Calculating Text Extents of Bold and Italic Text

 Last reviewed: November 2, 1995
Article ID: Q74298
The information in this article applies to:
  • Microsoft Windows Software Development Kit (SDK) for Windows versions 3.1 and 3.0
  • Microsoft Win32 Application Programming Interface (API) included with: 

        - Microsoft Windows NT versions 3.5 and 3.51
    - Microsoft Windows 95 version 4.0

SUMMARY

GetTextExtent() can be used to calculate the extent of a string. The value returned may need to be adjusted, depending upon the style of the font. When an italic or bold font is requested and none are available, the graphics device interface (GDI) may simulate those styles using an existing raster or vector font.

MORE INFORMATION

GDI-simulated bold and italic fonts both include overhangs. The overhang is specified in a TEXTMETRIC structure obtained by calling the GetTextMetrics function. The proper method for calculating the extent of a line of italic or bold text is shown below: 

   dwExtent = GetTextExtent(hDC, lpString, nCount);
   GetTextMetrics(hDC, &tm);
   xExtent = LOWORD(dwExtent) - tm.tmOverhang;
Listed below are examples of italic text alignment. If the next character is not italic, the overhang should not be subtracted from the extent returned from the GetTextExtent function. The overhang needs to be subtracted only when the next character has the same style. 

                                        GetTextExtent yields
                                        this as the extent:

                                              ||
       /   /                                  \/
      /   /           /   / /   /         /   /|   |
     /---/           /   / /   /         /   / |   |
    /   /           /---/ /---/         /---/  |---|
   /   /           /   / /   /         /   /   |   |
       -----      /   / /   /         /   /    |   |
         ^            /\                      /\
      Overhang        ||                      ||
               Because the next        Start the nonitalic H
               character is italic,    here because it does not
               start the next          slant and would partially
               character within the    overwrite the previous
               overhang of the         italic character.
               current character
The overhang for bold characters synthesized by GDI is generally 1 because GDI synthesizes bold fonts by outputting the text twice, offsetting the second output by one pixel, effectively increasing the width of each character by one pixel. Calculating the extent of the bold text is similar to the method for italic text. The GetTextExtent function always returns the extent of the text plus 1 for bold text. Thus by subtracting the tmOverhang(1), the proper extent is achieved. 

        ||   ||
        ||   ||
        ||===||
        ||   ||
        ||   ||
              ---<= This line represents the "extra" overhang of 1.
                /\
                ||
             GetTextExtent yields
             this as the extent of the
             bold H.

Additional reference words: 3.00 3.10 3.50 4.00 95
KBCategory: kbgraphic
KBSubcategory: GdiFnt

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.

Last reviewed: November 2, 1995
© 1998 Microsoft Corporation. All rights reserved. Terms of Use.