BufferedGraphics flicker

Question

I have tried to implement custom double buffering, but it causes flicker.

This is code in control (custom control that inherits from Control) constructor:

bufferContext = new BufferedGraphicsContext();
SetStyle(ControlStyles.OptimizedDoubleBuffer, false);
SetStyle(ControlStyles.DoubleBuffer, false);
SetStyle(ControlStyles.ResizeRedraw, false);
SetStyle(ControlStyles.AllPaintingInWmPaint | ControlStyles.UserPaint, true);
SetStyle(ControlStyles.Opaque, true);

OnPaint event:

protected override void OnPaint(PaintEventArgs e)
{
    if (buffer == null)
    {
        Draw(e);
        return;
    }

    if (Repaint)
    {
        Repaint = false;
        PaintEventArgs pe = new PaintEventArgs(buffer.Graphics, e.ClipRectangle);
        Draw(pe);
    }

    buffer.Render(e.Graphics);
}

Also, this code is activated on resize related to buffering:

Graphics g = this.CreateGraphics();

if (buffer != null)
{
    buffer.Dispose();
    buffer = null;
}

if (!(bufferContext == null || DisplayRectangle.Width <= 0 || DisplayRectangle.Height <= 0))
{
    buffer = bufferContext.Allocate(g, DisplayRectangle);
    Repaint = true;
}

Draw method is complicated, but it first fills control with BackColor, other is irrelevant.

I can spot with my eyes that there is flicker sometimes, mostly when resizing window. As I perceive, black is painted first over control, and then graphics from buffer, and it causes flicker. However, BackColor is never black.

What to do to stop this?

TomZee TomZee · Accepted Answer · 2015-08-24T14:04:27

This example shows how to use Buffered Graphics Correctly:

using System;
using System.Collections.Generic;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace GDI_PAINTING_EXAMPLE
{
    public class PaintingExample : Control
    {
        public Graphics G;
        public Bitmap Frame = new Bitmap(256, 256);
        public Bitmap Buffer = new Bitmap(256, 256);

        public PaintingExample()
        {
            // Create a new Graphics instance.
            G = Graphics.FromImage(Buffer);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            // Clears Buffer To White
            G.Clear(Color.White);



            //
            // Do Your Painting Routine
            //

            //
            // End Your Painting Routine
            //



            // Set Frame to draw as Buffer
            Frame = Buffer;

            // Draw Frame with Paint Event Graphics as one image.
            e.Graphics.DrawImage(Frame, new Point(0, 0));
        }
        protected override void OnPaintBackground(PaintEventArgs pevent)
        {
        }
    }
}

BufferedGraphics flicker

1 Answers