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

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with: Microsoft Visual C++, 32-bit Edition, 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.