Question

I have some keyboard-handling code in my application, for example, Ctrl + C.

Some of the users of my application are very quick on the keyboard (pressing Ctrl and immediately pressing C and releasing both), so that the eventhandler doesn’t get it fast enough.

The effect occurs on both Windows Forms and WPF.

Please take a look at this Windows Forms example. I’d be happy, if you have any suggestions on how to fasten things up. You might use this sample to reproduce it (but you have to be quick).

I’m wondering how the other applications are programmed. Take Visual Studio. There it is irrelevant how fast you enter that shortcut. It behaves as expected.

Sample: I have a window containing one panel which gets colored red for 100 ms, when the shortcut got captured successfully.

using System;
using System.Drawing;
using System.Threading;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace KeyboardShortcutTest
{
    public partial class Form1 : Form
    {
        private TaskScheduler _uiScheduler;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            _uiScheduler = TaskScheduler.FromCurrentSynchronizationContext();
            KeyUp += Form1_KeyUp;
        }

        private void Form1_KeyUp(object sender, KeyEventArgs e)
        {
            if (e.Control && e.KeyCode == Keys.C)
            {
                ColorizePanelRed(_displayPanel);
            }
        }

        private void ColorizePanelRed(Panel panel)
        {
            Color c = panel.BackColor;

            Task.Factory.StartNew(() => { panel.BackColor = Color.Red; }, CancellationToken.None, TaskCreationOptions.None, _uiScheduler)
                .ContinueWith(t => { Thread.Sleep(100); })
                .ContinueWith(t => { panel.BackColor = c; }, _uiScheduler);
        }
    }
}

Answer 1

The problem may be that some users are too quick to let go of Ctrl before they let go of the C key. I think catching the KeyDown event instead of the KeyUp would be a good way to avoid those issues.