SDL.NET no longer detecting modifier keys

Question

I'm using SDL.NET with C#. Recently, a bug has appeared where the library does not detect if the shift key is held down; although it used to do so.

private static void KeyboardEventHandler(object sender, KeyboardEventArgs args)
    {
            case (Key.Comma):

                if (args.Mod == ModifierKeys.LeftShift || args.Mod == ModifierKeys.RightShift || args.Mod == ModifierKeys.ShiftKeys) { actionBuffer = GameAction.MoveU; Console.WriteLine("Going up..."); }
                else { actionBuffer = GameAction.Pickup; }
                break;

            case (Key.Period):
                if (args.Mod == ModifierKeys.LeftShift || args.Mod == ModifierKeys.RightShift || args.Mod == ModifierKeys.ShiftKeys) { actionBuffer = GameAction.MoveD; Console.WriteLine("Going down..."); }
                else { actionBuffer = GameAction.Wait; }
                break;

            default:
                actionBuffer = GameAction.Null;
                break;
        }
    }

However, recently, the checks to see if a shift key is held have returned incorrectly false, despite previously previously evaluating to true.

This means the function never returns the "MoveU" or "MoveD" values, just the "Pickup" and "Wait" values. Why is this? Thanks in advance.

Answer 1

The modifier keys can be combined with OR-bits. You need to use AND-bits to test for the modifier flags since it could contain all of CTRL+ALT+SHIFT (Left AND Right) and even some other modifier keys.

For example, if NumLock or CapsLock is ON, the value will never be == to LeftShift.

See the documentation for the ModifierKeys.

It is also not necessary to test for LeftShift, RightShift and ShiftKeys all at the same time. Just ShiftKeys is sufficient if you are treating them both the same.

ModifierKeys.ShiftKeys == (ModifierKeys.LeftShift | ModifierKeys.RightShift)

Try:

private static void KeyboardEventHandler(object sender, KeyboardEventArgs args)
{
        case (Key.Comma):

            if ((args.Mod & ModifierKeys.ShiftKeys) != 0) { actionBuffer = GameAction.MoveU; Console.WriteLine("Going up..."); }
            else { actionBuffer = GameAction.Pickup; }
            break;

        case (Key.Period):
            if ((args.Mod & ModifierKeys.ShiftKeys) != 0) { actionBuffer = GameAction.MoveD; Console.WriteLine("Going down..."); }
            else { actionBuffer = GameAction.Wait; }
            break;

        default:
            actionBuffer = GameAction.Null;
            break;
    }
}