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Q173638: BUG: "What’s This?" Button Disappears from MDI Child Forms

Article: Q173638
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0
Operating System(s): 
Keyword(s): kbVBp500 kbGrpDSVBDB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Control Creation Edition for Windows, version 5.0 
- Microsoft Visual Basic Learning Edition for Windows, version 5.0 
- Microsoft Visual Basic Professional Edition for Windows, version 5.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 5.0 
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SYMPTOMS
========

Setting both the WhatsThisButton property and the WhatsThisHelp property of an
MDI child form to True does not enable the What's This button to appear in the
title bar of the form.

RESOLUTION
==========

According to the Help for Visual Basic 5.0, the What's This? button will appear
in the title bar of a form when the WhatsThisHelp property and the
WhatsThisButton property are both set to True and the following properties are
also set as shown:

     ControlBox = True

     MinButton = False and/or MaxButton = False
     BorderStyle = 1 - Fixed Single or BorderStyle = 2 - Sizable
        Or
     BorderStyle = 3 - Fixed Dialog

However, the What's This? button fails to appear in the title bar of an MDI child
form even when the conditions above are met.

To work around this problem, you can use the Windows SetParent API to make one
form the child of another and create the illusion of an MDI form in which the
What's This button is functional.

Step-by-Step Instructions
-------------------------

1. Start a new Standard EXE project. Form1 is added by default.

2. Add another form (Form2) to the project.

3. Set the following properties of Form2:

        MaxButton = False
        MinButton = False
        WhatsThisButton = True
        WhatsThisHelp = True

4. Insert the following code to Form1's General Declarations section:

        Private Declare Function SetParent Lib "user32" _
        (ByVal hWndChild As Long, ByVal hWndNewParent As Long) As Long

        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

        Const WS_CHILDWINDOW = &H40000000
        Const GWL_STYLE = (-16)

5. Insert the following code to Form1's Load event procedure:

        Private Sub Form_Load()
           Dim x As Long
           Dim y As Long
           'Set Form1 as the parent of form2
           x = SetParent(Form2.hwnd, Form1.hwnd)
           Form2.Show

           x = GetWindowLong(Form2.hwnd, GWL_STYLE)
           y = x + WS_CHILDWINDOW
           x = SetWindowLong(Form2.hwnd, GWL_STYLE, y)
        End Sub

6. Press the F5 key to run the program. You will see Form2 acting as Form1's
  child with a What's This? Button on its toolbar.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this bug and will post new
information here in the Microsoft Knowledge Base as it becomes available.

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

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

1. Start a new Standard EXE project. Form1 is added by default.

2. Add a MDI form (MDIForm1) to the project.

3. Set the following properties of Form1:

     MaxButton = False
     MDIChild = True
     MinButton = False
     WhatsThisButton = True
     WhatsThisHelp = True

4. Press the F5 key to run the project. The What's This ('?') button disappears
  from Form1's title bar.

Additional query words: vb5

======================================================================
Keywords          : kbVBp500 kbGrpDSVBDB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVBA500Search kbVBA500 kbVB500 kbZNotKeyword3
Version           : WINDOWS:5.0
Hardware          : x86
Issue type        : kbbug

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