DoubleBuffering

using System.Drawing;
using System.Drawing.Imaging;

namespace EctoUI
{
    /// <summary>
    /// Class to implement Double Buffering
    /// NT Almond
    /// 24 July 2003
    /// </summary>
    ///
    public class DBGraphics
    {
        private Graphics _graphics;
        private Bitmap _memoryBitmap;
        private int _width;
        private int _height;
        private int _left;
        private int _top;

        /// <summary>
        /// Default constructor
        /// </summary>
        public DBGraphics ()
        {
            _width = 0;
            _height = 0;
            _left = 0;
            _top = 0;
        }

        /// <summary>
        /// Creates double buffer object
        /// </summary>
        /// <param name="g">Window forms Graphics Object</param>
        /// <param name="width">width of paint area</param>
        /// <param name="height">height of paint area</param>
        /// <returns>true/false if double buffer is created</returns>
        public bool CreateDoubleBuffer ( Graphics g, int width, int height, int left = 0, int top = 0 )
        {
            if ( _memoryBitmap != null )
            {
                _memoryBitmap.Dispose();
                _memoryBitmap = null;
            }

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

            if ( width == 0 || height == 0 )
            {
                return false;
            }

            if ( ( width != _width ) || ( height != _height ) )
            {
                _width = width;
                _height = height;
                _left = left;
                _top = top;

                _memoryBitmap = new Bitmap(width, height);
                _graphics = Graphics.FromImage(_memoryBitmap);
            }

            return true;
        }


        /// <summary>
        /// Renders the double buffer to the screen
        /// </summary>
        /// <param name="gr">Window forms Graphics Object</param>
        public void Render ( Graphics gr )
        {
            if ( _memoryBitmap != null )
            {
                gr.DrawImage(_memoryBitmap, new Rectangle(_left, _top, _width, _height), _left, _top, _width, _height, GraphicsUnit.Pixel);
            }
        }

        /// <summary>
        ///
        /// </summary>
        /// <returns>true if double buffering can be achieved</returns>
        public bool CanDoubleBuffer ()
        {
            return _graphics != null;
        }

        /// <summary>
        /// Accessor for memory graphics object
        /// </summary>
        public Graphics g
        {
            get
            {
                return _graphics;
            }
        }
    }
}