[Bug 38759] WM_USER (and +1, +2) are being sent to application windows

https://bugs.winehq.org/show_bug.cgi?id=38759

--- Comment #2 from Jason  ---
Hi Nikolay,

I'm glad you asked, as I realised I'm running Win-MONO on WINE for this
software, so I should test that on Windows with MONO instead of making
assumptions about WINE...  It also fails there too, so it's a MONO bug, not a
WINE bug.

Anyway, this is a standard C# winforms project that shows the issue when the
mouse passes over the window.

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

namespace TestWine
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

public const int WM_USER = 0x0400;

protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case WM_USER:
                case WM_USER + 1:
                case WM_USER + 2:
                    MessageBox.Show("Ouch! Msg=" + m.Msg);
                    break;

default:
                    break;
            }
            base.WndProc(ref m);
        }
    }
}

Sorry for the bogus bug report,
Jason.