C# get form to invalidate when form is resized?

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hi all,

so i have just had a challenge to create a checkerboard 64 equal rectangles/squares alternating in color so i managed to do that (i know my code is probably very ugly) but i technically have done the challenge but being curious i notice when the user resizes the form dragging it the form constantly repaints itself giving almost like a stutter of the image. i was wonderin with the code i wrote maybe i could throw some type of code in to make it only invalidate once the user finishes resizing?

C#

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



public class checkerboard : Form
{
    public checkerboard()
    {
        Size = new Size(400, 400);
        Text = "CheckerBoard";
        BackColor = Color.Red;
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        Graphics g = e.Graphics;

        int h = DisplayRectangle.Height;
        int w = DisplayRectangle.Width;

        for (int i = 0; i < 8; i = i + 2)

            for (int j = 0; j < 8; j = j + 2)
            {
                Color Black = Color.Black;
                Brush brush = new SolidBrush(Black);
                g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
            }


        for (int i = 1; i < 8; i = i + 2)
            for (int j = 0; j < 8; j = j + 2)
            {
                Color White = Color.White;
                Brush brush = new SolidBrush(White);
                g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
            }
        for (int i = 1; i < 8; i = i + 2)

            for (int j = 1; j < 8; j = j + 2)
            {
                Color Black = Color.Black;
                Brush brush = new SolidBrush(Black);
                g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
            }
        for (int i = 0; i < 8; i = i + 2)
            for (int j = 1; j < 8; j = j + 2)
            {
                Color White = Color.White;
                Brush brush = new SolidBrush(White);
                g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
            }
                base.OnPaint(e);
               
            }

    static void Main()
    {
        Application.Run(new checkerboard());
    }
}

Posted 10-Jan-13 7:26am

crohnsandme

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Comments

Jibesh 10-Jan-13 16:04pm

You can subscribe the Form.Resize event in your constructor to notify when your form is resized. i made few more changes to work it better check my solution.

Sergey Alexandrovich Kryukov 11-Jan-13 0:26am

Absolutely no need. I explained it in my answer, please see.
—SA

Jibesh 11-Jan-13 1:48am

based on his drawing code he must call the invalidate. situation is when he resizes the forms it takes a new DisplayRectangle and starts drawing the graphics for the new size.

Sergey Alexandrovich Kryukov 11-Jan-13 1:59am

You know, you are right: somehow, I just missed that only a part of the scene will be invalidated...
(Strange, just a few days ago I called Invalidate from Resize handle myself... :-))
And I have to fix my answer...
Thank you very much for pointing it out.
—SA

1 solution

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This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

Jibesh · Accepted Answer · 2013-01-10T10:00:00

You can call Invalidate method inside the Form Resize handler. In addition to this move your code from OnPaint to OnPainBackground to avoid flickering. Check the code modifications.

C#

public checkerboard()
{
  Size = new Size(400, 400);
  Text = "CheckerBoard";
  BackColor = Color.Red;
  DoubleBuffered = true;
  Resize += new System.EventHandler(this.Form1_Resize);
}

protected override void OnPaintBackground(PaintEventArgs e)
{
   Graphics g = e.Graphics;

   int h = DisplayRectangle.Height;
   int w = DisplayRectangle.Width;

     for (int i = 0; i < 8; i = i + 2)
     for (int j = 0; j < 8; j = j + 2)
     {
        Color Black = Color.Black;
        Brush brush = new SolidBrush(Black);
        g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
        brush.Dispose(); // added this line to clear object else this will produce resource leak
     }


    for (int i = 1; i < 8; i = i + 2)
    for (int j = 0; j < 8; j = j + 2)
    {
      Color White = Color.White;
      Brush brush = new SolidBrush(White);
      g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
       brush.Dispose(); // added this line to clear object else this will produce resource leak
    }
    for (int i = 1; i < 8; i = i + 2)

    for (int j = 1; j < 8; j = j + 2)
    {
      Color Black = Color.Black;
      Brush brush = new SolidBrush(Black);
      g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
      brush.Dispose(); // added this line to clear object else this will produce resource leak
    }
    for (int i = 0; i < 8; i = i + 2)
    for (int j = 1; j < 8; j = j + 2)
    {
      Color White = Color.White;
      Brush brush = new SolidBrush(White);
      g.FillRectangle(brush, i * w / 8, j * h / 8, w / 8, h / 8);
       brush.Dispose();
     }          
 }
private void Form1_Resize(object sender, EventArgs e)
{
  this.Invalidate();
}

C# get form to invalidate when form is resized?

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C# get form to invalidate when form is resized?

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