Q192254: BUG: SetWindowPos API Does Not Set Topmost Window in VB

Article: Q192254
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

When using the SetWindowPos() API in Visual Basic to set the Topmost window
flag, these known problems may occur:

1. When an application is running in the Visual Basic IDE, clicking on the
  Desktop or My Computer icon causes the Topmost window setting to be turned
  off. This does not occur when the application is a compiled EXE. Please see
  the REFERENCES section below for more information.

2. Setting the Topmost flag for a parent form does not set it for that form's
  children. This conflicts with the documented behavior of the SetWindowPos
  function.

3. When calling SetWindowPos with the NoTopmost flag for a Visual Basic form,
  all forms in the project are set to NoTopmost.

STATUS
======

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

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

It is possible to use the SetWindowPos API function to make a Visual Basic Form
stay topmost in the z-order (always on top), even when focus is on another
window. However, the problems listed above may result.

Steps to Reproduce Behavior
---------------------------

1. Start Visual Basic and create a standard EXE project. Form1 is created by
  default.

2. From the Project menu, add another Form to the project. It should be called
  Form2.

3. From the Project menu, add a Basic Module (.BAS) to the project and add the
  following code:

        ' SetWindowPos Function
        Declare Function SetWindowPos Lib "user32" _
           (ByVal hwnd As Long, ByVal hWndInsertAfter As Long, _
            ByVal x As Long, ByVal y As Long, ByVal cx As Long, _
            ByVal cy As Long, ByVal wFlags As Long) As Long

        ' SetWindowPos Flags
        Public Const SWP_NOSIZE = &H1
        Public Const SWP_NOMOVE = &H2
        Public Const HWND_TOPMOST = -1
        Public Const HWND_NOTOPMOST = -2

4. Add two CommandButtons to Form2 and add the following code to its Code
  Window:

        Private Sub Form_Load()
           Command1.Caption = "Make Topmost"
           Command2.Caption = "Unload Form2"
        End Sub

        Private Sub Command1_Click()
           Call SetWindowPos(Me.hWnd, HWND_TOPMOST, 0, 0, 0, 0, _
                             SWP_NOSIZE Or SWP_NOMOVE)
        End Sub

        Private Sub Command2_Click()
           Call SetWindowPos(Me.hWnd, HWND_NOTOPMOST, 0, 0, 0, 0, _
                             SWP_NOSIZE Or SWP_NOMOVE)
           Unload Me
        End Sub

5. Now add a CommandButton to Form1 and add the following code to its Code
  Window:

        Private Sub Form_Load()
           Command1.Caption = "Show Form2"
           Call SetWindowPos(Me.hWnd, HWND_TOPMOST, 0, 0, 0, 0, _
                             SWP_NOSIZE Or SWP_NOMOVE)
        End Sub

        Private Sub Command1_Click()
           Form2.Show vbModeless, Me
        End Sub

6. Compile the program and run it as an EXE (outside the Debugger).

  RESULTS: Form1 appears as a Topmost window. Pressing the "Show Form2" button
  makes Form2 visible, but you will notice that Form2 (a child of Form1) is not
  the topmost window. In fact, you may need to move Form1 to see Form2. This
  behavior is contrary to the product documentation. Now press the "Make
  Topmost" button of Form2. This should make Form2 a topmost window. Pressing
  the "Unload Form2" button will cause Form2 to clear its Topmost flag before
  closing. This causes Form1's Topmost flag to be cleared as well.

  NOTE: Form1 may remain topmost in the z-order until you switch to another
  window and then switch back. This can give the impression that Form1 is still
  a topmost window, but the topmost flag has been cleared.

REFERENCES
==========

For more information, please see the following articles in the Microsoft
Knowledge Base:

  Q150233 : BUG: Topmost Window Does Not Stay on Top in Design Environment

  Q184297 : HOWTO: Create a Form That Always Stays on Top

Additional query words: kbDSupport kbDSD kbVBp kbVBp600bug kbVBp500bug kbAPI kbSDKWin32 kbUserGrp

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Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbbug

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