How do I draw a checkerboard pattern?

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Hi, I am trying to draw a checkerboard pattern onto my windows form. I am using the following code but it means that whenever the window gets repainted (e.g. hover over a button) it causes the pattern to be redrawn and flicker. Is there a better way to achieve this?

The code to draw the checkerboard is:

private void drawBoard(Graphics g) {
    bool dark = true;
    for (int i = 0; i < 8; i++) {
        dark = !dark;
        for (int j = 0; j < 8; j++) {
            dark = !dark;

            Pen blackPen = new Pen(Color.Black, 2);
            SolidBrush brush;
            if (dark) {
                brush = new SolidBrush(Color.LightGray);
            } else {
                brush = new SolidBrush(Color.Gray);
            }

            int x = 50 * i + 10;
            int y = 50 * j + 10;
            int width = 50;
            int height = 50;
            // Draw rectangle to screen.
            g.DrawRectangle(blackPen, x, y, width, height);
            g.FillRectangle(brush, x, y, width, height);
        }
    }
}

The main form just calls this function when the Paint event handler is called.

Posted 7-Feb-11 16:49pm

nomad143

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2 solutions

Solution 2

While I like SAKryukovs' solution, another option is to use a bitmap - paint 4 of your squares using your favourite paint program, and use the bitmap as the BackgroundImage[^] for the form. Set BackgroundImageLayout[^] to ImageLayout.Tile[^].

This way you can have your checkboard pattern without writing a single line of code, and still avoid the flickering :)

Now, if you want to take this further you can always draw the complete checkboard pattern to a Bitmap using System.Drawing - or use a drawing package to create an enhanced metafile containing your checkboard pattern - this will scale pretty well too.

Regards
Espen Harlinn

Posted 8-Feb-11 9:38am

Espen Harlinn

Updated 8-Feb-11 11:38am

v2

Comments

JOAT-MON 8-Feb-11 17:28pm

+4 Utilizing a bitmap is a valid alternative, but if you look at the OP's code, he is trying to create an 8 X 8 board, not just the pattern as a background. For the OP's scenario, he would need to have a bitmap that was his full board(8 X 8) and ImageLayout not set to Tile.

Espen Harlinn 8-Feb-11 17:36pm

As I mentioned, I like SAKryukovs' solution - using the BackgroundImage property, the way I mentions is just a simple alternative. Now, if he wanted to take it further he can always draw his complete checkboard pattern to a Bitmap using System.Drawing - or he could use a drawing package to create an enhanced metafile containing his checkboard pattern.

I just wanted to draw attention to the BackgroundImage property - there are numerous ways this can be used to accomplish his task :)

JOAT-MON 8-Feb-11 17:43pm

So true. We could probably create a rather big page full of alternatives to accomplish that. :)

JF2015 10-Feb-11 1:15am

Good alternative. 5+

Espen Harlinn 10-Feb-11 15:34pm

Thank you JF2015!

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Sergey Alexandrovich Kryukov · Accepted Answer · 2011-02-07T17:18:00

Solution 1

All correct. Consider using Control.DoubleBuffered, assign it to true — usual effective tool to overcome flickering. To do that, you need to create your own control for drawing, because this member is protected:

C#

internal class MyControl : Control {
    internal MyControl() { DoubleBuffered = true; }
    //...
}

Also, something not related to flicker, but helpful to improve performance: when you change something in graphics, to trigger control's Paint event you will need to call Control.Invalidate. Instead of usual parameter-less Invalidate use Invalidate with parameters, which allows you to invalidate only a modified part of the scene.

[EDIT]
Do yourself a favor, use custom Control for painting (sub-classed as I show above), not Form. With Form you loose bit chunk of flexibility.

—SA

Posted 7-Feb-11 17:18pm

Sergey Alexandrovich Kryukov

Updated 8-Feb-11 14:01pm

v3

Comments

JOAT-MON 7-Feb-11 23:36pm

Just one thing, he is painting from form: Form.DoubleBuffered is public. (+5 agree with advice)

Sergey Alexandrovich Kryukov 8-Feb-11 1:09am

Sorry, it is not:
http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doublebuffered.aspx says:
protected virtual bool DoubleBuffered { get; set; }
Also, I test my codelets as I answer, compile it, etc.

JOAT-MON 8-Feb-11 5:03am

Understood, the point I was making is that he is not drawing from the Control class, but rather from the Form class. The Control.DoubleBuffered is protected virtual, and the Form class implements it as a public property: http://msdn.microsoft.com/en-us/library/system.windows.forms.form.aspx

I felt it was relevant because Form class is the level at which the OP is drawing, meaning it is not necessary to create your own control...the DoubleBuffered is already publicly implemented for this class.

Sergey Alexandrovich Kryukov 8-Feb-11 18:44pm

Oh, good point. It should better be Control, not Form.
Thank you for the note.
--SA

Henry Minute 8-Feb-11 19:00pm

Even for Control, it is possible.

Take a look at SetStyle http://msdn.microsoft.com/en-us/library/system.windows.forms.control.setstyle%28v=VS.90%29.aspx.

This doesn't invalidate your answer though.

Sergey Alexandrovich Kryukov 8-Feb-11 19:37pm

Sorry, I just looked at you reference and immediately spotted the word "protected" -- please look.
I answered like this because I remember, when I worked tightly with graphics like that, I remembered: sub-classing required.
--SA

Henry Minute 8-Feb-11 19:49pm

Quite right. For Control subclassing is needed.
I was thinking Form again. :)

Sergey Alexandrovich Kryukov 8-Feb-11 20:00pm

No problem at all. The key advice is delivered.
Thank you for your participation.
Best,
--SA

nomad143 8-Feb-11 0:57am

Thanks for the help

Sergey Alexandrovich Kryukov 8-Feb-11 1:10am

You're welcome.
Thanks for accepting my answer.
Call again.
--SA

Espen Harlinn 8-Feb-11 15:28pm

Good answer, a 5