Q168039: PRB: Lockscreen with Assert Dialog Causes Problems with Controls

Article: Q168039
Product(s): Microsoft FoxPro
Version(s): 5.0,5.0a
Operating System(s): 
Keyword(s): kbvfp
Last Modified: 26-APR-2001

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The information in this article applies to:

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

When you run a form, clicking on a checkbox does not change its state. If there
are option buttons on the form, clicking the checkbox may change the state of
the option buttons. Clicking the checkbox may even select more than one option
button in the same option group. Clicking one of the option buttons may change
the state of the checkbox. In other words, the checkboxes and option buttons are
malfunctioning.

CAUSE
=====

Several factors lead to this behavior. First, ASSERTS must be set ON and the
LockScreen property of the form changed to true (.T.) before an expression that
is ASSERTed evaluates to false (.F.). Next, Ignore or Ignore All must be chosen
in the message box displayed by the ASSERT command. Finally, LockScreen must be
changed back to false (.F.).

RESOLUTION
==========

Do not use LockScreen when using the ASSERT command.

MORE INFORMATION
================

When SET ASSERTS is ON, the ASSERT command will display a message box if a
logical expression evaluates to false (.F.).

The following commands issued from within a program file will illustrate:

     SET ASSERTS ON
     ASSERT 1=2       && will cause a message box.

Steps to Reproduce Behavior
---------------------------

1. Place the following code in a program file and run the program:

        SET ASSERTS ON
        oForm1 = CREATEOBJECT("test")
        oForm1.Visible = .t.
        READ EVENTS

        DEFINE CLASS test AS form
        ADD OBJECT cmdNewForm AS ccmdNewForm
        ADD OBJECT chkBox AS CheckBox WITH ;
               left = 10, ;
               top = 30
        ADD OBJECT opgBox AS OptionGroup WITH ;
               Width = 80, ;
               Height = 50, ;
               ButtonCount = 2, ;
               option1.Caption = "Option1", ;
               option1.Autosize = .T., ;
               option2.Caption = "Option2", ;
               option2.Autosize = .T., ;
               left = 10, ;
               top = 50

           FUNCTION Destroy
               CLEAR EVENTS
           ENDFUNC
        ENDDEFINE

        DEFINE CLASS ccmdNewForm AS CommandButton
           Caption = "Dialog"

           FUNCTION Click
                Thisform.LockScreen = .T.
                ASSERT 1=2
                Thisform.LockScreen = .F.
                ?Thisform.LockScreen
                CLEAR
           ENDFUNC
        ENDDEFINE

2. When the program is run, a form with a command button, a checkbox and an
  option group is displayed. Click on the checkbox and option buttons to verify
  that they work normally.

3. Now click on the command button. This should bring up the message box from
  the ASSERT command. It should have the message:

  "Assertion failed on line 2 of procedure test1.cmdnewform.click"

  Choose the Ignore button.

4. Back on the form, click on the Chkbox and note that it does not become
  checked. Then click on Option2 and note that Chkbox checks. Then click on the
  Chkbox and note that both option buttons are selected.

REFERENCES
==========

Visual FoxPro Online Help

Additional query words:

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Keywords          : kbvfp 
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP500a
Version           : :5.0,5.0a

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