Merge pull request #668 from tig/button_non_printable_whitespace

Fixes non printable chars in Button

Terminal.Gui/Views/Button.cs

@@ -166,6 +166,14 @@ namespace Terminal.Gui {
 			else
 				shown_text = ustring.Make (_leftBracket) + " " + text + " " + ustring.Make (_rightBracket);
 
+			shown_text = shown_text
+				.Replace ("\f", "\u21a1")		// U+21A1 ↡ DOWNWARDS TWO HEADED ARROW
+				.Replace ("\n", "\u240a")		// U+240A (SYMBOL FOR LINE FEED, ␊)
+				.Replace ("\r", "\u240d")		// U+240D (SYMBOL FOR CARRIAGE RETURN, ␍)
+				.Replace ("\t", "\u2409")		// U+2409 ␉ SYMBOL FOR HORIZONTAL TABULATION
+				.Replace ("\v", "\u240b")		// U+240B ␋ SYMBOL FOR VERTICAL TABULATION
+				.TrimSpace ();
+
 			shown_text = GetTextFromHotKey (shown_text, '_', out hot_pos, out hot_key);
 
 			SetNeedsDisplay ();