KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q92410: PRB: Average & Maximum Char Widths Different for TT Fixed Font

Article: Q92410
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1,95; winnt:3.5,3.51,4.0
Operating System(s): 
Keyword(s): kbOSWinNT350 kbOSWinNT351 kbOSWinNT400 kbOSWin95 kbSDKWin16
Last Modified: 12-MAY-2001

3.10 4.00 | 3.50 3.51
WINDOWS   | WINDOWS NT
kbgraphic kbprb

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

- Microsoft Windows Software Development Kit (SDK) 3.1 
- Microsoft Win32 Application Programming Interface (API) 
-------------------------------------------------------------------------------

SYMPTOMS
========

The tmAveCharWidth and tmMaxCharWidth fields of the TEXTMETRIC structure are not
equal for a fixed-pitch TrueType (TT) font such as Courier New.

RESOLUTION
==========

This is by TrueType design. The tmMaxCharWidth denotes the maximum possible ink
width of the font rather than maximum cell width of the font.

STATUS
======

This behavior is by design.

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

TrueType fonts use ABC character spacing. The "A" width is the distance that is
added to the current position before placing the TrueType glyph. The "B" width
is the width of the black part (ink width) of the TT glyph. The "C" width is the
distance from the end of the "B" width to the beginning of the next character.
Advanced width (cell width) is equal to A+B+C.

The physical TT fonts that are passed to drivers have just the "B" part of the
characters, so all fonts at the level of the driver appear to be proportional
width fonts. The tmMaxCharWidth is the least width in which the "B" part of all
characters will fit. The tmAveCharWidth is the average advance width (A+B+C).
For a fixed-pitch TT font such as Courier New, the A+B+C width is the same for
all characters; however, the maximum width as defined above can be different.

tmMaxCharWidth is greater than tmAveCharWidth only if A+C is negative. This is
possible for a fixed-pitch font.

Please see section 18.2.4.1 of the Windows 3.1 SDK "Guide to Programming" for
more information about ABC character spacing.

Additional query words: 3.10 4.00

======================================================================
Keywords          : kbOSWinNT350 kbOSWinNT351 kbOSWinNT400 kbOSWin95 kbSDKWin16 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWin32sSearch kbWin32API kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1,95; winnt:3.5,3.51,4.0
Issue type        : kbprb

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.