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Base Interface

Synopsis

This section describes the most important public high-level API functions of FreeType 2.

FT_Library

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_LibraryRec_  *FT_Library;

A handle to a FreeType library instance. Each ‘library’ is completely independent from the others; it is the ‘root’ of a set of objects like fonts, faces, sizes, etc.

It also embeds a memory manager (see FT_Memory), as well as a scan-line converter object (see FT_Raster).

[Since 2.5.6] In multi-threaded applications it is easiest to use one FT_Library object per thread. In case this is too cumbersome, a single FT_Library object across threads is possible also, as long as a mutex lock is used around FT_New_Face and FT_Done_Face.

note

Library objects are normally created by FT_Init_FreeType, and destroyed with FT_Done_FreeType. If you need reference-counting (cf. FT_Reference_Library), use FT_New_Library and FT_Done_Library.


FT_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_FaceRec_*  FT_Face;

A handle to a typographic face object. A face object models a given typeface, in a given style.

note

A face object also owns a single FT_GlyphSlot object, as well as one or more FT_Size objects.

Use FT_New_Face or FT_Open_Face to create a new face object from a given filepath or a custom input stream.

Use FT_Done_Face to destroy it (along with its slot and sizes).

An FT_Face object can only be safely used from one thread at a time. Similarly, creation and destruction of FT_Face with the same FT_Library object can only be done from one thread at a time. On the other hand, functions like FT_Load_Glyph and its siblings are thread-safe and do not need the lock to be held as long as the same FT_Face object is not used from multiple threads at the same time.

also

See FT_FaceRec for the publicly accessible fields of a given face object.


FT_Size

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_SizeRec_*  FT_Size;

A handle to an object that models a face scaled to a given character size.

note

An FT_Face has one active FT_Size object that is used by functions like FT_Load_Glyph to determine the scaling transformation that in turn is used to load and hint glyphs and metrics.

You can use FT_Set_Char_Size, FT_Set_Pixel_Sizes, FT_Request_Size or even FT_Select_Size to change the content (i.e., the scaling values) of the active FT_Size.

You can use FT_New_Size to create additional size objects for a given FT_Face, but they won't be used by other functions until you activate it through FT_Activate_Size. Only one size can be activated at any given time per face.

also

See FT_SizeRec for the publicly accessible fields of a given size object.


FT_GlyphSlot

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_GlyphSlotRec_*  FT_GlyphSlot;

A handle to a given ‘glyph slot’. A slot is a container that can hold any of the glyphs contained in its parent face.

In other words, each time you call FT_Load_Glyph or FT_Load_Char, the slot's content is erased by the new glyph data, i.e., the glyph's metrics, its image (bitmap or outline), and other control information.

also

See FT_GlyphSlotRec for the publicly accessible glyph fields.


FT_CharMap

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_CharMapRec_*  FT_CharMap;

A handle to a character map (usually abbreviated to ‘charmap’). A charmap is used to translate character codes in a given encoding into glyph indexes for its parent's face. Some font formats may provide several charmaps per font.

Each face object owns zero or more charmaps, but only one of them can be ‘active’, providing the data used by FT_Get_Char_Index or FT_Load_Char.

The list of available charmaps in a face is available through the face->num_charmaps and face->charmaps fields of FT_FaceRec.

The currently active charmap is available as face->charmap. You should call FT_Set_Charmap to change it.

note

When a new face is created (either through FT_New_Face or FT_Open_Face), the library looks for a Unicode charmap within the list and automatically activates it. If there is no Unicode charmap, FreeType doesn't set an ‘active’ charmap.

also

See FT_CharMapRec for the publicly accessible fields of a given character map.


FT_Encoding

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef enum  FT_Encoding_
  {
    FT_ENC_TAG( FT_ENCODING_NONE, 0, 0, 0, 0 ),

    FT_ENC_TAG( FT_ENCODING_MS_SYMBOL, 's', 'y', 'm', 'b' ),
    FT_ENC_TAG( FT_ENCODING_UNICODE,   'u', 'n', 'i', 'c' ),

    FT_ENC_TAG( FT_ENCODING_SJIS,    's', 'j', 'i', 's' ),
    FT_ENC_TAG( FT_ENCODING_PRC,     'g', 'b', ' ', ' ' ),
    FT_ENC_TAG( FT_ENCODING_BIG5,    'b', 'i', 'g', '5' ),
    FT_ENC_TAG( FT_ENCODING_WANSUNG, 'w', 'a', 'n', 's' ),
    FT_ENC_TAG( FT_ENCODING_JOHAB,   'j', 'o', 'h', 'a' ),

