RICHTEXTBOX NUMÉROTÉ (NUMÉROS DE LIGNES)

/*
 * Numerated RichTextBox
 * Développé par Jérôme Ray le 03.07.2009
 * Basé sur le code de Petr Minarik: http://www.codeproject.com/KB/edit/numberedtextbox.aspx
 * 
 * Ce code peut être réutilisé librement dans n'importe que projet, commercial ou non
 * */

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace NumRichTextBox
{
    public partial class TextEditor : Form
    {
        public TextEditor()
        {
            InitializeComponent();

            SetStyle(ControlStyles.UserPaint, true);
            SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            SetStyle(ControlStyles.DoubleBuffer, true);
            SetStyle(ControlStyles.ResizeRedraw, true);
        }

        public void OpenFile(string filename)
        {
            try
            {
                // Load specified file in the RichTextBox
                this.richTextBox.LoadFile(filename, RichTextBoxStreamType.PlainText);
            }
            catch (Exception)
            {
                // Display error message
                MessageBox.Show("Unable to open specified file!", "Error", MessageBoxButtons.OK, MessageBoxIcon.Error);
                // Close window
                this.Close(); 
            }

        }

        private void DrawLines(Graphics g, int firstLine)
        {
            // Number of text lines
            int linesCount = richTextBox.Lines.Length;

            // Last visible line (used to determine numbers panel width)
            int lastChar = this.richTextBox.GetCharIndexFromPosition(new Point(this.richTextBox.ClientRectangle.Width, this.richTextBox.ClientRectangle.Height));
            int lastLine = this.richTextBox.GetLineFromCharIndex(lastChar);

            // Line numbers layout (position, width)
            int rightMargin = 2, leftMargin = 5, topMargin = 2, bottomMargin = 15, verticalMargin = 2;
            SizeF maxTextSize = g.MeasureString(new string((char)48, lastLine.ToString().Length), this.richTextBox.Font);
            this.panelNum.Width = (int)maxTextSize.Width + leftMargin + rightMargin;

            // Clear existing numbers
            g.Clear(this.panelNum.BackColor);

            // First line name
            int lineNumber = firstLine + 1;

            // Y position for first line number
            int firstLineY = this.richTextBox.GetPositionFromCharIndex(this.richTextBox.GetFirstCharIndexFromLine(firstLine)).Y;
            int lineY = topMargin + firstLineY;

            // Write all visible line numbers
            while (true)
            {
                // Draw line number string
                string lineNumberLabel = lineNumber.ToString().PadLeft(lastLine.ToString().Length);
                g.DrawString(lineNumberLabel, this.richTextBox.Font, Brushes.Black, leftMargin, lineY);

                // Next line
                lineNumber += 1;
                lineY += Font.Height + verticalMargin;

                // End of numeration if and of text content or end of RichTextBox height
                if (lineY > ClientRectangle.Height - bottomMargin || lineNumber > linesCount)
                    break;
            }
        }

        private void panelNum_Paint(object sender, System.Windows.Forms.PaintEventArgs e)
        {
            // Update the line numbers
            int firstChar = this.richTextBox.GetCharIndexFromPosition(new Point(0, 0));
            int firstLine = this.richTextBox.GetLineFromCharIndex(firstChar);

            DrawLines(e.Graphics, firstLine);
        }

        private void richTextBox_SelectionChanged(object sender, System.EventArgs e)
        {
            this.panelNum.Invalidate(); // Request repaint => line numbers update
        }

        private void richTextBox_VScroll(object sender, System.EventArgs e)
        {
            this.panelNum.Invalidate(); // Request repaint => line numbers update
        }

        private void TextEditor_Load(object sender, EventArgs e)
        {
            // Required properties
            this.richTextBox.ScrollBars = RichTextBoxScrollBars.Both;
            this.richTextBox.WordWrap = false;

            // Required events
            this.richTextBox.SelectionChanged += new System.EventHandler(this.richTextBox_SelectionChanged);
            this.richTextBox.VScroll += new System.EventHandler(this.richTextBox_VScroll);
            this.panelNum.Paint += new PaintEventHandler(this.panelNum_Paint);
        }

    }
}