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Q176765: BUG: Placing Icons in Picture Object Causes Memory Leak

Article: Q176765
Product(s): Microsoft FoxPro
Version(s): 3.0b,5.0,5.0a,6.0
Operating System(s): 
Keyword(s): kbvfp kbvfp300 kbvfp500 kbvfp500a kbGrpDSFox
Last Modified: 22-OCT-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0b, 5.0, 5.0a, 6.0 
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SYMPTOMS
========

A program that loads a series of icon files into the Picture property of a
Visual FoxPro image object causes a memory leak in Visual FoxPro 3.0b, 5.0x, and
6.0. Eventually, the operating system becomes unstable and the computer locks.

CAUSE
=====

Loading the icon files may create a leak in process memory. As the program runs,
increasing amounts of RAM are consumed. When the program starts using virtual
memory, performance suffers and the computer may lock.

RESOLUTION
==========

Currently, there is no resolution, but following are two workarounds:

- Use a bitmap instead of an icon file to display an image in the Picture
  property.

-or-

- Use an OLE container control that contains the Visual FoxPro HWND .ocx
  control to display the icon.

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
---------------------------

WARNING: Running the code below causes a low memory situation on the computer.
This condition may cause the operating system to become unstable. Close all open
applications and save your data before using this procedure. In Microsoft
Windows 95 and Microsoft Windows NT, press the CTRL+ALT+DEL keys simultaneously
to invoke the Close Dialog window or the Task Manager, respectively.

Create and run a program that contains the following code:

     LOCAL ARRAY laIcons[1,1]
     LOCAL loForm, lnI, lnFile, lnFiles

     loForm = CREATEOBJECT('Form')
     loForm.HEIGHT = 600
     loForm.WIDTH = 200

     FOR lnI = 1 TO 10
     loForm.ADDOBJECT('imgObject' + ALLTRIM(STR(lnI)), 'Image')
     WITH loForm.CONTROLS[lnI]
     .LEFT    = 10
     .TOP     = 10 + (lnI ) * 50
     .WIDTH   = 25
     .HEIGHT  = 25
     .VISIBLE = .T.
     ENDWITH
     ENDFOR

     loForm.ADDOBJECT('lblCounter', 'Label')
     loForm.lblCounter.TOP      = 1
     loForm.lblCounter.LEFT     = 1
     loForm.lblCounter.AUTOSIZE = .T.
     loForm.lblCounter.VISIBLE  = .T.
     loForm.SHOW()
     lnFiles = ADIR(laIcons, HOME() ;
     + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\*.ICO')

     FOR lnI = 1 TO 1000
     loForm.lblCounter.CAPTION = 'Loop :' + PADL(lnI, 4)
     FOR lnFile = 1 TO lnFiles - 10
     loForm.CONTROLS[ 1].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile , 1]
     loForm.CONTROLS[ 2].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile+1, 1]
     loForm.CONTROLS[ 3].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+ laIcons[lnFile+2, 1]
     loForm.CONTROLS[ 4].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 3, 1]
     loForm.CONTROLS[ 5].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 4, 1]
     loForm.CONTROLS[ 6].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 5, 1]
     loForm.CONTROLS[ 7].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\'+laIcons[lnFile + 6, 1]
     loForm.CONTROLS[ 8].PICTURE = ;
     HOME() + 'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile+7, 1]
     loForm.CONTROLS[ 9].PICTURE = ;
     HOME()+'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile + 8, 1]
     loForm.CONTROLS[10].PICTURE = ;
     HOME()+'SAMPLES\GRAPHICS\ICONS\COMPUTER\' + laIcons[lnFile + 9, 1]
     IF INKEY(0.001, 'HM') = 27
     CANCEL
     ENDIF
     ENDFOR
     ENDFOR

The first indication of a memory problem appears when the icons no longer appear
in the individual image objects. The number of iterations before this symptom
appears depends on the amount of physical RAM installed on the computer. Once
the memory leak consumes all the physical RAM, Visual FoxPro begins using
virtual memory. At this point, performance suffers greatly and the operating
system may lock.

REFERENCES
==========

Visual FoxPro Help 3.0b, 5.0, 5.0a; search on: Visual FoxPro HWND Control

Additional query words:

======================================================================
Keywords          : kbvfp kbvfp300 kbvfp500 kbvfp500a kbGrpDSFox 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300b kbVFP500 kbVFP600 kbVFP500a
Version           : :3.0b,5.0,5.0a,6.0
Issue type        : kbbug
Solution Type     : kbfix

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