Winforms - Adjust width of vertical scrollbar on CheckedListBox

Question

I have a CheckListBox on my form but I want to make the scrollbar wider as users are using touch screens not a mouse.

How can I change the scroll bar width?

Answer 1

To change the physical size of the scrollbar, see this.

This came from the following page: Horizontal Scrollbar in ListBox. I modified it for Winforms and it worked for me:

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

namespace CheckedListBoxScrollBarsWidth
{
   public partial class Form1 : Form
   {
      const int LB_GETHORIZONTALEXTENT = 0x0193;
      const int LB_SETHORIZONTALEXTENT = 0x0194;

      const long WS_HSCROLL = 0x00100000L;

      const int SWP_FRAMECHANGED = 0x0020;
      const int SWP_NOMOVE = 0x0002;
      const int SWP_NOSIZE = 0x0001;
      const int SWP_NOZORDER = 0x0004;

      const int GWL_STYLE = (-16);    

      public Form1()
      {
         InitializeComponent();
         checkedListBox1.HorizontalScrollbar = true;
         AddStyle(checkedListBox1.Handle, (uint)WS_HSCROLL);
         SendMessage(checkedListBox1.Handle, LB_SETHORIZONTALEXTENT, 1000, 0);
      }

      [DllImport("user32.dll")]
      static extern int SendMessage(IntPtr hwnd, int msg, int wParam, int lParam);

      [DllImport("user32.dll")]
      static extern uint GetWindowLong(IntPtr hwnd, int index);

      [DllImport("user32.dll")]
      static extern void SetWindowLong(IntPtr hwnd, int index, uint value);

      [DllImport("user32.dll")]
      static extern bool SetWindowPos(IntPtr hWnd, IntPtr hWndInsertAfter, int X,
            int Y, int cx, int cy, uint uFlags);


      private void AddStyle(IntPtr handle, uint addStyle)
      {
         // Get current window style
         uint windowStyle = GetWindowLong(handle, GWL_STYLE);

         // Modify style
         SetWindowLong(handle, GWL_STYLE, windowStyle | addStyle);

         // Let the window know of the changes
         SetWindowPos(handle, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOZORDER | SWP_NOSIZE | SWP_FRAMECHANGED);
      }
   }
}

Answer 2

The following code makes use of SPI_SETNONCLIENTMETRICS to change the system wide setting for the scrollbar width. NOTE that it will change all applications on the system not just a single one. You should probably make this a configuration item so that you can change the width back to a default if you need to.

 [DllImport("user32", CharSet = CharSet.Auto)]
    private static extern int SystemParametersInfo(int uAction, int uParam, ref NONCLIENTMETRICS lpvParam, int fuWinIni);

    private const int LF_FACESIZE = 32;

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
    private struct LOGFONT
    {
        public int lfHeight;
        public int lfWidth;
        public int lfEscapement;
        public int lfOrientation;
        public int lfWeight;
        public byte lfItalic;
        public byte lfUnderline;
        public byte lfStrikeOut;
        public byte lfCharSet;
        public byte lfOutPrecision;
        public byte lfClipPrecision;
        public byte lfQuality;
        public byte lfPitchAndFamily;

        /// <summary>
        /// <see cref="UnmanagedType.ByValTStr"/> means that the string
        /// should be marshalled as an array of TCHAR embedded in the
        /// structure.  This implies that the font names can be no larger
        /// than <see cref="LF_FACESIZE"/> including the terminating '\0'.
        /// That works out to 31 characters.
        /// </summary>
        [MarshalAs(UnmanagedType.ByValTStr, SizeConst = LF_FACESIZE)]
        public string lfFaceName;

        // to shut it up about the warnings
        public LOGFONT(string lfFaceName)
        {
            this.lfFaceName = lfFaceName;
            lfHeight = lfWidth = lfEscapement = lfOrientation = lfWeight = 0;
            lfItalic = lfUnderline = lfStrikeOut = lfCharSet = lfOutPrecision
            = lfClipPrecision = lfQuality = lfPitchAndFamily = 0;
        }
    }

    private struct NONCLIENTMETRICS
    {
        public int cbSize;
        public int iBorderWidth;
        public int iScrollWidth;
        public int iScrollHeight;
        public int iCaptionWidth;
        public int iCaptionHeight;
        /// <summary>
        /// Since <see cref="LOGFONT"/> is a struct instead of a class,
        /// we don't have to do any special marshalling here.  Much
        /// simpler this way.
        /// </summary>
        public LOGFONT lfCaptionFont;
        public int iSMCaptionWidth;
        public int iSMCaptionHeight;
        public LOGFONT lfSMCaptionFont;
        public int iMenuWidth;
        public int iMenuHeight;
        public LOGFONT lfMenuFont;
        public LOGFONT lfStatusFont;
        public LOGFONT lfMessageFont;
    }

    private const int SPI_GETNONCLIENTMETRICS = 41;
    private const int SPI_SETNONCLIENTMETRICS = 42;
    private const int SPIF_SENDCHANGE = 2;

You can then use this code to see the current value for the scrollbar width

NONCLIENTMETRICS metrics = new NONCLIENTMETRICS();
metrics.cbSize = Marshal.SizeOf(metrics);
SystemParametersInfo(SPI_GETNONCLIENTMETRICS, 0, ref metrics, 0);

MessageBox.Show(metrics.iScrollWidth.ToString());

You can then use this code to change the size of the scrollbar...

NONCLIENTMETRICS metrics = new NONCLIENTMETRICS();
metrics.cbSize = Marshal.SizeOf(metrics);

metrics.iScrollWidth = 17;

SystemParametersInfo(SPI_SETNONCLIENTMETRICS, metrics.cbSize, ref metrics, SPIF_SENDCHANGE);

Answer 3

You can only do that by creating a custom CLB control and overriding the OnPaint event.

Edit: Ok, still very basic, but this article on CodeProject might help you: http://www.codeproject.com/KB/miscctrl/cutebutton.aspx

Edit 2: You might like the following example of a customized scrollbar: http://www.codeproject.com/KB/miscctrl/MotifScrollBars.aspx