		/// Runs the application by calling <see cref="Run(Toplevel, bool)"/> with the value of <see cref="Top"/>
+		/// </summary>
+		public static void Run ()
+		{
+			Run (Top);
+		}
+
+		/// <summary>
+		/// Runs the application by calling <see cref="Run(Toplevel, bool)"/> with a new instance of the specified <see cref="Toplevel"/>-derived class
+		/// </summary>
+		public static void Run<T> () where T : Toplevel, new()
+		{
+			Init (() => new T ());
+			Run (Top);
+		}
+
+		/// <summary>
+		///   Runs the main loop on the given <see cref="Toplevel"/> container.
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///     This method is used to start processing events
+		///     for the main application, but it is also used to
+		///     run other modal <see cref="View"/>s such as <see cref="Dialog"/> boxes.
+		///   </para>
+		///   <para>
+		///     To make a <see cref="Run(Toplevel, bool)"/> stop execution, call <see cref="Application.RequestStop"/>.
+		///   </para>
+		///   <para>
+		///     Calling <see cref="Run(Toplevel, bool)"/> is equivalent to calling <see cref="Begin(Toplevel)"/>, followed by <see cref="RunLoop(RunState, bool)"/>,
+		///     and then calling <see cref="End(RunState, bool)"/>.
+		///   </para>
+		///   <para>
+		///     Alternatively, to have a program control the main loop and 
+		///     process events manually, call <see cref="Begin(Toplevel)"/> to set things up manually and then
+		///     repeatedly call <see cref="RunLoop(RunState, bool)"/> with the wait parameter set to false.   By doing this
+		///     the <see cref="RunLoop(RunState, bool)"/> method will only process any pending events, timers, idle handlers and
+		///     then return control immediately.
+		///   </para>
+		/// </remarks>
+		public static void Run (Toplevel view, bool closeDriver = true)
+		{
+			var runToken = Begin (view);
+			RunLoop (runToken);
+			End (runToken, closeDriver);
+		}
+
+		/// <summary>
+		/// Stops running the most recent <see cref="Toplevel"/>. 
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///   This will cause <see cref="Application.Run()"/> to return.
+		///   </para>
+		///   <para>
+		///     Calling <see cref="Application.RequestStop"/> is equivalent to setting the <see cref="Toplevel.Running"/> property on the curently running <see cref="Toplevel"/> to false.
+		///   </para>
+		/// </remarks>
+		public static void RequestStop ()
+		{
+			Current.Running = false;
+		}
+
+		/// <summary>
+		/// Event arguments for the <see cref="Application.Resized"/> event.
+		/// </summary>
+		public class ResizedEventArgs : EventArgs {
+			/// <summary>
+			/// The number of rows in the resized terminal.
+			/// </summary>
+			public int Rows { get; set; }
+			/// <summary>
+			/// The number of columns in the resized terminal.
+			/// </summary>
+			public int Cols { get; set; }
+		}
+
+		/// <summary>
+		/// Invoked when the terminal was resized. The new size of the terminal is provided.
+		/// </summary>
+		public static event EventHandler<ResizedEventArgs> Resized;
+
+		static void TerminalResized ()
+		{
+			var full = new Rect (0, 0, Driver.Cols, Driver.Rows);
+			Resized?.Invoke (null, new ResizedEventArgs () { Cols = full.Width, Rows = full.Height });
+			Driver.Clip = full;
+			foreach (var t in toplevels) {
+				t.PositionToplevels ();
+				t.RelativeLayout (full);
+				t.LayoutSubviews ();
+			}
+			Refresh ();
+		}
+	}
+}

Terminal.Gui/Core/Core.cs

@@ -1,2651 +0,0 @@
-//
-// Core.cs: The core engine for gui.cs
-//
-// Authors:
-//   Miguel de Icaza ([email protected])
-//
-// Pending:
-//   - Check for NeedDisplay on the hierarchy and repaint
-//   - Layout support
-//   - "Colors" type or "Attributes" type?
-//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
-//
-// Optimziations
-//   - Add rendering limitation to the exposed area
-using System;
-using System.Collections;
-using System.Collections.Generic;
-using System.Threading;
-using System.Linq;
-using NStack;
-using System.ComponentModel;
-
-namespace Terminal.Gui {
-
-	/// <summary>
-	/// Responder base class implemented by objects that want to participate on keyboard and mouse input.
-	/// </summary>
-	public class Responder {
-		/// <summary>
-		/// Gets or sets a value indicating whether this <see cref="Responder"/> can focus.
-		/// </summary>
-		/// <value><c>true</c> if can focus; otherwise, <c>false</c>.</value>
-		public virtual bool CanFocus { get; set; }
-
-		/// <summary>
-		/// Gets or sets a value indicating whether this <see cref="Responder"/> has focus.
-		/// </summary>
-		/// <value><c>true</c> if has focus; otherwise, <c>false</c>.</value>
-		public virtual bool HasFocus { get; internal set; }
-
-		// Key handling
-		/// <summary>
-		///   This method can be overwritten by view that
-		///     want to provide accelerator functionality
-		///     (Alt-key for example).
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///     Before keys are sent to the subview on the
-		///     current view, all the views are
-		///     processed and the key is passed to the widgets
-		///     to allow some of them to process the keystroke
-		///     as a hot-key. </para>
-		///  <para>
-		///     For example, if you implement a button that
-		///     has a hotkey ok "o", you would catch the
-		///     combination Alt-o here.  If the event is
-		///     caught, you must return true to stop the
-		///     keystroke from being dispatched to other
-		///     views.
-		///  </para>
-		/// </remarks>
-
-		public virtual bool ProcessHotKey (KeyEvent kb)
-		{
-			return false;
-		}
-
-		/// <summary>
-		///   If the view is focused, gives the view a
-		///   chance to process the keystroke.
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///     Views can override this method if they are
-		///     interested in processing the given keystroke.
-		///     If they consume the keystroke, they must
-		///     return true to stop the keystroke from being
-		///     processed by other widgets or consumed by the
-		///     widget engine.    If they return false, the
-		///     keystroke will be passed using the ProcessColdKey
-		///     method to other views to process.
-		///   </para>
-		///   <para>
-		///     The View implementation does nothing but return false,
-		///     so it is not necessary to call base.ProcessKey if you
-		///     derive directly from View, but you should if you derive
-		///     other View subclasses.
-		///   </para>
-		/// </remarks>
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		public virtual bool ProcessKey (KeyEvent keyEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		///   This method can be overwritten by views that
-		///     want to provide accelerator functionality
-		///     (Alt-key for example), but without
-		///     interefering with normal ProcessKey behavior.
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///     After keys are sent to the subviews on the
-		///     current view, all the view are
-		///     processed and the key is passed to the views
-		///     to allow some of them to process the keystroke
-		///     as a cold-key. </para>
-		///  <para>
-		///    This functionality is used, for example, by
-		///    default buttons to act on the enter key.
-		///    Processing this as a hot-key would prevent
-		///    non-default buttons from consuming the enter
-		///    keypress when they have the focus.
-		///  </para>
-		/// </remarks>
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		public virtual bool ProcessColdKey (KeyEvent keyEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a key is pressed.
-		/// </summary>
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		/// <returns>true if the event was handled</returns>
-		public virtual bool OnKeyDown (KeyEvent keyEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a key is released.
-		/// </summary>
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		/// <returns>true if the event was handled</returns>
-		public virtual bool OnKeyUp (KeyEvent keyEvent)
-		{
-			return false;
-		}
-
-
-		/// <summary>
-		/// Method invoked when a mouse event is generated
-		/// </summary>
-		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
-		/// <param name="mouseEvent">Contains the details about the mouse event.</param>
-		public virtual bool MouseEvent (MouseEvent mouseEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a mouse event is generated for the first time.
-		/// </summary>
-		/// <param name="mouseEvent"></param>
-		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
-		public virtual bool OnMouseEnter (MouseEvent mouseEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a mouse event is generated for the last time.
-		/// </summary>
-		/// <param name="mouseEvent"></param>
-		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
-		public virtual bool OnMouseLeave (MouseEvent mouseEvent)
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a view gets focus.
-		/// </summary>
-		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
-		public virtual bool OnEnter ()
-		{
-			return false;
-		}
-
-		/// <summary>
-		/// Method invoked when a view loses focus.
-		/// </summary>
-		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
-		public virtual bool OnLeave ()
-		{
-			return false;
-		}
-	}
-
-	/// <summary>
-	/// Determines the LayoutStyle for a view, if Absolute, during LayoutSubviews, the
-	/// value from the Frame will be used, if the value is Computer, then the Frame
-	/// will be updated from the X, Y Pos objects and the Width and Height Dim objects.
-	/// </summary>
-	public enum LayoutStyle {
-		/// <summary>
-		/// The position and size of the view are based on the Frame value.
-		/// </summary>
-		Absolute,
-
-		/// <summary>
-		/// The position and size of the view will be computed based on the
-		/// X, Y, Width and Height properties and set on the Frame.
-		/// </summary>
-		Computed
-	}
-
-	/// <summary>
-	/// View is the base class for all views on the screen and represents a visible element that can render itself and contains zero or more nested views.
-	/// </summary>
-	/// <remarks>
-	/// <para>
-	///    The View defines the base functionality for user interface elements in Terminal/gui.cs.  Views
-	///    can contain one or more subviews, can respond to user input and render themselves on the screen.
-	/// </para>
-	/// <para>
-	///    Views can either be created with an absolute position, by calling the constructor that takes a
-	///    Rect parameter to specify the absolute position and size (the Frame of the View) or by setting the
-	///    X, Y, Width and Height properties on the view.    Both approaches use coordinates that are relative
-	///    to the container they are being added to.
-	/// </para>
-	/// <para>
-	///    When you do not specify a Rect frame you can use the more flexible
-	///    Dim and Pos objects that can dynamically update the position of a view.
-	///    The X and Y properties are of type <see cref="Pos"/>
-	///    and you can use either absolute positions, percentages or anchor
-	///    points.   The Width and Height properties are of type
-	///    <see cref="Dim"/> and can use absolute position,
-	///    percentages and anchors.  These are useful as they will take
-	///    care of repositioning your views if your view's frames are resized
-	///    or if the terminal size changes.
-	/// </para>
-	/// <para>
-	///    When you specify the Rect parameter to a view, you are setting the LayoutStyle to Absolute, and the
-	///    view will always stay in the position that you placed it.   To change the position change the
-	///    Frame property to the new position.
-	/// </para>
-	/// <para>
-	///    Subviews can be added to a View by calling the Add method.   The container of a view is the
-	///    Superview.
-	/// </para>
-	/// <para>
-	///    Developers can call the SetNeedsDisplay method on the view to flag a region or the entire view
-	///    as requiring to be redrawn.
-	/// </para>
-	/// <para>
-	///    Views have a ColorScheme property that defines the default colors that subviews
-	///    should use for rendering.   This ensures that the views fit in the context where
-	///    they are being used, and allows for themes to be plugged in.   For example, the
-	///    default colors for windows and toplevels uses a blue background, while it uses
-	///    a white background for dialog boxes and a red background for errors.
-	/// </para>
-	/// <para>
-	///    If a ColorScheme is not set on a view, the result of the ColorScheme is the
-	///    value of the SuperView and the value might only be valid once a view has been
-	///    added to a SuperView, so your subclasses should not rely on ColorScheme being
-	///    set at construction time.
-	/// </para>
-	/// <para>
-	///    Using ColorSchemes has the advantage that your application will work both
-	///    in color as well as black and white displays.
-	/// </para>
-	/// <para>
-	///    Views that are focusable should implement the PositionCursor to make sure that
-	///    the cursor is placed in a location that makes sense.   Unix terminals do not have
-	///    a way of hiding the cursor, so it can be distracting to have the cursor left at
-	///    the last focused view.   So views should make sure that they place the cursor
-	///    in a visually sensible place.
-	/// </para>
-	/// <para>
-	///    The metnod LayoutSubviews is invoked when the size or layout of a view has
-	///    changed.   The default processing system will keep the size and dimensions
-	///    for views that use the LayoutKind.Absolute, and will recompute the
-	///    frames for the vies that use LayoutKind.Computed.
-	/// </para>
-	/// </remarks>
-	public class View : Responder, IEnumerable {
-		internal enum Direction {
-			Forward,
-			Backward
-		}
-
-		View container = null;
-		View focused = null;
-		Direction focusDirection;
-
-		/// <summary>
-		/// Event fired when the view get focus.
-		/// </summary>
-		public event EventHandler Enter;
-
-		/// <summary>
-		/// Event fired when the view lost focus.
-		/// </summary>
-		public event EventHandler Leave;
-
-		/// <summary>
-		/// Event fired when the view receives the mouse event for the first time.
-		/// </summary>
-		public event EventHandler<MouseEvent> MouseEnter;
-
-		/// <summary>
-		/// Event fired when the view loses mouse event for the last time.
-		/// </summary>
-		public event EventHandler<MouseEvent> MouseLeave;
-
-		internal Direction FocusDirection {
-			get => SuperView?.FocusDirection ?? focusDirection;
-			set {
-				if (SuperView != null)
-					SuperView.FocusDirection = value;
-				else
-					focusDirection = value;
-			}
-		}
-
-		/// <summary>
-		/// Points to the current driver in use by the view, it is a convenience property
-		/// for simplifying the development of new views.
-		/// </summary>
-		public static ConsoleDriver Driver { get { return Application.Driver; } }
-
-		static IList<View> empty = new List<View> (0).AsReadOnly ();
-
-		// This is null, and allocated on demand.
-		List<View> subviews;
-
-		/// <summary>
-		/// This returns a list of the subviews contained by this view.
-		/// </summary>
-		/// <value>The subviews.</value>
-		public IList<View> Subviews => subviews == null ? empty : subviews.AsReadOnly ();
-
-		// Internally, we use InternalSubviews rather than subviews, as we do not expect us
-		// to make the same mistakes our users make when they poke at the Subviews.
-		internal IList<View> InternalSubviews => subviews ?? empty;
-
-		internal Rect NeedDisplay { get; private set; } = Rect.Empty;
-
-		// The frame for the object
-		Rect frame;
-
-		/// <summary>
-		/// Gets or sets an identifier for the view;
-		/// </summary>
-		/// <value>The identifier.</value>
-		public ustring Id { get; set; } = "";
-
-		/// <summary>
-		/// Returns a value indicating if this View is currently on Top (Active)
-		/// </summary>
-		public bool IsCurrentTop {
-			get {
-				return Application.Current == this;
-			}
-		}
-
-		/// <summary>
-		/// Gets or sets a value indicating whether this <see cref="View"/> want mouse position reports.
-		/// </summary>
-		/// <value><c>true</c> if want mouse position reports; otherwise, <c>false</c>.</value>
-		public virtual bool WantMousePositionReports { get; set; } = false;
-
-		/// <summary>
-		/// Gets or sets a value indicating whether this <see cref="View"/> want continuous button pressed event.
-		/// </summary>
-		public virtual bool WantContinuousButtonPressed { get; set; } = false;
-		/// <summary>
-		/// Gets or sets the frame for the view.
-		/// </summary>
-		/// <value>The frame.</value>
-		/// <remarks>
-		///    Altering the Frame of a view will trigger the redrawing of the
-		///    view as well as the redrawing of the affected regions in the superview.
-		/// </remarks>
-		public virtual Rect Frame {
-			get => frame;
-			set {
-				if (SuperView != null) {
-					SuperView.SetNeedsDisplay (frame);
-					SuperView.SetNeedsDisplay (value);
-				}
-				frame = value;
-
-				SetNeedsLayout ();
-				SetNeedsDisplay (frame);
-			}
-		}
-
-		/// <summary>
-		/// Gets an enumerator that enumerates the subviews in this view.
-		/// </summary>
-		/// <returns>The enumerator.</returns>
-		public IEnumerator GetEnumerator ()
-		{
-			foreach (var v in InternalSubviews)
-				yield return v;
-		}
-
-		LayoutStyle layoutStyle;
-
-		/// <summary>
-		/// Controls how the view's Frame is computed during the LayoutSubviews method, if Absolute, then
-		/// LayoutSubviews does not change the Frame properties, otherwise the Frame is updated from the
-		/// values in X, Y, Width and Height properties.
-		/// </summary>
-		/// <value>The layout style.</value>
-		public LayoutStyle LayoutStyle {
-			get => layoutStyle;
-			set {
-				layoutStyle = value;
-				SetNeedsLayout ();
-			}
-		}
-
-		/// <summary>
-		/// The bounds represent the View-relative rectangle used for this view.   Updates to the Bounds update the Frame, and has the same side effects as updating the frame.
-		/// </summary>
-		/// <value>The bounds.</value>
-		public Rect Bounds {
-			get => new Rect (Point.Empty, Frame.Size);
-			set {
-				Frame = new Rect (frame.Location, value.Size);
-			}
-		}
-
-		Pos x, y;
-		/// <summary>
-		/// Gets or sets the X position for the view (the column).  This is only used when the LayoutStyle is Computed, if the
-		/// LayoutStyle is set to Absolute, this value is ignored.
-		/// </summary>
-		/// <value>The X Position.</value>
-		public Pos X {
-			get => x;
-			set {
-				x = value;
-				SetNeedsLayout ();
-			}
-		}
-
-		/// <summary>
-		/// Gets or sets the Y position for the view (line).  This is only used when the LayoutStyle is Computed, if the
-		/// LayoutStyle is set to Absolute, this value is ignored.
-		/// </summary>
-		/// <value>The y position (line).</value>
-		public Pos Y {
-			get => y;
-			set {
-				y = value;
-				SetNeedsLayout ();
-			}
-		}
-
-		Dim width, height;
-
-		/// <summary>
-		/// Gets or sets the width for the view. This is only used when the LayoutStyle is Computed, if the
-		/// LayoutStyle is set to Absolute, this value is ignored.
-		/// </summary>
-		/// <value>The width.</value>
-		public Dim Width {
-			get => width;
-			set {
-				width = value;
-				SetNeedsLayout ();
-			}
-		}
-
-		/// <summary>
-		/// Gets or sets the height for the view. This is only used when the LayoutStyle is Computed, if the
-		/// LayoutStyle is set to Absolute, this value is ignored.
-		/// </summary>
-		/// <value>The height.</value>
-		public Dim Height {
-			get => height;
-			set {
-				height = value;
-				SetNeedsLayout ();
-			}
-		}
-
-		/// <summary>
-		/// Returns the container for this view, or null if this view has not been added to a container.
-		/// </summary>
-		/// <value>The super view.</value>
-		public View SuperView => container;
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="View"/> class with the absolute
-		/// dimensions specified in the frame.   If you want to have Views that can be positioned with
-		/// Pos and Dim properties on X, Y, Width and Height, use the empty constructor.
-		/// </summary>
-		/// <param name="frame">The region covered by this view.</param>
-		public View (Rect frame)
-		{
-			this.Frame = frame;
-			CanFocus = false;
-			LayoutStyle = LayoutStyle.Absolute;
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="View"/> class and sets the
-		/// view up for Computed layout, which will use the values in X, Y, Width and Height to
-		/// compute the View's Frame.
