Added MaxWidthLine into the TextFormatter class.

Terminal.Gui/Core/TextFormatter.cs

@@ -835,6 +835,18 @@ namespace Terminal.Gui {
 			return max;
 		}
 
+		/// <summary>
+		/// Determines the line with the highest width in the 
+		/// <paramref name="text"/> if it contains newlines.
+		/// </summary>
+		/// <param name="text">Text, may contain newlines.</param>
+		/// <returns>The highest line width.</returns>
+		public static int MaxWidthLine (ustring text)
+		{
+			var result = TextFormatter.SplitNewLine (text);
+			return result.Max (x => x.ConsoleWidth);
+		}
+
 		/// <summary>
 		/// Gets the total width of the passed text.
 		/// </summary>

UnitTests/TextFormatterTests.cs

@@ -4054,5 +4054,15 @@ e
 			Assert.Equal ("Third Line 界", splited [2]);
 			Assert.Equal ("", splited [^1]);
 		}
+
+		[Fact]
+		public void MaxWidthLine_With_And_Without_Newlines ()
+		{
+			var text = "Single Line 界";
+			Assert.Equal (14, TextFormatter.MaxWidthLine (text));
+
+			text = $"First Line 界\nSecond Line 界\nThird Line 界\n";
+			Assert.Equal (14, TextFormatter.MaxWidthLine (text));
+		}
 	}
 }