Question

Hi I have tried to draw an rubberband rectangle on a form using the mouse in C#.

Problems

1) After the mouse release the rectangle disappears. [I want it to stay on the form]

2) I also need to find the coordinates of the four points of the drawn rectangle

3) I also need to erase the rectangle to draw a new one when necessary

Form :

---

CODE

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

namespace rubberbandrectangle
{
public partial class Form1 : Form
{
    Boolean bHaveMouse;
    Point ptOriginal = new Point();
    Point ptLast = new Point();


    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_MouseDown(object sender, MouseEventArgs e)
    {
        bHaveMouse = true;
        ptOriginal.X = e.X;
        ptOriginal.Y = e.Y;
        ptLast.X = -1;
        ptLast.Y = -1;
    }

    private void MyDrawReversibleRectangle(Point p1, Point p2)
    {
        Rectangle rc = new Rectangle();

        p1 = PointToScreen(p1);
        p2 = PointToScreen(p2);
        if (p1.X < p2.X)
        {
            rc.X = p1.X;
            rc.Width = p2.X - p1.X;
        }
        else
        {
            rc.X = p2.X;
            rc.Width = p1.X - p2.X;
        }
        if (p1.Y < p2.Y)
        {
            rc.Y = p1.Y;
            rc.Height = p2.Y - p1.Y;
        }
        else
        {
            rc.Y = p2.Y;
            rc.Height = p1.Y - p2.Y;
        }
        ControlPaint.DrawReversibleFrame(rc,
                        Color.Red, FrameStyle.Dashed);
    }

    private void Form1_MouseUp(object sender, MouseEventArgs e)
    {
        bHaveMouse = false;
        if (ptLast.X != -1)
        {
            Point ptCurrent = new Point(e.X, e.Y);
            MyDrawReversibleRectangle(ptOriginal, ptLast);
        }
        ptLast.X = -1;
        ptLast.Y = -1;
        ptOriginal.X = -1;
        ptOriginal.Y = -1;
    }

    private void Form1_MouseMove(object sender, MouseEventArgs e)
    {
        Point ptCurrent = new Point(e.X, e.Y);
        if (bHaveMouse)
        {
            if (ptLast.X != -1)
            {
                MyDrawReversibleRectangle(ptOriginal, ptLast);
            }
            ptLast = ptCurrent;
                MyDrawReversibleRectangle(ptOriginal, ptCurrent);
        }
    }

    private void Form1_Load(object sender, EventArgs e)
    {
        MouseDown += new MouseEventHandler(Form1_MouseDown);
        MouseUp += new MouseEventHandler(Form1_MouseUp);
        MouseMove += new MouseEventHandler(Form1_MouseMove);
        bHaveMouse = false;
    }





}
}

---

Thanks for reading

Answer 1

1) After the mouse release the rectangle disappears. [I want it to stay on the form]

You need to override the form’s OnPaint method in order to continually draw your rectangle. Right now, you draw it when the mouse moves, but it needs to be drawn afterwards, as well.

2) I also need to find the coordinates of the four points of the drawn rectangle

These should be in your ptOriginal and ptLast variables – What more do you need?

3) I also need to erase the rectangle to draw a new one when necessary

Just stop drawing the rectangle, and draw the new one in the OnPaint.