-		/// </summary>
-		public View ()
-		{
-			CanFocus = false;
-			LayoutStyle = LayoutStyle.Computed;
-		}
-
-		/// <summary>
-		/// Invoke to flag that this view needs to be redisplayed, by any code
-		/// that alters the state of the view.
-		/// </summary>
-		public void SetNeedsDisplay ()
-		{
-			SetNeedsDisplay (Bounds);
-		}
-
-		internal bool layoutNeeded = true;
-
-		internal void SetNeedsLayout ()
-		{
-			if (layoutNeeded)
-				return;
-			layoutNeeded = true;
-			if (SuperView == null)
-				return;
-			SuperView.SetNeedsLayout ();
-		}
-
-		/// <summary>
-		/// Flags the specified rectangle region on this view as needing to be repainted.
-		/// </summary>
-		/// <param name="region">The region that must be flagged for repaint.</param>
-		public void SetNeedsDisplay (Rect region)
-		{
-			if (NeedDisplay == null || NeedDisplay.IsEmpty)
-				NeedDisplay = region;
-			else {
-				var x = Math.Min (NeedDisplay.X, region.X);
-				var y = Math.Min (NeedDisplay.Y, region.Y);
-				var w = Math.Max (NeedDisplay.Width, region.Width);
-				var h = Math.Max (NeedDisplay.Height, region.Height);
-				NeedDisplay = new Rect (x, y, w, h);
-			}
-			if (container != null)
-				container.ChildNeedsDisplay ();
-			if (subviews == null)
-				return;
-			foreach (var view in subviews)
-				if (view.Frame.IntersectsWith (region)) {
-					var childRegion = Rect.Intersect (view.Frame, region);
-					childRegion.X -= view.Frame.X;
-					childRegion.Y -= view.Frame.Y;
-					view.SetNeedsDisplay (childRegion);
-				}
-		}
-
-		internal bool childNeedsDisplay;
-
-		/// <summary>
-		/// Flags this view for requiring the children views to be repainted.
-		/// </summary>
-		public void ChildNeedsDisplay ()
-		{
-			childNeedsDisplay = true;
-			if (container != null)
-				container.ChildNeedsDisplay ();
-		}
-
-		/// <summary>
-		///   Adds a subview to this view.
-		/// </summary>
-		/// <remarks>
-		/// </remarks>
-		public virtual void Add (View view)
-		{
-			if (view == null)
-				return;
-			if (subviews == null)
-				subviews = new List<View> ();
-			subviews.Add (view);
-			view.container = this;
-			if (view.CanFocus)
-				CanFocus = true;
-			SetNeedsLayout ();
-			SetNeedsDisplay ();
-		}
-
-		/// <summary>
-		/// Adds the specified views to the view.
-		/// </summary>
-		/// <param name="views">Array of one or more views (can be optional parameter).</param>
-		public void Add (params View [] views)
-		{
-			if (views == null)
-				return;
-			foreach (var view in views)
-				Add (view);
-		}
-
-		/// <summary>
-		///   Removes all the widgets from this container.
-		/// </summary>
-		/// <remarks>
-		/// </remarks>
-		public virtual void RemoveAll ()
-		{
-			if (subviews == null)
-				return;
-
-			while (subviews.Count > 0) {
-				Remove (subviews [0]);
-			}
-		}
-
-		/// <summary>
-		///   Removes a widget from this container.
-		/// </summary>
-		/// <remarks>
-		/// </remarks>
-		public virtual void Remove (View view)
-		{
-			if (view == null || subviews == null)
-				return;
-
-			SetNeedsLayout ();
-			SetNeedsDisplay ();
-			var touched = view.Frame;
-			subviews.Remove (view);
-			view.container = null;
-
-			if (subviews.Count < 1)
-				this.CanFocus = false;
-
-			foreach (var v in subviews) {
-				if (v.Frame.IntersectsWith (touched))
-					view.SetNeedsDisplay ();
-			}
-		}
-
-		void PerformActionForSubview (View subview, Action<View> action)
-		{
-			if (subviews.Contains (subview)) {
-				action (subview);
-			}
-
-			SetNeedsDisplay ();
-			subview.SetNeedsDisplay ();
-		}
-
-		/// <summary>
-		/// Brings the specified subview to the front so it is drawn on top of any other views.
-		/// </summary>
-		/// <param name="subview">The subview to send to the front</param>
-		/// <remarks>
-		///   <seealso cref="SendSubviewToBack"/>.
-		/// </remarks>
-		public void BringSubviewToFront (View subview)
-		{
-			PerformActionForSubview (subview, x => {
-				subviews.Remove (x);
-				subviews.Add (x);
-			});
-		}
-
-		/// <summary>
-		/// Sends the specified subview to the front so it is the first view drawn
-		/// </summary>
-		/// <param name="subview">The subview to send to the front</param>
-		/// <remarks>
-		///   <seealso cref="BringSubviewToFront(View)"/>.
-		/// </remarks>
-		public void SendSubviewToBack (View subview)
-		{
-			PerformActionForSubview (subview, x => {
-				subviews.Remove (x);
-				subviews.Insert (0, subview);
-			});
-		}
-
-		/// <summary>
-		/// Moves the subview backwards in the hierarchy, only one step
-		/// </summary>
-		/// <param name="subview">The subview to send backwards</param>
-		/// <remarks>
-		/// If you want to send the view all the way to the back use SendSubviewToBack.
-		/// </remarks>
-		public void SendSubviewBackwards (View subview)
-		{
-			PerformActionForSubview (subview, x => {
-				var idx = subviews.IndexOf (x);
-				if (idx > 0) {
-					subviews.Remove (x);
-					subviews.Insert (idx - 1, x);
-				}
-			});
-		}
-
-		/// <summary>
-		/// Moves the subview backwards in the hierarchy, only one step
-		/// </summary>
-		/// <param name="subview">The subview to send backwards</param>
-		/// <remarks>
-		/// If you want to send the view all the way to the back use SendSubviewToBack.
-		/// </remarks>
-		public void BringSubviewForward (View subview)
-		{
-			PerformActionForSubview (subview, x => {
-				var idx = subviews.IndexOf (x);
-				if (idx + 1 < subviews.Count) {
-					subviews.Remove (x);
-					subviews.Insert (idx + 1, x);
-				}
-			});
-		}
-
-		/// <summary>
-		///   Clears the view region with the current color.
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///     This clears the entire region used by this view.
-		///   </para>
-		/// </remarks>
-		public void Clear ()
-		{
-			var h = Frame.Height;
-			var w = Frame.Width;
-			for (int line = 0; line < h; line++) {
-				Move (0, line);
-				for (int col = 0; col < w; col++)
-					Driver.AddRune (' ');
-			}
-		}
-
-		/// <summary>
-		///   Clears the specified rectangular region with the current color
-		/// </summary>
-		public void Clear (Rect r)
-		{
-			var h = r.Height;
-			var w = r.Width;
-			for (int line = r.Y; line < r.Y + h; line++) {
-				Driver.Move (r.X, line);
-				for (int col = 0; col < w; col++)
-					Driver.AddRune (' ');
-			}
-		}
-
-		/// <summary>
-		/// Converts the (col,row) position from the view into a screen (col,row).  The values are clamped to (0..ScreenDim-1)
-		/// </summary>
-		/// <param name="col">View-based column.</param>
-		/// <param name="row">View-based row.</param>
-		/// <param name="rcol">Absolute column, display relative.</param>
-		/// <param name="rrow">Absolute row, display relative.</param>
-		/// <param name="clipped">Whether to clip the result of the ViewToScreen method, if set to true, the rcol, rrow values are clamped to the screen dimensions.</param>
-		internal void ViewToScreen (int col, int row, out int rcol, out int rrow, bool clipped = true)
-		{
-			// Computes the real row, col relative to the screen.
-			rrow = row + frame.Y;
-			rcol = col + frame.X;
-			var ccontainer = container;
-			while (ccontainer != null) {
-				rrow += ccontainer.frame.Y;
-				rcol += ccontainer.frame.X;
-				ccontainer = ccontainer.container;
-			}
-
-			// The following ensures that the cursor is always in the screen boundaries.
-			if (clipped) {
-				rrow = Math.Max (0, Math.Min (rrow, Driver.Rows - 1));
-				rcol = Math.Max (0, Math.Min (rcol, Driver.Cols - 1));
-			}
-		}
-
-		/// <summary>
-		/// Converts a point from screen coordinates into the view coordinate space.
-		/// </summary>
-		/// <returns>The mapped point.</returns>
-		/// <param name="x">X screen-coordinate point.</param>
-		/// <param name="y">Y screen-coordinate point.</param>
-		public Point ScreenToView (int x, int y)
-		{
-			if (SuperView == null) {
-				return new Point (x - Frame.X, y - frame.Y);
-			} else {
-				var parent = SuperView.ScreenToView (x, y);
-				return new Point (parent.X - frame.X, parent.Y - frame.Y);
-			}
-		}
-
-		// Converts a rectangle in view coordinates to screen coordinates.
-		internal Rect RectToScreen (Rect rect)
-		{
-			ViewToScreen (rect.X, rect.Y, out var x, out var y, clipped: false);
-			return new Rect (x, y, rect.Width, rect.Height);
-		}
-
-		// Clips a rectangle in screen coordinates to the dimensions currently available on the screen
-		internal Rect ScreenClip (Rect rect)
-		{
-			var x = rect.X < 0 ? 0 : rect.X;
-			var y = rect.Y < 0 ? 0 : rect.Y;
-			var w = rect.X + rect.Width >= Driver.Cols ? Driver.Cols - rect.X : rect.Width;
-			var h = rect.Y + rect.Height >= Driver.Rows ? Driver.Rows - rect.Y : rect.Height;
-
-			return new Rect (x, y, w, h);
-		}
-
-		/// <summary>
-		/// Sets the Console driver's clip region to the current View's Bounds.
-		/// </summary>
-		/// <returns>The existing driver's Clip region, which can be then set by setting the Driver.Clip property.</returns>
-		public Rect ClipToBounds ()
-		{
-			return SetClip (Bounds);
-		}
-
-		/// <summary>
-		/// Sets the clipping region to the specified region, the region is view-relative
-		/// </summary>
-		/// <returns>The previous clip region.</returns>
-		/// <param name="rect">Rectangle region to clip into, the region is view-relative.</param>
-		public Rect SetClip (Rect rect)
-		{
-			var bscreen = RectToScreen (rect);
-			var previous = Driver.Clip;
-			Driver.Clip = ScreenClip (RectToScreen (Bounds));
-			return previous;
-		}
-
-		/// <summary>
-		/// Draws a frame in the current view, clipped by the boundary of this view
-		/// </summary>
-		/// <param name="rect">Rectangular region for the frame to be drawn.</param>
-		/// <param name="padding">The padding to add to the drawn frame.</param>
-		/// <param name="fill">If set to <c>true</c> it fill will the contents.</param>
-		public void DrawFrame (Rect rect, int padding = 0, bool fill = false)
-		{
-			var scrRect = RectToScreen (rect);
-			var savedClip = Driver.Clip;
-			Driver.Clip = ScreenClip (RectToScreen (Bounds));
-			Driver.DrawFrame (scrRect, padding, fill);
-			Driver.Clip = savedClip;
-		}
-
-		/// <summary>
-		/// Utility function to draw strings that contain a hotkey
-		/// </summary>
-		/// <param name="text">String to display, the underscoore before a letter flags the next letter as the hotkey.</param>
-		/// <param name="hotColor">Hot color.</param>
-		/// <param name="normalColor">Normal color.</param>
-		public void DrawHotString (ustring text, Attribute hotColor, Attribute normalColor)
-		{
-			Driver.SetAttribute (normalColor);
-			foreach (var rune in text) {
-				if (rune == '_') {
-					Driver.SetAttribute (hotColor);
-					continue;
-				}
-				Driver.AddRune (rune);
-				Driver.SetAttribute (normalColor);
-			}
-		}
-
-		/// <summary>
-		/// Utility function to draw strings that contains a hotkey using a colorscheme and the "focused" state.
-		/// </summary>
-		/// <param name="text">String to display, the underscoore before a letter flags the next letter as the hotkey.</param>
-		/// <param name="focused">If set to <c>true</c> this uses the focused colors from the color scheme, otherwise the regular ones.</param>
-		/// <param name="scheme">The color scheme to use.</param>
-		public void DrawHotString (ustring text, bool focused, ColorScheme scheme)
-		{
-			if (focused)
-				DrawHotString (text, scheme.HotFocus, scheme.Focus);
-			else
-				DrawHotString (text, scheme.HotNormal, scheme.Normal);
-		}
-
-		/// <summary>
-		/// This moves the cursor to the specified column and row in the view.
-		/// </summary>
-		/// <returns>The move.</returns>
-		/// <param name="col">Col.</param>
-		/// <param name="row">Row.</param>
-		public void Move (int col, int row)
-		{
-			ViewToScreen (col, row, out var rcol, out var rrow);
-			Driver.Move (rcol, rrow);
-		}
-
-		/// <summary>
-		///   Positions the cursor in the right position based on the currently focused view in the chain.
-		/// </summary>
-		public virtual void PositionCursor ()
-		{
-			if (focused != null)
-				focused.PositionCursor ();
-			else
-				Move (frame.X, frame.Y);
-		}
-
-		/// <inheritdoc cref="HasFocus"/>
-		public override bool HasFocus {
-			get {
-				return base.HasFocus;
-			}
-			internal set {
-				if (base.HasFocus != value)
-					if (value)
-						OnEnter ();
-					else
-						OnLeave ();
-				SetNeedsDisplay ();
-				base.HasFocus = value;
-
-				// Remove focus down the chain of subviews if focus is removed
-				if (!value && focused != null) {
-					focused.OnLeave ();
-					focused.HasFocus = false;
-					focused = null;
-				}
-			}
-		}
-
-		/// <inheritdoc cref="OnEnter"/>
-		public override bool OnEnter ()
-		{
-			Enter?.Invoke (this, new EventArgs ());
-			return base.OnEnter ();
-		}
-
-		/// <inheritdoc cref="OnLeave"/>
-		public override bool OnLeave ()
-		{
-			Leave?.Invoke (this, new EventArgs ());
-			return base.OnLeave ();
-		}
-
-		/// <summary>
-		/// Returns the currently focused view inside this view, or null if nothing is focused.
-		/// </summary>
-		/// <value>The focused.</value>
-		public View Focused => focused;
-
-		/// <summary>
-		/// Returns the most focused view in the chain of subviews (the leaf view that has the focus).
-		/// </summary>
-		/// <value>The most focused.</value>
-		public View MostFocused {
-			get {
-				if (Focused == null)
-					return null;
-				var most = Focused.MostFocused;
-				if (most != null)
-					return most;
-				return Focused;
-			}
-		}
-
-		/// <summary>
-		/// The color scheme for this view, if it is not defined, it returns the parent's
-		/// color scheme.
-		/// </summary>
-		public ColorScheme ColorScheme {
-			get {
-				if (colorScheme == null)
-					return SuperView?.ColorScheme;
-				return colorScheme;
-			}
-			set {
-				colorScheme = value;
-			}
-		}
-
-		ColorScheme colorScheme;
-
-		/// <summary>
-		/// Displays the specified character in the specified column and row.
-		/// </summary>
-		/// <param name="col">Col.</param>
-		/// <param name="row">Row.</param>
-		/// <param name="ch">Ch.</param>
-		public void AddRune (int col, int row, Rune ch)
-		{
-			if (row < 0 || col < 0)
-				return;
-			if (row > frame.Height - 1 || col > frame.Width - 1)
-				return;
-			Move (col, row);
-			Driver.AddRune (ch);
-		}
-
-		/// <summary>
-		/// Removes the SetNeedsDisplay and the ChildNeedsDisplay setting on this view.
-		/// </summary>
-		protected void ClearNeedsDisplay ()
-		{
-			NeedDisplay = Rect.Empty;
-			childNeedsDisplay = false;
-		}
-
-		/// <summary>
-		/// Performs a redraw of this view and its subviews, only redraws the views that have been flagged for a re-display.
-		/// </summary>
-		/// <param name="region">The region to redraw, this is relative to the view itself.</param>
-		/// <remarks>
-		/// <para>
-		///    Views should set the color that they want to use on entry, as otherwise this will inherit
-		///    the last color that was set globaly on the driver.
-		/// </para>
-		/// </remarks>
-		public virtual void Redraw (Rect region)
-		{
-			var clipRect = new Rect (Point.Empty, frame.Size);
-
-			if (subviews != null) {
-				foreach (var view in subviews) {
-					if (view.NeedDisplay != null && (!view.NeedDisplay.IsEmpty || view.childNeedsDisplay)) {
-						if (view.Frame.IntersectsWith (clipRect) && view.Frame.IntersectsWith (region)) {
-
-							// FIXED: optimize this by computing the intersection of region and view.Bounds
-							if (view.layoutNeeded)
-								view.LayoutSubviews ();
-							Application.CurrentView = view;
-							view.Redraw (view.Bounds);
-						}
-						view.NeedDisplay = Rect.Empty;
-						view.childNeedsDisplay = false;
-					}
-				}
-			}
-			ClearNeedsDisplay ();
-		}
-
-		/// <summary>
-		/// Focuses the specified sub-view.
-		/// </summary>
-		/// <param name="view">View.</param>
-		public void SetFocus (View view)
-		{
-			if (view == null)
-				return;
-			//Console.WriteLine ($"Request to focus {view}");
-			if (!view.CanFocus)
-				return;
-			if (focused == view)
-				return;
-
-			// Make sure that this view is a subview
-			View c;
-			for (c = view.container; c != null; c = c.container)
-				if (c == this)
-					break;
-			if (c == null)
-				throw new ArgumentException ("the specified view is not part of the hierarchy of this view");
-
-			if (focused != null)
-				focused.HasFocus = false;
-
-			focused = view;
-			focused.HasFocus = true;
-			focused.EnsureFocus ();
-
-			// Send focus upwards
-			SuperView?.SetFocus (this);
-		}
-
-		/// <summary>
-		/// Specifies the event arguments for <see cref="KeyEvent"/>
-		/// </summary>
-		public class KeyEventEventArgs : EventArgs {
-			/// <summary>
-			/// Constructs.
-			/// </summary>
-			/// <param name="ke"></param>
-			public KeyEventEventArgs (KeyEvent ke) => KeyEvent = ke;
-			/// <summary>
-			/// The <see cref="KeyEvent"/> for the event.
-			/// </summary>
-			public KeyEvent KeyEvent { get; set; }
-			/// <summary>
-			/// Indicates if the current Key event has already been processed and the driver should stop notifying any other event subscriber.
-			/// Its important to set this value to true specially when updating any View's layout from inside the subscriber method.
-			/// </summary>
-			public bool Handled { get; set; } = false;
-		}
-
-		/// <summary>
-		/// Invoked when a character key is pressed and occurs after the key up event.
