Q156630: PRB: Incremental Search with Grid Causes Screen Flicker

Article: Q156630
Product(s): Microsoft FoxPro
Version(s): 5.00
Operating System(s): 
Keyword(s): 
Last Modified: 21-AUG-1999

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

The Refresh method of the Grid control does not move the record pointer in the
grid to the selected record when the record pointer is moved from a control
external to the grid. The grid has to get the focus in order for the record
pointer in it to move to the selected record. Because of this problem, an
incremental search routine, involving the grid and another control, causes the
screen to flicker every time a character is entered.

This article describes a way to avoid the screen flicker when using an
incremental search routine with a grid.

WORKAROUND
==========

You can use the LockScreen property of the Form to eliminate most of the screen
flicker. For example, you can make the following modifications to the Form
created in the STEPS TO REPRODUCE BEHAVIOR section below:

1. Create a New Property for the Form and name it lRefreshingGrid. Set the
  property to .F.

2. Change the code in Text1.InterActiveChange event as follows:

        ThisForm.lRefreshingGrid = .T.
        ThisForm.LockScreen = .T.
        SELECT customer
        SEEK UPPER(ALLTRIM(ThisForm.Text1.Value))
        ThisForm.grid1.SetFocus
        ThisForm.text1.SetFocus
        ThisForm.LockScreen = .F.
        ThisForm.lRefreshingGrid = .F.

3. To ensure that the Valid event of the text box does not fire when the focus
  is moved to the grid and then back to the text box, add the following code to
  the Valid event of the text box:

        IF ThisForm.lRefreshingGrid
           RETURN .T.
        ENDIF

STATUS
======

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

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

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

1. Create a Form, and set the LockScreen property to False (.F.).

2. Add the Customer table, in the home()+"SAMPLES\DATA" folder, to the Data
  Environment. By default, the table is added to the Data Environment with the
  Name "cursor1". Set the Order property of the cursor to "cust_id".

3. Drag the table onto the form to create a grid. Set the Name property of the
  Grid to "Grid1".

4. Add a TextBox control to the form. Make sure that SelectOnEntry property of
  the Textbox control is set to .F. (the default). Add the following code to
  the TextBox control's InterActiveChange event:

        SELECT customer
        SEEK UPPER(ALLTRIM(This.Value))
        ThisForm.Grid1.Refresh

5. Run the Form and type a few characters in the text box.

6. Although the REFRESH method of the grid is being called from
  Text1.InterActiveChangeEvent, the record pointer in the grid does not move to
  the correct record.

7. Now change the code in Text1.InterActiveChange event as follows:

        SELECT customer
        SEEK UPPER(ALLTRIM(This.Value))
        ThisForm.grid1.SetFocus
        ThisForm.text1.SetFocus

8. Repeat step 5.

9. Now the Record Pointer in the grid is moving correctly but there is a lot of
  screen flicker every time a character is entered into the text box.

Additional query words: kbdse VFoxWin Flash

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP500 kbVFP600
Version           : 5.00

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