PRB: Lockscreen with Assert Dialog Causes Problems with Controls (168039)


The information in this article applies to:

  • Microsoft Visual FoxPro for Windows 5.0
  • Microsoft Visual FoxPro for Windows 5.0a
This article was previously published under Q168039

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
Modification Type:MajorLast Reviewed:4/26/2001
Keywords:KB168039
©2002 Microsoft Corporation. All rights reserved.