BUG: Resource Leak with 256 Color Bitmap/UseZOrder PaletteMode

ID: Q192050

The information in this article applies to:

Microsoft Visual Basic Learning, Professional, and Enterprise Editions for Windows, version 6.0

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.

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.

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

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

Add a CommandButton and an Image control to Form1.

Set the PaletteMode property of Form1 to UseZOrder.

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

From the File menu, choose Make Project1.exe.

Save the project and close Visual Basic.

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

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: kbDSupport kbDSD kbVBp kbVBp600bug kbBitmap

Keywords : kbGrpVB
Version : WINDOWS:6.0
Platform : WINDOWS
Issue type : kbbug