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Q130831: Converter: How the Position of Screens Is Converted

Article: Q130831
Product(s): Microsoft FoxPro
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbcode
Last Modified: 15-FEB-2000

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The information in this article applies to:

- Microsoft Visual FoxPro for Windows, version 3.0 
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SUMMARY
=======

This article addresses the issue of positioning converted screens. It explains
how window position is calculated in FoxPro version 2.x for Windows and in
Visual FoxPro. It also describes how the converter converts screen position. The
source code to the CONVERT.APP application is included with the Professional
Edition of Visual FoxPro, and is installed in the TOOLS\CONVERT directory.

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

FoxPro version 2.x for Windows uses foxels to calculate window and object
location. A foxel is a unit of measure unique to FoxPro that is equivalent to
the average height and width of a character. In FoxPro versions 2.x for Windows,
a window position is based on the font of its container. In other words, if a
user window is defined on the desktop, the font of the main FoxPro window
determines the top and left position of the screen. Developers often place a
MODIFY WINDOW SCREEN FONT <fontname>,<fontsize> statement in the
Setup code of a FoxPro version 2.x screen to ensure that windows are
consistently displayed at the same location on different systems.

A screen added to a FoxPro version 2.x project can be positioned by using the
Arrange button. The window's coordinates are saved in foxels in the Project
Manager (ARRANGED field of the PJX table). The information relative to the
position of the window is not stored anywhere if the screen is not included in a
project.

A Visual FoxPro form can use pixels or foxels. A pixel is the smallest element
that can be displayed on a screen. It is resolution dependent but is not
affected by font information.

Visual FoxPro provides an application (CONVERT.APP) that converts FoxPro 2.x
projects to a Visual FoxPro format. The converter dialog is displayed when you
open a FoxPro version 2.x project in Visual FoxPro. Screen sets are converted to
form sets, and each screen contained in a screen set is converted to a form. The
SCALEMODE property of a converted form is set to 3- Pixels.

During the conversion process, CONVERT.APP converts the window position from
foxels to pixels. The calculation is defined in the AddPos method of the
FP25FORM class in the CONVERT.PRG file. CONVERT.APP uses the font of the desktop
in the current Visual FoxPro session as a basis for the conversion.

For example, if the desktop font is MSSansSerif 10, the converter uses the
fontmetrics of MSSansSerif 10 to convert the position of the form window. On the
other hand, if the desktop font is MSSansSerif 12, MSSansSerif 12 is the basis
for the conversion from foxel to pixel, and the resulting window appears at a
lower position than it was previously located.

Therefore, to ensure that windows are located at the same absolute position in a
converted screen, verify that the font of the main FoxPro window is the same as
the one used by FoxPro version 2.6 screens.

NOTE: When the SCALEMODE property of a form is set to 0-Foxels, the window
position is based on the font it uses. As opposed to windows defined with a
DEFINE WINDOW command used in FoxPro version 2.x screen definition, the top and
left positions of a Visual FoxPro form are not set by the font of the container
window. Thus, in Visual FoxPro, the MODIFY WINDOW SCREEN FONT <FontName>
command does not alter the position of a form.

The following example code illustrates the fact that the position of a window is
based on its font:

     omyform1=CREATEOBJECT('myform')
     omyform1.show

     oMyform2=CREATEOBJECT('myform2')
     omyform2.show

     suspend

     DEFINE CLASS MyForm2 AS Form
        caption = "Arial, 18"
        scalemode = 0
        fontname="Arial"
        fontsize=18
        top = 1
        left = 1
        height = 10
        width = 20
     ENDDEFINE

     DEFINE CLASS MyForm AS Form
        caption= "Arial,10"
        scalemode = 0
        fontname="Arial"
        fontsize=10
        top = 1
        left = 1
        height = 10
        width = 20
     ENDDEFINE

Additional query words: VFoxWin

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Keywords          : kbcode 
Technology        : kbVFPsearch kbAudDeveloper kbVFP300
Version           : WINDOWS:3.0

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