Q178401: PRB: Message Box Appears Behind Form Set as Top-Most Window

Article: Q178401
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport
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
========

A Visual Basic form can be displayed as the top z-ordered (or top-most) window
by using the SetWindowPos API function. Under Windows 95 or Windows 98, if the
top-most window then displays a message box, the message box may display behind
the top-most window. The user cannot continue or exit the program because the
user cannot close the message box.

RESOLUTION
==========

Do not display a message box from a form set as the top-most window. If you must
use a message box from the form, unload the form first before displaying the
message box.

STATUS
======

This behavior is by design.

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

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

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

2. Add the two CommandButtons to Form1 form. Set the following Form1 form
  properties:

  Form1 Form Property            Setting
  ---------------------------------------
  BorderStyle                    0-None
  StartUpPosition                2-CenterScreen

3. Copy the following code to the Code window of Form1 form:

        Option Explicit

        Private 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
        Const HWND_TOPMOST = -1
        Const SWP_NOMOVE = &H2
        Const SWP_NOSIZE = &H1

        Private Sub Form_Load()
            Dim lngWindowPosition As Long
            Command1.Caption = "Show Message Box"
            Command2.Caption = "End Program"
            LngWindowPosition = SetWindowPos(Form1.hwnd, _
                                             HWND_TOPMOST, _
                                             0, _
                                             0, _
                                             0, _
                                             0, _
                                             SWP_NOMOVE Or SWP_NOSIZE)
        End Sub

        Private Sub Command1_Click()
            MsgBox "From Message Box", vbSystemModal
        End Sub

        Private Sub Command2_Click()
            End
        End Sub

4. Save the Project and compile the project into an executable file. This
  problem only occurs from an EXE file.

5. Run the executable file.

6. Click Show Message Box to display the message box.

7. Click on the desktop or another application to de-activate Project1.

8. Click on the form of Project1 to activate Project1.

9. Click OK to dismiss the message box.

NOTE: You may need to repeat steps 6-9 several times to reproduce the problem
where the Message Box is displayed behind the top-most window and cannot be
dismissed.

Additional query words: topmost top most modal

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Keywords          : kbAPI kbSDKWin32 kbVBp kbVBp500 kbVBp600 kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbprb

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