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Q149032: PRB: VB 3.0 OLE Clients Do not Repaint Before OLE Call Returns

Article: Q149032
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:4.0
Operating System(s): 
Keyword(s): kbVBp400
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Standard Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Professional Edition, 32-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows, version 4.0 
- Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows, version 4.0 
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SUMMARY
=======

When calling a method or accessing a property of an OLE server from Visual Basic
3.0, no painting takes place on any of the Visual Basic 3.0 forms that are
showing. This behavior remains until the call to the OLE server method or
property returns. This behavior occurs with OLE servers built in any
environment, including, but not limited to, Visual Basic 4.0. OLE automation
clients built with Visual Basic 4.0 do not show this characteristic.

CAUSE
=====

To receive Windows paint messages while in a synchronous OLE call, an OLE
automation client must implement the IMessageFilter interface. Visual Basic 3.0
does not implement this interface, and so Visual Basic 3.0 windows cannot
receive any paint messages until a synchronous call returns. Because Visual
Basic 4.0 does implement this interface, painting can continue without problem
before a call has returned.

STATUS
======

This behavior is by design.


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

Steps To Reproduce Problem
--------------------------

1. Following the instructions in Q129801, "How to Create and Use a Minimal OLE
  Automation Server," create a simple OLE server with Visual Basic 4.0. To
  obtain this article, query on the following words here in the Microsoft
  Knowledge Base:

  " vbwin and chocolates and step " (without the quotation marks)

2. Add a single form to this OLE server project by clickng Form on the Insert
  menu.

3. Add this procedure to the class module in the OLE server project:

        Public Sub ShowForm()
           Form1.Show vbModal
        End Sub

4. Compile the OLE server project and exit Visual Basic 4.0.

5. Start Visual Basic 3.0. Form1 is created by default.

6. Add this code to the Form_Click event in the Visual Basic 3.0 project:

        Sub Form_Click()
           Dim o As Object

           ' If the ProgID has been changed then modify it below.
           Set o = CreateObject("Project1.Class1")
           o.ShowForm
           MsgBox "Method returned"
        End Sub

7. Press F5 or click Start on the Run menu to run the application. Click once on
  the form and notice how no repainting occurs while the modal form displays.
  Unloading the modal form causes the message box to display and also resumes
  all Windows messages to the Visual Basic 3.0 project.


Additional query words:

======================================================================
Keywords          : kbVBp400 
Technology        : kbVBSearch kbAudDeveloper kbVB400Search kbVB400 kbVB16bitSearch
Version           : WINDOWS:4.0
Issue type        : kbprb

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