Rectangle drawing dynamically

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I want to draw the Rectangle by mouse dynamically on Form but required results are not there.Means I want to grab the mouse on the form so rectangle can be draw.
Somebody Please help me......

C#

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 rect
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        Point startPos;      // mouse-down position
        Point currentPos;    // current mouse position
        bool drawing;        // busy drawing
        List<Rectangle> rectangles = new List<Rectangle>();  // previous rectangles

        private Rectangle getRectangle()
        {
            return new Rectangle(
                Math.Min(startPos.X, currentPos.X),
                Math.Min(startPos.Y, currentPos.Y),
                Math.Abs(startPos.X - currentPos.X),
                Math.Abs(startPos.Y - currentPos.Y));
        }

        private void canevas_MouseDown(object sender, MouseEventArgs e)
        {
            currentPos = startPos = e.Location;
            drawing = true;
        }

        private void canevas_MouseMove(object sender, MouseEventArgs e)
        {
            currentPos = e.Location;
            if (drawing)
                Invalidate();
        }

        private void canevas_MouseUp(object sender, MouseEventArgs e)
        {
            if (drawing)
            {
                drawing = false;
                var rc = getRectangle();
                if (rc.Width > 0 && rc.Height > 0) rectangles.Add(rc);
                Invalidate();
            }
        }

        private void canevas_Paint(object sender, PaintEventArgs e)
        {
            if (rectangles.Count > 0) e.Graphics.DrawRectangles(Pens.Black, rectangles.ToArray());
            if (drawing) e.Graphics.DrawRectangle(Pens.Red, getRectangle());
        }
    
        private void rectangleShape1_Click(object sender, EventArgs e)
        {
            getRectangle();
        }
    }
}

Posted 28-Apr-13 20:35pm

Naeem Ahmed

Updated 28-Apr-13 23:35pm

v2

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Comments

Sergey Alexandrovich Kryukov 29-Apr-13 2:40am

"Not working" is not informative. The general idea looks correct.
—SA

Naeem Ahmed 29-Apr-13 5:10am

"Not Working" means when I debug my project. Form of application load accurately but drawing of Rectangle do not take place on the form.....

Sergey Alexandrovich Kryukov 29-Apr-13 8:06am

When asking such questions, you need to show all "+=" operations for all event instances, declaration of "canevas". And, by the way, it would be much better to add handlers to the invocation lists of event instance without the designer, using anonymous delegate syntax (you did not worry to show the auto-generated code):
canevas.Paint += (sender, eventArgs) => { eventArgs.Graphics.Draw... };
And you can debug it all using the breakpoints, etc. The code is quite simple for find out everything...
—SA

Rob Philpott 29-Apr-13 5:56am

Essentially it looks ok to me. What is 'canevas'? Are the events hooked up correctly? Put breakpoints in to confirm the mouse events are being received. Put a breakpoint on the Paint method and inspect what getRectangle gives you....

lukeer 29-Apr-13 5:59am

Does canevas_Paint ever get called?
If so, what data is present in rectangles?

Add that info to your question using the "Improve question" link.

Sergey Alexandrovich Kryukov 29-Apr-13 8:01am

1) There is no such event. 2) Events are never called. (No, this is not just terminology. Event handler method is called when an event is invoked.)
Good idea to use "Improve question".
—SA

lukeer 29-Apr-13 9:16am

a) Strictly speaking, your 1) and 2) are pointless since I merely asked about calling canevas_Paint and never mentioned the term "event".
b) In general, and this is no exception, terminology is important for all of us to enable understanding each other.

Sergey Alexandrovich Kryukov 29-Apr-13 9:26am

I'm sorry, I misread "even" as "event", that means your point was correct. What data presents in rectangles is clear. The problem is pure logic, solved by some debugging.
Thank you for this note.
—SA

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gggustafson · Answer 1 · 2013-05-02T14:32:00

The following code performs what you want to do.

C#

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Windows.Forms;

namespace CodeProject
    {

    // *************************************** class DynamicRectangles
    
    public partial class DynamicRectangles : Form
        {

        Point               current_mouse_position;
        Point               mouse_down_position;
        bool                drawing = false;
        List < Rectangle >  rectangles = new List < Rectangle > ( );

        // ***************************************** DynamicRectangles
        
        public DynamicRectangles ( )
            {
            
            InitializeComponent ( );
            }

        // ***************************************** current_rectangle
        
        private Rectangle current_rectangle ( )
            {
            return new Rectangle(
                Math.Min ( mouse_down_position.X, 
                           current_mouse_position.X ),
                Math.Min ( mouse_down_position.Y, 
                           current_mouse_position.Y ),
                Math.Abs ( mouse_down_position.X - 
                           current_mouse_position.X ),
                Math.Abs ( mouse_down_position.Y - 
                           current_mouse_position.Y ) );
            }

        // *********************************************** OnMouseDown
        
        protected override void OnMouseDown ( MouseEventArgs e )
            {
            
            base.OnMouseDown ( e );

            drawing = true;

            current_mouse_position = e.Location;
            mouse_down_position = e.Location;
            }

        // *********************************************** OnMouseMove
        
        protected override void OnMouseMove ( MouseEventArgs e )
            {
            
            base.OnMouseMove ( e );

            current_mouse_position = e.Location;
            if ( drawing )
                {
                Invalidate ( );
                }
            }

        // ************************************************* OnMouseUp
        
        protected override void OnMouseUp ( MouseEventArgs e )
            {
            Rectangle  rectangle;
            base.OnMouseUp ( e );

            drawing = false;

            rectangle = current_rectangle ( );
            if ( ( rectangle.Width > 0 ) && ( rectangle.Height > 0 ) )
                {
                rectangles.Add ( rectangle );
                }
            Invalidate ( );
            }

        // *************************************************** OnPaint
        
        protected override void OnPaint ( PaintEventArgs e )
            {
            
            base.OnPaint ( e );

            if ( rectangles.Count > 0 )
                {
                e.Graphics.DrawRectangles ( new Pen ( Color.Black ),
                                            rectangles.ToArray ( ) );
                }
            if ( drawing )
                {
                e.Graphics.DrawRectangle ( new Pen ( Color.Red ), 
                                           current_rectangle ( ) );
                }
            }
            
        } // class DynamicRectangles

    } // namespace CodeProject

I have a couple of observations about your code.

1. From MSDN

The On... methods allow derived classes to handle the event without attaching a delegate.
This is the preferred technique for handling the event in a derived class.

I suggest that you use the On... form of event handler declaration. All you need to enter is protected override in your code and Intellisence will provide you with a list from which you can choose what you want.

2. I am ignoring the canevas [sic] variable.
3. I am ignoring the event handler rectangleShape1_Click.

Hope that helps.

Gus