Mouse wheel scrolling Toolstrip menu items

Question

I have some menus that contain many menuitems. Mouse wheel doesn't scroll them. I have to use the keyboard arrows or click the arrows at top and bottom. Is it possible to use the mouse wheel to scroll toolstrip menu items? Thanks

Answer 1

A working solution:

1. Register for MouseWheel event of your form and DropDownClosed event of your root MenuStripItem (here, rootItem) in the Load event of the form

       this.MouseWheel += Form3_MouseWheel;
       rootItem.DropDownOpened += rootItem_DropDownOpened;
       rootItem.DropDownClosed += rootItem_DropDownClosed;
   

2. Add the code for Keyboard class which simulate key presses

   public static class Keyboard
   {
       [DllImport("user32.dll")]
       static extern uint keybd_event(byte bVk, byte bScan, int dwFlags, int dwExtraInfo);
   
   
       const byte VK_UP = 0x26; // Arrow Up key
       const byte VK_DOWN = 0x28; // Arrow Down key
   
       const int KEYEVENTF_EXTENDEDKEY = 0x0001; //Key down flag, the key is going to be pressed
       const int KEYEVENTF_KEYUP = 0x0002; //Key up flag, the key is going to be released
   
       public static void KeyDown()
       {
           keybd_event(VK_DOWN, 0, KEYEVENTF_EXTENDEDKEY, 0);
           keybd_event(VK_DOWN, 0, KEYEVENTF_KEYUP, 0);
       }
   
       public static void KeyUp()
       {
           keybd_event(VK_UP, 0, KEYEVENTF_EXTENDEDKEY, 0);
           keybd_event(VK_UP, 0, KEYEVENTF_KEYUP, 0);
       }
   }
   

3. Add the code for DropDownOpened, DropDownClosed, MouseWheel events:

   bool IsMenuStripOpen  = false;
   
   void rootItem_DropDownOpened(object sender, EventArgs e)
   {
       IsMenuStripOpen = true;
   }
   
   
   void rootItem_DropDownClosed(object sender, EventArgs e)
   {
       IsMenuStripOpen = false;
   }
   
   void Form3_MouseWheel(object sender, MouseEventArgs e)
   {
       if (IsMenuStripOpen)
       {
           if (e.Delta > 0)
           {
               Keyboard.KeyUp();
           }
           else
           {
               Keyboard.KeyDown();
           }
       }
   }
   

Answer 2

You can enable it application wide with this class:

public class DropDownMenuScrollWheelHandler : System.Windows.Forms.IMessageFilter
{
    private static DropDownMenuScrollWheelHandler Instance;
    public static void Enable(bool enabled)
    {
        if (enabled)
        {
            if (Instance == null)
            {
                Instance = new DropDownMenuScrollWheelHandler();
                Application.AddMessageFilter(Instance);
            }
        }
        else
        {
            if (Instance != null)
            {
                Application.RemoveMessageFilter(Instance);
                Instance = null;
            }
        }
    }
    private IntPtr activeHwnd;
    private ToolStripDropDown activeMenu;

    public bool PreFilterMessage(ref Message m)
    {
        if (m.Msg == 0x200 && activeHwnd != m.HWnd) // WM_MOUSEMOVE
        {
            activeHwnd = m.HWnd;
            this.activeMenu = Control.FromHandle(m.HWnd) as ToolStripDropDown;
        }
        else if (m.Msg == 0x20A && this.activeMenu != null) // WM_MOUSEWHEEL
        {
            int delta = (short)(ushort)(((uint)(ulong)m.WParam) >> 16);
            handleDelta(this.activeMenu, delta);
            return true;
        }
        return false;
    }

    private static readonly Action<ToolStrip, int> ScrollInternal
        = (Action<ToolStrip, int>)Delegate.CreateDelegate(typeof(Action<ToolStrip, int>),
            typeof(ToolStrip).GetMethod("ScrollInternal",
                System.Reflection.BindingFlags.NonPublic
                | System.Reflection.BindingFlags.Instance));

    private void handleDelta(ToolStripDropDown ts, int delta)
    {
        if (ts.Items.Count == 0)
            return;
        var firstItem = ts.Items[0];
        var lastItem = ts.Items[ts.Items.Count - 1];
        if (lastItem.Bounds.Bottom < ts.Height && firstItem.Bounds.Top > 0)
            return;
        delta = delta / -4;
        if (delta < 0 && firstItem.Bounds.Top - delta > 9)
        {
            delta = firstItem.Bounds.Top - 9;
        }
        else if (delta > 0 && delta > lastItem.Bounds.Bottom - ts.Height + 9)
        {
            delta = lastItem.Bounds.Bottom - owner.Height + 9;
        }
        if (delta != 0)
            ScrollInternal(ts, delta);
    }
}

Answer 3

This is very simply using a submenu (ToolStripMenuItem) of the context menu :

Assuming using a form1 (or UserControl) and a contextMenuStrip1 :

private void form1_Load( object sender , EventArgs e )
{
    //this.MouseWheel -= When_MouseWheel;
    this.MouseWheel += When_MouseWheel;
}
void When_MouseWheel( object sender , MouseEventArgs e )
{
    if ( this.contextMenuStrip1.IsDropDown ) {
         //this.Focus();
         if ( e.Delta > 0 ) SendKeys.SendWait( "{UP}" );
         else SendKeys.SendWait( "{DOWN}" );         
    }
}

Answer 4

I modified Mohsen Afshin's answer to click the up/down arrows instead of sending up/down key presses. My application had a ContextMenuStrip called menu. Here's the code.

In the initialization:

    menu.VisibleChanged += (s, e) =>
    {
        if (menu.Visible)
        {
            MouseWheel += ScrollMenu;
            menu.MouseWheel += ScrollMenu;
        }
        else
        {
            MouseWheel -= ScrollMenu;
            menu.MouseWheel -= ScrollMenu;
        }
    };

The ScrollMenu function:

[System.Runtime.InteropServices.DllImport("user32.dll")]
private static extern void mouse_event(uint dwFlags, uint dx, uint dy, uint cButtons, uint dwExtraInfo);

private void ScrollMenu(object sender, MouseEventArgs e)
{
    Point origin = Cursor.Position;
    int clicks;

    if (e.Delta < 0)
    {
        Cursor.Position = menu.PointToScreen(new Point(menu.DisplayRectangle.Left + 5, menu.DisplayRectangle.Bottom + 5));
        clicks = e.Delta / -40;
    }
    else
    {
        Cursor.Position = menu.PointToScreen(new Point(menu.DisplayRectangle.Left + 5, menu.DisplayRectangle.Top - 5));
        clicks = e.Delta / 40;
    }

    for (int i = 0; i < clicks; i++)
        mouse_event(0x0006, 0, 0, 0, 0);//Left mouse button up and down on cursor position
    Cursor.Position = origin;
}

I was having trouble getting the mouse_event function to click a specific location, so I moved the cursor, clicked, and then moved the cursor back. It doesn't seem the cleanest, but it works.