PRB: Insufficient Memory in Visual FoxPro on Fast Computers

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

SYMPTOMS

When using a large table, cursor, or array (over 275 records) as the row source of a combo box, you may see the following error message:

   There is not enough memory to complete this operation.

RESOLUTION

Here are four workarounds for this problem:

• Upgrade to Visual FoxPro version 5.0.

  -or-

• Use a grid control.

  -or-

• Use a list box control.

  -or-

• Limit the size of the underlying table, cursor, or array to 275 records or less.

To use a grid instead of a combo box, replace the cbocombo class definition with the following code:

   DEFINE CLASS cboCombo AS GRID
      LEFT = 10
      TOP = 25
      WIDTH=140
      HEIGHT=100
      VISIBLE=.T.
      RECORDSOURCETYPE=1
      RECORDSOURCE="Customer"
   ENDDEFINE

   DEFINE CLASS cboCombo AS LISTBOX
      LEFT = 10
      TOP = 25
      WIDTH=140
      HEIGHT=100
      VISIBLE=.T.
      ROWSOURCETYPE=6
      ROWSOURCE="Customer.cust_id"
   ENDDEFINE

STATUS

Microsoft is researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION

This behavior does not occur in Visual FoxPro 5.0 or 5.0a nor does this behavior occur with Visual FoxPro 3.0 when either of the following conditions is true:

• The combo box Style property is set to 0 - Dropdown Combo. -or-
• The combo box has been opened using the mouse.

• The Combo box Style property is set to 2 - Dropdown List.

  -or-

• The Combo box RowSourceType property is set to one of the following:

        2 - Alias
        3 - SQL Statement
        4 - Query (.qpr)
        5 - Array
        6 – Fields
  

  -or-

• The Combo box is being navigated using the keyboard.

  -or-

• Visual FoxPro 3.0 is being run on a computers with a clock speeds of 166 MHz or greater.

Steps to Reproduce Behavior

1. Create a program called FrmCombo.prg using the following code:

         ofrmcombo = CREATEOBJECT("frmcombo")
         ofrmcombo.VISIBLE = .T.
         ofrmcombo.ADDOBJECT("cboCombo1","cbocombo")
         ofrmcombo.ADDOBJECT("btnExit","cmdExit")
   

         READ EVENTS
   

         DEFINE CLASS frmcombo AS FORM
            CAPTION="Combo Form"
            TOP=0
            LEFT=0
            HEIGHT=150
            WIDTH=225
            PROCEDURE LOAD
               CREATE CURSOR customer (cust_id c(10))
               FOR i=1 TO 350
                  INSERT INTO customer (cust_id) VALUES (SYS(2015))
               NEXT
               GO TOP
            ENDPROC
            PROCEDURE ACTIVATE
               THISFORM.REFRESH
            ENDPROC
         ENDDEFINE
   
         DEFINE CLASS cbocombo AS COMBOBOX
            LEFT = 10
            TOP = 25
            WIDTH = 140
            HEIGHT = 25
            VISIBLE = .T.
            INCREMENTALSEARCH=.F.
            CONTROLSOURCE="Customer.cust_id"
            ROWSOURCETYPE=6
            ROWSOURCE="Customer.cust_id"
            STYLE=2
         ENDDEFINE
   
         DEFINE CLASS cmdexit AS COMMANDBUTTON
            CAPTION = "Exit"
            LEFT = 155
            TOP = 25
            WIDTH = 50
            HEIGHT = 25
            VISIBLE = .T.
            PROCEDURE CLICK
               THISFORM.RELEASE
               CLEAR EVENTS
            ENDPROC
         ENDDEFINE
   
   

2. Run the program. Once the form appears, move through the data in the combo box by holding down the DOWN ARROW key. The data appears to scroll through the combo box. At some point, the error occurs.

Keywords          : FxenvError FxotherSample vfoxwin
Version           : WINDOWS:3.0,3.0b
Platform          : WINDOWS
Issue type        : kbprb