Keyboard stack

var keyboardStack = new keyboardStack(Keyboard);
 
keyboardStack.AddKeyDown( ControlA.KeyDown);
keyboardStack.AddKeyDown( ControlB.KeyDown);
 
//here, controlA, controlB will receive input
 
keyboardStack.Push();
keyboardStack.AddKeyDown( ControlC.KeyDown);
 
//here, only control C will receive input
 
keyboardStack.Push();
keyboardStack.AddKeyDown( ControlD.KeyDown);
 
//here, only control D will receive input
 
keyboardStack.Pop();
 
//here, only control C again
 
keyboardStack.Pop();
 
//here, only controlA, controlB again
 
keyboardStack.Pop();
 
//nothing will receive input

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using OpenTK.Input;
 
namespace JOpenTKUtils
{
    public class KeyboardStack 
    {
        private KeyboardDevice keyboardDevice;
        private Stack<HandlerLists> handlerStack;
 
        private class HandlerLists
        {
            public List<EventHandler<KeyboardKeyEventArgs>> KeyDownList = new List<EventHandler<KeyboardKeyEventArgs>>();
            public List<EventHandler<KeyboardKeyEventArgs>> KeyUpList = new List<EventHandler<KeyboardKeyEventArgs>>();
        }
 
 
        public void AddKeyDown(EventHandler<KeyboardKeyEventArgs> keyDown)
        {
            if (handlerStack.Count == 0)
                Push();
 
            handlerStack.Peek().KeyDownList.Add(keyDown);
            keyboardDevice.KeyDown += keyDown;
        }
 
 
        public void AddKeyUp(EventHandler<KeyboardKeyEventArgs> keyUp)
        {
            if (handlerStack.Count == 0)
                Push();
 
            handlerStack.Peek().KeyUpList.Add(keyUp);
            keyboardDevice.KeyUp += keyUp;
        }
 
        public void RemoveKeyDown(EventHandler<KeyboardKeyEventArgs> keyDown)
        {
            if (handlerStack.Count == 0)
                return;
 
            handlerStack.Peek().KeyDownList.Remove(keyDown);
            keyboardDevice.KeyDown -= keyDown;
        }
 
 
        public void RemoveKeyUp(EventHandler<KeyboardKeyEventArgs> keyUp)
        {
            if (handlerStack.Count == 0)
                return;
 
            handlerStack.Peek().KeyUpList.Remove(keyUp);
            keyboardDevice.KeyUp -= keyUp;
        }
 
 
 
 
        private void RemoveAllHandlers(HandlerLists lists)
        {
            foreach (var handler in lists.KeyDownList)
                keyboardDevice.KeyDown -= handler;
 
            foreach (var handler in lists.KeyUpList)
                keyboardDevice.KeyUp -= handler;
        }
 
        private void AddAllHandlers(HandlerLists lists)
        {
            foreach (var handler in lists.KeyDownList)
                keyboardDevice.KeyDown += handler;
 
            foreach (var handler in lists.KeyUpList)
                keyboardDevice.KeyUp += handler;
        }
 
 
        public void Push()
        {
 
            if(handlerStack.Count != 0)
                RemoveAllHandlers(handlerStack.Peek());
 
            var handlerLists = new HandlerLists();
            handlerStack.Push(handlerLists);
 
        }
 
        public void Pop()
        {
            if (handlerStack.Count == 0)
                throw new Exception("Attempted to pop an empty KeyboardStack.");
 
            RemoveAllHandlers(handlerStack.Pop());
 
            if (handlerStack.Count != 0)
                AddAllHandlers(handlerStack.Peek());
        }
 
 
        public KeyboardStack(KeyboardDevice keyboard)
        {
 
            handlerStack = new Stack<HandlerLists>();
            this.keyboardDevice = keyboard;
        }
 
 
    }
}