    /* for backward compatibility */
    FT_ENCODING_GB2312     = FT_ENCODING_PRC,
    FT_ENCODING_MS_SJIS    = FT_ENCODING_SJIS,
    FT_ENCODING_MS_GB2312  = FT_ENCODING_PRC,
    FT_ENCODING_MS_BIG5    = FT_ENCODING_BIG5,
    FT_ENCODING_MS_WANSUNG = FT_ENCODING_WANSUNG,
    FT_ENCODING_MS_JOHAB   = FT_ENCODING_JOHAB,

    FT_ENC_TAG( FT_ENCODING_ADOBE_STANDARD, 'A', 'D', 'O', 'B' ),
    FT_ENC_TAG( FT_ENCODING_ADOBE_EXPERT,   'A', 'D', 'B', 'E' ),
    FT_ENC_TAG( FT_ENCODING_ADOBE_CUSTOM,   'A', 'D', 'B', 'C' ),
    FT_ENC_TAG( FT_ENCODING_ADOBE_LATIN_1,  'l', 'a', 't', '1' ),

    FT_ENC_TAG( FT_ENCODING_OLD_LATIN_2, 'l', 'a', 't', '2' ),

    FT_ENC_TAG( FT_ENCODING_APPLE_ROMAN, 'a', 'r', 'm', 'n' )

  } FT_Encoding;


  /* these constants are deprecated; use the corresponding `FT_Encoding` */
  /* values instead                                                      */
#define ft_encoding_none            FT_ENCODING_NONE
#define ft_encoding_unicode         FT_ENCODING_UNICODE
#define ft_encoding_symbol          FT_ENCODING_MS_SYMBOL
#define ft_encoding_latin_1         FT_ENCODING_ADOBE_LATIN_1
#define ft_encoding_latin_2         FT_ENCODING_OLD_LATIN_2
#define ft_encoding_sjis            FT_ENCODING_SJIS
#define ft_encoding_gb2312          FT_ENCODING_PRC
#define ft_encoding_big5            FT_ENCODING_BIG5
#define ft_encoding_wansung         FT_ENCODING_WANSUNG
#define ft_encoding_johab           FT_ENCODING_JOHAB

#define ft_encoding_adobe_standard  FT_ENCODING_ADOBE_STANDARD
#define ft_encoding_adobe_expert    FT_ENCODING_ADOBE_EXPERT
#define ft_encoding_adobe_custom    FT_ENCODING_ADOBE_CUSTOM
#define ft_encoding_apple_roman     FT_ENCODING_APPLE_ROMAN

An enumeration to specify character sets supported by charmaps. Used in the FT_Select_Charmap API function.

note

Despite the name, this enumeration lists specific character repertories (i.e., charsets), and not text encoding methods (e.g., UTF-8, UTF-16, etc.).

Other encodings might be defined in the future.

values

FT_ENCODING_NONE

The encoding value 0 is reserved for all formats except BDF, PCF, and Windows FNT; see below for more information.

FT_ENCODING_UNICODE

The Unicode character set. This value covers all versions of the Unicode repertoire, including ASCII and Latin-1. Most fonts include a Unicode charmap, but not all of them.

For example, if you want to access Unicode value U+1F028 (and the font contains it), use value 0x1F028 as the input value for FT_Get_Char_Index.

FT_ENCODING_MS_SYMBOL

Microsoft Symbol encoding, used to encode mathematical symbols and wingdings. For more information, see ‘https://www.microsoft.com/typography/otspec/recom.htm’, ‘http://www.kostis.net/charsets/symbol.htm’, and ‘http://www.kostis.net/charsets/wingding.htm’.

This encoding uses character codes from the PUA (Private Unicode Area) in the range U+F020-U+F0FF.

FT_ENCODING_SJIS

Shift JIS encoding for Japanese. More info at ‘https://en.wikipedia.org/wiki/Shift_JIS’. See note on multi-byte encodings below.

FT_ENCODING_PRC

Corresponds to encoding systems mainly for Simplified Chinese as used in People's Republic of China (PRC). The encoding layout is based on GB 2312 and its supersets GBK and GB 18030.

