(VB)创建透明窗体

创建透明窗体
     透明窗体，顾名思义，就是窗体是透明的，透过窗体可以看到窗体下面
的东西。实现透明窗体的原理也很简单：首先得到主窗口的矩形区域，
再得到客户区的矩形区域，然后用CombineRgn函数，使用异或操作，将
重叠部分去除，再使用SetWindowRgn函数设置窗体区域，就行了。
下面的例子实现了该功能。
>>步骤1----建立新工程。
>>步骤2----编写如下代码：

Private Declare Function GetWindowRect Lib "user32" (ByVal hWnd _
    As Long, lpRECT As RECT) As Long
Private Declare Function GetClientRect Lib "user32" (ByVal hWnd _
    As Long, lpRECT As RECT) As Long
Private Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn _
    As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, _
    ByVal nCombineMode As Long) As Long
Private Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As _
    Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) _
    As Long
Private Declare Function ScreenToClient Lib "user32" (ByVal hWnd _
    As Long, lpPoint As POINTAPI) As Long
Private Declare Function SetWindowRgn Lib "user32" (ByVal hWnd As _
    Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long

Const RGN_XOR = 3

Private Type POINTAPI
    x As Long
    Y As Long
End Type

Private Type RECT
    Left As Long
    Top As Long
    Right As Long
    Bottom As Long
End Type

Private rctClient As RECT, rctFrame As RECT
Private hClient As Long, hFrame As Long

Public Sub MakeTransparent(frm As Form)
    GetFrameClientRgn frm
    SetWindowRgn frm.hWnd, hFrame, True
End Sub

Private Sub GetFrameClientRgn(frm As Form)
    GetWindowRect frm.hWnd, rctFrame
    GetClientRect frm.hWnd, rctClient

    '将窗口矩形坐标转换为屏幕坐标
    Dim lpTL As POINTAPI, lpBR As POINTAPI
    lpTL.x = rctFrame.Left
    lpTL.Y = rctFrame.Top
    lpBR.x = rctFrame.Right
    lpBR.Y = rctFrame.Bottom
    ScreenToClient frm.hWnd, lpTL
    ScreenToClient frm.hWnd, lpBR
    rctFrame.Left = lpTL.x
    rctFrame.Top = lpTL.Y
    rctFrame.Right = lpBR.x
    rctFrame.Bottom = lpBR.Y
    rctClient.Left = Abs(rctFrame.Left)
    rctClient.Top = Abs(rctFrame.Top)
    rctClient.Right = rctClient.Right + Abs(rctFrame.Left)
    rctClient.Bottom = rctClient.Bottom + Abs(rctFrame.Top)
    rctFrame.Right = rctFrame.Right + Abs(rctFrame.Left)
    rctFrame.Bottom = rctFrame.Bottom + Abs(rctFrame.Top)
    rctFrame.Top = 0
    rctFrame.Left = 0

    hClient = CreateRectRgn(rctClient.Left, rctClient.Top, _
    rctClient.Right, rctClient.Bottom)
    hFrame = CreateRectRgn(rctFrame.Left, rctFrame.Top, _
    rctFrame.Right, rctFrame.Bottom)

    CombineRgn hFrame, hClient, hFrame, RGN_XOR
End Sub

Private Sub Form_Resize()
    MakeTransparent Me
End Sub

>>步骤3----编译运行，是不是看到效果了。