-		/// </summary>
-		public event EventHandler<KeyEventEventArgs> KeyPress;
-
-		/// <inheritdoc cref="ProcessKey"/>
-		public override bool ProcessKey (KeyEvent keyEvent)
-		{
-
-			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
-			KeyPress?.Invoke (this, args);
-			if (args.Handled)
-				return true;
-			if (Focused?.ProcessKey (keyEvent) == true)
-				return true;
-
-			return false;
-		}
-
-		/// <inheritdoc cref="ProcessHotKey"/>
-		public override bool ProcessHotKey (KeyEvent keyEvent)
-		{
-			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
-			KeyPress?.Invoke (this, args);
-			if (args.Handled)
-				return true;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-			foreach (var view in subviews)
-				if (view.ProcessHotKey (keyEvent))
-					return true;
-			return false;
-		}
-
-		/// <inheritdoc cref="ProcessColdKey"/>
-		public override bool ProcessColdKey (KeyEvent keyEvent)
-		{
-			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
-			KeyPress?.Invoke (this, args);
-			if (args.Handled)
-				return true;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-			foreach (var view in subviews)
-				if (view.ProcessColdKey (keyEvent))
-					return true;
-			return false;
-		}
-
-		/// <summary>
-		/// Invoked when a key is pressed
-		/// </summary>
-		public event EventHandler<KeyEventEventArgs> KeyDown;
-
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		public override bool OnKeyDown (KeyEvent keyEvent)
-		{
-			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
-			KeyDown?.Invoke (this, args);
-			if (args.Handled)
-				return true;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-			foreach (var view in subviews)
-				if (view.OnKeyDown (keyEvent))
-					return true;
-
-			return false;
-		}
-
-		/// <summary>
-		/// Invoked when a key is released
-		/// </summary>
-		public event EventHandler<KeyEventEventArgs> KeyUp;
-
-		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
-		public override bool OnKeyUp (KeyEvent keyEvent)
-		{
-			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
-			KeyUp?.Invoke (this, args);
-			if (args.Handled)
-				return true;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-			foreach (var view in subviews)
-				if (view.OnKeyUp (keyEvent))
-					return true;
-
-			return false;
-		}
-
-		/// <summary>
-		/// Finds the first view in the hierarchy that wants to get the focus if nothing is currently focused, otherwise, it does nothing.
-		/// </summary>
-		public void EnsureFocus ()
-		{
-			if (focused == null)
-				if (FocusDirection == Direction.Forward)
-					FocusFirst ();
-				else
-					FocusLast ();
-		}
-
-		/// <summary>
-		/// Focuses the first focusable subview if one exists.
-		/// </summary>
-		public void FocusFirst ()
-		{
-			if (subviews == null) {
-				SuperView?.SetFocus (this);
-				return;
-			}
-
-			foreach (var view in subviews) {
-				if (view.CanFocus) {
-					SetFocus (view);
-					return;
-				}
-			}
-		}
-
-		/// <summary>
-		/// Focuses the last focusable subview if one exists.
-		/// </summary>
-		public void FocusLast ()
-		{
-			if (subviews == null) {
-				SuperView?.SetFocus (this);
-				return;
-			}
-
-			for (int i = subviews.Count; i > 0;) {
-				i--;
-
-				View v = subviews [i];
-				if (v.CanFocus) {
-					SetFocus (v);
-					return;
-				}
-			}
-		}
-
-		/// <summary>
-		/// Focuses the previous view.
-		/// </summary>
-		/// <returns><c>true</c>, if previous was focused, <c>false</c> otherwise.</returns>
-		public bool FocusPrev ()
-		{
-			FocusDirection = Direction.Backward;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-
-			if (focused == null) {
-				FocusLast ();
-				return focused != null;
-			}
-			int focused_idx = -1;
-			for (int i = subviews.Count; i > 0;) {
-				i--;
-				View w = subviews [i];
-
-				if (w.HasFocus) {
-					if (w.FocusPrev ())
-						return true;
-					focused_idx = i;
-					continue;
-				}
-				if (w.CanFocus && focused_idx != -1) {
-					focused.HasFocus = false;
-
-					if (w != null && w.CanFocus)
-						w.FocusLast ();
-
-					SetFocus (w);
-					return true;
-				}
-			}
-			if (focused != null) {
-				focused.HasFocus = false;
-				focused = null;
-			}
-			return false;
-		}
-
-		/// <summary>
-		/// Focuses the next view.
-		/// </summary>
-		/// <returns><c>true</c>, if next was focused, <c>false</c> otherwise.</returns>
-		public bool FocusNext ()
-		{
-			FocusDirection = Direction.Forward;
-			if (subviews == null || subviews.Count == 0)
-				return false;
-
-			if (focused == null) {
-				FocusFirst ();
-				return focused != null;
-			}
-			int n = subviews.Count;
-			int focused_idx = -1;
-			for (int i = 0; i < n; i++) {
-				View w = subviews [i];
-
-				if (w.HasFocus) {
-					if (w.FocusNext ())
-						return true;
-					focused_idx = i;
-					continue;
-				}
-				if (w.CanFocus && focused_idx != -1) {
-					focused.HasFocus = false;
-
-					if (w != null && w.CanFocus)
-						w.FocusFirst ();
-
-					SetFocus (w);
-					return true;
-				}
-			}
-			if (focused != null) {
-				focused.HasFocus = false;
-				focused = null;
-			}
-			return false;
-		}
-
-		/// <summary>
-		/// Computes the RelativeLayout for the view, given the frame for its container.
-		/// </summary>
-		/// <param name="hostFrame">The Frame for the host.</param>
-		internal void RelativeLayout (Rect hostFrame)
-		{
-			int w, h, _x, _y;
-
-			if (x is Pos.PosCenter) {
-				if (width == null)
-					w = hostFrame.Width;
-				else
-					w = width.Anchor (hostFrame.Width);
-				_x = x.Anchor (hostFrame.Width - w);
-			} else {
-				if (x == null)
-					_x = 0;
-				else
-					_x = x.Anchor (hostFrame.Width);
-				if (width == null)
-					w = hostFrame.Width;
-				else
-					w = width.Anchor (hostFrame.Width - _x);
-			}
-
-			if (y is Pos.PosCenter) {
-				if (height == null)
-					h = hostFrame.Height;
-				else
-					h = height.Anchor (hostFrame.Height);
-				_y = y.Anchor (hostFrame.Height - h);
-			} else {
-				if (y == null)
-					_y = 0;
-				else
-					_y = y.Anchor (hostFrame.Height);
-				if (height == null)
-					h = hostFrame.Height;
-				else
-					h = height.Anchor (hostFrame.Height - _y);
-			}
-			Frame = new Rect (_x, _y, w, h);
-			// layoutNeeded = false;
-		}
-
-		// https://en.wikipedia.org/wiki/Topological_sorting
-		List<View> TopologicalSort (HashSet<View> nodes, HashSet<(View From, View To)> edges)
-		{
-			var result = new List<View> ();
-
-			// Set of all nodes with no incoming edges
-			var S = new HashSet<View> (nodes.Where (n => edges.All (e => e.To.Equals (n) == false)));
-
-			while (S.Any ()) {
-				//  remove a node n from S
-				var n = S.First ();
-				S.Remove (n);
-
-				// add n to tail of L
-				if (n != this?.SuperView)
-					result.Add (n);
-
-				// for each node m with an edge e from n to m do
-				foreach (var e in edges.Where (e => e.From.Equals (n)).ToArray ()) {
-					var m = e.To;
-
-					// remove edge e from the graph
-					edges.Remove (e);
-
-					// if m has no other incoming edges then
-					if (edges.All (me => me.To.Equals (m) == false) && m != this?.SuperView) {
-						// insert m into S
-						S.Add (m);
-					}
-				}
-			}
-
-			// if graph has edges then
-			if (edges.Any ()) {
-				// return error (graph has at least one cycle)
-				return null;
-			} else {
-				// return L (a topologically sorted order)
-				return result;
-			}
-		}
-
-		/// <summary>
-		/// This virtual method is invoked when a view starts executing or
-		/// when the dimensions of the view have changed, for example in
-		/// response to the container view or terminal resizing.
-		/// </summary>
-		public virtual void LayoutSubviews ()
-		{
-			if (!layoutNeeded)
-				return;
-
-			// Sort out the dependencies of the X, Y, Width, Height properties
-			var nodes = new HashSet<View> ();
-			var edges = new HashSet<(View, View)> ();
-
-			foreach (var v in InternalSubviews) {
-				nodes.Add (v);
-				if (v.LayoutStyle == LayoutStyle.Computed) {
-					if (v.X is Pos.PosView vX)
-						edges.Add ((vX.Target, v));
-					if (v.Y is Pos.PosView vY)
-						edges.Add ((vY.Target, v));
-					if (v.Width is Dim.DimView vWidth)
-						edges.Add ((vWidth.Target, v));
-					if (v.Height is Dim.DimView vHeight)
-						edges.Add ((vHeight.Target, v));
-				}
-			}
-
-			var ordered = TopologicalSort (nodes, edges);
-			if (ordered == null)
-				throw new Exception ("There is a recursive cycle in the relative Pos/Dim in the views of " + this);
-
-			foreach (var v in ordered) {
-				if (v.LayoutStyle == LayoutStyle.Computed)
-					v.RelativeLayout (Frame);
-
-				v.LayoutSubviews ();
-				v.layoutNeeded = false;
-
-			}
-
-			if (SuperView == Application.Top && layoutNeeded && ordered.Count == 0 && LayoutStyle == LayoutStyle.Computed) {
-				RelativeLayout (Frame);
-			}
-
-			layoutNeeded = false;
-		}
-
-		/// <inheritdoc cref="ToString"/>
-		public override string ToString ()
-		{
-			return $"{GetType ().Name}({Id})({Frame})";
-		}
-
-		/// <inheritdoc cref="OnMouseEnter(Gui.MouseEvent)"/>
-		public override bool OnMouseEnter (MouseEvent mouseEvent)
-		{
-			if (!base.OnMouseEnter (mouseEvent)) {
-				MouseEnter?.Invoke (this, mouseEvent);
-				return false;
-			}
-			return true;
-		}
-
-		/// <inheritdoc cref="OnMouseLeave(Gui.MouseEvent)"/>
-		public override bool OnMouseLeave (MouseEvent mouseEvent)
-		{
-			if (!base.OnMouseLeave (mouseEvent)) {
-				MouseLeave?.Invoke (this, mouseEvent);
-				return false;
-			}
-			return true;
-		}
-	}
-
-	/// <summary>
-	/// Toplevel views can be modally executed.
-	/// </summary>
-	/// <remarks>
-	///   <para>
-	///     Toplevels can be modally executing views, and they return control
-	///     to the caller when the "Running" property is set to false, or
-	///     by calling <see cref="M:Terminal.Gui.Application.RequestStop()"/>
-	///   </para>
-	///   <para>
-	///     There will be a toplevel created for you on the first time use
-	///     and can be accessed from the property <see cref="P:Terminal.Gui.Application.Top"/>,
-	///     but new toplevels can be created and ran on top of it.   To run, create the
-	///     toplevel and then invoke <see cref="M:Terminal.Gui.Application.Run"/> with the
-	///     new toplevel.
-	///   </para>
-	///   <para>
-	///     TopLevels can also opt-in to more sophisticated initialization
-	///     by implementing <see cref="ISupportInitialize"/>. When they do
-	///     so, the <see cref="ISupportInitialize.BeginInit"/> and
-	///     <see cref="ISupportInitialize.EndInit"/> methods will be called
-	///     before running the view.
-	///     If first-run-only initialization is preferred, the <see cref="ISupportInitializeNotification"/>
-	///     can be implemented too, in which case the <see cref="ISupportInitialize"/>
-	///     methods will only be called if <see cref="ISupportInitializeNotification.IsInitialized"/>
-	///     is <see langword="false"/>. This allows proper View inheritance hierarchies
-	///     to override base class layout code optimally by doing so only on first run,
-	///     instead of on every run.
-	///   </para>
-	/// </remarks>
-	public class Toplevel : View {
-		/// <summary>
-		/// Gets or sets whether the Mainloop for this <see cref="Toplevel"/> is running or not. Setting
-		/// this property to false will cause the MainLoop to exit. 
-		/// </summary>
-		public bool Running { get; set; }
-
-		/// <summary>
-		/// Fired once the Toplevel's MainLoop has started it's first iteration. 
-		/// Subscribe to this event to perform tasks when the <see cref="Toplevel"/> has been laid out and focus has been set.
-		/// changes. A Ready event handler is a good place to finalize initialization after calling `<see cref="Application.Run()"/>(topLevel)`. 
-		/// </summary>
-		public event EventHandler Ready;
-
-		/// <summary>
-		/// Called from Application.RunLoop after the <see cref="Toplevel"/> has entered it's first iteration of the loop. 
-		/// </summary>
-		internal virtual void OnReady ()
-		{
-			Ready?.Invoke (this, EventArgs.Empty);
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Toplevel"/> class with the specified absolute layout.
-		/// </summary>
-		/// <param name="frame">Frame.</param>
-		public Toplevel (Rect frame) : base (frame)
-		{
-			Initialize ();
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Toplevel"/> class with Computed layout, defaulting to <see langword="async"/> full screen.
-		/// </summary>
-		public Toplevel () : base ()
-		{
-			Initialize ();
-			Width = Dim.Fill ();
-			Height = Dim.Fill ();
-		}
-
-		void Initialize ()
-		{
-			ColorScheme = Colors.Base;
-		}
-
-		/// <summary>
-		/// Convenience factory method that creates a new toplevel with the current terminal dimensions.
-		/// </summary>
-		/// <returns>The create.</returns>
-		public static Toplevel Create ()
-		{
-			return new Toplevel (new Rect (0, 0, Driver.Cols, Driver.Rows));
-		}
-
-		/// <summary>
-		/// Gets or sets a value indicating whether this <see cref="Toplevel"/> can focus.
-		/// </summary>
-		/// <value><c>true</c> if can focus; otherwise, <c>false</c>.</value>
-		public override bool CanFocus {
-			get => true;
-		}
-
-		/// <summary>
-		/// Determines whether the <see cref="Toplevel"/> is modal or not.
-		/// Causes <see cref="ProcessKey(KeyEvent)"/> to propagate keys upwards
-		/// by default unless set to <see langword="true"/>.
-		/// </summary>
-		public bool Modal { get; set; }
-
-		/// <summary>
-		/// Check id current toplevel has menu bar
-		/// </summary>
-		public MenuBar MenuBar { get; set; }
-
-		/// <summary>
-		/// Check id current toplevel has status bar
-		/// </summary>
-		public StatusBar StatusBar { get; set; }
-
-		///<inheritdoc cref="ProcessKey"/>
-		public override bool ProcessKey (KeyEvent keyEvent)
-		{
-			if (base.ProcessKey (keyEvent))
-				return true;
-
-			switch (keyEvent.Key) {
-			case Key.ControlQ:
-				// FIXED: stop current execution of this container
-				Application.RequestStop ();
-				break;
-			case Key.ControlZ:
-				Driver.Suspend ();
-				return true;
-
-#if false
-			case Key.F5:
-				Application.DebugDrawBounds = !Application.DebugDrawBounds;
-				SetNeedsDisplay ();
-				return true;
-#endif
-			case Key.Tab:
-			case Key.CursorRight:
-			case Key.CursorDown:
-			case Key.ControlI: // Unix
-				var old = Focused;
-				if (!FocusNext ())
-					FocusNext ();
-				if (old != Focused) {
-					old?.SetNeedsDisplay ();
-					Focused?.SetNeedsDisplay ();
-				}
-				return true;
-			case Key.CursorLeft:
-			case Key.CursorUp:
-			case Key.BackTab:
-				old = Focused;
-				if (!FocusPrev ())
-					FocusPrev ();
-				if (old != Focused) {
-					old?.SetNeedsDisplay ();
-					Focused?.SetNeedsDisplay ();
-				}
-				return true;
-
-			case Key.ControlL:
-				Application.Refresh ();
-				return true;
-			}
-			return false;
-		}
-
-		///<inheritdoc cref="Add"/>
-		public override void Add (View view)
-		{
-			if (this == Application.Top) {
-				if (view is MenuBar)
-					MenuBar = view as MenuBar;
-				if (view is StatusBar)
-					StatusBar = view as StatusBar;
-			}
-			base.Add (view);
-		}
-
-		///<inheritdoc cref="Remove"/>
-		public override void Remove (View view)
-		{
-			if (this == Application.Top) {
-				if (view is MenuBar)
-					MenuBar = null;
-				if (view is StatusBar)
-					StatusBar = null;
-			}
-			base.Remove (view);
-		}
-
-		///<inheritdoc cref="RemoveAll"/>
-		public override void RemoveAll ()
-		{
-			if (this == Application.Top) {
-				MenuBar = null;
-				StatusBar = null;
-			}
-			base.RemoveAll ();
-		}
-
-		internal void EnsureVisibleBounds (Toplevel top, int x, int y, out int nx, out int ny)
-		{
-			nx = Math.Max (x, 0);
-			nx = nx + top.Frame.Width > Driver.Cols ? Math.Max (Driver.Cols - top.Frame.Width, 0) : nx;
-			bool m, s;
-			if (SuperView == null || SuperView.GetType () != typeof (Toplevel))
-				m = Application.Top.MenuBar != null;
-			else
-				m = ((Toplevel)SuperView).MenuBar != null;
-			int l = m ? 1 : 0;
-			ny = Math.Max (y, l);
-			if (SuperView == null || SuperView.GetType () != typeof (Toplevel))
-				s = Application.Top.StatusBar != null;
-			else
-				s = ((Toplevel)SuperView).StatusBar != null;
-			l = s ? Driver.Rows - 1 : Driver.Rows;
-			ny = Math.Min (ny, l);
-			ny = ny + top.Frame.Height > l ? Math.Max (l - top.Frame.Height, m ? 1 : 0) : ny;
-		}
-
-		internal void PositionToplevels ()
-		{
-			if (this != Application.Top) {
-				EnsureVisibleBounds (this, Frame.X, Frame.Y, out int nx, out int ny);
-				if ((nx != Frame.X || ny != Frame.Y) && LayoutStyle != LayoutStyle.Computed) {
-					X = nx;
-					Y = ny;
-				}
-			} else {
-				foreach (var top in Subviews) {
-					if (top is Toplevel) {
-						EnsureVisibleBounds ((Toplevel)top, top.Frame.X, top.Frame.Y, out int nx, out int ny);
-						if ((nx != top.Frame.X || ny != top.Frame.Y) && top.LayoutStyle != LayoutStyle.Computed) {
-							top.X = nx;
-							top.Y = ny;
-						}
-						if (StatusBar != null) {
-							if (ny + top.Frame.Height > Driver.Rows - 1) {
-								if (top.Height is Dim.DimFill)
-									top.Height = Dim.Fill () - 1;
-							}
-							if (StatusBar.Frame.Y != Driver.Rows - 1) {
-								StatusBar.Y = Driver.Rows - 1;
-								SetNeedsDisplay ();
-							}
-						}
-					}
-				}
-			}
-		}
-
-		///<inheritdoc cref="Redraw"/>
-		public override void Redraw (Rect region)
-		{
-			Application.CurrentView = this;
-
-			if (IsCurrentTop) {
-				if (NeedDisplay != null && !NeedDisplay.IsEmpty) {
-					Driver.SetAttribute (Colors.TopLevel.Normal);
-					Clear (region);
-					Driver.SetAttribute (Colors.Base.Normal);
-				}
-				foreach (var view in Subviews) {
-					if (view.Frame.IntersectsWith (region)) {
-						view.SetNeedsLayout ();
-						view.SetNeedsDisplay (view.Bounds);
-					}
-				}
-
-				ClearNeedsDisplay ();
-			}
-
-			base.Redraw (base.Bounds);
-		}
-
-		/// <summary>
-		/// This method is invoked by Application.Begin as part of the Application.Run after
-		/// the views have been laid out, and before the views are drawn for the first time.
