Send MouseWheel messages to System.Windows.Forms.WebBrowser - winforms

Question

I wanted to forward MouseWheel events produced at the form level, so that they would be processed by an embedded WebBrowser control, even when that control didn't have the focus.
Here is what I have done:
Implemented IMessageFilter.PreFilterMessage.
Registered the filter it with Application.AddMessageFilter.
In the filter, listen for WM_MOUSEWHEEL messages.
Forward the messages using SendMessage to the target control (in my case WebBrowser).
In code, this looks like this:
bool IMessageFilter.PreFilterMessage(ref Message m)
{
if (m.Msg == 0x20A) // WM_MOUSEWHEEL
{
if (this.target != null)
{
var handle = this.target.Handle;
Native.SendMessage (handle, m.Message, m.WParam, m.LParam);
return true;
}
}
return false;
}
// Registering the message filter:
System.Windows.Forms.Application.AddMessageFilter (this);
// Win32 code:
protected static class NativeMethods
{
[System.Runtime.InteropServices.DllImport ("user32.dll")]
public static extern System.IntPtr SendMessage(System.IntPtr hWnd, System.Int32 Msg, System.IntPtr wParam, System.IntPtr lParam);
}
This does not work. Nothing happens.
However, if instead of a WebBrowser I specify a Panel as the target, then this works wonderfully well.

Answer 1

Pierre's answer works for me (can't up vote as not enough reputation). However, it requires a tweak to work in VB.NET so I thought I'd post in case there's anyone stuck on this point:
Imports System.Runtime.InteropServices
Public Class Form1 Implements IMessageFilter
Public Sub New()
' This call is required by the designer.
InitializeComponent()
' Add any initialization after the InitializeComponent() call.
System.Windows.Forms.Application.AddMessageFilter(Me)
End Sub
Private Sub Form1_Load(sender As Object, e As EventArgs) Handles Me.Load
Me.WebBrowser1.Navigate("D:\Development\test3.html")
End Sub
Private Function IMessageFilter_PreFilterMessage(ByRef m As Message) As Boolean Implements IMessageFilter.PreFilterMessage
If m.Msg = &H20A Then
' WM_MOUSEWHEEL
If m.HWnd <> 0 Then
Dim handle = m.HWnd
handle = NativeMethods.FindWindowEx(handle, IntPtr.Zero, "Shell Embedding", Nothing)
handle = NativeMethods.FindWindowEx(handle, IntPtr.Zero, "Shell DocObject View", Nothing)
handle = NativeMethods.FindWindowEx(handle, IntPtr.Zero, "Internet Explorer_Server", Nothing)
NativeMethods.SendMessage(handle, m.Msg, m.WParam, m.LParam)
Return True
End If
End If
Return False
End Function
Protected NotInheritable Class NativeMethods
Private Sub New()
End Sub
<System.Runtime.InteropServices.DllImport("user32.dll")> _
Public Shared Function SendMessage(hWnd As System.IntPtr, Msg As System.Int32, wParam As System.IntPtr, lParam As System.IntPtr) As System.IntPtr
End Function
<System.Runtime.InteropServices.DllImport("user32.dll")> _
Public Shared Function FindWindowEx(hwndParent As System.IntPtr, hwndChildAfter As System.IntPtr, className As String, windowName As String) As System.IntPtr
End Function
End Class
End Class

Answer 2

Investigating with Spy++ revealed that the WebBrowser control in WinForms is using several layers of containers to wrap the real IE component:
System.Windows.Forms.WebBrowser
Shell Embedding
Shell DocObject View
Internet Explorer_Server
Sending the events to any container won't have any effect. The WM_MOUSEWHEEL events have to be sent to the Internet Explorer_Server handle in order for this to work.
Here is the modified code, which finds the IE component by digging into the containers:
bool IMessageFilter.PreFilterMessage(ref Message m)
{
if (m.Msg == 0x20A) // WM_MOUSEWHEEL
{
if (this.target != null)
{
var handle = this.target.Handle;
handle = NativeMethods.FindWindowEx (handle, IntPtr.Zero, "Shell Embedding", null);
handle = NativeMethods.FindWindowEx (handle, IntPtr.Zero, "Shell DocObject View", null);
handle = NativeMethods.FindWindowEx (handle, IntPtr.Zero, "Internet Explorer_Server", null);
Native.SendMessage (handle, m.Msg, m.WParam, m.LParam);
return true;
}
}
return false;
}
protected static class NativeMethods
{
[System.Runtime.InteropServices.DllImport ("user32.dll")]
public static extern System.IntPtr SendMessage(System.IntPtr hWnd, System.Int32 Msg, System.IntPtr wParam, System.IntPtr lParam);
[System.Runtime.InteropServices.DllImport ("user32.dll")]
public static extern System.IntPtr FindWindowEx(System.IntPtr hwndParent, System.IntPtr hwndChildAfter, string className, string windowName);
}