Drag and Drop something

Question

I made a class Schalter (eng. switch) and now I want to drag and drop this to an other position. The Schalter is a just an object with 0 or 1 as output and it has some drawing in it. I tried something but it just worked half. When I move it it moves much too fast. Here the code I tried:

namespace Schaltungszeichner {
public partial class Form1 : Form {
    public Form1() {
        InitializeComponent();
        s = new Schalter(this);
        this.DoubleBuffered = true;
    }

    private bool myMouseDown = false;
    private int myMouseX, myMouseY;

    Schalter s;

    private void Form1_Paint(object sender, PaintEventArgs e) {
        s.zeichnen(e.Graphics);
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e) {
        if (myMouseDown) {
            s.X += e.X - myMouseX;
            s.Y += e.Y - myMouseY;
        }
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e) {
        myMouseDown = false;
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e) {
        if (s.isClicked(e.X, e.Y)) {
            s.Out = !s.Out;
            myMouseDown = true;
            myMouseX = e.X;
            myMouseY = e.Y;

        }
    }
}
}

Answer 1

The problem is that MouseEventArgs holds the mouse position relative to the object which owns the event and not the object being moved. You need to account for this by subtracting the starting position of the moving object.

In Form1_MouseDown change:

myMouseX = e.X;
myMouseY = e.Y;

to:

myMouseX = e.X - s.X;
myMouseY = e.Y - s.Y;

And in Form1_MouseMove change:

s.X += e.X - myMouseX;
s.Y += e.Y - myMouseY;

to:

s.X = e.X - myMouseX;
s.Y = e.Y - myMouseY;

I would also consider renaming myMouseX and myMouseY to something that reflects the values that they now hold, like differenceX and differenceY.