Looking for a way to do a Multiline cue banner textbox

Question

I am trying to figure out if it is possible and if anyone knows how to do a multiline version of this Cue Banner(Watermark) textbox. I got the single line version of this working fine but for my project i really need a multiline that will have a paragraph of text in the box at load and when the user clicks the text goes away and as long as they input something in the box it stays gone but if they delete whatever they put in the textbox my paragraph goes back. I hope that makes sense.

Thanks for any replies.

Answer 1

I googled a bit and found a better solution that works for both muli- and singleline textboxes:

// Thank you author of http://nate.deepcreek.org.au/svn/tools/ComskipToCuttermaran/trunk/CSharpControls/GlassTextBox.cs

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

public class CueTextBox : TextBox 
{
    #region Fields
    private Bitmap _bitmap;
    private bool _paintedFirstTime = false;

    const int WM_PAINT = 0x000F;
    const int WM_PRINT = 0x0317;

    const int PRF_CLIENT = 0x00000004;
    const int PRF_ERASEBKGND = 0x00000008;

    private string _cue;
    #endregion

    #region Properties
    public string Cue 
    {
        get { return _cue; }
        set {
            _cue = value;
            Invalidate(true);
        }
    }

    public new BorderStyle BorderStyle 
    {
        get { return base.BorderStyle; }
        set {
            if (_paintedFirstTime)
                SetStyle(ControlStyles.UserPaint, false);
            base.BorderStyle = value;
            if (_paintedFirstTime)
                SetStyle(ControlStyles.UserPaint, true);
        }
    }

    public override bool Multiline 
    {
        get { return base.Multiline; }
        set {
            if (_paintedFirstTime)
                SetStyle(ControlStyles.UserPaint, false);
            base.Multiline = value;
            if (_paintedFirstTime)
                SetStyle(ControlStyles.UserPaint, true);
        }
    }
    #endregion

    #region Constructor
    public CueTextBox()
        : base() 
    {
        SetStyle(ControlStyles.UserPaint, false);
        SetStyle(ControlStyles.AllPaintingInWmPaint, true);
        SetStyle(ControlStyles.DoubleBuffer, true);
    }
    #endregion

    #region Functions
    [DllImport("USER32.DLL", EntryPoint = "SendMessage")]
    public static extern int SendMessage(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam);

    protected override void Dispose(bool disposing) 
    {
        if (_bitmap != null)
            _bitmap.Dispose();

        base.Dispose(disposing);
    }

    protected override void WndProc(ref Message m) 
    {
        if (m.Msg == WM_PAINT) 
        {
            _paintedFirstTime = true;
            CaptureBitmap();
            SetStyle(ControlStyles.UserPaint, true);
            base.WndProc(ref m);
            SetStyle(ControlStyles.UserPaint, false);
            return;
        }

        base.WndProc(ref m);
    }

    private void CaptureBitmap() 
    {
        if (_bitmap != null)
            _bitmap.Dispose();

        _bitmap = new Bitmap(this.ClientRectangle.Width, this.ClientRectangle.Height, PixelFormat.Format32bppArgb);

        using (var graphics = Graphics.FromImage(_bitmap)) 
        {
            int lParam = PRF_CLIENT | PRF_ERASEBKGND;

            System.IntPtr hdc = graphics.GetHdc();
            SendMessage(this.Handle, WM_PRINT, hdc, new IntPtr(lParam));
            graphics.ReleaseHdc(hdc);
        }
    }

    protected override void OnPaint(PaintEventArgs e) 
    {
        SetStyle(ControlStyles.UserPaint, true);
        if (_bitmap == null)
            e.Graphics.FillRectangle(Brushes.CornflowerBlue, ClientRectangle);
        else
            e.Graphics.DrawImageUnscaled(_bitmap, 0, 0);

        if (_cue != null && Text.Length == 0)
            e.Graphics.DrawString(_cue, Font, Brushes.Gray, -1f, 1f);

        SetStyle(ControlStyles.UserPaint, false);
    }

    protected override void OnKeyDown(KeyEventArgs e) 
    {
        base.OnKeyDown(e);
        Invalidate();
    }

    protected override void OnKeyUp(KeyEventArgs e) 
    {
        base.OnKeyUp(e);
        Invalidate();
    }

    protected override void OnMouseDown(MouseEventArgs e)     
    {
        base.OnMouseDown(e);
        Invalidate();
    }

    protected override void OnMouseMove(MouseEventArgs e) 
    {
        base.OnMouseMove(e);
        Invalidate();
    }

    protected override void OnFontChanged(EventArgs e) 
    {
        if (_paintedFirstTime)
            SetStyle(ControlStyles.UserPaint, false);
        base.OnFontChanged(e);
        if (_paintedFirstTime)
            SetStyle(ControlStyles.UserPaint, true);
    }
    #endregion
}

Basically I used the code of GlassTextBox and added a few lines in the OnPaint function to be able to draw the cue.