FT_ENCODING_BIG5

Corresponds to an encoding system for Traditional Chinese as used in Taiwan and Hong Kong.

FT_ENCODING_WANSUNG

Corresponds to the Korean encoding system known as Extended Wansung (MS Windows code page 949). For more information see ‘https://www.unicode.org/Public/MAPPINGS/VENDORS/MICSFT/WindowsBestFit/bestfit949.txt’.

FT_ENCODING_JOHAB

The Korean standard character set (KS C 5601-1992), which corresponds to MS Windows code page 1361. This character set includes all possible Hangul character combinations.

FT_ENCODING_ADOBE_LATIN_1

Corresponds to a Latin-1 encoding as defined in a Type 1 PostScript font. It is limited to 256 character codes.

FT_ENCODING_ADOBE_STANDARD

Adobe Standard encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes.

FT_ENCODING_ADOBE_EXPERT

Adobe Expert encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes.

FT_ENCODING_ADOBE_CUSTOM

Corresponds to a custom encoding, as found in Type 1, CFF, and OpenType/CFF fonts. It is limited to 256 character codes.

FT_ENCODING_APPLE_ROMAN

Apple roman encoding. Many TrueType and OpenType fonts contain a charmap for this 8-bit encoding, since older versions of Mac OS are able to use it.

FT_ENCODING_OLD_LATIN_2

This value is deprecated and was neither used nor reported by FreeType. Don't use or test for it.

FT_ENCODING_MS_SJIS

Same as FT_ENCODING_SJIS. Deprecated.

FT_ENCODING_MS_GB2312

Same as FT_ENCODING_PRC. Deprecated.

FT_ENCODING_MS_BIG5

Same as FT_ENCODING_BIG5. Deprecated.

FT_ENCODING_MS_WANSUNG

Same as FT_ENCODING_WANSUNG. Deprecated.

FT_ENCODING_MS_JOHAB

Same as FT_ENCODING_JOHAB. Deprecated.

note

By default, FreeType enables a Unicode charmap and tags it with FT_ENCODING_UNICODE when it is either provided or can be generated from PostScript glyph name dictionaries in the font file. All other encodings are considered legacy and tagged only if explicitly defined in the font file. Otherwise, FT_ENCODING_NONE is used.

FT_ENCODING_NONE is set by the BDF and PCF drivers if the charmap is neither Unicode nor ISO-8859-1 (otherwise it is set to FT_ENCODING_UNICODE). Use FT_Get_BDF_Charset_ID to find out which encoding is really present. If, for example, the cs_registry field is ‘KOI8’ and the cs_encoding field is ‘R’, the font is encoded in KOI8-R.

FT_ENCODING_NONE is always set (with a single exception) by the winfonts driver. Use FT_Get_WinFNT_Header and examine the charset field of the FT_WinFNT_HeaderRec structure to find out which encoding is really present. For example, FT_WinFNT_ID_CP1251 (204) means Windows code page 1251 (for Russian).

FT_ENCODING_NONE is set if platform_id is TT_PLATFORM_MACINTOSH and encoding_id is not TT_MAC_ID_ROMAN (otherwise it is set to FT_ENCODING_APPLE_ROMAN).

If platform_id is TT_PLATFORM_MACINTOSH, use the function FT_Get_CMap_Language_ID to query the Mac language ID that may be needed to be able to distinguish Apple encoding variants. See

https://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/Readme.txt

to get an idea how to do that. Basically, if the language ID is 0, don't use it, otherwise subtract 1 from the language ID. Then examine encoding_id. If, for example, encoding_id is TT_MAC_ID_ROMAN and the language ID (minus 1) is TT_MAC_LANGID_GREEK, it is the Greek encoding, not Roman. TT_MAC_ID_ARABIC with TT_MAC_LANGID_FARSI means the Farsi variant the Arabic encoding.


FT_ENC_TAG

Defined in FT_FREETYPE_H (freetype/freetype.h).

#ifndef FT_ENC_TAG
#define FT_ENC_TAG( value, a, b, c, d )         \
          value = ( ( (FT_UInt32)(a) << 24 ) |  \
                    ( (FT_UInt32)(b) << 16 ) |  \
                    ( (FT_UInt32)(c) <<  8 ) |  \
                      (FT_UInt32)(d)         )

#endif /* FT_ENC_TAG */

This macro converts four-letter tags into an unsigned long. It is used to define ‘encoding’ identifiers (see FT_Encoding).

note

Since many 16-bit compilers don't like 32-bit enumerations, you should redefine this macro in case of problems to something like this:

  #define FT_ENC_TAG( value, a, b, c, d )  value

to get a simple enumeration without assigning special numbers.


