Q179287: FIX: Insufficient Memory in Visual FoxPro on Fast Computers

Article: Q179287
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b
Operating System(s): 
Keyword(s): kbvfp kbvfp300 kbvfp300b
Last Modified: 24-MAR-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 3.0, 3.0b 
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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.

The following code snippets illustrate implementation of the grid and list box
workarounds based on the code example provided in the MORE INFORMATION section.

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

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

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

STATUS
======

Microsoft has confirmed this to be a problem in the Microsoft products listed at
the beginning of this article. This has been corrected in Visual FoxPro 6.0.

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 problem does occur under the following conditions:

- 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 [ASCII 150] 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.

Additional query words:

======================================================================
Keywords          : kbvfp kbvfp300 kbvfp300b 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version           : WINDOWS:3.0,3.0b
Issue type        : kbbug kbprb
Solution Type     : kbfix

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