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

• Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 5.0 on the following platform: Win95

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, 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.