Clipz - A Friendly Introduction to the Windows 7 Taskbar Features

using System;
using System.Drawing;
using System.Runtime.InteropServices;
using System.Windows.Forms;
using Clipz.NativeMethods;

namespace Clipz
{
    public class RichTextHost : RichTextBox
    {
        private const double Inch = 14.4; // represents one inch

        public int Print(int charFrom, int charTo, Graphics gr, Rectangle bounds)
        {
            RECT rectToPrint;
            rectToPrint.Top = 0;
            rectToPrint.Bottom = (int)(bounds.Height * Inch);
            rectToPrint.Left = 0;
            rectToPrint.Right = (int)(bounds.Width * Inch);

            RECT rectPage;
            rectPage.Top = 0;
            rectPage.Bottom = (int)(gr.ClipBounds.Height * Inch);
            rectPage.Left = 0;
            rectPage.Right = (int)(gr.ClipBounds.Right * Inch);

            var hdc = gr.GetHdc();
            FORMATRANGE fmtRange;
            fmtRange.chrg.cpMax = charTo;
            fmtRange.chrg.cpMin = charFrom;
            fmtRange.hdc = hdc; 
            fmtRange.hdcTarget = hdc;
            fmtRange.rc = rectToPrint; 
            fmtRange.rcPage = rectPage;

            var res = IntPtr.Zero;
            var wparam = IntPtr.Zero;
            wparam = new IntPtr(1);

            var lparam = IntPtr.Zero;
            lparam = Marshal.AllocCoTaskMem(Marshal.SizeOf(fmtRange));
            Marshal.StructureToPtr(fmtRange, lparam, false);

            // Send the rendered data for 'printing'
            res = User32.SendMessage(Handle, (int)WindowsMessages.EM_FORMATRANGE, wparam, lparam);
            Marshal.FreeCoTaskMem(lparam);
            gr.ReleaseHdc(hdc);
            
            return res.ToInt32();
        }
    }
}