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Q192050: BUG: Resource Leak with 256 Color Bitmap/UseZOrder PaletteMode

Article: Q192050
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:6.0
Operating System(s): 
Keyword(s): kbBitmap kbVBp kbVBp600bug 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, version 6.0 
- Microsoft Visual Basic Professional Edition for Windows, version 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0 
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SYMPTOMS
========

You may see a loss of System and GDI resources when repeatedly loading a picture
if the Form's PaletteMode is set to UseZOrder and the Windows system display
color settings are set to 256 colors. Because of the differences in the way that
Windows 95/98 and Window NT manage memory, the consequences of this problem may
be more apparent on a computer running Windows 95/98 than on a computer running
Windows NT/2000.

RESOLUTION
==========

Set the PaletteMode property of the form to a setting other than UseZOrder.

STATUS
======

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

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

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

These steps require that you have a 256 color bitmap. If you have a bitmap you
would like to use, substitute it for "C:\test.bmp" in step 5. If not, create a 2
x 2 inch bitmap using Paint or other software capable of creating a bitmap.

1. On a machine running Windows 95/98, set the Windows display system color
  setting to 256 colors.

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

3. Add a CommandButton and an Image control to Form1.

4. Set the PaletteMode property of Form1 to UseZOrder.

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

        Private Sub Command1_Click()
        Dim b As Boolean
        Dim i As Integer

        For i = 1 To 500
           Caption = Str(i)
           b = Not b
           If b Then
              Image1.Picture = LoadPicture("c:\test.bmp")
           Else
              Image1.Picture = LoadPicture("")
           End If
        Next i
        End Sub

6. From the File menu, choose Make Project1.exe.

7. Save the project and close Visual Basic.

8. Start the Windows Resource Meter, and display the Resource Meter window by
  right-clicking on the icon in the TaskBar, and selecting Details.

9. Run Project1.exe and click on the CommandButton. You should see the System
  and GDI resources decreasing. These resources are not reclaimed until you
  exit Project1.exe.

Additional query words:

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

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

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