Fixes gui-cs#2810. Pressing Alt key on a Toplevel with only a MenuBar…

… throws System.InvalidOperationException.

Terminal.Gui/Application.cs

@@ -54,7 +54,7 @@ public static partial class Application {
 
 		// For Unit testing - ignores UseSystemConsole
 		internal static bool _forceFakeConsole;
-		
+
 		private static List<CultureInfo> _cachedSupportedCultures;
 
 		/// <summary>
@@ -242,7 +242,7 @@ static void ResetState ()
 
 			// BUGBUG: OverlappedTop is not cleared here, but it should be?
 
-			MainLoop?.Stop();
+			MainLoop?.Stop ();
 			MainLoop = null;
 			Driver?.End ();
 			Driver = null;
@@ -518,7 +518,7 @@ public static void Run (Toplevel view, Func<Exception, bool> errorHandler = null
 		public static void Refresh ()
 		{
 			// TODO: Figure out how to remove this call to ClearContents. Refresh should just repaint damaged areas, not clear
-			Driver.ClearContents();
+			Driver.ClearContents ();
 			View last = null;
 			foreach (var v in _toplevels.Reverse ()) {
 				if (v.Visible) {
@@ -657,8 +657,8 @@ public static void RunMainLoopIteration (ref RunState state, bool wait, ref bool
 			}
 			firstIteration = false;
 
-			if (state.Toplevel != Top && 
-				(Top.NeedsDisplay|| Top.SubViewNeedsDisplay || Top.LayoutNeeded)) {
+			if (state.Toplevel != Top &&
+				(Top.NeedsDisplay || Top.SubViewNeedsDisplay || Top.LayoutNeeded)) {
 				state.Toplevel.SetNeedsDisplay (state.Toplevel.Frame);
 				Top.Clear ();
 				Top.Draw ();
@@ -678,9 +678,9 @@ public static void RunMainLoopIteration (ref RunState state, bool wait, ref bool
 				state.Toplevel.Clear ();
 			}
 
-			if (state.Toplevel.NeedsDisplay || 
-				state.Toplevel.SubViewNeedsDisplay || 
-				state.Toplevel.LayoutNeeded || 
+			if (state.Toplevel.NeedsDisplay ||
+				state.Toplevel.SubViewNeedsDisplay ||
+				state.Toplevel.LayoutNeeded ||
 				OverlappedChildNeedsDisplay ()) {
 				state.Toplevel.Clear ();
 				state.Toplevel.Draw ();
@@ -689,9 +689,9 @@ public static void RunMainLoopIteration (ref RunState state, bool wait, ref bool
 			} else {
 				Driver.UpdateCursor ();
 			}
-			if (state.Toplevel != Top && 
+			if (state.Toplevel != Top &&
 				!state.Toplevel.Modal &&
-				(Top.NeedsDisplay|| Top.SubViewNeedsDisplay || Top.LayoutNeeded)) {
+				(Top.NeedsDisplay || Top.SubViewNeedsDisplay || Top.LayoutNeeded)) {
 				Top.Draw ();
 			}
 		}
@@ -832,7 +832,8 @@ public static void End (RunState runState)
 					OverlappedTop.OnAllChildClosed ();
 				} else {
 					SetCurrentOverlappedAsTop ();
-					Current.OnEnter (Current);
+					runState.Toplevel.OnLeave (Current);
+					Current.OnEnter (runState.Toplevel);
 				}
 				Refresh ();
 			}

Terminal.Gui/Views/Toplevel.cs

@@ -553,6 +553,7 @@ void FocusNearestView (IEnumerable<View> views, Direction direction)
 		///<inheritdoc/>
 		public override void Add (View view)
 		{
+			CanFocus = true;
 			AddMenuStatusBar (view);
 			base.Add (view);
 		}

UnitTests/Views/ToplevelTests.cs

@@ -962,7 +962,98 @@ public void OnEnter_OnLeave_Triggered_On_Application_Begin_End ()
 			Application.End (rs);
 
