Q142398: How the Paint Event of a Form Works

Article: Q142398
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0,3.0b
Operating System(s): 
Keyword(s): 
Last Modified: 10-FEB-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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SUMMARY
=======

In the Help file or reference manual for the Paint event, it says that the Paint
event will fire when part or all of a form or toolbar is exposed after it has
been moved or sized -- or after a window that was covering the form or toolbar
has been moved.

This is true, but the Paint event also fires at other times, such as when a value
of an object changes or when moving the cursor from one object to another object
on the form. With this in mind, you should be aware of the consequences of
certain code that is placed in the Paint event.

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

The Paint event is an event of the form and is useful for checking the status of
objects, forms, variables, or a toolbar. It is wise to not place any code in the
Paint event that would affect the size or appearance of any objects or
properties. Changing the caption of an object or changing the value of an object
on a form would be examples of code that would make the form act strange.

Example
-------

1. Create a form and add a new property for the form. On the Form menu, click
  New Property, and in the Name box, type:

  " numcount " (without the quotation marks)

  In the Properties sheet under the Other tab, scroll to the bottom, and change
  the .F. beside the numcount property to the numeric value of 1.

2. Add a text box to the form.

3. In the Paint event of the form, add the following code:

     THISFORM.NUMCOUNT = THISFORM.NUMCOUNT + 1
     THISFORM.TEXT1.VALUE = STR(THISFORM.NUMCOUNT)

4. Run the form. Note that the text box is being constantly updated with a new
  number. This is because the Paint event is being called repeatedly. Every
  time the value of the text box is changed in Paint event, the Paint event is
  called again because it sees that the value of an object in the form has
  changed.

Additional query words: VFoxWin

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Keywords          :  
Technology        : kbVFPsearch kbAudDeveloper kbVFP300 kbVFP300b
Version           : WINDOWS:3.0,3.0b

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