-		/// </summary>
-		public virtual void WillPresent ()
-		{
-			FocusFirst ();
-		}
-	}
-
-	/// <summary>
-	/// A <see cref="Toplevel"/> <see cref="View"/> that draws a frame around its region and has a "ContentView" subview where the contents are added.
-	/// </summary>
-	public class Window : Toplevel, IEnumerable {
-		View contentView;
-		ustring title;
-
-		/// <summary>
-		/// The title to be displayed for this window.
-		/// </summary>
-		/// <value>The title.</value>
-		public ustring Title {
-			get => title;
-			set {
-				title = value;
-				SetNeedsDisplay ();
-			}
-		}
-
-		class ContentView : View {
-			public ContentView (Rect frame) : base (frame) { }
-			public ContentView () : base () { }
-#if false
-			public override void Redraw (Rect region)
-			{
-				Driver.SetAttribute (ColorScheme.Focus);
-
-				for (int y = 0; y < Frame.Height; y++) {
-					Move (0, y);
-					for (int x = 0; x < Frame.Width; x++) {
-
-						Driver.AddRune ('x');
-					}
-				}
-			}
-#endif
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Gui.Window"/> class with an optional title and a set frame.
-		/// </summary>
-		/// <param name="frame">Frame.</param>
-		/// <param name="title">Title.</param>
-		public Window (Rect frame, ustring title = null) : this (frame, title, padding: 0)
-		{
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Window"/> class with an optional title.
-		/// </summary>
-		/// <param name="title">Title.</param>
-		public Window (ustring title = null) : this (title, padding: 0)
-		{
-		}
-
-		int padding;
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Window"/> with
-		/// the specified frame for its location, with the specified border
-		/// an optional title.
-		/// </summary>
-		/// <param name="frame">Frame.</param>
-		/// <param name="padding">Number of characters to use for padding of the drawn frame.</param>
-		/// <param name="title">Title.</param>
-		public Window (Rect frame, ustring title = null, int padding = 0) : base (frame)
-		{
-			this.Title = title;
-			int wb = 2 * (1 + padding);
-			this.padding = padding;
-			var cFrame = new Rect (1 + padding, 1 + padding, frame.Width - wb, frame.Height - wb);
-			contentView = new ContentView (cFrame);
-			base.Add (contentView);
-		}
-
-		/// <summary>
-		/// Initializes a new instance of the <see cref="Window"/> with
-		/// the specified frame for its location, with the specified border
-		/// an optional title.
-		/// </summary>
-		/// <param name="padding">Number of characters to use for padding of the drawn frame.</param>
-		/// <param name="title">Title.</param>
-		public Window (ustring title = null, int padding = 0) : base ()
-		{
-			this.Title = title;
-			int wb = 1 + padding;
-			this.padding = padding;
-			contentView = new ContentView () {
-				X = wb,
-				Y = wb,
-				Width = Dim.Fill (wb),
-				Height = Dim.Fill (wb)
-			};
-			base.Add (contentView);
-		}
-
-		/// <summary>
-		/// Enumerates the various <see cref="View"/>s in the embedded <see cref="ContentView"/>.
-		/// </summary>
-		/// <returns>The enumerator.</returns>
-		public new IEnumerator GetEnumerator ()
-		{
-			return contentView.GetEnumerator ();
-		}
-
-		/// <summary>
-		/// Add the specified view to the <see cref="ContentView"/>.
-		/// </summary>
-		/// <param name="view">View to add to the window.</param>
-		public override void Add (View view)
-		{
-			contentView.Add (view);
-			if (view.CanFocus)
-				CanFocus = true;
-		}
-
-
-		/// <summary>
-		///   Removes a widget from this container.
-		/// </summary>
-		/// <remarks>
-		/// </remarks>
-		public override void Remove (View view)
-		{
-			if (view == null)
-				return;
-
-			SetNeedsDisplay ();
-			var touched = view.Frame;
-			contentView.Remove (view);
-
-			if (contentView.InternalSubviews.Count < 1)
-				this.CanFocus = false;
-		}
-
-		/// <summary>
-		///   Removes all widgets from this container.
-		/// </summary>
-		/// <remarks>
-		/// </remarks>
-		public override void RemoveAll ()
-		{
-			contentView.RemoveAll ();
-		}
-
-		///<inheritdoc cref="Redraw"/>
-		public override void Redraw (Rect bounds)
-		{
-			Application.CurrentView = this;
-			var scrRect = RectToScreen (new Rect (0, 0, Frame.Width, Frame.Height));
-			var savedClip = Driver.Clip;
-			Driver.Clip = ScreenClip (RectToScreen (Bounds));
-
-			if (NeedDisplay != null && !NeedDisplay.IsEmpty) {
-				Driver.SetAttribute (ColorScheme.Normal);
-				Driver.DrawFrame (scrRect, padding, true);
-			}
-			contentView.Redraw (contentView.Bounds);
-			ClearNeedsDisplay ();
-			Driver.SetAttribute (ColorScheme.Normal);
-			Driver.DrawFrame (scrRect, padding, false);
-
-			if (HasFocus)
-				Driver.SetAttribute (ColorScheme.HotNormal);
-			Driver.DrawWindowTitle (scrRect, Title, padding, padding, padding, padding);
-			Driver.Clip = savedClip;
-			Driver.SetAttribute (ColorScheme.Normal);
-		}
-
-		//
-		// FIXED:It does not look like the event is raised on clicked-drag
-		// need to figure that out.
-		//
-		internal static Point? dragPosition;
-		Point start;
-		///<inheritdoc cref="MouseEvent(Gui.MouseEvent)"/>
-		public override bool MouseEvent (MouseEvent mouseEvent)
-		{
-			// FIXED:The code is currently disabled, because the
-			// Driver.UncookMouse does not seem to have an effect if there is
-			// a pending mouse event activated.
-
-			int nx, ny;
-			if ((mouseEvent.Flags == (MouseFlags.Button1Pressed | MouseFlags.ReportMousePosition) ||
-				mouseEvent.Flags == MouseFlags.Button3Pressed)) {
-				if (dragPosition.HasValue) {
-					if (SuperView == null) {
-						Application.Top.SetNeedsDisplay (Frame);
-						Application.Top.Redraw (Frame);
-					} else {
-						SuperView.SetNeedsDisplay (Frame);
-					}
-					EnsureVisibleBounds (this, mouseEvent.X + mouseEvent.OfX - start.X,
-						mouseEvent.Y + mouseEvent.OfY, out nx, out ny);
-
-					dragPosition = new Point (nx, ny);
-					Frame = new Rect (nx, ny, Frame.Width, Frame.Height);
-					X = nx;
-					Y = ny;
-					//Demo.ml2.Text = $"{dx},{dy}";
-
-					// FIXED: optimize, only SetNeedsDisplay on the before/after regions.
-					SetNeedsDisplay ();
-					return true;
-				} else {
-					// Only start grabbing if the user clicks on the title bar.
-					if (mouseEvent.Y == 0) {
-						start = new Point (mouseEvent.X, mouseEvent.Y);
-						dragPosition = new Point ();
-						nx = mouseEvent.X - mouseEvent.OfX;
-						ny = mouseEvent.Y - mouseEvent.OfY;
-						dragPosition = new Point (nx, ny);
-						Application.GrabMouse (this);
-					}
-
-					//Demo.ml2.Text = $"Starting at {dragPosition}";
-					return true;
-				}
-			}
-
-			if (mouseEvent.Flags == MouseFlags.Button1Released && dragPosition.HasValue) {
-				Application.UngrabMouse ();
-				Driver.UncookMouse ();
-				dragPosition = null;
-			}
-
-			//Demo.ml.Text = me.ToString ();
-			return false;
-		}
-
-	}
-
-	/// <summary>
-	/// The application driver for Terminal.Gui.
-	/// </summary>
-	/// <remarks>
-	///   <para>
-	///     You can hook up to the Iteration event to have your method
-	///     invoked on each iteration of the mainloop.
-	///   </para>
-	///   <para>
-	///     Creates a mainloop to process input events, handle timers and
-	///     other sources of data.   It is accessible via the MainLoop property.
-	///   </para>
-	///   <para>
-	///     When invoked sets the SynchronizationContext to one that is tied
-	///     to the mainloop, allowing user code to use async/await.
-	///   </para>
-	/// </remarks>
-	public static class Application {
-		/// <summary>
-		/// The current <see cref="ConsoleDriver"/> in use.
-		/// </summary>
-		public static ConsoleDriver Driver;
-
-		/// <summary>
-		/// The <see cref="Toplevel"/> object used for the application on startup (<seealso cref="Application.Top"/>)
-		/// </summary>
-		/// <value>The top.</value>
-		public static Toplevel Top { get; private set; }
-
-		/// <summary>
-		/// The current <see cref="Toplevel"/> object. This is updated when <see cref="Application.Run()"/> enters and leaves to point to the current <see cref="Toplevel"/> .
-		/// </summary>
-		/// <value>The current.</value>
-		public static Toplevel Current { get; private set; }
-
-		/// <summary>
-		/// TThe current <see cref="View"/> object being redrawn.
-		/// </summary>
-		/// /// <value>The current.</value>
-		public static View CurrentView { get; set; }
-
-		/// <summary>
-		/// The <see cref="MainLoop"/>  driver for the applicaiton
-		/// </summary>
-		/// <value>The main loop.</value>
-		public static MainLoop MainLoop { get; private set; }
-
-		static Stack<Toplevel> toplevels = new Stack<Toplevel> ();
-
-		/// <summary>
-		///   This event is raised on each iteration of the <see cref="MainLoop"/> 
-		/// </summary>
-		/// <remarks>
-		///   See also <see cref="Timeout"/>
-		/// </remarks>
-		public static event EventHandler Iteration;
-
-		/// <summary>
-		/// Returns a rectangle that is centered in the screen for the provided size.
-		/// </summary>
-		/// <returns>The centered rect.</returns>
-		/// <param name="size">Size for the rectangle.</param>
-		public static Rect MakeCenteredRect (Size size)
-		{
-			return new Rect (new Point ((Driver.Cols - size.Width) / 2, (Driver.Rows - size.Height) / 2), size);
-		}
-
-		//
-		// provides the sync context set while executing code in Terminal.Gui, to let
-		// users use async/await on their code
-		//
-		class MainLoopSyncContext : SynchronizationContext {
-			MainLoop mainLoop;
-
-			public MainLoopSyncContext (MainLoop mainLoop)
-			{
-				this.mainLoop = mainLoop;
-			}
-
-			public override SynchronizationContext CreateCopy ()
-			{
-				return new MainLoopSyncContext (MainLoop);
-			}
-
-			public override void Post (SendOrPostCallback d, object state)
-			{
-				mainLoop.AddIdle (() => {
-					d (state);
-					return false;
-				});
-				//mainLoop.Driver.Wakeup ();
-			}
-
-			public override void Send (SendOrPostCallback d, object state)
-			{
-				mainLoop.Invoke (() => {
-					d (state);
-				});
-			}
-		}
-
-		/// <summary>
-		/// If set, it forces the use of the System.Console-based driver.
-		/// </summary>
-		public static bool UseSystemConsole;
-
-		/// <summary>
-		/// Initializes a new instance of <see cref="Terminal.Gui"/> Application. 
-		/// </summary>
-		/// <remarks>
-		/// <para>
-		/// Call this method once per instance (or after <see cref="Shutdown"/> has been called).
-		/// </para>
-		/// <para>
-		/// Loads the right <see cref="ConsoleDriver"/> for the platform.
-		/// </para>
-		/// <para>
-		/// Creates a <see cref="Toplevel"/> and assigns it to <see cref="Top"/> and <see cref="CurrentView"/>
-		/// </para>
-		/// </remarks>
-		public static void Init () => Init (() => Toplevel.Create ());
-
-		internal static bool _initialized = false;
-
-		/// <summary>
-		/// Initializes the Terminal.Gui application
-		/// </summary>
-		static void Init (Func<Toplevel> topLevelFactory)
-		{
-			if (_initialized) return;
-
-			if (Driver == null) {
-				var p = Environment.OSVersion.Platform;
-				IMainLoopDriver mainLoopDriver;
-
-				if (UseSystemConsole) {
-					mainLoopDriver = new NetMainLoop ();
-					Driver = new NetDriver ();
-				} else if (p == PlatformID.Win32NT || p == PlatformID.Win32S || p == PlatformID.Win32Windows) {
-					var windowsDriver = new WindowsDriver ();
-					mainLoopDriver = windowsDriver;
-					Driver = windowsDriver;
-				} else {
-					mainLoopDriver = new UnixMainLoop ();
-					Driver = new CursesDriver ();
-				}
-				Driver.Init (TerminalResized);
-				MainLoop = new MainLoop (mainLoopDriver);
-				SynchronizationContext.SetSynchronizationContext (new MainLoopSyncContext (MainLoop));
-			}
-			Top = topLevelFactory ();
-			Current = Top;
-			CurrentView = Top;
-			_initialized = true;
-		}
-
-		/// <summary>
-		/// Captures the execution state for the provided <see cref="Toplevel"/>  view.
-		/// </summary>
-		public class RunState : IDisposable {
-			internal bool closeDriver = true;
-
-			internal RunState (Toplevel view)
-			{
-				Toplevel = view;
-			}
-			internal Toplevel Toplevel;
-
-			/// <summary>
-			/// Releases alTop = l resource used by the <see cref="Application.RunState"/> object.
-			/// </summary>
-			/// <remarks>Call <see cref="Dispose()"/> when you are finished using the <see cref="Application.RunState"/>. The
-			/// <see cref="Dispose()"/> method leaves the <see cref="Application.RunState"/> in an unusable state. After
-			/// calling <see cref="Dispose()"/>, you must release all references to the
-			/// <see cref="Application.RunState"/> so the garbage collector can reclaim the memory that the
-			/// <see cref="Application.RunState"/> was occupying.</remarks>
-			public void Dispose ()
-			{
-				Dispose (closeDriver);
-				GC.SuppressFinalize (this);
-			}
-
-			/// <summary>
-			/// Dispose the specified disposing.
-			/// </summary>
-			/// <returns>The dispose.</returns>
-			/// <param name="disposing">If set to <c>true</c> disposing.</param>
-			protected virtual void Dispose (bool disposing)
-			{
-				if (Toplevel != null) {
-					End (Toplevel, disposing);
-					Toplevel = null;
-				}
-			}
-		}
-
-		static void ProcessKeyEvent (KeyEvent ke)
-		{
-
-			var chain = toplevels.ToList ();
-			foreach (var topLevel in chain) {
-				if (topLevel.ProcessHotKey (ke))
-					return;
-				if (topLevel.Modal)
-					break;
-			}
-
-			foreach (var topLevel in chain) {
-				if (topLevel.ProcessKey (ke))
-					return;
-				if (topLevel.Modal)
-					break;
-			}
-
-			foreach (var topLevel in chain) {
-				// Process the key normally
-				if (topLevel.ProcessColdKey (ke))
-					return;
-				if (topLevel.Modal)
-					break;
-			}
-		}
-
-		static void ProcessKeyDownEvent (KeyEvent ke)
-		{
-			var chain = toplevels.ToList ();
-			foreach (var topLevel in chain) {
-				if (topLevel.OnKeyDown (ke))
-					return;
-				if (topLevel.Modal)
-					break;
-			}
-		}
-
-
-		static void ProcessKeyUpEvent (KeyEvent ke)
-		{
-			var chain = toplevels.ToList ();
-			foreach (var topLevel in chain) {
-				if (topLevel.OnKeyUp (ke))
-					return;
-				if (topLevel.Modal)
-					break;
-			}
-		}
-
-		static View FindDeepestView (View start, int x, int y, out int resx, out int resy)
-		{
-			var startFrame = start.Frame;
-
-			if (!startFrame.Contains (x, y)) {
-				resx = 0;
-				resy = 0;
-				return null;
-			}
-
-			if (start.InternalSubviews != null) {
-				int count = start.InternalSubviews.Count;
-				if (count > 0) {
-					var rx = x - startFrame.X;
-					var ry = y - startFrame.Y;
-					for (int i = count - 1; i >= 0; i--) {
-						View v = start.InternalSubviews [i];
-						if (v.Frame.Contains (rx, ry)) {
-							var deep = FindDeepestView (v, rx, ry, out resx, out resy);
-							if (deep == null)
-								return v;
-							return deep;
-						}
-					}
-				}
-			}
-			resx = x - startFrame.X;
-			resy = y - startFrame.Y;
-			return start;
-		}
-
-		internal static View mouseGrabView;
-
-		/// <summary>
-		/// Grabs the mouse, forcing all mouse events to be routed to the specified view until UngrabMouse is called.
-		/// </summary>
-		/// <returns>The grab.</returns>
-		/// <param name="view">View that will receive all mouse events until UngrabMouse is invoked.</param>
-		public static void GrabMouse (View view)
-		{
-			if (view == null)
-				return;
-			mouseGrabView = view;
-			Driver.UncookMouse ();
-		}
-
-		/// <summary>
-		/// Releases the mouse grab, so mouse events will be routed to the view on which the mouse is.
