We have a co-worker who doesn’t understand that he’s got to lock his computer when he steps away from it, so we all decided to play a prank on him. Of course, there’s the standard “tape over laser under mouse” maneuver. Then there’s the “change his desktop backgrounds” or “change his Windows sounds” tactic. Mine was a bit more devious.

Below is the source code for a tiny program to run in the background, detectable only through task manager, that randomly moves the mouse pointer.

(Note: I use the .settings file because I can change the settings later to fine-tune them)

And here’s the Program.cs code. Create a Windows Form application (this is the important part – don’t create a Console app!), then delete the form and replace the Program.cs code with the code below. Compile and enjoy!

using System;
using System.Collections.Generic;
using System.Linq;
using System.Windows.Forms;
using System.Drawing;
using System.Threading;

namespace mmr_e12
{
    /// <summary>
    /// Move Mouse Randomly Event 2012 Application
    /// </summary>
    static class Program
    {
        #region Settings

        /// <summary>
        /// The update speed for the Timer
        /// </summary>
        static int _MaxInterval = 2000;

        /// <summary>
        /// The maximum distance from the initial mouse position
        /// </summary>
        static int _MouseRadius = 100;

        /// <summary>
        /// Whether or not to use smooth mouse transitions
        /// </summary>
        static bool _UseSmoothness = true;

        /// <summary>
        /// The duration in seconds for the smooth mouse transition
        /// </summary>
        static double _SmoothnessDuration = 0.1;

        /// <summary>
        /// The perceived speed of the smooth transition
        /// (if Frame Time = 10ms, Perceived Speed = 100.0)
        /// </summary>
        static double _PerceivedSpeed = 500.0;

        #endregion Settings
        
        //**********************************



        /// <summary>
        /// The main entry point for the application.
        /// </summary>
        [STAThread]
        static void Main() {
            try {
                // Create a Random Number Generator
                Random r = new Random();

                // Create a Windows Form Timer
                System.Windows.Forms.Timer timer = new System.Windows.Forms.Timer();

                // Set the initial Interval low to get it going.
                timer.Interval = 100;

                // Set the Tick Event to update the mouse position
                timer.Tick += (sender, args) => {
                    
                    // Randomly determine change in position
                    var dx = r.Next(0, _MouseRadius * 2) - _MouseRadius;
                    var dy = r.Next(0, _MouseRadius * 2) - _MouseRadius;
                    
                    // Randomly determine next update interval
                    var z = (int)(_MaxInterval * r.NextDouble());
                    
                    // Prevent zero for update interval
                    if (z <= 0) z = 1;

                    // Move the cursor
                    if (_UseSmoothness)
                        SmoothMouseMove(dx, dy, _SmoothnessDuration);
                    else
                        Cursor.Position = new Point(Cursor.Position.X + dx, Cursor.Position.Y + dy);

                    // Update the Interval to increase the randomness
                    timer.Interval = z;
                };

                // Start the Timer
                timer.Start();

                // Run the Application Thread
                Application.Run();
            }
            catch (Exception Error) {
                // Show Error - no fun if failed!
                MessageBox.Show(string.Format("{0}", Error), "Application Error");
                
                // Exit application thread.
                Application.Exit();
            }
        }

        /// <summary>
        /// Smoothly transition the mouse pointer between it's current position and it's new position
        /// </summary>
        /// <param name="dx">Change in X Position</param>
        /// <param name="dy">Change in Y Position</param>
        /// <param name="durationInSeconds">The length of the transition time.</param>
        static void SmoothMouseMove(int dx, int dy, double durationInSeconds) {
            
            // Check for divide-by-zero & transition time
            if (!(durationInSeconds > 0))
                throw new ArgumentException("Transition Duration must be greater than 0.", "durationInSeconds");

            // Number of frames to "render"
            double frames = durationInSeconds * _PerceivedSpeed;

            // Length of pause time between frames
            int frameSleepLength = (int)((durationInSeconds / frames) * _PerceivedSpeed);

            // Create the change vector
            PointF vector = new PointF((float)(dx / frames), (float)(dy / frames));
            
            // Get the initial mouse position
            PointF mousePos = Cursor.Position;

            // Move through each frame of animation
            for (int i = 0; i < frames; i++) {
                
                // Set the new Cursor Position
                Cursor.Position = new Point((int)(mousePos.X += vector.X), (int)(mousePos.Y += vector.Y));

                // Sleep to transition over perceived time
                Thread.Sleep(frameSleepLength);
            }

        }
    }

    
}