KB185626 - BUG: PictureBox Cannot be Made Transparent Using SetWindowLong

Article ID: 185626

Article Last Modified on 3/11/2005

Microsoft Visual Basic 5.0 Control Creation Edition
Microsoft Visual Basic 5.0 Learning Edition
Microsoft Visual Basic 5.0 Professional Edition
Microsoft Visual Basic 5.0 Enterprise Edition

This article was previously published under Q185626

SYMPTOMS

Attempting to use the Windows SetWindowLong API function to set the window style of a Visual Basic Picturebox to transparent does not work. However, this method was successful with earlier versions of Visual Basic.

RESOLUTION

There is not a solution that allows the API to work in this manner on the intrinsic Visual Basic 5.0 PictureBox control. To work around this problem, you can replace the PictureBox control with a custom or third party control that offers the same basic functionality as the PictureBox control but does not exhibit the same SetWindowLong limitation.

With Visual Basic 6.0, you can build a Transparent UserControl that responds to mouse events. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:

185882 HOWTO: Use the HitTest Event and HitBehavior Property

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

Create a new Standard EXE project. Form1 is created by default.
Add two PictureBox controls, named Picture1 and Picture2, to Form1.
Set the BackColor property of Picture1 to red.
Position Picture2 so that it partially overlaps the Picture1 control.

Place the following code in the code module of Form1:

      Option Explicit
      Const GWL_EXSTYLE = (-20)
      Const WS_EX_TRANSPARENT = &H20&

      Private Declare Function SetWindowLong Lib "user32" Alias _
          "SetWindowLongA" (ByVal hwnd As Long, ByVal nIndex As Long, _
          ByVal dwNewLong As Long) As Long

      Private Sub Form_Load()
          Dim result As Long
          Picture2.ZOrder
          result = SetWindowLong(Picture2.hwnd, GWL_EXSTYLE, _
             WS_EX_TRANSPARENT)
      End Sub

Run the sample project.

RESULT: The Picture2 control is not made transparent so Picture1 is not completely revealed. In earlier versions of Visual Basic this code allowed Picture1 to be completely revealed.

Additional query words: kbSDKWin32 kbAPI kbVBp kbdsd kbDSupport kbVBp500

Keywords: kbbug KB185626