BUG: Placing Icons in Picture Object Causes Memory Leak

• Microsoft Visual FoxPro for Windows, versions 3.0b, 5.0, 5.0a

SYMPTOMS

A program that loads a series of icon files into the Picture property of a FoxPro image object causes a memory leak in Visual FoxPro 3.0b and 5.0x. 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

Here are two workarounds:

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

• 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. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available.

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 Windows 95 and 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

REFERENCES

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