Experimental only

The auto-hinter provides various script modules to hint glyphs. Examples of supported scripts are Latin or CJK. Before a glyph is auto-hinted, the Unicode character map of the font gets examined, and the script is then determined based on Unicode character ranges, see below.

OpenType fonts, however, often provide much more glyphs than character codes (small caps, superscripts, ligatures, swashes, etc.), to be controlled by so-called ‘features’. Handling OpenType features can be quite complicated and thus needs a separate library on top of FreeType.

The mapping between glyph indices and scripts (in the auto-hinter sense, see the FT_AUTOHINTER_SCRIPT_XXX values) is stored as an array with ‘num_glyphs’ elements, as found in the font's FT_Face structure. The ‘glyph-to-script-map’ property returns a pointer to this array, which can be modified as needed. Note that the modification should happen before the first glyph gets processed by the auto-hinter so that the global analysis of the font shapes actually uses the modified mapping.

The following example code demonstrates how to access it (omitting the error handling).

  FT_Library                library;
  FT_Face                   face;
  FT_Prop_GlyphToScriptMap  prop;


  FT_Init_FreeType( &library );
  FT_New_Face( library, "foo.ttf", 0, &face );

  prop.face = face;

  FT_Property_Get( library, "autofitter",
                            "glyph-to-script-map", &prop );

  // adjust `prop.map' as needed right here

  FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT );

#define FT_AUTOHINTER_SCRIPT_NONE   0
#define FT_AUTOHINTER_SCRIPT_LATIN  1
#define FT_AUTOHINTER_SCRIPT_CJK    2
#define FT_AUTOHINTER_SCRIPT_INDIC  3

Experimental only

A list of constants used for the glyph-to-script-map property to specify the script submodule the auto-hinter should use for hinting a particular glyph.

   typedef struct  FT_Prop_GlyphToScriptMap_
   {
     FT_Face   face;
     FT_Byte*  map;

   } FT_Prop_GlyphToScriptMap;

Experimental only

The data exchange structure for the glyph-to-script-map property.

Experimental only

If no auto-hinter script module can be assigned to a glyph, a fallback script gets assigned to it (see also the glyph-to-script-map property). By default, this is FT_AUTOHINTER_SCRIPT_CJK. Using the ‘fallback-script’ property, this fallback value can be changed.

  FT_Library  library;
  FT_UInt     fallback_script = FT_AUTOHINTER_SCRIPT_NONE;


  FT_Init_FreeType( &library );

  FT_Property_Set( library, "autofitter",
                            "fallback-script", &fallback_script );

This property can be used with FT_Property_Get also.

It's important to use the right timing for changing this value: The creation of the glyph-to-script map that eventually uses the fallback script value gets triggered either by setting or reading a face-specific property like glyph-to-script-map, or by auto-hinting any glyph from that face. In particular, if you have already created an FT_Face structure but not loaded any glyph (using the auto-hinter), a change of the fallback glyph will affect this face.

For ppem values in the range 6 <= ppem <= ‘increase-x-height’, round up the font's x height much more often than normally. If the value is set to 0, which is the default, this feature is switched off. Use this property to improve the legibility of small font sizes if necessary.

  FT_Library               library;
  FT_Face                  face;
  FT_Prop_IncreaseXHeight  prop;


  FT_Init_FreeType( &library );
  FT_New_Face( library, "foo.ttf", 0, &face );
  FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 );

  prop.face  = face;
  prop.limit = 14;

  FT_Property_Set( library, "autofitter",
                            "increase-x-height", &prop );

This property can be used with FT_Property_Get also.

Set this value right after calling FT_Set_Char_Size, but before loading any glyph (using the auto-hinter).

   typedef struct  FT_Prop_IncreaseXHeight_
   {
     FT_Face  face;
     FT_UInt  limit;

   } FT_Prop_IncreaseXHeight;

The data exchange structure for the increase-x-height property.