Painting Vista's Aero NonClientArea in VB.NET

Imports WindowsApplication1.Dwm
Imports WindowsApplication1.WinApi
Imports WindowsApplication1.NcRender
Imports System
Imports System.Collections.Generic
Imports System.ComponentModel
Imports System.Data
Imports System.Drawing
Imports System.Text
Imports System.Windows.Forms
Imports System.Runtime.InteropServices
Imports System.Diagnostics
Imports System.Drawing.Drawing2D

Public Class Form1

#Region "Fields"
    Private dwmMargins As Dwm.MARGINS
    Private _marginOk As Boolean
    Private _aeroEnabled As Boolean
#End Region
#Region "Ctor"
    Public Sub New()
        SetStyle(ControlStyles.ResizeRedraw, True)

        InitializeComponent()

        DoubleBuffered = True

        CheckGlassEnabled()
    End Sub
#End Region
#Region "Props"
    Public ReadOnly Property AeroEnabled() As Boolean
        Get
            Return _aeroEnabled
        End Get
    End Property
#End Region
#Region "Methods"
    ''' <summary>
    ''' Sets the value of AeroEnabled
    ''' </summary>
    Private Sub CheckGlassEnabled()
        If Environment.OSVersion.Version.Major >= 6 Then
            Dim enabled As Integer = 0
            Dim response As Integer = Dwm.dwmIsCompositionEnabled(enabled)

            _aeroEnabled = enabled = 1
        End If
    End Sub
    ''' <summary>
    ''' Equivalent to the LoWord C Macro
    ''' </summary>
    ''' <param name="dwValue"></param>
    ''' <returns></returns>
    Public Shared Function LoWord(ByVal dwValue As Integer) As Integer
        Return dwValue And &HFFFF
    End Function
    ''' <summary>
    ''' Equivalent to the HiWord C Macro
    ''' </summary>
    ''' <param name="dwValue"></param>
    ''' <returns></returns>
    Public Shared Function HiWord(ByVal dwValue As Integer) As Integer
        Return (dwValue >> 16) And &HFFFF
    End Function
#End Region

    Private Sub Form1_Activated(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Activated

        Dwm.DwmExtendFrameIntoClientArea(Me.Handle, dwmMargins)
    End Sub

    Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint
        If _aeroEnabled Then
            e.Graphics.Clear(Color.Transparent)
        Else
            e.Graphics.Clear(Color.FromArgb(&HC2, &HD9, &HF7))
        End If

        e.Graphics.FillRectangle(SystemBrushes.ButtonFace, Rectangle.FromLTRB(dwmMargins.cxLeftWidth - 0, dwmMargins.cyTopHeight - 0, Width - dwmMargins.cxRightWidth - 0, Height - dwmMargins.cyBottomHeight - 0))
    End Sub

    Protected Overloads Overrides Sub WndProc(ByRef m As Message)
        Dim WM_NCCALCSIZE As Integer = &H83
        Dim WM_NCHITTEST As Integer = &H84
        Dim result As IntPtr

        Dim dwmHandled As Integer = Dwm.DwmDefWindowProc(m.HWnd, m.Msg, m.WParam, m.LParam, result)

        If dwmHandled = 1 Then
            m.Result = result
            Exit Sub
        End If

        If m.Msg = WM_NCCALCSIZE AndAlso CInt(m.WParam) = 1 Then
            Dim nccsp As NCCALCSIZE_PARAMS = DirectCast(Marshal.PtrToStructure(m.LParam, GetType(NCCALCSIZE_PARAMS)), NCCALCSIZE_PARAMS)

            ' Adjust (shrink) the client rectangle to accommodate the border:
            nccsp.rect0.Top += 0
            nccsp.rect0.Bottom += 0
            nccsp.rect0.Left += 0
            nccsp.rect0.Right += 0

            If Not _marginOk Then
                'Set what client area would be for passing to DwmExtendIntoClientArea
                dwmMargins.cyTopHeight = nccsp.rect2.Top - nccsp.rect1.Top
                dwmMargins.cxLeftWidth = nccsp.rect2.Left - nccsp.rect1.Left
                dwmMargins.cyBottomHeight = nccsp.rect1.Bottom - nccsp.rect2.Bottom
                dwmMargins.cxRightWidth = nccsp.rect1.Right - nccsp.rect2.Right
                _marginOk = True
            End If

