Fixes gui-cs#2970. ScrollView doesn't remove a view that was previous…

…ly added on both versions.

Terminal.Gui/Views/ScrollView.cs

@@ -277,6 +277,37 @@ public override void Add (View view)
 		SetNeedsLayout ();
 	}
 
+	/// <summary>
+	/// Removes the view from the scrollview.
+	/// </summary>
+	/// <param name="view">The view to remove from the scrollview.</param>
+	public override void Remove (View view)
+	{
+		if (view == null) {
+			return;
+		}
+
+		SetNeedsDisplay ();
+		var container = view?.SuperView;
+		if (container == this) {
+			base.Remove (view);
+		} else {
+			container?.Remove (view);
+		}
+
+		if (_contentView.InternalSubviews.Count < 1) {
+			this.CanFocus = false;
+		}
+	}
+
+	/// <summary>
+	///   Removes all widgets from this container.
+	/// </summary>
+	public override void RemoveAll ()
+	{
+		_contentView.RemoveAll ();
+	}
+
 	void View_MouseLeave (object sender, MouseEventEventArgs e)
 	{
 		if (Application.MouseGrabView != null && Application.MouseGrabView != _vertical && Application.MouseGrabView != _horizontal) {
@@ -318,16 +349,6 @@ public bool ShowHorizontalScrollIndicator {
 		}
 	}
 
-	/// <summary>
-	///   Removes all widgets from this container.
-	/// </summary>
-	/// <remarks>
-	/// </remarks>
-	public override void RemoveAll ()
-	{
-		_contentView.RemoveAll ();
-	}
-
 	/// <summary>
 	/// Gets or sets the visibility for the vertical scroll indicator.
 	/// </summary>

UnitTests/Views/ScrollViewTests.cs

@@ -927,5 +927,28 @@ public void DrawTextFormatter_Respects_The_Clip_Bounds ()
 			pos = TestHelpers.AssertDriverContentsWithFrameAre (expected, output);
 			Assert.Equal (new Rect (1, 1, 21, 14), pos);
 		}
+
+		[Fact, AutoInitShutdown]
+		public void Remove_Added_View_Is_Allowed ()
+		{
+			var sv = new ScrollView () {
+				Width = 20,
+				Height = 20,
+				ContentSize = new Size (100, 100)
+			};
+			sv.Add (new View () { Width = Dim.Fill (), Height = Dim.Fill (50), Id = "View1" },
+				new View () { Y = 51, Width = Dim.Fill (), Height = Dim.Fill (), Id = "View2" });
+
+			Application.Top.Add (sv);
+			Application.Begin (Application.Top);
+
+			Assert.Equal (4, sv.Subviews.Count);
+			Assert.Equal (2, sv.Subviews [0].Subviews.Count);
+
+			sv.Remove (sv.Subviews [0].Subviews [1]);
+			Assert.Equal (4, sv.Subviews.Count);
+			Assert.Single (sv.Subviews [0].Subviews);
+			Assert.Equal ("View1", sv.Subviews [0].Subviews [0].Id);
+		}
 	}
 }