From 03e0f086c39392bf5e19da568bbebb74da32db59 Mon Sep 17 00:00:00 2001
From: BDisp <bd.bdisp@gmail.com>
Date: Tue, 3 Jan 2023 13:18:09 +0000
Subject: [PATCH] Fixes #2267. Toplevel.EnsureVisibleBounds throws an exception
 if border is null.

---
 Terminal.Gui/Core/Toplevel.cs |  9 +++++----
 UnitTests/ToplevelTests.cs    | 13 +++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/Terminal.Gui/Core/Toplevel.cs b/Terminal.Gui/Core/Toplevel.cs
index a170d0c56..fddabb692 100644
--- a/Terminal.Gui/Core/Toplevel.cs
+++ b/Terminal.Gui/Core/Toplevel.cs
@@ -613,8 +613,9 @@ namespace Terminal.Gui {
 			}
 			nx = Math.Max (x, 0);
 			nx = nx + top.Frame.Width > l ? Math.Max (l - top.Frame.Width, 0) : nx;
-			if (nx + (top.Border != null && top.Border.DrawMarginFrame ? 2 : 1) > top.Frame.X + top.Frame.Width) {
-				nx = Math.Max (top.Frame.Right - (top.Border.DrawMarginFrame ? 2 : 1), 0);
+			var mfLength = top.Border?.DrawMarginFrame == true ? 2 : 1;
+			if (nx + mfLength > top.Frame.X + top.Frame.Width) {
+				nx = Math.Max (top.Frame.Right - mfLength, 0);
 			}
 			//System.Diagnostics.Debug.WriteLine ($"nx:{nx}, rWidth:{rWidth}");
 			bool m, s;
@@ -653,8 +654,8 @@ namespace Terminal.Gui {
 			}
 			ny = Math.Min (ny, l);
 			ny = ny + top.Frame.Height >= l ? Math.Max (l - top.Frame.Height, m ? 1 : 0) : ny;
-			if (ny + (top.Border != null && top.Border.DrawMarginFrame ? 2 : 1) > top.Frame.Y + top.Frame.Height) {
-				ny = Math.Max (top.Frame.Bottom - (top.Border.DrawMarginFrame ? 2 : 1), 0);
+			if (ny + mfLength > top.Frame.Y + top.Frame.Height) {
+				ny = Math.Max (top.Frame.Bottom - mfLength, 0);
 			}
 			//System.Diagnostics.Debug.WriteLine ($"ny:{ny}, rHeight:{rHeight}");
 
diff --git a/UnitTests/ToplevelTests.cs b/UnitTests/ToplevelTests.cs
index a528a3a61..16a6daf5d 100644
--- a/UnitTests/ToplevelTests.cs
+++ b/UnitTests/ToplevelTests.cs
@@ -967,5 +967,18 @@ namespace Terminal.Gui.Core {
 
 			Application.Run ();
 		}
+
+		[Fact, AutoInitShutdown]
+		public void EnsureVisibleBounds_With_Border_Null_Not_Throws ()
+		{
+			var top = new Toplevel ();
+			Application.Begin (top);
+
+			var exception = Record.Exception (() => ((FakeDriver)Application.Driver).SetBufferSize (0, 10));
+			Assert.Null (exception);
+
+			exception = Record.Exception (() => ((FakeDriver)Application.Driver).SetBufferSize (10, 0));
+			Assert.Null (exception);
+		}
 	}
 }
\ No newline at end of file