            Marshal.StructureToPtr(nccsp, m.LParam, False)

            m.Result = IntPtr.Zero
        ElseIf m.Msg = WM_NCHITTEST AndAlso CInt(m.Result) = 0 Then
            m.Result = HitTestNCA(m.HWnd, m.WParam, m.LParam)
        Else
            MyBase.WndProc(m)
        End If
    End Sub

    Private Function HitTestNCA(ByVal hwnd As IntPtr, ByVal wparam As IntPtr, ByVal lparam As IntPtr) As IntPtr
        Dim HTNOWHERE As Integer = 0
        Dim HTCLIENT As Integer = 1
        Dim HTCAPTION As Integer = 2
        Dim HTGROWBOX As Integer = 4
        Dim HTSIZE As Integer = HTGROWBOX
        Dim HTMINBUTTON As Integer = 8
        Dim HTMAXBUTTON As Integer = 9
        Dim HTLEFT As Integer = 10
        Dim HTRIGHT As Integer = 11
        Dim HTTOP As Integer = 12
        Dim HTTOPLEFT As Integer = 13
        Dim HTTOPRIGHT As Integer = 14
        Dim HTBOTTOM As Integer = 15
        Dim HTBOTTOMLEFT As Integer = 16
        Dim HTBOTTOMRIGHT As Integer = 17
        Dim HTREDUCE As Integer = HTMINBUTTON
        Dim HTZOOM As Integer = HTMAXBUTTON
        Dim HTSIZEFIRST As Integer = HTLEFT
        Dim HTSIZELAST As Integer = HTBOTTOMRIGHT

        Dim p As New Point(LoWord(CInt(lparam)), HiWord(CInt(lparam)))

        Dim topleft As Rectangle = RectangleToScreen(New Rectangle(0, 0, dwmMargins.cxLeftWidth, dwmMargins.cxLeftWidth))

        If topleft.Contains(p) Then
            Return New IntPtr(HTTOPLEFT)
        End If

        Dim topright As Rectangle = RectangleToScreen(New Rectangle(Width - dwmMargins.cxRightWidth, 0, dwmMargins.cxRightWidth, dwmMargins.cxRightWidth))

        If topright.Contains(p) Then
            Return New IntPtr(HTTOPRIGHT)
        End If

        Dim botleft As Rectangle = RectangleToScreen(New Rectangle(0, Height - dwmMargins.cyBottomHeight, dwmMargins.cxLeftWidth, dwmMargins.cyBottomHeight))

        If botleft.Contains(p) Then
            Return New IntPtr(HTBOTTOMLEFT)
        End If

        Dim botright As Rectangle = RectangleToScreen(New Rectangle(Width - dwmMargins.cxRightWidth, Height - dwmMargins.cyBottomHeight, dwmMargins.cxRightWidth, dwmMargins.cyBottomHeight))

        If botright.Contains(p) Then
            Return New IntPtr(HTBOTTOMRIGHT)
        End If

        Dim top As Rectangle = RectangleToScreen(New Rectangle(0, 0, Width, dwmMargins.cxLeftWidth))

        If top.Contains(p) Then
            Return New IntPtr(HTTOP)
        End If

        Dim cap As Rectangle = RectangleToScreen(New Rectangle(0, dwmMargins.cxLeftWidth, Width, dwmMargins.cyTopHeight - dwmMargins.cxLeftWidth))

        If cap.Contains(p) Then
            Return New IntPtr(HTCAPTION)
        End If

        Dim left As Rectangle = RectangleToScreen(New Rectangle(0, 0, dwmMargins.cxLeftWidth, Height))

        If left.Contains(p) Then
            Return New IntPtr(HTLEFT)
        End If

        Dim right As Rectangle = RectangleToScreen(New Rectangle(Width - dwmMargins.cxRightWidth, 0, dwmMargins.cxRightWidth, Height))

        If right.Contains(p) Then
            Return New IntPtr(HTRIGHT)
        End If

        Dim bottom As Rectangle = RectangleToScreen(New Rectangle(0, Height - dwmMargins.cyBottomHeight, Width, dwmMargins.cyBottomHeight))

        If bottom.Contains(p) Then
            Return New IntPtr(HTBOTTOM)
        End If

        Return New IntPtr(HTCLIENT)
    End Function

    
End Class