 			Assert.True (isEnter);
-			Assert.False (isLeave);
+			Assert.False (isLeave);  // Leave event cannot be trigger because it v.Enter was performed and v is focused
+			Assert.True (v.HasFocus);
+		}
+
+		[Fact, AutoInitShutdown]
+		public void OnEnter_OnLeave_Triggered_On_Application_Begin_End_With_More_Toplevels ()
+		{
+			var iterations = 0;
+			var steps = new int [5];
+			var isEnterTop = false;
+			var isLeaveTop = false;
+			var vt = new View ();
+			var top = Application.Top;
+			var diag = new Dialog ();
+
+			vt.Enter += (s, e) => {
+				iterations++;
+				isEnterTop = true;
+				if (iterations == 1) {
+					steps [0] = iterations;
+					Assert.Null (e.View);
+				} else {
+					steps [4] = iterations;
+					Assert.Equal (diag, e.View);
+				}
+			};
+			vt.Leave += (s, e) => {
+				iterations++;
+				steps [1] = iterations;
+				isLeaveTop = true;
+				Assert.Equal (diag, e.View);
+			};
+			top.Add (vt);
+
+			Assert.False (vt.CanFocus);
+			var exception = Record.Exception (() => top.OnEnter (top));
+			Assert.Null (exception);
+			exception = Record.Exception (() => top.OnLeave (top));
+			Assert.Null (exception);
+
+			vt.CanFocus = true;
+			Application.Begin (top);
+
+			Assert.True (isEnterTop);
+			Assert.False (isLeaveTop);
+
+			isEnterTop = false;
+			var isEnterDiag = false;
+			var isLeaveDiag = false;
+			var vd = new View ();
+			vd.Enter += (s, e) => {
+				iterations++;
+				steps [2] = iterations;
+				isEnterDiag = true;
+				Assert.Null (e.View);
+			};
+			vd.Leave += (s, e) => {
+				iterations++;
+				steps [3] = iterations;
+				isLeaveDiag = true;
+				Assert.Equal (top, e.View);
+			};
+			diag.Add (vd);
+
+			Assert.False (vd.CanFocus);
+			exception = Record.Exception (() => diag.OnEnter (diag));
+			Assert.Null (exception);
+			exception = Record.Exception (() => diag.OnLeave (diag));
+			Assert.Null (exception);
+
+			vd.CanFocus = true;
+			var rs = Application.Begin (diag);
+
+			Assert.True (isEnterDiag);
+			Assert.False (isLeaveDiag);
+			Assert.False (isEnterTop);
+			Assert.True (isLeaveTop);
+
+			isEnterDiag = false;
+			isLeaveTop = false;
+			Application.End (rs);
+
+			Assert.False (isEnterDiag);
+			Assert.True (isLeaveDiag);
+			Assert.True (isEnterTop);
+			Assert.False (isLeaveTop);  // Leave event cannot be trigger because it v.Enter was performed and v is focused
+			Assert.True (vt.HasFocus);
+			Assert.Equal (1, steps [0]);
+			Assert.Equal (2, steps [1]);
+			Assert.Equal (3, steps [2]);
+			Assert.Equal (4, steps [3]);
+			Assert.Equal (5, steps [^1]);
 		}
 
 		[Fact, AutoInitShutdown]
@@ -1494,5 +1585,22 @@ void Current_DrawContentComplete (object sender, DrawEventArgs e)
 
 			Application.End (rs);
 		}
+
+		[Fact, AutoInitShutdown]
+		public void Activating_MenuBar_By_Alt_Key_Does_Not_Throw ()
+		{
+			var menu = new MenuBar (new MenuBarItem [] {
+				new MenuBarItem ("Child", new MenuItem [] {
+					new MenuItem ("_Create Child", "", null)
+				})
+			});
+			var topChild = new Toplevel ();
+			topChild.Add (menu);
+			Application.Top.Add (topChild);
+			Application.Begin (Application.Top);
+
+			var exception = Record.Exception (() => topChild.ProcessHotKey (new KeyEvent (Key.AltMask, new KeyModifiers { Alt = true })));
+			Assert.Null (exception);
+		}
 	}
 }