Create Transparent richtextbox C# Windows Forms

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

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public class TransparentRichTextBox : RichTextBox
{
    private const int WS_EX_TRANSPARENT = 0x20;

    [DllImport("user32.dll")]
    private static extern int SetWindowLong(IntPtr hWnd, int nIndex, int dwNewLong);

    [DllImport("user32.dll")]
    private static extern int GetWindowLong(IntPtr hWnd, int nIndex);

    public TransparentRichTextBox()
    {
        SetStyle(
                 ControlStyles.SupportsTransparentBackColor |
                 ControlStyles.AllPaintingInWmPaint |
                 ControlStyles.OptimizedDoubleBuffer, true);
        //SetStyle(ControlStyles.UserPaint, true);
        BackColor = Color.Transparent;
        Font = new Font(Font.FontFamily, 12);
      
    }


    [DllImport("kernel32.dll")]
    private static extern IntPtr LoadLibrary(string lpFileName);
    protected override CreateParams CreateParams
    {
        get
        {
            CreateParams cp = base.CreateParams;
            cp.ExStyle |= 0x20; // WS_EX_TRANSPARENT
            if (LoadLibrary("msftedit.dll") != IntPtr.Zero)
            {
                cp.ClassName = "RICHEDIT50W"; //-----------behave like richtextbox  If you want it to be TextBox change "RICHEDIT50W" to "EDIT"
            }
            else if (LoadLibrary("riched20.dll") != IntPtr.Zero)
            {
                cp.ClassName = "RichEdit20W";
            }
            return cp;
        }
    }

    protected override void OnPaint(PaintEventArgs e)
    {
        base.OnPaint(e);

        // Render text on a transparent background
        using (Brush brush = new SolidBrush(this.ForeColor))
        {
            e.Graphics.DrawString(this.Text, this.Font, brush, 0, 0);
        }
    }
}

 

[Skydiver]

How can lines 54-63 possibly work for a RichTextBox? Recall that a RichTextBox can have multiple runs of text in different colors, fonts, justification, and spacing. Simply calling DrawString() and passing in this.Text is not going to cut it.

(I helped write the original RichEdit 1.0 on which RichEdit 2.0 and later versions were based on. We had over 3000 lines of code for laying out and painting lines. This is why I was curious to see how you did your painting.)