TextHelper.cs

using System;
using System.Drawing;
using System.Runtime.InteropServices;
 
namespace be.gaudry.model
{
    public class TextHelper
    {
        public enum KEY 
        {
            CANCEL = 0x03,
            BACK = 0x08,
            TAB = 0x09,
            CLEAR = 0x0C,
            RETURN = 0x0D,
            SHIFT = 0x10,
            CONTROL = 0x11,
            ALT = 0x12,
            PAUSE = 0x13
        };
        #region key values info
        /*
        VK_LBUTTON        = 0x01,
		VK_RBUTTON        = 0x02,
		VK_CANCEL         = 0x03,
		VK_MBUTTON        = 0x04 ,   // NOT contiguous with L & RBUTTON
		VK_BACK           = 0x08,
		VK_TAB            = 0x09,
		VK_CLEAR          = 0x0C,
		VK_RETURN         = 0x0D,
		VK_SHIFT          = 0x10,
		VK_CONTROL        = 0x11,
		VK_MENU           = 0x12,
		VK_PAUSE          = 0x13,
		VK_CAPITAL        = 0x14,
		VK_KANA           = 0x15,
		VK_HANGEUL        = 0x15, // old name - should be here for compatibility 
		VK_HANGUL         = 0x15,
		VK_JUNJA          = 0x17,
		VK_FINAL          = 0x18,
		VK_HANJA          = 0x19,
		VK_KANJI          = 0x19,
		VK_ESCAPE         = 0x1B,
		VK_CONVERT        = 0x1C,
		VK_NONCONVERT     = 0x1D,
		VK_ACCEPT         = 0x1E,
		VK_MODECHANGE     = 0x1F,
		VK_SPACE          = 0x20,
		VK_PRIOR          = 0x21,
		VK_NEXT           = 0x22,
		VK_END            = 0x23,
		VK_HOME           = 0x24,
		VK_LEFT           = 0x25,
		VK_UP             = 0x26,
		VK_RIGHT          = 0x27,
		VK_DOWN           = 0x28,
		VK_SELECT         = 0x29,
		VK_PRINT          = 0x2A,
		VK_EXECUTE        = 0x2B,
		VK_SNAPSHOT       = 0x2C,
		VK_INSERT         = 0x2D,
		VK_DELETE         = 0x2E,
		VK_HELP           = 0x2F,
 
		VK_0			  = 0x30,
		VK_1			  = 0x31,
		VK_2			  = 0x32,
		VK_3			  = 0x33,
		VK_4			  = 0x34,
		VK_5			  = 0x35,
		VK_6			  = 0x36,
		VK_7			  = 0x37,
		VK_8			  = 0x38,
		VK_9			  = 0x39,
 
		VK_A			  = 0x41,
		VK_B			  = 0x42,
		VK_C			  = 0x43,
		VK_D			  = 0x44,
		VK_E			  = 0x45,
		VK_F			  = 0x46,
		VK_G			  = 0x47,
		VK_H			  = 0x48,
		VK_I			  = 0x49,
		VK_J			  = 0x4A,
		VK_K			  = 0x4B,
		VK_L			  = 0x4C,
		VK_M			  = 0x4D,
		VK_N			  = 0x4E,
		VK_O			  = 0x4F,
		VK_P			  = 0x50,
		VK_Q			  = 0x51,
		VK_R			  = 0x52,
		VK_S			  = 0x53,
		VK_T			  = 0x54,
		VK_U			  = 0x55,
		VK_V			  = 0x56,
		VK_W			  = 0x57,
		VK_X			  = 0x58,
		VK_Y			  = 0x59,
		VK_Z			  = 0x5A,
 