-		/// </summary>
-		public static void UngrabMouse ()
-		{
-			mouseGrabView = null;
-			Driver.CookMouse ();
-		}
-
-		/// <summary>
-		/// Merely a debugging aid to see the raw mouse events
-		/// </summary>
-		public static Action<MouseEvent> RootMouseEvent;
-
-		internal static View wantContinuousButtonPressedView;
-		static View lastMouseOwnerView;
-
-		static void ProcessMouseEvent (MouseEvent me)
-		{
-			var view = FindDeepestView (Current, me.X, me.Y, out int rx, out int ry);
-
-			if (view != null && view.WantContinuousButtonPressed)
-				wantContinuousButtonPressedView = view;
-			else
-				wantContinuousButtonPressedView = null;
-
-			RootMouseEvent?.Invoke (me);
-			if (mouseGrabView != null) {
-				var newxy = mouseGrabView.ScreenToView (me.X, me.Y);
-				var nme = new MouseEvent () {
-					X = newxy.X,
-					Y = newxy.Y,
-					Flags = me.Flags,
-					OfX = me.X - newxy.X,
-					OfY = me.Y - newxy.Y,
-					View = view
-				};
-				if (OutsideFrame (new Point (nme.X, nme.Y), mouseGrabView.Frame))
-					lastMouseOwnerView.OnMouseLeave (me);
-				if (mouseGrabView != null) {
-					mouseGrabView.MouseEvent (nme);
-					return;
-				}
-			}
-
-			if (view != null) {
-				var nme = new MouseEvent () {
-					X = rx,
-					Y = ry,
-					Flags = me.Flags,
-					OfX = rx,
-					OfY = ry,
-					View = view
-				};
-
-				if (lastMouseOwnerView == null) {
-					lastMouseOwnerView = view;
-					view.OnMouseEnter (nme);
-				} else if (lastMouseOwnerView != view) {
-					lastMouseOwnerView.OnMouseLeave (nme);
-					view.OnMouseEnter (nme);
-					lastMouseOwnerView = view;
-				}
-
-				if (!view.WantMousePositionReports && me.Flags == MouseFlags.ReportMousePosition)
-					return;
-
-				if (view.WantContinuousButtonPressed)
-					wantContinuousButtonPressedView = view;
-				else
-					wantContinuousButtonPressedView = null;
-
-				// Should we bubbled up the event, if it is not handled?
-				view.MouseEvent (nme);
-			}
-		}
-
-		static bool OutsideFrame (Point p, Rect r)
-		{
-			return p.X < 0 || p.X > r.Width - 1 || p.Y < 0 || p.Y > r.Height - 1;
-		}
-
-		/// <summary>
-		/// This event is fired once when the application is first loaded. The dimensions of the
-		/// terminal are provided.
-		/// </summary>
-		public static event EventHandler<ResizedEventArgs> Loaded;
-
-		/// <summary>
-		/// Building block API: Prepares the provided <see cref="Toplevel"/>  for execution.
-		/// </summary>
-		/// <returns>The runstate handle that needs to be passed to the <see cref="End(RunState, bool)"/> method upon completion.</returns>
-		/// <param name="toplevel">Toplevel to prepare execution for.</param>
-		/// <remarks>
-		///  This method prepares the provided toplevel for running with the focus,
-		///  it adds this to the list of toplevels, sets up the mainloop to process the
-		///  event, lays out the subviews, focuses the first element, and draws the
-		///  toplevel in the screen. This is usually followed by executing
-		///  the <see cref="RunLoop"/> method, and then the <see cref="End(RunState, bool)"/> method upon termination which will
-		///   undo these changes.
-		/// </remarks>
-		public static RunState Begin (Toplevel toplevel)
-		{
-			if (toplevel == null)
-				throw new ArgumentNullException (nameof (toplevel));
-			var rs = new RunState (toplevel);
-
-			Init ();
-			if (toplevel is ISupportInitializeNotification initializableNotification &&
-			    !initializableNotification.IsInitialized) {
-				initializableNotification.BeginInit ();
-				initializableNotification.EndInit ();
-			} else if (toplevel is ISupportInitialize initializable) {
-				initializable.BeginInit ();
-				initializable.EndInit ();
-			}
-			toplevels.Push (toplevel);
-			Current = toplevel;
-			Driver.PrepareToRun (MainLoop, ProcessKeyEvent, ProcessKeyDownEvent, ProcessKeyUpEvent, ProcessMouseEvent);
-			if (toplevel.LayoutStyle == LayoutStyle.Computed)
-				toplevel.RelativeLayout (new Rect (0, 0, Driver.Cols, Driver.Rows));
-			toplevel.LayoutSubviews ();
-			Loaded?.Invoke (null, new ResizedEventArgs () { Rows = Driver.Rows, Cols = Driver.Cols });
-			toplevel.WillPresent ();
-			Redraw (toplevel);
-			toplevel.PositionCursor ();
-			Driver.Refresh ();
-
-			return rs;
-		}
-
-		/// <summary>
-		/// Building block API: completes the execution of a <see cref="Toplevel"/>  that was started with <see cref="Begin(Toplevel)"/> .
-		/// </summary>
-		/// <param name="runState">The runstate returned by the <see cref="Begin(Toplevel)"/> method.</param>
-		/// <param name="closeDriver"><c>true</c>Closes the application.<c>false</c>Closes the toplevels only.</param>
-		public static void End (RunState runState, bool closeDriver = true)
-		{
-			if (runState == null)
-				throw new ArgumentNullException (nameof (runState));
-
-			runState.closeDriver = closeDriver;
-			runState.Dispose ();
-		}
-
-		/// <summary>
-		/// Shutdown an application initialized with <see cref="Init()"/>
-		/// </summary>
-		/// /// <param name="closeDriver"><c>true</c>Closes the application.<c>false</c>Closes toplevels only.</param>
-		public static void Shutdown (bool closeDriver = true)
-		{
-			// Shutdown is the bookend for Init. As such it needs to clean up all resources
-			// Init created. Apps that do any threading will need to code defensively for this.
-			// e.g. see Issue #537
-			// TODO: Some of this state is actually related to Begin/End (not Init/Shutdown) and should be moved to `RunState` (#520)
-			foreach (var t in toplevels) {
-				t.Running = false;
-			}
-			toplevels.Clear ();
-			Current = null;
-			CurrentView = null;
-			Top = null;
-
-			// Closes the application if it's true.
-			if (closeDriver) {
-				MainLoop = null;
-				Driver.End ();
-			}
-
-			_initialized = false;
-		}
-
-		static void Redraw (View view)
-		{
-			Application.CurrentView = view;
-
-			view.Redraw (view.Bounds);
-			Driver.Refresh ();
-		}
-
-		static void Refresh (View view)
-		{
-			view.Redraw (view.Bounds);
-			Driver.Refresh ();
-		}
-
-		/// <summary>
-		/// Triggers a refresh of the entire display.
-		/// </summary>
-		public static void Refresh ()
-		{
-			Driver.UpdateScreen ();
-			View last = null;
-			foreach (var v in toplevels.Reverse ()) {
-				v.SetNeedsDisplay ();
-				v.Redraw (v.Bounds);
-				last = v;
-			}
-			last?.PositionCursor ();
-			Driver.Refresh ();
-		}
-
-		internal static void End (View view, bool closeDriver = true)
-		{
-			if (toplevels.Peek () != view)
-				throw new ArgumentException ("The view that you end with must be balanced");
-			toplevels.Pop ();
-			if (toplevels.Count == 0)
-				Shutdown (closeDriver);
-			else {
-				Current = toplevels.Peek ();
-				Refresh ();
-			}
-		}
-
-		/// <summary>
-		///   Building block API: Runs the main loop for the created dialog
-		/// </summary>
-		/// <remarks>
-		///   Use the wait parameter to control whether this is a
-		///   blocking or non-blocking call.
-		/// </remarks>
-		/// <param name="state">The state returned by the Begin method.</param>
-		/// <param name="wait">By default this is true which will execute the runloop waiting for events, if you pass false, you can use this method to run a single iteration of the events.</param>
-		public static void RunLoop (RunState state, bool wait = true)
-		{
-			if (state == null)
-				throw new ArgumentNullException (nameof (state));
-			if (state.Toplevel == null)
-				throw new ObjectDisposedException ("state");
-
-			bool firstIteration = true;
-			for (state.Toplevel.Running = true; state.Toplevel.Running;) {
-				if (MainLoop.EventsPending (wait)) {
-					// Notify Toplevel it's ready
-					if (firstIteration) {
-						state.Toplevel.OnReady ();
-					}
-					firstIteration = false;
-
-					MainLoop.MainIteration ();
-					Iteration?.Invoke (null, EventArgs.Empty);
-				} else if (wait == false)
-					return;
-				if (state.Toplevel.NeedDisplay != null && (!state.Toplevel.NeedDisplay.IsEmpty || state.Toplevel.childNeedsDisplay)) {
-					state.Toplevel.Redraw (state.Toplevel.Bounds);
-					if (DebugDrawBounds)
-						DrawBounds (state.Toplevel);
-					state.Toplevel.PositionCursor ();
-					Driver.Refresh ();
-				} else
-					Driver.UpdateCursor ();
-			}
-		}
-
-		internal static bool DebugDrawBounds = false;
-
-		// Need to look into why this does not work properly.
-		static void DrawBounds (View v)
-		{
-			v.DrawFrame (v.Frame, padding: 0, fill: false);
-			if (v.InternalSubviews != null && v.InternalSubviews.Count > 0)
-				foreach (var sub in v.InternalSubviews)
-					DrawBounds (sub);
-		}
-
-		/// <summary>
-		/// Runs the application by calling <see cref="Run(Toplevel, bool)"/> with the value of <see cref="Top"/>
-		/// </summary>
-		public static void Run ()
-		{
-			Run (Top);
-		}
-
-		/// <summary>
-		/// Runs the application by calling <see cref="Run(Toplevel, bool)"/> with a new instance of the specified <see cref="Toplevel"/>-derived class
-		/// </summary>
-		public static void Run<T> () where T : Toplevel, new()
-		{
-			Init (() => new T ());
-			Run (Top);
-		}
-
-		/// <summary>
-		///   Runs the main loop on the given <see cref="Toplevel"/> container.
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///     This method is used to start processing events
-		///     for the main application, but it is also used to
-		///     run other modal <see cref="View"/>s such as <see cref="Dialog"/> boxes.
-		///   </para>
-		///   <para>
-		///     To make a <see cref="Run(Toplevel, bool)"/> stop execution, call <see cref="Application.RequestStop"/>.
-		///   </para>
-		///   <para>
-		///     Calling <see cref="Run(Toplevel, bool)"/> is equivalent to calling <see cref="Begin(Toplevel)"/>, followed by <see cref="RunLoop(RunState, bool)"/>,
-		///     and then calling <see cref="End(RunState, bool)"/>.
-		///   </para>
-		///   <para>
-		///     Alternatively, to have a program control the main loop and 
-		///     process events manually, call <see cref="Begin(Toplevel)"/> to set things up manually and then
-		///     repeatedly call <see cref="RunLoop(RunState, bool)"/> with the wait parameter set to false.   By doing this
-		///     the <see cref="RunLoop(RunState, bool)"/> method will only process any pending events, timers, idle handlers and
-		///     then return control immediately.
-		///   </para>
-		/// </remarks>
-		public static void Run (Toplevel view, bool closeDriver = true)
-		{
-			var runToken = Begin (view);
-			RunLoop (runToken);
-			End (runToken, closeDriver);
-		}
-
-		/// <summary>
-		/// Stops running the most recent <see cref="Toplevel"/>. 
-		/// </summary>
-		/// <remarks>
-		///   <para>
-		///   This will cause <see cref="Application.Run()"/> to return.
-		///   </para>
-		///   <para>
-		///     Calling <see cref="Application.RequestStop"/> is equivalent to setting the <see cref="Toplevel.Running"/> property on the curently running <see cref="Toplevel"/> to false.
-		///   </para>
-		/// </remarks>
-		public static void RequestStop ()
-		{
-			Current.Running = false;
-		}
-
-		/// <summary>
-		/// Event arguments for the <see cref="Application.Resized"/> event.
-		/// </summary>
-		public class ResizedEventArgs : EventArgs {
-			/// <summary>
-			/// The number of rows in the resized terminal.
-			/// </summary>
-			public int Rows { get; set; }
-			/// <summary>
-			/// The number of columns in the resized terminal.
-			/// </summary>
-			public int Cols { get; set; }
-		}
-
-		/// <summary>
-		/// Invoked when the terminal was resized. The new size of the terminal is provided.
-		/// </summary>
-		public static event EventHandler<ResizedEventArgs> Resized;
-
-		static void TerminalResized ()
-		{
-			var full = new Rect (0, 0, Driver.Cols, Driver.Rows);
-			Resized?.Invoke (null, new ResizedEventArgs () { Cols = full.Width, Rows = full.Height });
-			Driver.Clip = full;
-			foreach (var t in toplevels) {
-				t.PositionToplevels ();
-				t.RelativeLayout (full);
-				t.LayoutSubviews ();
-			}
-			Refresh ();
-		}
-	}
-}

Terminal.Gui/Core/Responder.cs

@@ -0,0 +1,185 @@
+//
+// Core.cs: The core engine for gui.cs
+//
+// Authors:
+//   Miguel de Icaza ([email protected])
+//
+// Pending:
+//   - Check for NeedDisplay on the hierarchy and repaint
+//   - Layout support
+//   - "Colors" type or "Attributes" type?
+//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
+//
+// Optimziations
+//   - Add rendering limitation to the exposed area
+
+namespace Terminal.Gui {
+	/// <summary>
+	/// Responder base class implemented by objects that want to participate on keyboard and mouse input.
+	/// </summary>
+	public class Responder {
+		/// <summary>
+		/// Gets or sets a value indicating whether this <see cref="Responder"/> can focus.
+		/// </summary>
+		/// <value><c>true</c> if can focus; otherwise, <c>false</c>.</value>
+		public virtual bool CanFocus { get; set; }
+
+		/// <summary>
+		/// Gets or sets a value indicating whether this <see cref="Responder"/> has focus.
+		/// </summary>
+		/// <value><c>true</c> if has focus; otherwise, <c>false</c>.</value>
+		public virtual bool HasFocus { get; internal set; }
+
+		// Key handling
+		/// <summary>
+		///   This method can be overwritten by view that
+		///     want to provide accelerator functionality
+		///     (Alt-key for example).
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///     Before keys are sent to the subview on the
+		///     current view, all the views are
+		///     processed and the key is passed to the widgets
+		///     to allow some of them to process the keystroke
+		///     as a hot-key. </para>
+		///  <para>
+		///     For example, if you implement a button that
+		///     has a hotkey ok "o", you would catch the
+		///     combination Alt-o here.  If the event is
+		///     caught, you must return true to stop the
+		///     keystroke from being dispatched to other
+		///     views.
+		///  </para>
+		/// </remarks>
+
+		public virtual bool ProcessHotKey (KeyEvent kb)
+		{
+			return false;
+		}
+
+		/// <summary>
+		///   If the view is focused, gives the view a
+		///   chance to process the keystroke.
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///     Views can override this method if they are
+		///     interested in processing the given keystroke.
+		///     If they consume the keystroke, they must
+		///     return true to stop the keystroke from being
+		///     processed by other widgets or consumed by the
+		///     widget engine.    If they return false, the
+		///     keystroke will be passed using the ProcessColdKey
+		///     method to other views to process.
+		///   </para>
+		///   <para>
+		///     The View implementation does nothing but return false,
+		///     so it is not necessary to call base.ProcessKey if you
+		///     derive directly from View, but you should if you derive
+		///     other View subclasses.
+		///   </para>
+		/// </remarks>
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		public virtual bool ProcessKey (KeyEvent keyEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		///   This method can be overwritten by views that
+		///     want to provide accelerator functionality
+		///     (Alt-key for example), but without
+		///     interefering with normal ProcessKey behavior.
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///     After keys are sent to the subviews on the
+		///     current view, all the view are
+		///     processed and the key is passed to the views
+		///     to allow some of them to process the keystroke
+		///     as a cold-key. </para>
+		///  <para>
+		///    This functionality is used, for example, by
+		///    default buttons to act on the enter key.
+		///    Processing this as a hot-key would prevent
+		///    non-default buttons from consuming the enter
+		///    keypress when they have the focus.
+		///  </para>
+		/// </remarks>
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		public virtual bool ProcessColdKey (KeyEvent keyEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a key is pressed.
+		/// </summary>
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		/// <returns>true if the event was handled</returns>
+		public virtual bool OnKeyDown (KeyEvent keyEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a key is released.
+		/// </summary>
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		/// <returns>true if the event was handled</returns>
+		public virtual bool OnKeyUp (KeyEvent keyEvent)
+		{
+			return false;
+		}
+
+
+		/// <summary>
+		/// Method invoked when a mouse event is generated
+		/// </summary>
+		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
+		/// <param name="mouseEvent">Contains the details about the mouse event.</param>
+		public virtual bool MouseEvent (MouseEvent mouseEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a mouse event is generated for the first time.
+		/// </summary>
+		/// <param name="mouseEvent"></param>
+		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
+		public virtual bool OnMouseEnter (MouseEvent mouseEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a mouse event is generated for the last time.
+		/// </summary>
+		/// <param name="mouseEvent"></param>
+		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
+		public virtual bool OnMouseLeave (MouseEvent mouseEvent)
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a view gets focus.
+		/// </summary>
+		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
+		public virtual bool OnEnter ()
+		{
+			return false;
+		}
+
+		/// <summary>
+		/// Method invoked when a view loses focus.
+		/// </summary>
+		/// <returns><c>true</c>, if the event was handled, <c>false</c> otherwise.</returns>
+		public virtual bool OnLeave ()
+		{
+			return false;
+		}
+	}
+}

Terminal.Gui/Core/Toplevel.cs

@@ -0,0 +1,299 @@
+//
+// Core.cs: The core engine for gui.cs
+//
+// Authors:
+//   Miguel de Icaza ([email protected])
+//
+// Pending:
+//   - Check for NeedDisplay on the hierarchy and repaint
+//   - Layout support
+//   - "Colors" type or "Attributes" type?
+//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
+//
+// Optimziations
+//   - Add rendering limitation to the exposed area
+using System;
+using System.ComponentModel;
+
+namespace Terminal.Gui {
+	/// <summary>
+	/// Toplevel views can be modally executed.
+	/// </summary>
+	/// <remarks>
+	///   <para>
+	///     Toplevels can be modally executing views, and they return control
+	///     to the caller when the "Running" property is set to false, or
+	///     by calling <see cref="M:Terminal.Gui.Application.RequestStop()"/>
+	///   </para>
+	///   <para>
+	///     There will be a toplevel created for you on the first time use
+	///     and can be accessed from the property <see cref="P:Terminal.Gui.Application.Top"/>,
+	///     but new toplevels can be created and ran on top of it.   To run, create the
+	///     toplevel and then invoke <see cref="M:Terminal.Gui.Application.Run"/> with the
+	///     new toplevel.
+	///   </para>
+	///   <para>
+	///     TopLevels can also opt-in to more sophisticated initialization
+	///     by implementing <see cref="ISupportInitialize"/>. When they do
+	///     so, the <see cref="ISupportInitialize.BeginInit"/> and
+	///     <see cref="ISupportInitialize.EndInit"/> methods will be called
+	///     before running the view.
+	///     If first-run-only initialization is preferred, the <see cref="ISupportInitializeNotification"/>
+	///     can be implemented too, in which case the <see cref="ISupportInitialize"/>
+	///     methods will only be called if <see cref="ISupportInitializeNotification.IsInitialized"/>
+	///     is <see langword="false"/>. This allows proper View inheritance hierarchies
+	///     to override base class layout code optimally by doing so only on first run,
+	///     instead of on every run.
+	///   </para>
+	/// </remarks>
+	public class Toplevel : View {
+		/// <summary>
+		/// Gets or sets whether the Mainloop for this <see cref="Toplevel"/> is running or not. Setting
+		/// this property to false will cause the MainLoop to exit. 
