Q208654: BUG: FontChanged Fires Twice When a Font Object Property Changed

Article: Q208654
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s): 
Keyword(s): kbFont kbVBp kbVBp600bug kbGrpDSVB kbDSupport
Last Modified: 11-JAN-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The FontChanged event sink fires more than once if the user sets a Stdfont
object to a font more than once. Setting the font object twice may be necessary
if the font object is destroyed for some reason, and then recreated. The
expected behavior is that the FontChanged event fires only once when a property
is changed.

RESOLUTION
==========

Create the font object explicitly again after destroying it, and then set up the
properties again. This makes the event fire only once.

STATUS
======

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

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

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

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

2. Add a CommandButton control to Form1.

3. Add the following code to Form1's code module:

  Option Explicit
  Private WithEvents f As StdFont

  Private Sub Command1_Click()
      Me.Font.Bold = Not Me.Font.Bold
  End Sub

  Private Sub f_FontChanged(ByVal PropertyName As String)
      Print PropertyName
  End Sub

  Private Sub Form_Load()
      Set f = Me.Font
      Set f = Me.Font
  End Sub

4. Press the F5 key to run the project, and then click the CommandButton.

5. The Bold property is being changed. Note that the word Bold is printed twice
  on the form.

Step-by-Step Resolution
-----------------------

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

2. Add a CommandButton control to Form1.

3. Add the following code to the code module of Form1:

  Option Explicit
  Private WithEvents f As StdFont
  Private x As StdFont

  Private Sub Command1_Click()
     Me.Font.Bold = Not Me.Font.Bold
  End Sub

  Private Sub f_FontChanged(ByVal PropertyName As String)
      Print PropertyName
  End Sub

  Private Sub Form_Load()
     Set x = New StdFont
     x.Name = "Times New Roman"
     x.Bold = True
     x.Italic = True
     Set f = x
     Set Me.Font = f

     Set x = New StdFont
     x.Name = "Times New Roman"
     x.Bold = True
     x.Italic = False
     Set f = x
     Set Me.Font = f
  End Sub

4. Press the F5 key to run the project, click the CommandButton, and note that
  the word Bold is printed only once.

Additional query words:

======================================================================
Keywords          : kbFont kbVBp kbVBp600bug kbGrpDSVB kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB600Search kbVBA600 kbVB600
Version           : :6.0
Issue type        : kbbug
Solution Type     : kbpending

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1986-2002.