FT_FaceRec

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_FaceRec_
  {
    FT_Long           num_faces;
    FT_Long           face_index;

    FT_Long           face_flags;
    FT_Long           style_flags;

    FT_Long           num_glyphs;

    FT_String*        family_name;
    FT_String*        style_name;

    FT_Int            num_fixed_sizes;
    FT_Bitmap_Size*   available_sizes;

    FT_Int            num_charmaps;
    FT_CharMap*       charmaps;

    FT_Generic        generic;

    /*# The following member variables (down to `underline_thickness`) */
    /*# are only relevant to scalable outlines; cf. @FT_Bitmap_Size    */
    /*# for bitmap fonts.                                              */
    FT_BBox           bbox;

    FT_UShort         units_per_EM;
    FT_Short          ascender;
    FT_Short          descender;
    FT_Short          height;

    FT_Short          max_advance_width;
    FT_Short          max_advance_height;

    FT_Short          underline_position;
    FT_Short          underline_thickness;

    FT_GlyphSlot      glyph;
    FT_Size           size;
    FT_CharMap        charmap;

    /*@private begin */

    FT_Driver         driver;
    FT_Memory         memory;
    FT_Stream         stream;

    FT_ListRec        sizes_list;

    FT_Generic        autohint;   /* face-specific auto-hinter data */
    void*             extensions; /* unused                         */

    FT_Face_Internal  internal;

    /*@private end */

  } FT_FaceRec;

FreeType root face class structure. A face object models a typeface in a font file.

fields

num_faces

The number of faces in the font file. Some font formats can have multiple faces in a single font file.

face_index

This field holds two different values. Bits 0-15 are the index of the face in the font file (starting with value 0). They are set to 0 if there is only one face in the font file.

[Since 2.6.1] Bits 16-30 are relevant to GX and OpenType variation fonts only, holding the named instance index for the current face index (starting with value 1; value 0 indicates font access without a named instance). For non-variation fonts, bits 16-30 are ignored. If we have the third named instance of face 4, say, face_index is set to 0x00030004.

Bit 31 is always zero (this is, face_index is always a positive value).

[Since 2.9] Changing the design coordinates with FT_Set_Var_Design_Coordinates or FT_Set_Var_Blend_Coordinates does not influence the named instance index value (only FT_Set_Named_Instance does that).

face_flags

A set of bit flags that give important information about the face; see FT_FACE_FLAG_XXX for the details.

style_flags

The lower 16 bits contain a set of bit flags indicating the style of the face; see FT_STYLE_FLAG_XXX for the details.

[Since 2.6.1] Bits 16-30 hold the number of named instances available for the current face if we have a GX or OpenType variation (sub)font. Bit 31 is always zero (this is, style_flags is always a positive value). Note that a variation font has always at least one named instance, namely the default instance.

num_glyphs

The number of glyphs in the face. If the face is scalable and has sbits (see num_fixed_sizes), it is set to the number of outline glyphs.

For CID-keyed fonts (not in an SFNT wrapper) this value gives the highest CID used in the font.

family_name

The face's family name. This is an ASCII string, usually in English, that describes the typeface's family (like ‘Times New Roman’, ‘Bodoni’, ‘Garamond’, etc). This is a least common denominator used to list fonts. Some formats (TrueType & OpenType) provide localized and Unicode versions of this string. Applications should use the format-specific interface to access them. Can be NULL (e.g., in fonts embedded in a PDF file).

In case the font doesn't provide a specific family name entry, FreeType tries to synthesize one, deriving it from other name entries.

style_name

The face's style name. This is an ASCII string, usually in English, that describes the typeface's style (like ‘Italic’, ‘Bold’, ‘Condensed’, etc). Not all font formats provide a style name, so this field is optional, and can be set to NULL. As for family_name, some formats provide localized and Unicode versions of this string. Applications should use the format-specific interface to access them.

num_fixed_sizes

The number of bitmap strikes in the face. Even if the face is scalable, there might still be bitmap strikes, which are called ‘sbits’ in that case.

available_sizes

An array of FT_Bitmap_Size for all bitmap strikes in the face. It is set to NULL if there is no bitmap strike.

