RichTextBox内容写到Graphics

using System;using System.Windows.Forms;using System.Drawing;using System.Runtime.InteropServices;using System.Drawing.Printing;

namespace RichTextBoxPrintCtrl{    public class RichTextBoxPrintCtrl : RichTextBox    {        //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;

        [StructLayout(LayoutKind.Sequential)]        private struct RECT        {            public int Left;            public int Top;            public int Right;            public int Bottom;        }

        [StructLayout(LayoutKind.Sequential)]        private 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)]        private 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)        }

        private const int WM_USER = 0x0400;        private const int EM_FORMATRANGE = WM_USER + 57;

        [DllImport("USER32.dll")]        private static extern IntPtr SendMessage(IntPtr hWnd, int msg, IntPtr wp, IntPtr lp);

        // Render the contents of the RichTextBox for printing        // Return the last character printed + 1 (printing start from this point for next page)        public int Print(int charFrom, int charTo, PrintPageEventArgs e)        {            //Calculate the area to render and print            RECT rectToPrint;            rectToPrint.Top = (int)(e.MarginBounds.Top * anInch);            rectToPrint.Bottom = (int)(e.MarginBounds.Bottom * anInch);            rectToPrint.Left = (int)(e.MarginBounds.Left * anInch);            rectToPrint.Right = (int)(e.MarginBounds.Right * anInch);

            //Calculate the size of the page            RECT rectPage;            rectPage.Top = (int)(e.PageBounds.Top * anInch);            rectPage.Bottom = (int)(e.PageBounds.Bottom * anInch);            rectPage.Left = (int)(e.PageBounds.Left * anInch);            rectPage.Right = (int)(e.PageBounds.Right * anInch);

            IntPtr hdc = e.Graphics.GetHdc();

            FORMATRANGE fmtRange;            fmtRange.chrg.cpMax = charTo;    //Indicate character from to character to             fmtRange.chrg.cpMin = charFrom;            fmtRange.hdc = hdc;                    //Use the same DC for measuring and rendering            fmtRange.hdcTarget = hdc;              //Point at printer hDC            fmtRange.rc = rectToPrint;             //Indicate the area on page to print            fmtRange.rcPage = rectPage;            //Indicate size of page

            IntPtr res = IntPtr.Zero;

            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);

            //Send the rendered data for printing             res = SendMessage(Handle, EM_FORMATRANGE, wparam, lparam);

            //Free the block of memory allocated            Marshal.FreeCoTaskMem(lparam);

            //Release the device context handle obtained by a previous call            e.Graphics.ReleaseHdc(hdc);

            //Return last + 1 character printer            return res.ToInt32();        }

        // Render the contents of the RichTextBox for printing        // Return the last character printed + 1 (printing start from this point for next page)        public int PrintToGraphics(int charFrom, int charTo, Rectangle MarginBounds,Rectangle PageBounds,Graphics g)        {            //Calculate the area to render and print            RECT rectToPrint;            rectToPrint.Top = (int)(MarginBounds.Top * anInch);            rectToPrint.Bottom = (int)(MarginBounds.Bottom * anInch);            rectToPrint.Left = (int)(MarginBounds.Left * anInch);            rectToPrint.Right = (int)(MarginBounds.Right * anInch);

            //Calculate the size of the page            RECT rectPage;            rectPage.Top = (int)(PageBounds.Top * anInch);            rectPage.Bottom = (int)(PageBounds.Bottom * anInch);            rectPage.Left = (int)(PageBounds.Left * anInch);            rectPage.Right = (int)(PageBounds.Right * anInch);

            IntPtr hdc = g.GetHdc();

            FORMATRANGE fmtRange;            fmtRange.chrg.cpMax = charTo;    //Indicate character from to character to             fmtRange.chrg.cpMin = charFrom;            fmtRange.hdc = hdc;                    //Use the same DC for measuring and rendering            fmtRange.hdcTarget = hdc;              //Point at printer hDC            fmtRange.rc = rectToPrint;             //Indicate the area on page to print            fmtRange.rcPage = rectPage;            //Indicate size of page

            IntPtr res = IntPtr.Zero;

            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);

            //Send the rendered data for printing             res = SendMessage(Handle, 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(hdc);

            //Return last + 1 character printer            return res.ToInt32();        }    }}