+		/// </summary>
+		public bool Running { get; set; }
+
+		/// <summary>
+		/// Fired once the Toplevel's MainLoop has started it's first iteration. 
+		/// Subscribe to this event to perform tasks when the <see cref="Toplevel"/> has been laid out and focus has been set.
+		/// changes. A Ready event handler is a good place to finalize initialization after calling `<see cref="Application.Run()"/>(topLevel)`. 
+		/// </summary>
+		public event EventHandler Ready;
+
+		/// <summary>
+		/// Called from Application.RunLoop after the <see cref="Toplevel"/> has entered it's first iteration of the loop. 
+		/// </summary>
+		internal virtual void OnReady ()
+		{
+			Ready?.Invoke (this, EventArgs.Empty);
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Toplevel"/> class with the specified absolute layout.
+		/// </summary>
+		/// <param name="frame">Frame.</param>
+		public Toplevel (Rect frame) : base (frame)
+		{
+			Initialize ();
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Toplevel"/> class with Computed layout, defaulting to <see langword="async"/> full screen.
+		/// </summary>
+		public Toplevel () : base ()
+		{
+			Initialize ();
+			Width = Dim.Fill ();
+			Height = Dim.Fill ();
+		}
+
+		void Initialize ()
+		{
+			ColorScheme = Colors.Base;
+		}
+
+		/// <summary>
+		/// Convenience factory method that creates a new toplevel with the current terminal dimensions.
+		/// </summary>
+		/// <returns>The create.</returns>
+		public static Toplevel Create ()
+		{
+			return new Toplevel (new Rect (0, 0, Driver.Cols, Driver.Rows));
+		}
+
+		/// <summary>
+		/// Gets or sets a value indicating whether this <see cref="Toplevel"/> can focus.
+		/// </summary>
+		/// <value><c>true</c> if can focus; otherwise, <c>false</c>.</value>
+		public override bool CanFocus {
+			get => true;
+		}
+
+		/// <summary>
+		/// Determines whether the <see cref="Toplevel"/> is modal or not.
+		/// Causes <see cref="ProcessKey(KeyEvent)"/> to propagate keys upwards
+		/// by default unless set to <see langword="true"/>.
+		/// </summary>
+		public bool Modal { get; set; }
+
+		/// <summary>
+		/// Check id current toplevel has menu bar
+		/// </summary>
+		public MenuBar MenuBar { get; set; }
+
+		/// <summary>
+		/// Check id current toplevel has status bar
+		/// </summary>
+		public StatusBar StatusBar { get; set; }
+
+		///<inheritdoc cref="ProcessKey"/>
+		public override bool ProcessKey (KeyEvent keyEvent)
+		{
+			if (base.ProcessKey (keyEvent))
+				return true;
+
+			switch (keyEvent.Key) {
+			case Key.ControlQ:
+				// FIXED: stop current execution of this container
+				Application.RequestStop ();
+				break;
+			case Key.ControlZ:
+				Driver.Suspend ();
+				return true;
+
+#if false
+			case Key.F5:
+				Application.DebugDrawBounds = !Application.DebugDrawBounds;
+				SetNeedsDisplay ();
+				return true;
+#endif
+			case Key.Tab:
+			case Key.CursorRight:
+			case Key.CursorDown:
+			case Key.ControlI: // Unix
+				var old = Focused;
+				if (!FocusNext ())
+					FocusNext ();
+				if (old != Focused) {
+					old?.SetNeedsDisplay ();
+					Focused?.SetNeedsDisplay ();
+				}
+				return true;
+			case Key.CursorLeft:
+			case Key.CursorUp:
+			case Key.BackTab:
+				old = Focused;
+				if (!FocusPrev ())
+					FocusPrev ();
+				if (old != Focused) {
+					old?.SetNeedsDisplay ();
+					Focused?.SetNeedsDisplay ();
+				}
+				return true;
+
+			case Key.ControlL:
+				Application.Refresh ();
+				return true;
+			}
+			return false;
+		}
+
+		///<inheritdoc cref="Add"/>
+		public override void Add (View view)
+		{
+			if (this == Application.Top) {
+				if (view is MenuBar)
+					MenuBar = view as MenuBar;
+				if (view is StatusBar)
+					StatusBar = view as StatusBar;
+			}
+			base.Add (view);
+		}
+
+		///<inheritdoc cref="Remove"/>
+		public override void Remove (View view)
+		{
+			if (this == Application.Top) {
+				if (view is MenuBar)
+					MenuBar = null;
+				if (view is StatusBar)
+					StatusBar = null;
+			}
+			base.Remove (view);
+		}
+
+		///<inheritdoc cref="RemoveAll"/>
+		public override void RemoveAll ()
+		{
+			if (this == Application.Top) {
+				MenuBar = null;
+				StatusBar = null;
+			}
+			base.RemoveAll ();
+		}
+
+		internal void EnsureVisibleBounds (Toplevel top, int x, int y, out int nx, out int ny)
+		{
+			nx = Math.Max (x, 0);
+			nx = nx + top.Frame.Width > Driver.Cols ? Math.Max (Driver.Cols - top.Frame.Width, 0) : nx;
+			bool m, s;
+			if (SuperView == null || SuperView.GetType () != typeof (Toplevel))
+				m = Application.Top.MenuBar != null;
+			else
+				m = ((Toplevel)SuperView).MenuBar != null;
+			int l = m ? 1 : 0;
+			ny = Math.Max (y, l);
+			if (SuperView == null || SuperView.GetType () != typeof (Toplevel))
+				s = Application.Top.StatusBar != null;
+			else
+				s = ((Toplevel)SuperView).StatusBar != null;
+			l = s ? Driver.Rows - 1 : Driver.Rows;
+			ny = Math.Min (ny, l);
+			ny = ny + top.Frame.Height > l ? Math.Max (l - top.Frame.Height, m ? 1 : 0) : ny;
+		}
+
+		internal void PositionToplevels ()
+		{
+			if (this != Application.Top) {
+				EnsureVisibleBounds (this, Frame.X, Frame.Y, out int nx, out int ny);
+				if ((nx != Frame.X || ny != Frame.Y) && LayoutStyle != LayoutStyle.Computed) {
+					X = nx;
+					Y = ny;
+				}
+			} else {
+				foreach (var top in Subviews) {
+					if (top is Toplevel) {
+						EnsureVisibleBounds ((Toplevel)top, top.Frame.X, top.Frame.Y, out int nx, out int ny);
+						if ((nx != top.Frame.X || ny != top.Frame.Y) && top.LayoutStyle != LayoutStyle.Computed) {
+							top.X = nx;
+							top.Y = ny;
+						}
+						if (StatusBar != null) {
+							if (ny + top.Frame.Height > Driver.Rows - 1) {
+								if (top.Height is Dim.DimFill)
+									top.Height = Dim.Fill () - 1;
+							}
+							if (StatusBar.Frame.Y != Driver.Rows - 1) {
+								StatusBar.Y = Driver.Rows - 1;
+								SetNeedsDisplay ();
+							}
+						}
+					}
+				}
+			}
+		}
+
+		///<inheritdoc cref="Redraw"/>
+		public override void Redraw (Rect region)
+		{
+			Application.CurrentView = this;
+
+			if (IsCurrentTop) {
+				if (NeedDisplay != null && !NeedDisplay.IsEmpty) {
+					Driver.SetAttribute (Colors.TopLevel.Normal);
+					Clear (region);
+					Driver.SetAttribute (Colors.Base.Normal);
+				}
+				foreach (var view in Subviews) {
+					if (view.Frame.IntersectsWith (region)) {
+						view.SetNeedsLayout ();
+						view.SetNeedsDisplay (view.Bounds);
+					}
+				}
+
+				ClearNeedsDisplay ();
+			}
+
+			base.Redraw (base.Bounds);
+		}
+
+		/// <summary>
+		/// This method is invoked by Application.Begin as part of the Application.Run after
+		/// the views have been laid out, and before the views are drawn for the first time.
+		/// </summary>
+		public virtual void WillPresent ()
+		{
+			FocusFirst ();
+		}
+	}
+}

Terminal.Gui/Core/View.cs

@@ -0,0 +1,1313 @@
+//
+// Core.cs: The core engine for gui.cs
+//
+// Authors:
+//   Miguel de Icaza ([email protected])
+//
+// Pending:
+//   - Check for NeedDisplay on the hierarchy and repaint
+//   - Layout support
+//   - "Colors" type or "Attributes" type?
+//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
+//
+// Optimziations
+//   - Add rendering limitation to the exposed area
+using System;
+using System.Collections;
+using System.Collections.Generic;
+using System.Linq;
+using NStack;
+
+namespace Terminal.Gui {
+
+	/// <summary>
+	/// Determines the LayoutStyle for a view, if Absolute, during LayoutSubviews, the
+	/// value from the Frame will be used, if the value is Computer, then the Frame
+	/// will be updated from the X, Y Pos objects and the Width and Height Dim objects.
+	/// </summary>
+	public enum LayoutStyle {
+		/// <summary>
+		/// The position and size of the view are based on the Frame value.
+		/// </summary>
+		Absolute,
+
+		/// <summary>
+		/// The position and size of the view will be computed based on the
+		/// X, Y, Width and Height properties and set on the Frame.
+		/// </summary>
+		Computed
+	}
+
+	/// <summary>
+	/// View is the base class for all views on the screen and represents a visible element that can render itself and contains zero or more nested views.
+	/// </summary>
+	/// <remarks>
+	/// <para>
+	///    The View defines the base functionality for user interface elements in Terminal/gui.cs.  Views
+	///    can contain one or more subviews, can respond to user input and render themselves on the screen.
+	/// </para>
+	/// <para>
+	///    Views can either be created with an absolute position, by calling the constructor that takes a
+	///    Rect parameter to specify the absolute position and size (the Frame of the View) or by setting the
+	///    X, Y, Width and Height properties on the view.    Both approaches use coordinates that are relative
+	///    to the container they are being added to.
+	/// </para>
+	/// <para>
+	///    When you do not specify a Rect frame you can use the more flexible
+	///    Dim and Pos objects that can dynamically update the position of a view.
+	///    The X and Y properties are of type <see cref="Pos"/>
+	///    and you can use either absolute positions, percentages or anchor
+	///    points.   The Width and Height properties are of type
+	///    <see cref="Dim"/> and can use absolute position,
+	///    percentages and anchors.  These are useful as they will take
+	///    care of repositioning your views if your view's frames are resized
+	///    or if the terminal size changes.
+	/// </para>
+	/// <para>
+	///    When you specify the Rect parameter to a view, you are setting the LayoutStyle to Absolute, and the
+	///    view will always stay in the position that you placed it.   To change the position change the
+	///    Frame property to the new position.
+	/// </para>
+	/// <para>
+	///    Subviews can be added to a View by calling the Add method.   The container of a view is the
+	///    Superview.
+	/// </para>
+	/// <para>
+	///    Developers can call the SetNeedsDisplay method on the view to flag a region or the entire view
+	///    as requiring to be redrawn.
+	/// </para>
+	/// <para>
+	///    Views have a ColorScheme property that defines the default colors that subviews
+	///    should use for rendering.   This ensures that the views fit in the context where
+	///    they are being used, and allows for themes to be plugged in.   For example, the
+	///    default colors for windows and toplevels uses a blue background, while it uses
+	///    a white background for dialog boxes and a red background for errors.
+	/// </para>
+	/// <para>
+	///    If a ColorScheme is not set on a view, the result of the ColorScheme is the
+	///    value of the SuperView and the value might only be valid once a view has been
+	///    added to a SuperView, so your subclasses should not rely on ColorScheme being
+	///    set at construction time.
+	/// </para>
+	/// <para>
+	///    Using ColorSchemes has the advantage that your application will work both
+	///    in color as well as black and white displays.
+	/// </para>
+	/// <para>
+	///    Views that are focusable should implement the PositionCursor to make sure that
+	///    the cursor is placed in a location that makes sense.   Unix terminals do not have
+	///    a way of hiding the cursor, so it can be distracting to have the cursor left at
+	///    the last focused view.   So views should make sure that they place the cursor
+	///    in a visually sensible place.
+	/// </para>
+	/// <para>
+	///    The metnod LayoutSubviews is invoked when the size or layout of a view has
+	///    changed.   The default processing system will keep the size and dimensions
+	///    for views that use the LayoutKind.Absolute, and will recompute the
+	///    frames for the vies that use LayoutKind.Computed.
+	/// </para>
+	/// </remarks>
+	public class View : Responder, IEnumerable {
+		internal enum Direction {
+			Forward,
+			Backward
+		}
+
+		View container = null;
+		View focused = null;
+		Direction focusDirection;
+
+		/// <summary>
+		/// Event fired when the view get focus.
+		/// </summary>
+		public event EventHandler Enter;
+
+		/// <summary>
+		/// Event fired when the view lost focus.
+		/// </summary>
+		public event EventHandler Leave;
+
+		/// <summary>
+		/// Event fired when the view receives the mouse event for the first time.
+		/// </summary>
+		public event EventHandler<MouseEvent> MouseEnter;
+
+		/// <summary>
+		/// Event fired when the view loses mouse event for the last time.
+		/// </summary>
+		public event EventHandler<MouseEvent> MouseLeave;
+
+		internal Direction FocusDirection {
+			get => SuperView?.FocusDirection ?? focusDirection;
+			set {
+				if (SuperView != null)
+					SuperView.FocusDirection = value;
+				else
+					focusDirection = value;
+			}
+		}
+
+		/// <summary>
+		/// Points to the current driver in use by the view, it is a convenience property
+		/// for simplifying the development of new views.
+		/// </summary>
+		public static ConsoleDriver Driver { get { return Application.Driver; } }
+
+		static IList<View> empty = new List<View> (0).AsReadOnly ();
+
+		// This is null, and allocated on demand.
+		List<View> subviews;
+
+		/// <summary>
+		/// This returns a list of the subviews contained by this view.
+		/// </summary>
+		/// <value>The subviews.</value>
+		public IList<View> Subviews => subviews == null ? empty : subviews.AsReadOnly ();
+
+		// Internally, we use InternalSubviews rather than subviews, as we do not expect us
+		// to make the same mistakes our users make when they poke at the Subviews.
+		internal IList<View> InternalSubviews => subviews ?? empty;
+
+		internal Rect NeedDisplay { get; private set; } = Rect.Empty;
+
+		// The frame for the object
+		Rect frame;
+
+		/// <summary>
+		/// Gets or sets an identifier for the view;
+		/// </summary>
+		/// <value>The identifier.</value>
+		public ustring Id { get; set; } = "";
+
+		/// <summary>
+		/// Returns a value indicating if this View is currently on Top (Active)
+		/// </summary>
+		public bool IsCurrentTop {
+			get {
+				return Application.Current == this;
+			}
+		}
+
+		/// <summary>
+		/// Gets or sets a value indicating whether this <see cref="View"/> want mouse position reports.
+		/// </summary>
+		/// <value><c>true</c> if want mouse position reports; otherwise, <c>false</c>.</value>
+		public virtual bool WantMousePositionReports { get; set; } = false;
+
+		/// <summary>
+		/// Gets or sets a value indicating whether this <see cref="View"/> want continuous button pressed event.
+		/// </summary>
+		public virtual bool WantContinuousButtonPressed { get; set; } = false;
+		/// <summary>
+		/// Gets or sets the frame for the view.
+		/// </summary>
+		/// <value>The frame.</value>
+		/// <remarks>
+		///    Altering the Frame of a view will trigger the redrawing of the
+		///    view as well as the redrawing of the affected regions in the superview.
+		/// </remarks>
+		public virtual Rect Frame {
+			get => frame;
+			set {
+				if (SuperView != null) {
+					SuperView.SetNeedsDisplay (frame);
+					SuperView.SetNeedsDisplay (value);
+				}
+				frame = value;
+
+				SetNeedsLayout ();
+				SetNeedsDisplay (frame);
+			}
+		}
+
+		/// <summary>
+		/// Gets an enumerator that enumerates the subviews in this view.
+		/// </summary>
+		/// <returns>The enumerator.</returns>
+		public IEnumerator GetEnumerator ()
+		{
+			foreach (var v in InternalSubviews)
+				yield return v;
+		}
+
+		LayoutStyle layoutStyle;
+
+		/// <summary>
+		/// Controls how the view's Frame is computed during the LayoutSubviews method, if Absolute, then
+		/// LayoutSubviews does not change the Frame properties, otherwise the Frame is updated from the
+		/// values in X, Y, Width and Height properties.
+		/// </summary>
+		/// <value>The layout style.</value>
+		public LayoutStyle LayoutStyle {
+			get => layoutStyle;
+			set {
+				layoutStyle = value;
+				SetNeedsLayout ();
+			}
+		}
+
+		/// <summary>
+		/// The bounds represent the View-relative rectangle used for this view.   Updates to the Bounds update the Frame, and has the same side effects as updating the frame.
+		/// </summary>
+		/// <value>The bounds.</value>
+		public Rect Bounds {
+			get => new Rect (Point.Empty, Frame.Size);
+			set {
+				Frame = new Rect (frame.Location, value.Size);
+			}
+		}
+
+		Pos x, y;
+		/// <summary>
+		/// Gets or sets the X position for the view (the column).  This is only used when the LayoutStyle is Computed, if the
+		/// LayoutStyle is set to Absolute, this value is ignored.
+		/// </summary>
+		/// <value>The X Position.</value>
+		public Pos X {
+			get => x;
+			set {
+				x = value;
+				SetNeedsLayout ();
+			}
+		}
+
+		/// <summary>
+		/// Gets or sets the Y position for the view (line).  This is only used when the LayoutStyle is Computed, if the
+		/// LayoutStyle is set to Absolute, this value is ignored.
+		/// </summary>
+		/// <value>The y position (line).</value>
+		public Pos Y {
+			get => y;
+			set {
+				y = value;
+				SetNeedsLayout ();
+			}
+		}
+
+		Dim width, height;
+
+		/// <summary>
+		/// Gets or sets the width for the view. This is only used when the LayoutStyle is Computed, if the
+		/// LayoutStyle is set to Absolute, this value is ignored.
+		/// </summary>
+		/// <value>The width.</value>
+		public Dim Width {
+			get => width;
+			set {
+				width = value;
+				SetNeedsLayout ();
+			}
+		}
+
+		/// <summary>
+		/// Gets or sets the height for the view. This is only used when the LayoutStyle is Computed, if the
+		/// LayoutStyle is set to Absolute, this value is ignored.
+		/// </summary>
+		/// <value>The height.</value>
+		public Dim Height {
+			get => height;
+			set {
+				height = value;
+				SetNeedsLayout ();
+			}
+		}
+
+		/// <summary>
+		/// Returns the container for this view, or null if this view has not been added to a container.
+		/// </summary>
+		/// <value>The super view.</value>
+		public View SuperView => container;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="View"/> class with the absolute
+		/// dimensions specified in the frame.   If you want to have Views that can be positioned with
+		/// Pos and Dim properties on X, Y, Width and Height, use the empty constructor.
