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Q194323: PRB: Setting Printer.Font.Size with StdFont Gives Wrong Values

Article: Q194323
Product(s): Microsoft Visual Basic for Windows
Version(s): WINDOWS:5.0,6.0
Operating System(s): 
Keyword(s): kbGrpDSVB
Last Modified: 11-JAN-2001

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The information in this article applies to:

- Microsoft Visual Basic Learning Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Professional Edition for Windows, versions 5.0, 6.0 
- Microsoft Visual Basic Enterprise Edition for Windows, versions 5.0, 6.0 
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SYMPTOMS
========

When you set a font size by assigning a value directly to Printer.FontSize, or
Printer.Font.Size, you get a different value than when using a StdFont object.

CAUSE
=====

The issue here is that the default StdFont object is always based on the display
hDC (Device Context handle), not the printer hDC. So when executing a line such
as this:

     Set Printer.Font = MyStdFont

the actual font handle created is using the display Device Context (DC). Because
the printer has a slightly different scale than the display, the font size
generated is also a little different.

RESOLUTION
==========

As long as you consistently use a StdFont object (late binding) or consistently
set the FontSize directly (early binding) and do not try to use both techniques
in your code, this behavior should have no noticeable effect.

STATUS
======

This behavior is by design.

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

A Device Context (DC) is defined as a link between a Windows-based application,
a device driver, and an output device, such as a display, printer, or plotter.
These DCs are created as needed and are identified by a device context handle,
or hDC.

When a StdFont object is instantiated, it has no way of knowing what devices will
be using it. Therefore, to be consistent, it is always based on the display
Device Context. If it were to try and change its hDC to that of the device to
which it was being assigned, undesired behavior would result for shared Font
objects that are used across different devices.

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

1. Create a Standard EXE project in Visual Basic. Form1 is created by default.

2. Add a CommandButton to Form1.

3. Place the following code into Form1's code window:

        Private Sub Command1_Click()
          Printer.FontName = "Arial"
          Printer.FontSize = 8
          Debug.Print Printer.FontName;
          Debug.Print Printer.FontSize;
          Debug.Print Printer.TextWidth("TEST")

          Printer.Font.Name = "Arial"
          Printer.Font.Size = 8
          Debug.Print Printer.FontName;
          Debug.Print Printer.FontSize;
          Debug.Print Printer.TextWidth("TEST")

          Dim f As New StdFont
          f.Name = "Arial"
          f.Size = 8
          Set Printer.Font = f
          Debug.Print Printer.FontName;
          Debug.Print Printer.FontSize;
          Debug.Print Printer.TextWidth("TEST")
        End Sub

4. Run the project and click on Command1. You should see something similar to
  the following output in the Immediate window:

  Arial 7.92 413
  Arial 7.92 413
  Arial 8.16 422

  The first two values match, but the value when using StdFont is different.

REFERENCES
==========

For more information on Device Contexts, search Help for "hDC property" or
"device context handle."

For additional information, please see the following article in the Microsoft
Knowledge Base:

  Q190223 : PRB: StdFont Rescales When Shared with Printer Object

(c) Microsoft Corporation 1998. All Rights Reserved.
Contributions by Chris E. Jolley, Microsoft Corporation.


Additional query words: kbDSupport kbDSD kbVBp kbVBp600 kbVBp500 kbFont kbPrinting

======================================================================
Keywords          : kbGrpDSVB 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2 kbVB500Search kbVB600Search kbVBA500 kbVBA600 kbVB500 kbVB600
Version           : WINDOWS:5.0,6.0
Issue type        : kbprb

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