NHunspell Component for Visual Studio

using System;
using System.Drawing;
using System.Windows.Forms;

namespace NHunspellComponent.SupportClasses
{
   public class TextBoxAPIHelper
   {
      private const double anInch = 14.4;

      public static int GetBaselineOffsetAtCharIndex(System.Windows.Forms.TextBoxBase tb, int index)
      {
         System.Windows.Forms.RichTextBox rtb = tb as RichTextBox;
         if (rtb == null)
         {
            return tb.Font.Height;
         }

         int lineNumber = rtb.GetLineFromCharIndex(index);
         int lineIndex =
            NativeMethods.SendMessageInt(rtb.Handle, NativeMethods.EM_LINEINDEX, new IntPtr(lineNumber), IntPtr.Zero).
               ToInt32();
         int lineLength =
            NativeMethods.SendMessageInt(rtb.Handle, NativeMethods.EM_LINELENGTH, new IntPtr(lineNumber), IntPtr.Zero).
               ToInt32();


         NativeMethods.CHARRANGE charRange;
         charRange.cpMin = lineIndex;
         charRange.cpMax = lineIndex + lineLength;
         //			charRange.cpMin = index; 
         //			charRange.cpMax = index + 1; 


         NativeMethods.RECT rect;
         rect.Top = 0;
         rect.Bottom = (int) anInch;
         rect.Left = 0;
         rect.Right = 10000000; //(int)(rtb.Width * anInch + 20); 


         NativeMethods.RECT rectPage;
         rectPage.Top = 0;
         rectPage.Bottom = (int) anInch;
         rectPage.Left = 0;
         rectPage.Right = 10000000; //(int)(rtb.Width * anInch + 20); 

         Graphics canvas = Graphics.FromHwnd(rtb.Handle);
         IntPtr canvasHdc = canvas.GetHdc();

         NativeMethods.FORMATRANGE formatRange;
         formatRange.chrg = charRange;
         formatRange.hdc = canvasHdc;
         formatRange.hdcTarget = canvasHdc;
         formatRange.rc = rect;
         formatRange.rcPage = rectPage;

         NativeMethods.SendMessage(rtb.Handle, NativeMethods.EM_FORMATRANGE, IntPtr.Zero, ref formatRange).ToInt32();

         canvas.ReleaseHdc(canvasHdc);
         canvas.Dispose();

         return (int) ((formatRange.rc.Bottom - formatRange.rc.Top)/anInch);
      }

      /// <summary>
      /// Returns the index of the character under the specified 
      /// point in the control, or the nearest character if there
      /// is no character under the point.
      /// </summary>
      /// <param name="txt">The text box control to check.</param>
      /// <param name="pt">The point to find the character for, 
      /// specified relative to the client area of the text box.</param>
      /// <returns></returns>
      internal static int CharFromPos(System.Windows.Forms.TextBoxBase txt, Point pt)
      {
         unchecked
         {
            // Convert the point into a DWord with horizontal position
            // in the loword and vertical position in the hiword:
            int xy = (pt.X & 0xFFFF) + ((pt.Y & 0xFFFF) << 16);
            // Get the position from the text box.
            int res =
               NativeMethods.SendMessageInt(txt.Handle, NativeMethods.EM_CHARFROMPOS, IntPtr.Zero, new IntPtr(xy)).
                  ToInt32();
            // the Platform SDK appears to be incorrect on this matter.
            // the hiword is the line number and the loword is the index
            // of the character on this line
            int lineNumber = ((res & 0xFFFF) >> 16);
            int charIndex = (res & 0xFFFF);

            // Find the index of the first character on the line within 
            // the control:
            int lineStartIndex = NativeMethods.SendMessageInt(txt.Handle, NativeMethods.EM_LINEINDEX,
                                                              new IntPtr(lineNumber), IntPtr.Zero).ToInt32();
            // Return the combined index:
            return lineStartIndex + charIndex;
         }
      }

      /// <summary>
      /// Returns the position of the specified character
      /// </summary>
      /// <param name="txt">The text box to find the character in.</param>
      /// <param name="charIndex">The index of the character whose
      /// position needs to be found.</param>
      /// <returns>The position of the character relative to the client
      /// area of the control.</returns>
      internal static Point PosFromChar(System.Windows.Forms.TextBoxBase txt, int charIndex)
      {
         unchecked
         {
            int xy =
               NativeMethods.SendMessageInt(txt.Handle, NativeMethods.EM_POSFROMCHAR, new IntPtr(charIndex), IntPtr.Zero)
                  .ToInt32();
            return new Point(xy);
         }
      }

      internal static int GetFirstVisibleLine(System.Windows.Forms.TextBoxBase txt)
      {
         return
            NativeMethods.SendMessageInt(txt.Handle, NativeMethods.EM_GETFIRSTVISIBLELINE, IntPtr.Zero, IntPtr.Zero).
               ToInt32();
      }

      // private constructor, methods are static
      private TextBoxAPIHelper()
      {
         // intentionally left blank
      }
   }
}

/*internal static int GetTextWidthAtCharIndex(System.Windows.Forms.TextBoxBase tb, int index, int length)
    {
       System.Windows.Forms.RichTextBox rtb = tb as RichTextBox;

       //TODO!
       if (rtb == null) { return tb.Font.Height; }

       NativeMethods.CHARRANGE charRange;
       charRange.cpMin = index;
       charRange.cpMax = index + length;

       NativeMethods.RECT rect;
       rect.Top = 0;
       rect.Bottom = (int)anInch;
       rect.Left = 0;
       rect.Right = (int)(rtb.ClientSize.Width * anInch);

       NativeMethods.RECT rectPage;
       rectPage.Top = 0;
       rectPage.Bottom = (int)anInch;
       rectPage.Left = 0;
       rectPage.Right = (int)(rtb.ClientSize.Width * anInch);

       Graphics canvas = Graphics.FromHwnd(rtb.Handle);
       IntPtr canvasHdc = canvas.GetHdc();

       NativeMethods.FORMATRANGE formatRange;
       formatRange.chrg = charRange;
       formatRange.hdc = canvasHdc;
       formatRange.hdcTarget = canvasHdc;
       formatRange.rc = rect;
       formatRange.rcPage = rectPage;

       NativeMethods.SendMessage(rtb.Handle, NativeMethods.EM_FORMATRANGE, IntPtr.Zero, ref formatRange);

       canvas.ReleaseHdc(canvasHdc);
       canvas.Dispose();

       return (int)((formatRange.rc.Right - formatRange.rc.Left) / anInch);

    }
*/


/*
      /// <summary>
      /// Attempts to make the caret visible in a TextBox control.
      /// This will not always succeed since the TextBox control
      /// appears to destroy its caret fairly frequently.
      /// </summary>
      /// <param name="txt">The text box to show the caret in.</param>
      internal static void ShowCaret(System.Windows.Forms.TextBox txt)
      {
         bool ret = false;
         int iter = 0;
         while (!ret && iter < 10)
         {
            ret = NativeMethods.ShowCaretAPI(txt.Handle);
            iter++;
         }
      }
*/

/*
      }
*/

/*
      internal static int GetLineIndex(TextBoxBase txt, int line)
      {
         return NativeMethods.SendMessageInt(txt.Handle, 0xbb, new IntPtr(line), IntPtr.Zero).ToInt32();
      }
 */