+		/// </summary>
+		/// <param name="frame">The region covered by this view.</param>
+		public View (Rect frame)
+		{
+			this.Frame = frame;
+			CanFocus = false;
+			LayoutStyle = LayoutStyle.Absolute;
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="View"/> class and sets the
+		/// view up for Computed layout, which will use the values in X, Y, Width and Height to
+		/// compute the View's Frame.
+		/// </summary>
+		public View ()
+		{
+			CanFocus = false;
+			LayoutStyle = LayoutStyle.Computed;
+		}
+
+		/// <summary>
+		/// Invoke to flag that this view needs to be redisplayed, by any code
+		/// that alters the state of the view.
+		/// </summary>
+		public void SetNeedsDisplay ()
+		{
+			SetNeedsDisplay (Bounds);
+		}
+
+		internal bool layoutNeeded = true;
+
+		internal void SetNeedsLayout ()
+		{
+			if (layoutNeeded)
+				return;
+			layoutNeeded = true;
+			if (SuperView == null)
+				return;
+			SuperView.SetNeedsLayout ();
+		}
+
+		/// <summary>
+		/// Flags the specified rectangle region on this view as needing to be repainted.
+		/// </summary>
+		/// <param name="region">The region that must be flagged for repaint.</param>
+		public void SetNeedsDisplay (Rect region)
+		{
+			if (NeedDisplay == null || NeedDisplay.IsEmpty)
+				NeedDisplay = region;
+			else {
+				var x = Math.Min (NeedDisplay.X, region.X);
+				var y = Math.Min (NeedDisplay.Y, region.Y);
+				var w = Math.Max (NeedDisplay.Width, region.Width);
+				var h = Math.Max (NeedDisplay.Height, region.Height);
+				NeedDisplay = new Rect (x, y, w, h);
+			}
+			if (container != null)
+				container.ChildNeedsDisplay ();
+			if (subviews == null)
+				return;
+			foreach (var view in subviews)
+				if (view.Frame.IntersectsWith (region)) {
+					var childRegion = Rect.Intersect (view.Frame, region);
+					childRegion.X -= view.Frame.X;
+					childRegion.Y -= view.Frame.Y;
+					view.SetNeedsDisplay (childRegion);
+				}
+		}
+
+		internal bool childNeedsDisplay;
+
+		/// <summary>
+		/// Flags this view for requiring the children views to be repainted.
+		/// </summary>
+		public void ChildNeedsDisplay ()
+		{
+			childNeedsDisplay = true;
+			if (container != null)
+				container.ChildNeedsDisplay ();
+		}
+
+		/// <summary>
+		///   Adds a subview to this view.
+		/// </summary>
+		/// <remarks>
+		/// </remarks>
+		public virtual void Add (View view)
+		{
+			if (view == null)
+				return;
+			if (subviews == null)
+				subviews = new List<View> ();
+			subviews.Add (view);
+			view.container = this;
+			if (view.CanFocus)
+				CanFocus = true;
+			SetNeedsLayout ();
+			SetNeedsDisplay ();
+		}
+
+		/// <summary>
+		/// Adds the specified views to the view.
+		/// </summary>
+		/// <param name="views">Array of one or more views (can be optional parameter).</param>
+		public void Add (params View [] views)
+		{
+			if (views == null)
+				return;
+			foreach (var view in views)
+				Add (view);
+		}
+
+		/// <summary>
+		///   Removes all the widgets from this container.
+		/// </summary>
+		/// <remarks>
+		/// </remarks>
+		public virtual void RemoveAll ()
+		{
+			if (subviews == null)
+				return;
+
+			while (subviews.Count > 0) {
+				Remove (subviews [0]);
+			}
+		}
+
+		/// <summary>
+		///   Removes a widget from this container.
+		/// </summary>
+		/// <remarks>
+		/// </remarks>
+		public virtual void Remove (View view)
+		{
+			if (view == null || subviews == null)
+				return;
+
+			SetNeedsLayout ();
+			SetNeedsDisplay ();
+			var touched = view.Frame;
+			subviews.Remove (view);
+			view.container = null;
+
+			if (subviews.Count < 1)
+				this.CanFocus = false;
+
+			foreach (var v in subviews) {
+				if (v.Frame.IntersectsWith (touched))
+					view.SetNeedsDisplay ();
+			}
+		}
+
+		void PerformActionForSubview (View subview, Action<View> action)
+		{
+			if (subviews.Contains (subview)) {
+				action (subview);
+			}
+
+			SetNeedsDisplay ();
+			subview.SetNeedsDisplay ();
+		}
+
+		/// <summary>
+		/// Brings the specified subview to the front so it is drawn on top of any other views.
+		/// </summary>
+		/// <param name="subview">The subview to send to the front</param>
+		/// <remarks>
+		///   <seealso cref="SendSubviewToBack"/>.
+		/// </remarks>
+		public void BringSubviewToFront (View subview)
+		{
+			PerformActionForSubview (subview, x => {
+				subviews.Remove (x);
+				subviews.Add (x);
+			});
+		}
+
+		/// <summary>
+		/// Sends the specified subview to the front so it is the first view drawn
+		/// </summary>
+		/// <param name="subview">The subview to send to the front</param>
+		/// <remarks>
+		///   <seealso cref="BringSubviewToFront(View)"/>.
+		/// </remarks>
+		public void SendSubviewToBack (View subview)
+		{
+			PerformActionForSubview (subview, x => {
+				subviews.Remove (x);
+				subviews.Insert (0, subview);
+			});
+		}
+
+		/// <summary>
+		/// Moves the subview backwards in the hierarchy, only one step
+		/// </summary>
+		/// <param name="subview">The subview to send backwards</param>
+		/// <remarks>
+		/// If you want to send the view all the way to the back use SendSubviewToBack.
+		/// </remarks>
+		public void SendSubviewBackwards (View subview)
+		{
+			PerformActionForSubview (subview, x => {
+				var idx = subviews.IndexOf (x);
+				if (idx > 0) {
+					subviews.Remove (x);
+					subviews.Insert (idx - 1, x);
+				}
+			});
+		}
+
+		/// <summary>
+		/// Moves the subview backwards in the hierarchy, only one step
+		/// </summary>
+		/// <param name="subview">The subview to send backwards</param>
+		/// <remarks>
+		/// If you want to send the view all the way to the back use SendSubviewToBack.
+		/// </remarks>
+		public void BringSubviewForward (View subview)
+		{
+			PerformActionForSubview (subview, x => {
+				var idx = subviews.IndexOf (x);
+				if (idx + 1 < subviews.Count) {
+					subviews.Remove (x);
+					subviews.Insert (idx + 1, x);
+				}
+			});
+		}
+
+		/// <summary>
+		///   Clears the view region with the current color.
+		/// </summary>
+		/// <remarks>
+		///   <para>
+		///     This clears the entire region used by this view.
+		///   </para>
+		/// </remarks>
+		public void Clear ()
+		{
+			var h = Frame.Height;
+			var w = Frame.Width;
+			for (int line = 0; line < h; line++) {
+				Move (0, line);
+				for (int col = 0; col < w; col++)
+					Driver.AddRune (' ');
+			}
+		}
+
+		/// <summary>
+		///   Clears the specified rectangular region with the current color
+		/// </summary>
+		public void Clear (Rect r)
+		{
+			var h = r.Height;
+			var w = r.Width;
+			for (int line = r.Y; line < r.Y + h; line++) {
+				Driver.Move (r.X, line);
+				for (int col = 0; col < w; col++)
+					Driver.AddRune (' ');
+			}
+		}
+
+		/// <summary>
+		/// Converts the (col,row) position from the view into a screen (col,row).  The values are clamped to (0..ScreenDim-1)
+		/// </summary>
+		/// <param name="col">View-based column.</param>
+		/// <param name="row">View-based row.</param>
+		/// <param name="rcol">Absolute column, display relative.</param>
+		/// <param name="rrow">Absolute row, display relative.</param>
+		/// <param name="clipped">Whether to clip the result of the ViewToScreen method, if set to true, the rcol, rrow values are clamped to the screen dimensions.</param>
+		internal void ViewToScreen (int col, int row, out int rcol, out int rrow, bool clipped = true)
+		{
+			// Computes the real row, col relative to the screen.
+			rrow = row + frame.Y;
+			rcol = col + frame.X;
+			var ccontainer = container;
+			while (ccontainer != null) {
+				rrow += ccontainer.frame.Y;
+				rcol += ccontainer.frame.X;
+				ccontainer = ccontainer.container;
+			}
+
+			// The following ensures that the cursor is always in the screen boundaries.
+			if (clipped) {
+				rrow = Math.Max (0, Math.Min (rrow, Driver.Rows - 1));
+				rcol = Math.Max (0, Math.Min (rcol, Driver.Cols - 1));
+			}
+		}
+
+		/// <summary>
+		/// Converts a point from screen coordinates into the view coordinate space.
+		/// </summary>
+		/// <returns>The mapped point.</returns>
+		/// <param name="x">X screen-coordinate point.</param>
+		/// <param name="y">Y screen-coordinate point.</param>
+		public Point ScreenToView (int x, int y)
+		{
+			if (SuperView == null) {
+				return new Point (x - Frame.X, y - frame.Y);
+			} else {
+				var parent = SuperView.ScreenToView (x, y);
+				return new Point (parent.X - frame.X, parent.Y - frame.Y);
+			}
+		}
+
+		// Converts a rectangle in view coordinates to screen coordinates.
+		internal Rect RectToScreen (Rect rect)
+		{
+			ViewToScreen (rect.X, rect.Y, out var x, out var y, clipped: false);
+			return new Rect (x, y, rect.Width, rect.Height);
+		}
+
+		// Clips a rectangle in screen coordinates to the dimensions currently available on the screen
+		internal Rect ScreenClip (Rect rect)
+		{
+			var x = rect.X < 0 ? 0 : rect.X;
+			var y = rect.Y < 0 ? 0 : rect.Y;
+			var w = rect.X + rect.Width >= Driver.Cols ? Driver.Cols - rect.X : rect.Width;
+			var h = rect.Y + rect.Height >= Driver.Rows ? Driver.Rows - rect.Y : rect.Height;
+
+			return new Rect (x, y, w, h);
+		}
+
+		/// <summary>
+		/// Sets the Console driver's clip region to the current View's Bounds.
+		/// </summary>
+		/// <returns>The existing driver's Clip region, which can be then set by setting the Driver.Clip property.</returns>
+		public Rect ClipToBounds ()
+		{
+			return SetClip (Bounds);
+		}
+
+		/// <summary>
+		/// Sets the clipping region to the specified region, the region is view-relative
+		/// </summary>
+		/// <returns>The previous clip region.</returns>
+		/// <param name="rect">Rectangle region to clip into, the region is view-relative.</param>
+		public Rect SetClip (Rect rect)
+		{
+			var bscreen = RectToScreen (rect);
+			var previous = Driver.Clip;
+			Driver.Clip = ScreenClip (RectToScreen (Bounds));
+			return previous;
+		}
+
+		/// <summary>
+		/// Draws a frame in the current view, clipped by the boundary of this view
+		/// </summary>
+		/// <param name="rect">Rectangular region for the frame to be drawn.</param>
+		/// <param name="padding">The padding to add to the drawn frame.</param>
+		/// <param name="fill">If set to <c>true</c> it fill will the contents.</param>
+		public void DrawFrame (Rect rect, int padding = 0, bool fill = false)
+		{
+			var scrRect = RectToScreen (rect);
+			var savedClip = Driver.Clip;
+			Driver.Clip = ScreenClip (RectToScreen (Bounds));
+			Driver.DrawFrame (scrRect, padding, fill);
+			Driver.Clip = savedClip;
+		}
+
+		/// <summary>
+		/// Utility function to draw strings that contain a hotkey
+		/// </summary>
+		/// <param name="text">String to display, the underscoore before a letter flags the next letter as the hotkey.</param>
+		/// <param name="hotColor">Hot color.</param>
+		/// <param name="normalColor">Normal color.</param>
+		public void DrawHotString (ustring text, Attribute hotColor, Attribute normalColor)
+		{
+			Driver.SetAttribute (normalColor);
+			foreach (var rune in text) {
+				if (rune == '_') {
+					Driver.SetAttribute (hotColor);
+					continue;
+				}
+				Driver.AddRune (rune);
+				Driver.SetAttribute (normalColor);
+			}
+		}
+
+		/// <summary>
+		/// Utility function to draw strings that contains a hotkey using a colorscheme and the "focused" state.
+		/// </summary>
+		/// <param name="text">String to display, the underscoore before a letter flags the next letter as the hotkey.</param>
+		/// <param name="focused">If set to <c>true</c> this uses the focused colors from the color scheme, otherwise the regular ones.</param>
+		/// <param name="scheme">The color scheme to use.</param>
+		public void DrawHotString (ustring text, bool focused, ColorScheme scheme)
+		{
+			if (focused)
+				DrawHotString (text, scheme.HotFocus, scheme.Focus);
+			else
+				DrawHotString (text, scheme.HotNormal, scheme.Normal);
+		}
+
+		/// <summary>
+		/// This moves the cursor to the specified column and row in the view.
+		/// </summary>
+		/// <returns>The move.</returns>
+		/// <param name="col">Col.</param>
+		/// <param name="row">Row.</param>
+		public void Move (int col, int row)
+		{
+			ViewToScreen (col, row, out var rcol, out var rrow);
+			Driver.Move (rcol, rrow);
+		}
+
+		/// <summary>
+		///   Positions the cursor in the right position based on the currently focused view in the chain.
+		/// </summary>
+		public virtual void PositionCursor ()
+		{
+			if (focused != null)
+				focused.PositionCursor ();
+			else
+				Move (frame.X, frame.Y);
+		}
+
+		/// <inheritdoc cref="HasFocus"/>
+		public override bool HasFocus {
+			get {
+				return base.HasFocus;
+			}
+			internal set {
+				if (base.HasFocus != value)
+					if (value)
+						OnEnter ();
+					else
+						OnLeave ();
+				SetNeedsDisplay ();
+				base.HasFocus = value;
+
+				// Remove focus down the chain of subviews if focus is removed
+				if (!value && focused != null) {
+					focused.OnLeave ();
+					focused.HasFocus = false;
+					focused = null;
+				}
+			}
+		}
+
+		/// <inheritdoc cref="OnEnter"/>
+		public override bool OnEnter ()
+		{
+			Enter?.Invoke (this, new EventArgs ());
+			return base.OnEnter ();
+		}
+
+		/// <inheritdoc cref="OnLeave"/>
+		public override bool OnLeave ()
+		{
+			Leave?.Invoke (this, new EventArgs ());
+			return base.OnLeave ();
+		}
+
+		/// <summary>
+		/// Returns the currently focused view inside this view, or null if nothing is focused.
+		/// </summary>
+		/// <value>The focused.</value>
+		public View Focused => focused;
+
+		/// <summary>
+		/// Returns the most focused view in the chain of subviews (the leaf view that has the focus).
+		/// </summary>
+		/// <value>The most focused.</value>
+		public View MostFocused {
+			get {
+				if (Focused == null)
+					return null;
+				var most = Focused.MostFocused;
+				if (most != null)
+					return most;
+				return Focused;
+			}
+		}
+
+		/// <summary>
+		/// The color scheme for this view, if it is not defined, it returns the parent's
+		/// color scheme.
+		/// </summary>
+		public ColorScheme ColorScheme {
+			get {
+				if (colorScheme == null)
+					return SuperView?.ColorScheme;
+				return colorScheme;
+			}
+			set {
+				colorScheme = value;
+			}
+		}
+
+		ColorScheme colorScheme;
+
+		/// <summary>
+		/// Displays the specified character in the specified column and row.
+		/// </summary>
+		/// <param name="col">Col.</param>
+		/// <param name="row">Row.</param>
+		/// <param name="ch">Ch.</param>
+		public void AddRune (int col, int row, Rune ch)
+		{
+			if (row < 0 || col < 0)
+				return;
+			if (row > frame.Height - 1 || col > frame.Width - 1)
+				return;
+			Move (col, row);
+			Driver.AddRune (ch);
+		}
+
+		/// <summary>
+		/// Removes the SetNeedsDisplay and the ChildNeedsDisplay setting on this view.
+		/// </summary>
+		protected void ClearNeedsDisplay ()
+		{
+			NeedDisplay = Rect.Empty;
+			childNeedsDisplay = false;
+		}
+
+		/// <summary>
+		/// Performs a redraw of this view and its subviews, only redraws the views that have been flagged for a re-display.
+		/// </summary>
+		/// <param name="region">The region to redraw, this is relative to the view itself.</param>
+		/// <remarks>
+		/// <para>
+		///    Views should set the color that they want to use on entry, as otherwise this will inherit
+		///    the last color that was set globaly on the driver.
+		/// </para>
+		/// </remarks>
+		public virtual void Redraw (Rect region)
+		{
+			var clipRect = new Rect (Point.Empty, frame.Size);
+
+			if (subviews != null) {
+				foreach (var view in subviews) {
+					if (view.NeedDisplay != null && (!view.NeedDisplay.IsEmpty || view.childNeedsDisplay)) {
+						if (view.Frame.IntersectsWith (clipRect) && view.Frame.IntersectsWith (region)) {
+
+							// FIXED: optimize this by computing the intersection of region and view.Bounds
+							if (view.layoutNeeded)
+								view.LayoutSubviews ();
+							Application.CurrentView = view;
+							view.Redraw (view.Bounds);
+						}
+						view.NeedDisplay = Rect.Empty;
+						view.childNeedsDisplay = false;
+					}
+				}
+			}
+			ClearNeedsDisplay ();
+		}
+
+		/// <summary>
+		/// Focuses the specified sub-view.
+		/// </summary>
+		/// <param name="view">View.</param>
+		public void SetFocus (View view)
+		{
+			if (view == null)
+				return;
+			//Console.WriteLine ($"Request to focus {view}");
+			if (!view.CanFocus)
+				return;
+			if (focused == view)
+				return;
+
+			// Make sure that this view is a subview
+			View c;
+			for (c = view.container; c != null; c = c.container)
+				if (c == this)
+					break;
+			if (c == null)
+				throw new ArgumentException ("the specified view is not part of the hierarchy of this view");
+
+			if (focused != null)
+				focused.HasFocus = false;
+
+			focused = view;
+			focused.HasFocus = true;
+			focused.EnsureFocus ();
+
+			// Send focus upwards
+			SuperView?.SetFocus (this);
+		}
+
+		/// <summary>
+		/// Specifies the event arguments for <see cref="KeyEvent"/>
+		/// </summary>
+		public class KeyEventEventArgs : EventArgs {
+			/// <summary>
+			/// Constructs.
+			/// </summary>
+			/// <param name="ke"></param>
+			public KeyEventEventArgs (KeyEvent ke) => KeyEvent = ke;
+			/// <summary>
+			/// The <see cref="KeyEvent"/> for the event.
