C#Tips3------DrawrichtextlikeRichTextBox

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C# Code:

   
using System;
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.Windows.Forms;
  
public static class GraphicDrawRtfText
{
    private static RichTextBoxDrawer rtfDrawer;
  
  
    public static void DrawRtfText(Graphics graphics, string rtf, Rectangle layoutArea, Rectangle targetArea)
    {
        if (rtfDrawer == null)
        {
            rtfDrawer = new RichTextBoxDrawer();
        }
        rtfDrawer.Rtf = rtf;
        rtfDrawer.Draw(graphics, layoutArea, targetArea);
    }
  
  
    private class RichTextBoxDrawer : RichTextBox
    {
        //Code converted from code found here: http://support.microsoft.com/kb/812425/en-us
  
        //Convert the unit used by the .NET framework (1/100 inch) 
        //and the unit used by Win32 API calls (twips 1/1440 inch)
        private const double anInch = 14.4;
  
        protected override CreateParams CreateParams
        {
            get
            {
                CreateParams createParams = base.CreateParams;
                if (SafeNativeMethods.LoadLibrary("msftedit.dll") != IntPtr.Zero)
                {
                    createParams.ExStyle |= SafeNativeMethods.WS_EX_TRANSPARENT; // transparent
                    createParams.ClassName = "RICHEDIT50W";
                }
                return createParams;
            }
        }
  
  
        public void Draw(Graphics graphics, RectangleF layoutArea, RectangleF targetArea)
        {
            //Calculate the area to render.
            SafeNativeMethods.RECT rectLayoutArea;
            rectLayoutArea.Top = (int) (0*anInch);
            rectLayoutArea.Bottom = (int) (targetArea.Bottom*anInch);
            rectLayoutArea.Left = (int) (0*anInch);
            rectLayoutArea.Right = (int) (targetArea.Right*anInch);
  
  
            Bitmap Bmp = new Bitmap((int) layoutArea.Width,
                                    (int) layoutArea.Height, PixelFormat.Format32bppArgb);
  
  
            Graphics g = Graphics.FromImage(Bmp);
            IntPtr hdc = g.GetHdc();
  
            //create a metafile, convert the size to himetrics
            //Metafile metafile = new Metafile(hdc, new
            //RectangleF(0, 0, layoutArea.Width * 26, layoutArea.Height * 26));
  
            Metafile metafile = new Metafile(hdc, new
                                                      RectangleF(0, 0, layoutArea.Width, layoutArea.Height),
                                             MetafileFrameUnit.Pixel);
            g.ReleaseHdc(hdc);
            g.Dispose();
  
            g = Graphics.FromImage(metafile);
            IntPtr hDCEMF = g.GetHdc();
  
            SafeNativeMethods.FORMATRANGE fmtRange;
            fmtRange.chrg.cpMax = -1; //Indicate character from to character to
            fmtRange.chrg.cpMin = 0;
            fmtRange.hdc = hDCEMF; //Use the same DC for measuring and rendering
            fmtRange.hdcTarget = hDCEMF; //Point at printer hDC
            fmtRange.rc = rectLayoutArea; //Indicate the area on page  to print
            fmtRange.rcPage = rectLayoutArea; //Indicate size of page
  
            IntPtr wParam = IntPtr.Zero;
            wParam = new IntPtr(1);
  
            //Get the pointer to the FORMATRANGE structure in memory
            IntPtr lParam = IntPtr.Zero;
            lParam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
            Marshal.StructureToPtr(fmtRange, lParam, false);
  
            SafeNativeMethods.SendMessage(Handle,
                                          SafeNativeMethods.EM_FORMATRANGE, wParam, lParam);
  
            //Free the block of memory allocated
            Marshal.FreeCoTaskMem(lParam);
  
            //Release the device context handle obtained by a previous call
            g.ReleaseHdc(hDCEMF);
            g.Dispose();
  
  
            graphics.DrawImage(metafile, layoutArea.Location);
        }
  
        #region SafeNativeMethods
  
        private static class SafeNativeMethods
        {
            [DllImport("USER32.dll")]
            public static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);
  
            [DllImport("kernel32.dll", CharSet = CharSet.Auto)]
            public static extern IntPtr LoadLibrary(string lpFileName);
  
            [StructLayout(LayoutKind.Sequential)]
            public struct RECT
            {
                public int Left;
                public int Top;
                public int Right;
                public int Bottom;
            }
  
            [StructLayout(LayoutKind.Sequential)]
            public struct CHARRANGE
            {
                public int cpMin; //First character of range (0 for start of doc)
                public int cpMax; //Last character of range (-1 for end of doc)
            }
  
            [StructLayout(LayoutKind.Sequential)]
            public struct FORMATRANGE
            {
                public IntPtr hdc; //Actual DC to draw on
                public IntPtr hdcTarget; //Target DC for determining text formatting
                public RECT rc; //Region of the DC to draw to (in twips)
                public RECT rcPage; //Region of the whole DC (page size) (in twips)
                public CHARRANGE chrg; //Range of text to draw (see earlier declaration)
            }
  
            public const int WM_USER = 0x0400;
            public const int EM_FORMATRANGE = WM_USER + 57;
            public const int WS_EX_TRANSPARENT = 0x20;
       
        }
  
        #endregion
    }
}