Q257523: BUG: Resource Leak When Displaying WMF Files in PictureBox

Article: Q257523
Product(s): Microsoft Visual Basic for Windows
Version(s): 5.0,6.0
Operating System(s): 
Keyword(s): kbBrush kbVBp500 kbVBp500bug kbVBp600 kbVBp600bug kbDSupport
Last Modified: 26-JUN-2002

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

System and Graphical Device Interface (GDI) resources are not freed when you use
a PictureBox control in Visual Basic to view multiple Windows MetaFile (WMF)
images. Other image formats, such as BMP, JPG, and GIF, do not experience any
resource leaks.

CAUSE
=====

The resource leak is actually caused by a problem in the operating system. The
operating system fails to destroy brushes that it creates to "play" a metafile
image. Therefore, any application that uses the same operating system
functionality to draw metafiles will experience the same loss in resources.

RESOLUTION
==========

Currently, there is no known fix for this problem. One potential workaround,
however, is to avoid the WMF file format and instead use another picture format,
such as BMP, JPG, or GIF.

STATUS
======

Microsoft has confirmed that this is a bug in the Microsoft products that are
listed at the beginning of this article.

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

This resource leak only affects WMF files displayed on a Windows 95 or 98
operating system. Files in other formats, such as BMP, JPG, and GIF, are not
affected. In addition, resources are only leaked once for each WMF file. For
example, if you load one WMF file into a PictureBox 10 times resources leak only
once, but if you load 10 unique WMF files one time each this results in a loss
of 10 times as many resources.

Upon termination of the application, all leaked resources are released and
available to the system.

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

1. Create a new standard EXE project. Form1 is created by default.

2. Add a PictureBox control to Form1.

3. Add a command button to Form1.

4. Add a reference to "Microsoft Scripting Runtime".

5. Paste the following code into the Form1 code window:

  Private Sub Command1_Click()
     Dim fso As FileSystemObject
     Dim fld As Folder
     Dim fl As File

     Set fso = New FileSystemObject
     Set fld = fso.GetFolder(App.Path & "\wmf")

     For Each fl In fld.Files
        Picture1.Picture = LoadPicture(fl)
     Next fl

     Set fld = Nothing
     Set fso = Nothing
  End Sub

6. Save the project.

7. In the project directory, create a subfolder called "WMF".

8. Copy some WMF files (preferably at least 200) to the folder that you just
  created.

9. Start the Resource Meter (or any tool that can measure free resources).

10. Run the sample program.

11. Click the command button. As the images are displayed, you can see that the
  resources available begin to dwindle.

12. When all images have been processed, close the application. You should see
  the resources returned to the system.

Additional query words:

======================================================================
Keywords          : kbBrush kbVBp500 kbVBp500bug kbVBp600 kbVBp600bug kbDSupport 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVB500 kbVB600
Version           : :5.0,6.0
Issue type        : kbbug
Solution Type     : kbpending

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