Extending RichTextBox - Issues with UserPaint=true

[steve4king]

I've been fighting with this for a while now.
I wanted to add a nullValueDisplay string to a TextBox. (among other things) This way if the field is empty, it will say "(null)".
Simple right?

Well the problem is, in .net 3.5(and I don't know how long prior) TextBox does not use OnPrint by default. It uses some other inaccessible draw method.

Forcing:

SetStyle(System.Windows.Forms.ControlStyles.UserPaint, true);

causes OnPaint to fire, but results in flickering at best.. at worst, the contents of the control do not appear at all.

 SetStyle(ControlStyles.AllPaintingInWmPaint, true);

did not resolve the problem.

I found that RichTextBox did not have this issue, so I extended that as well with all of my new features. Problem solved right?!

Well.. not so much because now I need to figure out a more accurate method for calculating the field length(in pixels). Worse than that is that the cursor ends up in the wrong position. Usually half, to a full character behind, but potentially in-front of the text being typed. (So while the cursor is actually at the end of the word it will draw like this, "Grandma and Grand|pa")

Anyone dealt with these issues before?
Here's a snippet of my code:

public class RichTextBoxExt : RichTextBox
    {
        #region private variables
        private bool bFlow = false;
        private bool bAutoSize = false;

        private string sNullDisplayText = "";

        #endregion

        

        #region Public properties
        /// <summary>
        /// Text to display if the field is null.
        /// </summary>
        [Browsable(true)]
        public virtual string NullDisplayText
        {
            get { return sNullDisplayText; }
            set { sNullDisplayText = value; }
        }

        public RichTextBoxExt()
            : base()
        {
            //SetStyle(ControlStyles.AllPaintingInWmPaint, true);
            SetStyle(System.Windows.Forms.ControlStyles.UserPaint, true);
        }

        protected override void OnPaint(PaintEventArgs e)
        {
            //base.OnPaint(e);
            if (string.IsNullOrEmpty(this.Text) && !string.IsNullOrEmpty(sNullDisplayText))
            {
                e.Graphics.DrawString(sNullDisplayText, this.Font, new System.Drawing.SolidBrush(System.Drawing.Color.LightGray), this.ClientRectangle);
            }
            else
            {
                e.Graphics.DrawString(this.Text, this.Font, new System.Drawing.SolidBrush(System.Drawing.Color.Black), this.ClientRectangle);
            }
        }

    }