DOC: Incorrect Examples on Pages 69-75 of Developer's Guide

SUMMARY

The example that create a VCR control in the Visual FoxPro "Developer's Guide" on pages 69-75 creates a subclass of the VCR control. When an instance of VCR2 is created on a form, the container is not sized correctly; it is much wider than the form.

The following conditions lead to this problem:

• The ScaleMode of the form is in foxels.
• The width of the VCR2 container, expressed in foxels, is decimal.
• The width of the VCR2 container is used as a variable in the body of the class definition (in the DEFINE part). In this example, the specific lines are:

  Left=This.Width+.2
  Width=This.Width+This.CmdQuit.Width+.2

If all these conditions are true, then when an instance of the class is created, Visual FoxPro sees that the width of the container is in foxels. It converts the number to pixels, using the font of the form as the basis for conversion. That number is in turn used to size the container on the form, but it is not converted back to foxels. In this example, the Width of the container is converted from 6.2 foxels to 61 pixels. When the container is placed on the form, the same measure is used. However, the unit is no longer pixels, it is foxels. So the width of the container is 61 foxels.

Fix Status

This documentation error has been fixed in Visual FoxPro 5.0 for Windows.

   DEFINE CLASS vcr2 as vcr
   ADD OBJECT cmdQuit AS COMMANDBUTTON WITH ;
      Caption="Quit", ;
      Height=2, ;
      Width=6.8

   PROCEDURE INIT
   This.CmdQuit.Left=This.Width+.2
   This.Width=This.Width+This.CmdQuit.Width+.2
   ENDPROC

   PROCEDURE cmdQuit.CLICK
     Release Thisform
   ENDPROC

   ENDDEFINE