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Q149341: FIX: CreatePointFont() May Create Wrong Size Font in Preview

Article: Q149341
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1
Operating System(s): 
Keyword(s): kbprint kbFont kbMFC kbPrinting kbVC400 kbVC410 kbDSupport kbGrpDSMFCATL kbNoUpdate
Last Modified: 11-SEP-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), included with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

Calling CFont::CreatePointFont() results in a font displayed in print preview
mode that is not of the point size requested.

CAUSE
=====

The CDC class contains two member variables for its current device context,
m_hDC and m_hAttribDC. m_hDC (the output device context) is equal to m_hAttribDC
(the attribute device context) by default. However, when print preview is
active, these two variables will not be equal; at that point, the m_hDC contains
the screen's device context and m_hAttribDC contains the printer's device
context.

The implementation of CreatePointFont() looks at the m_hDC member of the CDC
class to calculate the proper size for the font rather than the m_hAttribDC
member. The result of this behavior is that CreatePointFont will always create a
font sized for the screen device context.

RESOLUTION
==========

The following sample code works around the problem by creating another CDC
object based on the m_hAttribDC member of the original CDC and uses this new CDC
to call CFont::CreatePointFont().

Sample Code
-----------

  /* Compile options needed: default
  */ 

  void CMyView::OnDraw(CDC* pDC)
  {
      // dcPrinter's m_hDC and m_hAttribDC member variables
      // will both be properly pointing to the printer DC.
      CDC dcPrinter;
      dcPrinter.Attach(pDC->m_hAttribDC);

      CFont font;
      font.CreatePointFont(110, "Courier New", &dcPrinter);

      // You must detach from the DC after using
      // our temporary dcPrinter object or problems will occur!
      dcPrinter.Detach();

      CFont* pOldFont = pDC->SelectObject(&font);

      // Use font here...
      pDC->SelectObject(pOldFont);
  }

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug was corrected in Visual C++ 32- bit Edition
version 4.2.

Additional query words: 4.00 4.10 4.20 vcfixlist420

======================================================================
Keywords          : kbprint kbFont kbMFC kbPrinting kbVC400 kbVC410 kbDSupport kbGrpDSMFCATL kbNoUpdate 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.0,4.1
Issue type        : kbbug
Solution Type     : kbfix

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