Question

I’m trying to implement the following method:
void Ball::DrawOn(Graphics g);

The method should draw all previous locations (stored in a queue) of the ball and finally the current location. I don’t know if that matters, but I print the previous locations using g.DrawEllipse(...) and the current location using g.FillEllipse(...).

The question is, that as you could imagine there is a lot of drawing to be done and thus the display starts to flicker much. I had searched for a way to double buffer, but all I could find is these 2 ways:

1. System.Windows.Forms.Control.DoubleBuffered = true;

2. SetStyle(ControlStyles.DoubleBuffer | ControlStyles.UserPaint | ControlStyles.AllPaintingInWmPaint, true);

while trying to use the first, I get the an error explaining that from in this method the Property DoubleBuffered is inaccessible due to its protection level. While I can’t figure how to use the SetStyle method.

Is it possible at all to double buffer while all the access I have is to the Graphics Object I get as input in the method?

Thanks in Advance,

Edit:
I had created the following class

namespace doubleBuffer
{
    class BufferedBall : System.Windows.Forms.Form
    {
        private Ball ball;
        public BufferedBall(Ball ball)
        {
            this.ball = ball;
        }

        public void DrawOn(Graphics g)
        {
            this.DoubleBuffered = true;
            int num = 0;
            Rectangle drawArea1 = new Rectangle(5, 35, 30, 100);
            LinearGradientBrush linearBrush1 =
            new LinearGradientBrush(drawArea1, Color.Green, Color.Orange, LinearGradientMode.Horizontal);
            Rectangle drawArea2 = new Rectangle(5, 35, 30, 100);
            LinearGradientBrush linearBrush2 =
               new LinearGradientBrush(drawArea2, Color.Black, Color.Red, LinearGradientMode.Vertical);
            foreach (Point point in ball.previousLocations)
            {
                Pen myPen1;
                if (num % 3 == 0)
                    myPen1 = new Pen(Color.Yellow, 1F);
                else if (num % 3 == 1)
                    myPen1 = new Pen(Color.Green, 2F);
                else
                    myPen1 = new Pen(Color.Red, 3F);
                num++;
                myPen1.DashStyle = System.Drawing.Drawing2D.DashStyle.Solid;
                myPen1.StartCap = System.Drawing.Drawing2D.LineCap.RoundAnchor;
                myPen1.EndCap = System.Drawing.Drawing2D.LineCap.AnchorMask;
                g.DrawEllipse(myPen1, (float)(point.X - ball.radius), (float)(point.Y + ball.radius), (float)(2 * ball.radius), (float)(2 * ball.radius));
            }
            if ((ball.Host.ElapsedTime * ball.Host.FPS * 10) % 2 == 0)
            {
                g.FillEllipse(linearBrush1, (float)(ball.Location.X - ball.radius), (float)(ball.Location.Y + ball.radius), (float)(2 * ball.radius), (float)(2 * ball.radius));
            }
            else
            {
                g.FillEllipse(linearBrush2, (float)(ball.Location.X - ball.radius), (float)(ball.Location.Y + ball.radius), (float)(2 * ball.radius), (float)(2 * ball.radius));
            }
        }
    }
}

and the ball drawOn looks like this:

new BufferedBall(this).DrawOn(g);

Is that what you meant? because it is still flickering?

Answer 1

Form class has DoubleBuffered property exposed as protected. http://msdn.microsoft.com/en-us/library/system.windows.forms.control.doublebuffered.aspx but since you derive your form from Form you can use it.