Draw a Polygon using Mouse Points in C#

Question

Hi,

I need to be able to draw a polygon using mouse click locations. Here is my current code:

 //the drawshape varible is called when a button is pressed to select use of this tool
             if (DrawShape == 4)
                {
                    Point[] pp = new Point[3];
                    pp[0] = new Point(e.Location.X, e.Location.Y);
                    pp[1] = new Point(e.Location.X, e.Location.Y);
                    pp[2] = new Point(e.Location.X, e.Location.Y);
                    Graphics G = this.CreateGraphics();
                    G.DrawPolygon(Pens.Black, pp);
                }

Thanks

Answer 1

First, add this code:

List<Point> points = new List<Point>();

On the object you are drawing on, capture the OnClick event. One of the arguments should have the X and Y coordinates of the click. Add them to the points array:

points.Add(new Point(xPos, yPos));

And then finally, where you're drawing the lines, use this code:

 if (DrawShape == 4)
 {
     Graphics G = this.CreateGraphics();
     G.DrawPolygon(Pens.Black, points.ToArray());
 }

EDIT:

Ok, so the above code isn't exactly correct. First of all, its most likely a Click event instead of a OnClick event. Second, To get the mouse position, you need two variables declared up with the points array,

    int x = 0, y = 0;

Then have a mouse move event:

    private void MouseMove(object sender, MouseEventArgs e)
    {
        x = e.X;
        y = e.Y;
    }

Then, in your Click event:

    private void Click(object sender, EventArgs e)
    {
        points.Add(new Point(x, y));
    }

Answer 2

Ok here is some sample code:

    private List<Point> polygonPoints = new List<Point>();

    private void TestForm_MouseClick(object sender, MouseEventArgs e)
    {
        switch(e.Button)
        {
            case MouseButtons.Left:
                //draw line
                polygonPoints.Add(new Point(e.X, e.Y));
                if (polygonPoints.Count > 1)
                {
                    //draw line
                    this.DrawLine(polygonPoints[polygonPoints.Count - 2], polygonPoints[polygonPoints.Count - 1]);
                }
                break;

            case MouseButtons.Right:
                //finish polygon
                if (polygonPoints.Count > 2)
                {
                    //draw last line
                    this.DrawLine(polygonPoints[polygonPoints.Count - 1], polygonPoints[0]);
                    polygonPoints.Clear();
                }
                break;
        }
    }

    private void DrawLine(Point p1, Point p2)
    {
        Graphics G = this.CreateGraphics();
        G.DrawLine(Pens.Black, p1, p2);
    }