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Q249341: HOWTO: Create Layered Window in Visual Basic

Article: Q249341
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:4.0,5.0,6.0
Operating System(s): 
Keyword(s): kbAPI kbOSWin2000 kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbForms kbGrpDSVB kbDSupp
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, versions 4.0, 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 4.0, 5.0, 6.0 
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SUMMARY
=======

Microsoft Windows 2000 has the ability to create translucent windows. These
windows are called layered windows. This article describes how to create a
layered window by using Visual Basic.

MORE INFORMATION
================

Step-by-Step Example
--------------------

1. Create a new Standard EXE project in Visual Basic. Form1 is created by
  default.

2. Add the following code to the General Declarations section of Form1:

  Private Declare Function GetWindowLong Lib "user32" Alias _
    "GetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
  Private Declare Function SetWindowLong Lib "user32" Alias _
    "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, _
    ByVal dwNewLong As Long) As Long
  Private Declare Function SetLayeredWindowAttributes Lib "user32" _
    (ByVal hwnd As Long, ByVal crey As Byte, ByVal bAlpha As Byte, _
    ByVal dwFlags As Long) As Long

  Private Const GWL_EXSTYLE = (-20)
  Private Const WS_EX_LAYERED = &H80000
  Private Const WS_EX_TRANSPARENT = &H20&
  Private Const LWA_ALPHA = &H2&

  Option Explicit

  Private Sub Form_Load()
      Dim lOldStyle As Long
      Dim bTrans As Byte ' The level of transparency (0 - 255)

      bTrans = 128
      lOldStyle = GetWindowLong(Me.hWnd, GWL_EXSTYLE)
      SetWindowLong Me.hWnd, GWL_EXSTYLE, lOldStyle Or WS_EX_LAYERED
      SetLayeredWindowAttributes Me.hWnd, 0, bTrans, LWA_ALPHA
  End Sub

3. Run the example program by pressing the F5 key. The form should look like a
  normal Visual Basic window. However, windows that are lower in the Z order
  should be partially visible through the window.

It is also possible to make mouse events go through to the lower windows by
changing the preceding code line

  SetWindowLong Me.hwnd, GWL_EXSTYLE, lOldStyle Or WS_EX_LAYERED

to:

  SetWindowLong Me.hwnd, GWL_EXSTYLE, lOldStyle Or WS_EX_LAYERED Or WS_EX_TRANSPARENT

However, the form does not remain topmost if another form is activated. See the
"Reference" section for information on how to create a form that remains on
top.

REFERENCES
==========

For additional information how to create a topmost window, click the article
number below to view the article in the Microsoft Knowledge Base:

  Q184297 HOWTO: Create a Form That Always Stays on Top

Additional query words:

======================================================================
Keywords          : kbAPI kbOSWin2000 kbSDKWin32 kbVBp kbVBp400 kbVBp500 kbVBp600 kbForms kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600 kbVB400Search kbVB400
Version           : WINDOWS:4.0,5.0,6.0
Issue type        : kbhowto

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