Added ControlScrollFilter

ControlScrollFilter can be added to the application's message filter
list to re-route all mousewheel events to the control the user is
current hovering over with their cursor.

DarkUI/DarkUI.csproj

@@ -124,9 +124,12 @@
       <DesignTime>True</DesignTime>
       <DependentUpon>TreeViewIcons.resx</DependentUpon>
     </Compile>
+    <Compile Include="Win32\ControlScrollFilter.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="Renderers\DarkMenuRenderer.cs" />
     <Compile Include="Renderers\DarkToolStripRenderer.cs" />
+    <Compile Include="Win32\Native.cs" />
+    <Compile Include="Win32\WindowsMessages.cs" />
   </ItemGroup>
   <ItemGroup>
     <EmbeddedResource Include="Forms\DarkDialog.resx">

DarkUI/Win32/ControlScrollFilter.cs

@@ -0,0 +1,27 @@
+using System.Drawing;
+using System.Windows.Forms;
+
+namespace DarkUI
+{
+    public class ControlScrollFilter : IMessageFilter
+    {
+        public bool PreFilterMessage(ref Message m)
+        {
+            switch (m.Msg)
+            {
+                case (int)WM.MOUSEWHEEL:
+                case (int)WM.MOUSEHWHEEL:
+                    var hControlUnderMouse = Native.WindowFromPoint(new Point((int)m.LParam));
+
+                    if (hControlUnderMouse == m.HWnd)
+                        return false; // Already headed for the right control.
+
+                    // Redirect the message to the control under the mouse.
+                    Native.SendMessage(hControlUnderMouse, (uint)m.Msg, m.WParam, m.LParam);
+                    return true;
+            }
+
+            return false;
+        }
+    }
+}

DarkUI/Win32/Native.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Drawing;
+using System.Runtime.InteropServices;
+
+namespace DarkUI
+{
+    public sealed class Native
+    {
+        [DllImport("user32.dll")]
+        public static extern IntPtr WindowFromPoint(Point point);
+
+        [DllImport("user32.dll", CharSet = CharSet.Auto)]
+        public static extern IntPtr SendMessage(IntPtr hWnd, UInt32 msg, IntPtr wParam, IntPtr lParam);
+    }
+}

Example/Forms/MainForm.cs

@@ -1,4 +1,5 @@
 using DarkUI;
+using System.Windows.Forms;
 
 namespace Example
 {
@@ -8,6 +9,10 @@ namespace Example
         {
             InitializeComponent();
 
+            // Add the control scroll message filter to re-route all mousewheel events
+            // to the control the user is currently hovering over with their cursor.
+            Application.AddMessageFilter(new ControlScrollFilter());
+
             // Build dummy list data
             for (var i = 0; i < 100; i++)
             {