+			/// </summary>
+			public KeyEvent KeyEvent { get; set; }
+			/// <summary>
+			/// Indicates if the current Key event has already been processed and the driver should stop notifying any other event subscriber.
+			/// Its important to set this value to true specially when updating any View's layout from inside the subscriber method.
+			/// </summary>
+			public bool Handled { get; set; } = false;
+		}
+
+		/// <summary>
+		/// Invoked when a character key is pressed and occurs after the key up event.
+		/// </summary>
+		public event EventHandler<KeyEventEventArgs> KeyPress;
+
+		/// <inheritdoc cref="ProcessKey"/>
+		public override bool ProcessKey (KeyEvent keyEvent)
+		{
+
+			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
+			KeyPress?.Invoke (this, args);
+			if (args.Handled)
+				return true;
+			if (Focused?.ProcessKey (keyEvent) == true)
+				return true;
+
+			return false;
+		}
+
+		/// <inheritdoc cref="ProcessHotKey"/>
+		public override bool ProcessHotKey (KeyEvent keyEvent)
+		{
+			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
+			KeyPress?.Invoke (this, args);
+			if (args.Handled)
+				return true;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+			foreach (var view in subviews)
+				if (view.ProcessHotKey (keyEvent))
+					return true;
+			return false;
+		}
+
+		/// <inheritdoc cref="ProcessColdKey"/>
+		public override bool ProcessColdKey (KeyEvent keyEvent)
+		{
+			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
+			KeyPress?.Invoke (this, args);
+			if (args.Handled)
+				return true;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+			foreach (var view in subviews)
+				if (view.ProcessColdKey (keyEvent))
+					return true;
+			return false;
+		}
+
+		/// <summary>
+		/// Invoked when a key is pressed
+		/// </summary>
+		public event EventHandler<KeyEventEventArgs> KeyDown;
+
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		public override bool OnKeyDown (KeyEvent keyEvent)
+		{
+			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
+			KeyDown?.Invoke (this, args);
+			if (args.Handled)
+				return true;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+			foreach (var view in subviews)
+				if (view.OnKeyDown (keyEvent))
+					return true;
+
+			return false;
+		}
+
+		/// <summary>
+		/// Invoked when a key is released
+		/// </summary>
+		public event EventHandler<KeyEventEventArgs> KeyUp;
+
+		/// <param name="keyEvent">Contains the details about the key that produced the event.</param>
+		public override bool OnKeyUp (KeyEvent keyEvent)
+		{
+			KeyEventEventArgs args = new KeyEventEventArgs (keyEvent);
+			KeyUp?.Invoke (this, args);
+			if (args.Handled)
+				return true;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+			foreach (var view in subviews)
+				if (view.OnKeyUp (keyEvent))
+					return true;
+
+			return false;
+		}
+
+		/// <summary>
+		/// Finds the first view in the hierarchy that wants to get the focus if nothing is currently focused, otherwise, it does nothing.
+		/// </summary>
+		public void EnsureFocus ()
+		{
+			if (focused == null)
+				if (FocusDirection == Direction.Forward)
+					FocusFirst ();
+				else
+					FocusLast ();
+		}
+
+		/// <summary>
+		/// Focuses the first focusable subview if one exists.
+		/// </summary>
+		public void FocusFirst ()
+		{
+			if (subviews == null) {
+				SuperView?.SetFocus (this);
+				return;
+			}
+
+			foreach (var view in subviews) {
+				if (view.CanFocus) {
+					SetFocus (view);
+					return;
+				}
+			}
+		}
+
+		/// <summary>
+		/// Focuses the last focusable subview if one exists.
+		/// </summary>
+		public void FocusLast ()
+		{
+			if (subviews == null) {
+				SuperView?.SetFocus (this);
+				return;
+			}
+
+			for (int i = subviews.Count; i > 0;) {
+				i--;
+
+				View v = subviews [i];
+				if (v.CanFocus) {
+					SetFocus (v);
+					return;
+				}
+			}
+		}
+
+		/// <summary>
+		/// Focuses the previous view.
+		/// </summary>
+		/// <returns><c>true</c>, if previous was focused, <c>false</c> otherwise.</returns>
+		public bool FocusPrev ()
+		{
+			FocusDirection = Direction.Backward;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+
+			if (focused == null) {
+				FocusLast ();
+				return focused != null;
+			}
+			int focused_idx = -1;
+			for (int i = subviews.Count; i > 0;) {
+				i--;
+				View w = subviews [i];
+
+				if (w.HasFocus) {
+					if (w.FocusPrev ())
+						return true;
+					focused_idx = i;
+					continue;
+				}
+				if (w.CanFocus && focused_idx != -1) {
+					focused.HasFocus = false;
+
+					if (w != null && w.CanFocus)
+						w.FocusLast ();
+
+					SetFocus (w);
+					return true;
+				}
+			}
+			if (focused != null) {
+				focused.HasFocus = false;
+				focused = null;
+			}
+			return false;
+		}
+
+		/// <summary>
+		/// Focuses the next view.
+		/// </summary>
+		/// <returns><c>true</c>, if next was focused, <c>false</c> otherwise.</returns>
+		public bool FocusNext ()
+		{
+			FocusDirection = Direction.Forward;
+			if (subviews == null || subviews.Count == 0)
+				return false;
+
+			if (focused == null) {
+				FocusFirst ();
+				return focused != null;
+			}
+			int n = subviews.Count;
+			int focused_idx = -1;
+			for (int i = 0; i < n; i++) {
+				View w = subviews [i];
+
+				if (w.HasFocus) {
+					if (w.FocusNext ())
+						return true;
+					focused_idx = i;
+					continue;
+				}
+				if (w.CanFocus && focused_idx != -1) {
+					focused.HasFocus = false;
+
+					if (w != null && w.CanFocus)
+						w.FocusFirst ();
+
+					SetFocus (w);
+					return true;
+				}
+			}
+			if (focused != null) {
+				focused.HasFocus = false;
+				focused = null;
+			}
+			return false;
+		}
+
+		/// <summary>
+		/// Computes the RelativeLayout for the view, given the frame for its container.
+		/// </summary>
+		/// <param name="hostFrame">The Frame for the host.</param>
+		internal void RelativeLayout (Rect hostFrame)
+		{
+			int w, h, _x, _y;
+
+			if (x is Pos.PosCenter) {
+				if (width == null)
+					w = hostFrame.Width;
+				else
+					w = width.Anchor (hostFrame.Width);
+				_x = x.Anchor (hostFrame.Width - w);
+			} else {
+				if (x == null)
+					_x = 0;
+				else
+					_x = x.Anchor (hostFrame.Width);
+				if (width == null)
+					w = hostFrame.Width;
+				else
+					w = width.Anchor (hostFrame.Width - _x);
+			}
+
+			if (y is Pos.PosCenter) {
+				if (height == null)
+					h = hostFrame.Height;
+				else
+					h = height.Anchor (hostFrame.Height);
+				_y = y.Anchor (hostFrame.Height - h);
+			} else {
+				if (y == null)
+					_y = 0;
+				else
+					_y = y.Anchor (hostFrame.Height);
+				if (height == null)
+					h = hostFrame.Height;
+				else
+					h = height.Anchor (hostFrame.Height - _y);
+			}
+			Frame = new Rect (_x, _y, w, h);
+			// layoutNeeded = false;
+		}
+
+		// https://en.wikipedia.org/wiki/Topological_sorting
+		List<View> TopologicalSort (HashSet<View> nodes, HashSet<(View From, View To)> edges)
+		{
+			var result = new List<View> ();
+
+			// Set of all nodes with no incoming edges
+			var S = new HashSet<View> (nodes.Where (n => edges.All (e => e.To.Equals (n) == false)));
+
+			while (S.Any ()) {
+				//  remove a node n from S
+				var n = S.First ();
+				S.Remove (n);
+
+				// add n to tail of L
+				if (n != this?.SuperView)
+					result.Add (n);
+
+				// for each node m with an edge e from n to m do
+				foreach (var e in edges.Where (e => e.From.Equals (n)).ToArray ()) {
+					var m = e.To;
+
+					// remove edge e from the graph
+					edges.Remove (e);
+
+					// if m has no other incoming edges then
+					if (edges.All (me => me.To.Equals (m) == false) && m != this?.SuperView) {
+						// insert m into S
+						S.Add (m);
+					}
+				}
+			}
+
+			// if graph has edges then
+			if (edges.Any ()) {
+				// return error (graph has at least one cycle)
+				return null;
+			} else {
+				// return L (a topologically sorted order)
+				return result;
+			}
+		}
+
+		/// <summary>
+		/// This virtual method is invoked when a view starts executing or
+		/// when the dimensions of the view have changed, for example in
+		/// response to the container view or terminal resizing.
+		/// </summary>
+		public virtual void LayoutSubviews ()
+		{
+			if (!layoutNeeded)
+				return;
+
+			// Sort out the dependencies of the X, Y, Width, Height properties
+			var nodes = new HashSet<View> ();
+			var edges = new HashSet<(View, View)> ();
+
+			foreach (var v in InternalSubviews) {
+				nodes.Add (v);
+				if (v.LayoutStyle == LayoutStyle.Computed) {
+					if (v.X is Pos.PosView vX)
+						edges.Add ((vX.Target, v));
+					if (v.Y is Pos.PosView vY)
+						edges.Add ((vY.Target, v));
+					if (v.Width is Dim.DimView vWidth)
+						edges.Add ((vWidth.Target, v));
+					if (v.Height is Dim.DimView vHeight)
+						edges.Add ((vHeight.Target, v));
+				}
+			}
+
+			var ordered = TopologicalSort (nodes, edges);
+			if (ordered == null)
+				throw new Exception ("There is a recursive cycle in the relative Pos/Dim in the views of " + this);
+
+			foreach (var v in ordered) {
+				if (v.LayoutStyle == LayoutStyle.Computed)
+					v.RelativeLayout (Frame);
+
+				v.LayoutSubviews ();
+				v.layoutNeeded = false;
+
+			}
+
+			if (SuperView == Application.Top && layoutNeeded && ordered.Count == 0 && LayoutStyle == LayoutStyle.Computed) {
+				RelativeLayout (Frame);
+			}
+
+			layoutNeeded = false;
+		}
+
+		/// <inheritdoc cref="ToString"/>
+		public override string ToString ()
+		{
+			return $"{GetType ().Name}({Id})({Frame})";
+		}
+
+		/// <inheritdoc cref="OnMouseEnter(Gui.MouseEvent)"/>
+		public override bool OnMouseEnter (MouseEvent mouseEvent)
+		{
+			if (!base.OnMouseEnter (mouseEvent)) {
+				MouseEnter?.Invoke (this, mouseEvent);
+				return false;
+			}
+			return true;
+		}
+
+		/// <inheritdoc cref="OnMouseLeave(Gui.MouseEvent)"/>
+		public override bool OnMouseLeave (MouseEvent mouseEvent)
+		{
+			if (!base.OnMouseLeave (mouseEvent)) {
+				MouseLeave?.Invoke (this, mouseEvent);
+				return false;
+			}
+			return true;
+		}
+	}
+}

Terminal.Gui/Core/Window.cs

@@ -0,0 +1,250 @@
+//
+// Core.cs: The core engine for gui.cs
+//
+// Authors:
+//   Miguel de Icaza ([email protected])
+//
+// Pending:
+//   - Check for NeedDisplay on the hierarchy and repaint
+//   - Layout support
+//   - "Colors" type or "Attributes" type?
+//   - What to surface as "BackgroundCOlor" when clearing a window, an attribute or colors?
+//
+// Optimziations
+//   - Add rendering limitation to the exposed area
+using System.Collections;
+using System.Linq;
+using NStack;
+
+namespace Terminal.Gui {
+	/// <summary>
+	/// A <see cref="Toplevel"/> <see cref="View"/> that draws a frame around its region and has a "ContentView" subview where the contents are added.
+	/// </summary>
+	public class Window : Toplevel, IEnumerable {
+		View contentView;
+		ustring title;
+
+		/// <summary>
+		/// The title to be displayed for this window.
+		/// </summary>
+		/// <value>The title.</value>
+		public ustring Title {
+			get => title;
+			set {
+				title = value;
+				SetNeedsDisplay ();
+			}
+		}
+
+		class ContentView : View {
+			public ContentView (Rect frame) : base (frame) { }
+			public ContentView () : base () { }
+#if false
+			public override void Redraw (Rect region)
+			{
+				Driver.SetAttribute (ColorScheme.Focus);
+
+				for (int y = 0; y < Frame.Height; y++) {
+					Move (0, y);
+					for (int x = 0; x < Frame.Width; x++) {
+
+						Driver.AddRune ('x');
+					}
+				}
+			}
+#endif
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Gui.Window"/> class with an optional title and a set frame.
+		/// </summary>
+		/// <param name="frame">Frame.</param>
+		/// <param name="title">Title.</param>
+		public Window (Rect frame, ustring title = null) : this (frame, title, padding: 0)
+		{
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Window"/> class with an optional title.
+		/// </summary>
+		/// <param name="title">Title.</param>
+		public Window (ustring title = null) : this (title, padding: 0)
+		{
+		}
+
+		int padding;
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Window"/> with
+		/// the specified frame for its location, with the specified border
+		/// an optional title.
+		/// </summary>
+		/// <param name="frame">Frame.</param>
+		/// <param name="padding">Number of characters to use for padding of the drawn frame.</param>
+		/// <param name="title">Title.</param>
+		public Window (Rect frame, ustring title = null, int padding = 0) : base (frame)
+		{
+			this.Title = title;
+			int wb = 2 * (1 + padding);
+			this.padding = padding;
+			var cFrame = new Rect (1 + padding, 1 + padding, frame.Width - wb, frame.Height - wb);
+			contentView = new ContentView (cFrame);
+			base.Add (contentView);
+		}
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="Window"/> with
+		/// the specified frame for its location, with the specified border
+		/// an optional title.
+		/// </summary>
+		/// <param name="padding">Number of characters to use for padding of the drawn frame.</param>
+		/// <param name="title">Title.</param>
+		public Window (ustring title = null, int padding = 0) : base ()
+		{
+			this.Title = title;
+			int wb = 1 + padding;
+			this.padding = padding;
+			contentView = new ContentView () {
+				X = wb,
+				Y = wb,
+				Width = Dim.Fill (wb),
+				Height = Dim.Fill (wb)
+			};
+			base.Add (contentView);
+		}
+
+		/// <summary>
+		/// Enumerates the various <see cref="View"/>s in the embedded <see cref="ContentView"/>.
+		/// </summary>
+		/// <returns>The enumerator.</returns>
+		public new IEnumerator GetEnumerator ()
+		{
+			return contentView.GetEnumerator ();
+		}
+
+		/// <summary>
+		/// Add the specified view to the <see cref="ContentView"/>.
+		/// </summary>
+		/// <param name="view">View to add to the window.</param>
+		public override void Add (View view)
+		{
+			contentView.Add (view);
+			if (view.CanFocus)
+				CanFocus = true;
+		}
+
+
+		/// <summary>
+		///   Removes a widget from this container.
+		/// </summary>
+		/// <remarks>
+		/// </remarks>
+		public override void Remove (View view)
+		{
+			if (view == null)
+				return;
+
+			SetNeedsDisplay ();
+			var touched = view.Frame;
+			contentView.Remove (view);
+
+			if (contentView.InternalSubviews.Count < 1)
+				this.CanFocus = false;
+		}
+
+		/// <summary>
+		///   Removes all widgets from this container.
+		/// </summary>
+		/// <remarks>
+		/// </remarks>
+		public override void RemoveAll ()
+		{
+			contentView.RemoveAll ();
+		}
+
+		///<inheritdoc cref="Redraw"/>
+		public override void Redraw (Rect bounds)
+		{
+			Application.CurrentView = this;
+			var scrRect = RectToScreen (new Rect (0, 0, Frame.Width, Frame.Height));
+			var savedClip = Driver.Clip;
+			Driver.Clip = ScreenClip (RectToScreen (Bounds));
+
+			if (NeedDisplay != null && !NeedDisplay.IsEmpty) {
+				Driver.SetAttribute (ColorScheme.Normal);
+				Driver.DrawFrame (scrRect, padding, true);
+			}
+			contentView.Redraw (contentView.Bounds);
+			ClearNeedsDisplay ();
+			Driver.SetAttribute (ColorScheme.Normal);
+			Driver.DrawFrame (scrRect, padding, false);
+
+			if (HasFocus)
+				Driver.SetAttribute (ColorScheme.HotNormal);
+			Driver.DrawWindowTitle (scrRect, Title, padding, padding, padding, padding);
+			Driver.Clip = savedClip;
+			Driver.SetAttribute (ColorScheme.Normal);
+		}
+
+		//
+		// FIXED:It does not look like the event is raised on clicked-drag
+		// need to figure that out.
+		//
+		internal static Point? dragPosition;
+		Point start;
+		///<inheritdoc cref="MouseEvent(Gui.MouseEvent)"/>
+		public override bool MouseEvent (MouseEvent mouseEvent)
+		{
+			// FIXED:The code is currently disabled, because the
+			// Driver.UncookMouse does not seem to have an effect if there is
+			// a pending mouse event activated.
+
+			int nx, ny;
+			if ((mouseEvent.Flags == (MouseFlags.Button1Pressed | MouseFlags.ReportMousePosition) ||
+				mouseEvent.Flags == MouseFlags.Button3Pressed)) {
+				if (dragPosition.HasValue) {
+					if (SuperView == null) {
+						Application.Top.SetNeedsDisplay (Frame);
+						Application.Top.Redraw (Frame);
+					} else {
+						SuperView.SetNeedsDisplay (Frame);
+					}
+					EnsureVisibleBounds (this, mouseEvent.X + mouseEvent.OfX - start.X,
+						mouseEvent.Y + mouseEvent.OfY, out nx, out ny);
+
+					dragPosition = new Point (nx, ny);
+					Frame = new Rect (nx, ny, Frame.Width, Frame.Height);
+					X = nx;
+					Y = ny;
+					//Demo.ml2.Text = $"{dx},{dy}";
+
+					// FIXED: optimize, only SetNeedsDisplay on the before/after regions.
+					SetNeedsDisplay ();
+					return true;
+				} else {
+					// Only start grabbing if the user clicks on the title bar.
+					if (mouseEvent.Y == 0) {
+						start = new Point (mouseEvent.X, mouseEvent.Y);
+						dragPosition = new Point ();
+						nx = mouseEvent.X - mouseEvent.OfX;
+						ny = mouseEvent.Y - mouseEvent.OfY;
+						dragPosition = new Point (nx, ny);
+						Application.GrabMouse (this);
+					}
+
+					//Demo.ml2.Text = $"Starting at {dragPosition}";
+					return true;
+				}
+			}
+
+			if (mouseEvent.Flags == MouseFlags.Button1Released && dragPosition.HasValue) {
+				Application.UngrabMouse ();
+				Driver.UncookMouse ();
+				dragPosition = null;
+			}
+
+			//Demo.ml.Text = me.ToString ();
+			return false;
+		}
+
+	}
+}