Aero Effects on User-drawn TabControl

Question

In my app, I would like to have my tabcontrol have an aero effect on the header. This works with the normal winforms tabcontrol using this code:

Imports System.Runtime.InteropServices

    <DllImport("dwmapi.dll")> _
     Private Shared Function DwmExtendFrameIntoClientArea(ByVal hwnd As IntPtr, ByRef pMarInset As MARGINS) As Integer
     End Function

<StructLayout(LayoutKind.Sequential)> _
Private Structure MARGINS
    Public cxLeftWidth As Integer
    Public cxRightWidth As Integer
    Public cyTopHeight As Integer
    Public cyBottomHeight As Integer
End Structure

Problem is, I have a custom tabcontrol class (the actual one is much larger and has a much more complicated OnPaint() override than below)

Public Class CustomTab
    Inherits TabControl

    Public Sub New()
        SetStyle(ControlStyles.UserPaint or ControlStyles.ResizeRedraw,True)
    End Sub

    Protected Overrides Sub OnPaint(e as PaintEventArgs)
        Dim g as Graphics = e.Graphics
        Dim r as Rectangle

        For i=0 to TabCount - 1
            If i = SelectedIndex
                r = GetTabRect(i)
                g.FillRectangle(New SolidBrush(My.Settings.TabColor),r)
            Else
                r = GetTabRect(i)
                g.FillRectangle(New SolidBrush(SystemColors.Control),r)
            End If
        Next
    End Sub
End Class

When I try the glass effects with this, it does not show in the header like normal. Does anyone know why the Userdrawn tabcontrol will not have the transparent header?

Working (Normal tabcontrol):

Not working (my tabcontrol):

Answer 1

Never Mind- Found the Answer. In the OnPaint() Sub, write

g.Clear(Color.Black)

this paints the background black, so the glass effects show