fix for SD-1713

src/AddIns/DisplayBindings/AvalonEdit.AddIn/Src/CodeEditorView.cs

@@ -252,7 +252,17 @@ namespace ICSharpCode.AvalonEdit.AddIn
 						toolTip.Closed += ToolTipClosed;
 					}
 					toolTip.PlacementTarget = this; // required for property inheritance
-					toolTip.Content = args.ContentToShow;
+									
+					if(args.ContentToShow is string) {
+						toolTip.Content = new TextBlock 
+						{
+							Text = args.ContentToShow as string,
+							TextWrapping = TextWrapping.Wrap
+						};
+					}
+					else 
+						toolTip.Content = args.ContentToShow;
+					
 					toolTip.IsOpen = true;
 					e.Handled = true;
 				}

src/Libraries/AvalonEdit/ICSharpCode.AvalonEdit/CodeCompletion/CompletionWindow.cs

@@ -70,7 +70,15 @@ namespace ICSharpCode.AvalonEdit.CodeCompletion
 				return;
 			object description = item.Description;
 			if (description != null) {
-				toolTip.Content = description;
+				if(description is string) {
+					toolTip.Content = new TextBlock 
+					{
+						Text = description as string,
+						TextWrapping = TextWrapping.Wrap
+					};
+				}
+				else 
+					toolTip.Content = description;
 				toolTip.IsOpen = true;
 			} else {
 				toolTip.IsOpen = false;