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

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.

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:

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.

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.

This behavior is by design.

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.

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:

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