ToolTipListBox - a list box with tool tips

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• Download demo project - 7 Kb

Introduction

I was working on a project where I needed to have a list-box that would show tool tips for items that will not fit within the width of the list-box. Initially I thought there would be a .NET BCL class that would have this facility. I've had forgettable experiences in the past where I'd waste my time writing something that was already available. But this time I found nothing that met my requirements. So I wrote my own list box class derived from the .NET System.Windows.Forms.ListBox class and called it ToolTipListBox.

What it does

Whenever an item in the ToolTipListBox list-box exceeds the width of the list-box control, a tool-tip is floated just over the item. Tool-tips are floated only for items that won't fit within the width of the list-box. For items that do fit in, the tool-tip will not be shown.

Using it

Simply declare your list-box objects as members of the ToolTipListBox class instead of the standard ListBox class. That's all. You'll also have to include the ToolTipListBox class source file in your project. Or you might even build a library and reference it instead.

Class source listing

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;
using System.Runtime.InteropServices;


public class ToolTipListBox : System.Windows.Forms.ListBox
{
    [StructLayout(LayoutKind.Sequential)]
    public struct SIZE
    {
        public int cx;
        public int cy;
    }
    [DllImport("gdi32.dll")]
    public static extern int GetTextExtentPoint32(IntPtr hdc, 
        String str, int len, ref SIZE size);

    [DllImport("user32.dll")]
    public static extern IntPtr GetDC(IntPtr hWnd);

    [DllImport("user32.dll")]
    public static extern int ReleaseDC(IntPtr hWnd,IntPtr hdc);


    public ToolTipListBox()
    {           
        tp.InitialDelay = 500;
        tp.ReshowDelay = 500;
        tp.AutoPopDelay = 3000;         
        tp.Active = true;           
    }   


    protected override void OnMouseMove(
        System.Windows.Forms.MouseEventArgs e)
    {               
        /* Get the index of the mouse-hovered item */
        int index = IndexFromPoint(e.X,e.Y);

        /* Ensure that there is an item */
        if(index != ListBox.NoMatches )
        {               
            /* 
              Check if the mouse has moved enough
              distance for a new index 
            */
            if( LastIndex != index )
            {
                string s = Items[index].ToString(); 

                /* Get the text extent */
                IntPtr hdc = GetDC(this.Handle);
                SIZE size;
                size.cx = 0;
                size.cy = 0;
                GetTextExtentPoint32(hdc,s,s.Length,ref size);
                ReleaseDC(this.Handle,hdc);

                /* If it won't fit show tool-tip */
                if(this.Width < size.cx)                    
                    tp.SetToolTip(this,s);

                LastIndex = index;              
            }                           
        }
    }

    private ToolTip tp = new ToolTip();
    private int LastIndex = -1;

}