		VK_LWIN           = 0x5B,
		VK_RWIN           = 0x5C,
		VK_APPS           = 0x5D,
		VK_SLEEP          = 0x5F,
		VK_NUMPAD0        = 0x60,
		VK_NUMPAD1        = 0x61,
		VK_NUMPAD2        = 0x62,
		VK_NUMPAD3        = 0x63,
		VK_NUMPAD4        = 0x64,
		VK_NUMPAD5        = 0x65,
		VK_NUMPAD6        = 0x66,
		VK_NUMPAD7        = 0x67,
		VK_NUMPAD8        = 0x68,
		VK_NUMPAD9        = 0x69,
		VK_MULTIPLY       = 0x6A,
		VK_ADD            = 0x6B,
		VK_SEPARATOR      = 0x6C,
		VK_SUBTRACT       = 0x6D,
		VK_DECIMAL        = 0x6E,
		VK_DIVIDE         = 0x6F,
		VK_F1             = 0x70,
		VK_F2             = 0x71,
		VK_F3             = 0x72,
		VK_F4             = 0x73,
		VK_F5             = 0x74,
		VK_F6             = 0x75,
		VK_F7             = 0x76,
		VK_F8             = 0x77,
		VK_F9             = 0x78,
		VK_F10            = 0x79,
		VK_F11            = 0x7A,
		VK_F12            = 0x7B,
		VK_F13            = 0x7C,
		VK_F14            = 0x7D,
		VK_F15            = 0x7E,
		VK_F16            = 0x7F,
		VK_F17            = 0x80,
		VK_F18            = 0x81,
		VK_F19            = 0x82,
		VK_F20            = 0x83,
		VK_F21            = 0x84,
		VK_F22            = 0x85,
		VK_F23            = 0x86,
		VK_F24            = 0x87,
		VK_NUMLOCK        = 0x90,
		VK_SCROLL         = 0x91,
		VK_OEM_NEC_EQUAL  = 0x92,   // '=' key on numpad
		VK_OEM_FJ_JISHO   = 0x92,   // 'Dictionary' key
		VK_OEM_FJ_MASSHOU = 0x93,   // 'Unregister word' key
		VK_OEM_FJ_TOUROKU = 0x94,   // 'Register word' key
		VK_OEM_FJ_LOYA    = 0x95,   // 'Left OYAYUBI' key
		VK_OEM_FJ_ROYA    = 0x96,   // 'Right OYAYUBI' key
		VK_LSHIFT         = 0xA0,
		VK_RSHIFT         = 0xA1,
		VK_LCONTROL       = 0xA2,
		VK_RCONTROL       = 0xA3,
		VK_LMENU          = 0xA4,
		VK_RMENU          = 0xA5,
 
		VK_OEM_1          = 0xBA,   // ';:' for US
		VK_OEM_PLUS       = 0xBB,   // '+' any country
		VK_OEM_COMMA      = 0xBC,   // ',' any country
		VK_OEM_MINUS      = 0xBD,   // '-' any country
		VK_OEM_PERIOD     = 0xBE,   // '.' any country
		VK_OEM_2          = 0xBF,   // '/?' for US
		VK_OEM_3          = 0xC0,   // '`~' for US
 
		VK_ATTN           = 0xF6,
		VK_CRSEL          = 0xF7,
		VK_EXSEL          = 0xF8,
		VK_EREOF          = 0xF9,
		VK_PLAY           = 0xFA,
		VK_ZOOM           = 0xFB,
		VK_NONAME         = 0xFC,
		VK_PA1            = 0xFD,
		VK_OEM_CLEAR      = 0xFE
        */
 
        #endregion
 
        #region Unmanaged Code
        [DllImport("user32", CharSet = CharSet.Auto, EntryPoint = "SendMessage")]
        private extern static int SendMessageInt(
           IntPtr handle,
           int msg,
           int wParam,
           int lParam
           );
        private const int EM_LINEINDEX = 0x00BB;
        private const int EM_POSFROMCHAR = 0x00D6;
        private const int EM_CHARFROMPOS = 0x00D7;
 
        [DllImport("user32")]
        private static extern int GetKeyState(KEY key);
 
        #endregion
 
        public static bool isKeyDown(KEY key)
        {
            return (((int)GetKeyState(key)) & 0x8000) == 0x8000;
        }
 
        /// <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>(int) index of the character under the specified 
        /// point in the control</returns>
        public static int CharFromPos(
           System.Windows.Forms.TextBox 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 = SendMessageInt(txt.Handle, EM_CHARFROMPOS, 0, xy);
                // 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 = SendMessageInt(txt.Handle, EM_LINEINDEX,
                 lineNumber, 0);
                // 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>
        public static Point PosFromChar(
           System.Windows.Forms.TextBox txt,
           int charIndex
           )
        {
            unchecked
            {
                int xy = SendMessageInt(txt.Handle, EM_POSFROMCHAR, charIndex, 0);
                return new Point(xy);
            }
        }
 
        // private constructor, methods are static
        private TextHelper()
        {
            // intentionally left blank
        }
    }
}