Find the velocity of the mouse in C#

Question

How can i find the instantaneous vertical speed of the mouse at the exact moment that the mouse is released? i have the users dragging over a custo

Answer 1

What I would do is sample the mouse movement constantly and keep track of -say- the last 10 positions. Then when the mouse button is released you would have an array of measurements that would allow you to estimate the mouse velocity when the mouse is released.

I wrote a quick winform app to play with this idea. This computes the velocity for every mouse move. You need to play with the queue length.

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Collections;

namespace MouseVelocity
{
    public partial class Form1 : Form
    {
        System.Diagnostics.Stopwatch sw = new System.Diagnostics.Stopwatch();
        Queue timePoints;

        public Form1()
        {
            sw.Start();
            timePoints = new Queue(100);
            InitializeComponent();
        }

        private void Form1_MouseMove(object sender, MouseEventArgs e)
        {
            addPoint(e);
        }

        private void addPoint(MouseEventArgs e)
        {
            timePoints.Enqueue(new TimePoint(new Point(e.X, e.Y), sw.ElapsedMilliseconds));
            if (timePoints.Count == 40) timePoints.Dequeue();
            object[] array = timePoints.ToArray();
            TimePoint tip = (TimePoint)array[array.Length - 1];
            TimePoint end = (TimePoint)array[0];
            long deltaX = tip.point.X - end.point.X;
            long deltaY = tip.point.Y - end.point.Y;

            long distance = deltaX * deltaX + deltaY * deltaY;

            long deltaT = tip.time - end.time;
            double velocity_modulo = Math.Sqrt(distance) / deltaT;
            double velocity_X = deltaX / (double)deltaT;
            double velocity_Y = deltaY / (double)deltaT;
            label1.Text = string.Format("|V| = {0}; Vx = {1}; Vy = {2}", velocity_modulo, velocity_X, velocity_Y);
        }

    }
    public class TimePoint
    {
        public Point point;
        public long time;

        public TimePoint(Point pt, long ms)
        {
            point = pt;
            time = ms;
        }
    }
}