INFO: A Discussion of Windows Fonts (10837)

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How Default Fonts Are Assigned

At the API level, Windows version 3.0 defines six stock fonts. Each of these fonts has a logical description. At Windows 3.0 boot time, GDI constructs the logical description of these fonts in the following manner:

1. During its initialization, GDI calls an internal function, InitFonts(), which is responsible for physically loading three basic fonts. Under a typical Windows 3.0 installation, the names of the font files for these fonts are listed in the [boot] section of the SYSTEM.ini file. For example, this section (in part) resembles the following:

      fixedfon.fon=vgafix.fon
      oemfonts.fon=vgaoem.fon
      fonts.fon=vgasys.fon
   						

   The system font is loaded first. GDI first checks the WIN.ini file in the [windows] section for the key name SystemFont=<file>, where <file> is a name of a bitmap font (such as HELV.FON). If GDI finds this keyname, it will attempt to load the specified file as thesystem font. Changing this value is one method the user can use to customize the system font. NOTE: If you change SystemFont=<font> you *must* also have the line fonts.fon=<font> in the [windows] section of the SYSTEM.INI file. Otherwise, Windows will not load properly.
   
   If GDI does not find this key name, it attempts to load the system font from a file called FONTS.fon using the GDI function AddFontResource. Notice that on typical installations of Windows 3.0, there is no file called FONTS.fon. AddFontResource calls LoadLibrary to load the specified file. If the file is not found, LoadLibrary will search the SYSTEM.ini file (in the [boot] section) for a redirection of the file. As shown above, the [boot] section of SYSTEM.ini for a VGA system contains the following:

      fonts.fon=vgasys.fon
   						

   This line indicates that the system font should be loaded from the file VGASYS.fon, which resides in the system directory.
2. Once the system font is physically loaded, GDI attempts to load a fixed-pitch font. GDI examines the [boot] section of the SYSTEM.ini file and extracts the filename from the fixedfon.fon= field. If no file is specified, the system font (loaded in step 1) is substituted for the system fixed-pitch font.
3. Next, the terminal font is loaded. GDI attempts to load the file OEMFONTS.fon (via AddFontResource). This file may be redirected in the same manner as the system font in step 1.
4. Later during its initialization, GDI gets the module handle of DISPLAY. Using the module handle, it does a FindResource() on the resource string "fonts", which is an array of three LOGFONT structures that have been defined by the display driver manufacturer. This is the resource that is included in the display driver's .RC file with the line:

      fonts   oembin  PRELOAD         fonts.bin
   						

   Once this resource is found, GDI steps through the array of LOGFONTS and calls CreateFontIndirect to create the stock font objects:

      OEM_FIXED_FONT
      ANSI_FIXED_FONT
      ANSI_VAR_FONT
   						

   These logical font definitions can be thought of as recommendations for a particular display by the display driver. In general, these logical font descriptions will map to one of the physical fonts loaded initially by GDI.
   
   However, when an application selects one of these stock fonts, the font mapper selects the closest matching font from a list of available physical fonts in the system. This list contains the initial system fonts that were loaded by GDI, in addition to other fonts that may have been loaded at a later time. Therefore, there is no guarantee that a given stock font will necessarily map to one of the three initial fonts loaded by GDI.
5. Once these three stock fonts have been defined, GDI defines the stock font SYSTEM_FONT. GDI does this by opening the system font file loaded in step 1 and builds a logical font structure that exactly matches the physical characteristics of the physical font. This is to ensure that the font mapper will select this physical font when the SYSTEM_FONT stock font is requested.
6. Finally, the logical description of the device default font (DEVICE_DEFAULT_FONT) is defined. This font is defined to be the same as the SYSTEM_FONT.

Why These Fonts Are Necessary

There are two reasons for having these six stock fonts. One reason is to provide an OEM font that displays well at 10 pitch on the machine. This font is also used to determine the height of dialog boxes. The second reason is to provide ANSI fonts that are based on proposed standards (device-independent) and match Microsoft's virtual-key definitions.

Please note that all of these fonts are required. The display driver must include the three logical fonts (described above) or GDI will not initialize properly.