Imports System.Math
 
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;
 
namespace csDrawCircleAtMousePoint
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            this.InitializeComponent();
        }
 
        private class Circle
        {
            private PointF _center;
            private float _radius;
 
            public Circle(Point p, float r)
            {
                _center = p;
                _radius = r;
            }
 
            public PointF Center 
            {
                get { return _center; }
                set { _center = value; }
            }
 
            public float Radius 
            {
                get { return _radius; }
                set { _radius = value; }
            }
 
            public RectangleF BoundingRectangle 
            {
                get { return new RectangleF(_center.X - _radius, _center.Y - _
                  _radius, 2 * _radius, 2 * _radius); }
            }
        } // Class Circle
 
        private List<Circle> circles = new List<Circle>();
 
        private void Form1_MouseDown(object sender, MouseEventArgs e)
        {
            Point p = new Point(e.X, e.Y);
            float r = 0;
 
            if (circles.Count == 0)
            {
                r = 30; // Default size
            }
            else
            {
                // draw largest circle possible without overlap
                r = float.MaxValue;
                foreach (Circle c in circles)
                {
                    float nr = (float)Math.Sqrt(Math.Pow(Math.Abs( _
                      p.X-c.Center.X), 2)+Math.Pow(Math.Abs(p.Y-c.Center.Y), _
                      2))-c.Radius-1;
                    if (nr < 0) return; // Exclude within another circle
                    if (nr < r) r = nr;
                }
            }
            circles.Add(new Circle(p, r));
            this.Refresh();
        }
 
        private void Form1_Paint(object sender, PaintEventArgs e)
        {
            foreach (Circle c in circles)
            {
                e.Graphics.DrawEllipse(Pens.Red, c.BoundingRectangle);
            }
        }
 
    } // Class Form1
}

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