There is one 
font-name-directory<%> object:
 
the-font-name-directory. It implements a mapping from font
 specifications (face, family, style, and weight) to information for
 rendering text on a specific device. Programmers rarely need to
 directly invoke methods of 
the-font-name-directory. It is
 used automatically when drawing text to a 
dc<%>
 object. Nevertheless, 
the-font-name-directory is available
 so that programmers can query or modify the mapping manually. A
 programmer may also need to understand how the face-and-family
 mapping works.
To extract mapping information from the-font-name-directory,
 first obtain a font ID, which is an index based on a family
 and optional face string. Font IDs are returned by
 find-or-create-font-id and
 get-font-id . A Font ID can be
 combined with a weight and style to obtain a specific mapping value
 via get-screen-name or
 get-post-script-name.
For a family without a face string, the corresponding font ID has a
 useful built-in mapping for every platform and device. For a family with a
 face string, the-font-name-directory interprets the string
 (in a platform-specific way) to generate a mapping for
 drawing (to a canvas’s dc<%>, a bitmap-dc%, or a
 printer-dc%).
Currently, on all platforms, a face string is interpreted as a
 Pango font description when it
 contains a comma, otherwise it is treated as a family name. A
 face can thus be just a family name such as "Helvetica", a family
 followed by a comma and font modifiers as in "Helvetica, Bold", or a sequence of comma-separated
 familie names followed by space-separated font options as an
 "Helvetica, Arial, bold italic". Any size in a font
 description is overridden by a given font%’s size. Any
 (slant) style or weight options in a font description are overridden
 by a non-'normal value for a given font%’s style or
 weight, respectively.
Gets the font ID representing the default font for a family. See
font% for information about font families.
Gets the face name for a font ID, initializing the mapping for
 the face name if necessary.
Font ID are useful only as mapping indices for
 the-font-name-directory.
Gets the face name for a font ID. If the font ID corresponds to
 the default font for a particular family, #f is returned.
Gets the family for a font ID. See
font% for information about font families.
Gets the font ID for a face name paired with a default family. If the
 mapping for the given pair is not already initialized, 
0 is
 returned. See also 
find-or-create-font-id.
Font ID are useful only as mapping indices for
 the-font-name-directory.
Gets a PostScript font description for a font ID, weight, and style
 combination.
See font% for information about weight and
 style.
Gets a platform-dependent screen font description (used for drawing to a
 canvas’s 
dc<%>, a 
bitmap-dc%, or a
 
printer-dc%) for a font ID, weight, and style combination.
See font% for information about weight and
style.
Sets a PostScript font description for a font ID, weight, and style
 combination. See also 
get-post-script-name.
See font% for information about weight and style.
Sets a platform-dependent screen font description (used for drawing to a
 canvas’s 
dc<%>, a 
bitmap-dc%, or a
 
printer-dc%) for a font ID, weight, and style combination.
See 
font% for information about 
weight and
 
style.