Question

I want to create an application which the user is able to manipulate the line he draw. Something like Deleting the line or Selecting it. How should I do that?

Thanks in advance

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I managed to do it using a hard coded rectangle. But I don’t still have an idea how to do it using the drawLine() Can I use drawPath to do the hit test?

Here is the code:

private bool selectGraph = false;
private Rectangle myrec = new Rectangle(50, 50, 100, 100);
private Graphics g;

private void panel1_Paint(object sender, PaintEventArgs e)
    {
        SolidBrush sb = new SolidBrush(Color.Blue);
        Pen p = new Pen(Color.Blue, 5);

        e.Graphics.DrawRectangle(p, myrec);
        e.Graphics.FillRectangle(sb, myrec);
    }

    private void panel1_MouseUp(object sender, MouseEventArgs e)
    {
        Point mPT = new Point(e.X, e.Y);

        if (e.Button == MouseButtons.Left)
        {
            if (myrec.Contains(mPT))
            {
                selectGraph = true;
                button1.Enabled = true;
            }
            else
            {
                selectGraph = false;
                button1.Enabled = false;
            }
        }
        Invalidate();
    }

Answer 1

Well you could start with something like a simple Line class:

public class Line
{
    public Point Start { get; set; }
    public Point End { get; set; }
}

Then you could have your form:

private Line Line = new Line();

protected override void OnPaint(PaintEventArgs e)
{
    e.Graphics.DrawLine(Pens.Red, this.Line.Start, this.Line.End);
}

protected override void OnMouseMove(MouseEventArgs e)
{
    if (e.Button == MouseButtons.Left)
    {
        this.Line.Start = e.Location;
        this.Refresh();
    }
    else if (e.Button == MouseButtons.Right)
    {
        this.Line.End = e.Location;
        this.Refresh();
    }
}

So basically then they could delete the this.Line maybe on “MiddleButton” click or something. This should be enough to get you started.

I’ve created a sample that shows how this can be done. Set some break points and see how things are done.