Note that FreeType tries to sanitize the strike data since they are sometimes sloppy or incorrect, but this can easily fail.

num_charmaps

The number of charmaps in the face.

charmaps

An array of the charmaps of the face.

generic

A field reserved for client uses. See the FT_Generic type description.

bbox

The font bounding box. Coordinates are expressed in font units (see units_per_EM). The box is large enough to contain any glyph from the font. Thus, bbox.yMax can be seen as the ‘maximum ascender’, and bbox.yMin as the ‘minimum descender’. Only relevant for scalable formats.

Note that the bounding box might be off by (at least) one pixel for hinted fonts. See FT_Size_Metrics for further discussion.

units_per_EM

The number of font units per EM square for this face. This is typically 2048 for TrueType fonts, and 1000 for Type 1 fonts. Only relevant for scalable formats.

ascender

The typographic ascender of the face, expressed in font units. For font formats not having this information, it is set to bbox.yMax. Only relevant for scalable formats.

descender

The typographic descender of the face, expressed in font units. For font formats not having this information, it is set to bbox.yMin. Note that this field is negative for values below the baseline. Only relevant for scalable formats.

height

This value is the vertical distance between two consecutive baselines, expressed in font units. It is always positive. Only relevant for scalable formats.

If you want the global glyph height, use ascender - descender.

max_advance_width

The maximum advance width, in font units, for all glyphs in this face. This can be used to make word wrapping computations faster. Only relevant for scalable formats.

max_advance_height

The maximum advance height, in font units, for all glyphs in this face. This is only relevant for vertical layouts, and is set to height for fonts that do not provide vertical metrics. Only relevant for scalable formats.

underline_position

The position, in font units, of the underline line for this face. It is the center of the underlining stem. Only relevant for scalable formats.

underline_thickness

The thickness, in font units, of the underline for this face. Only relevant for scalable formats.

glyph

The face's associated glyph slot(s).

size

The current active size for this face.

charmap

The current active charmap for this face.

note

Fields may be changed after a call to FT_Attach_File or FT_Attach_Stream.

For an OpenType variation font, the values of the following fields can change after a call to FT_Set_Var_Design_Coordinates (and friends) if the font contains an ‘MVAR’ table: ascender, descender, height, underline_position, and underline_thickness.

Especially for TrueType fonts see also the documentation for FT_Size_Metrics.


FT_HAS_HORIZONTAL

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_HORIZONTAL( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_HORIZONTAL )

A macro that returns true whenever a face object contains horizontal metrics (this is true for all font formats though).

also

FT_HAS_VERTICAL can be used to check for vertical metrics.


FT_HAS_VERTICAL

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_VERTICAL( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_VERTICAL )

A macro that returns true whenever a face object contains real vertical metrics (and not only synthesized ones).


FT_HAS_KERNING

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_KERNING( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_KERNING )

A macro that returns true whenever a face object contains kerning data that can be accessed with FT_Get_Kerning.


FT_HAS_FIXED_SIZES

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_FIXED_SIZES( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_FIXED_SIZES )

A macro that returns true whenever a face object contains some embedded bitmaps. See the available_sizes field of the FT_FaceRec structure.


FT_HAS_GLYPH_NAMES

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_GLYPH_NAMES( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_GLYPH_NAMES )

A macro that returns true whenever a face object contains some glyph names that can be accessed through FT_Get_Glyph_Name.


FT_HAS_COLOR

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_COLOR( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_COLOR )

A macro that returns true whenever a face object contains tables for color glyphs.

since

2.5.1


FT_HAS_MULTIPLE_MASTERS

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_MULTIPLE_MASTERS( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_MULTIPLE_MASTERS )

A macro that returns true whenever a face object contains some multiple masters. The functions provided by FT_MULTIPLE_MASTERS_H are then available to choose the exact design you want.


FT_IS_SFNT

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_SFNT( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_SFNT )

A macro that returns true whenever a face object contains a font whose format is based on the SFNT storage scheme. This usually means: TrueType fonts, OpenType fonts, as well as SFNT-based embedded bitmap fonts.

If this macro is true, all functions defined in FT_SFNT_NAMES_H and FT_TRUETYPE_TABLES_H are available.


FT_IS_SCALABLE

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_SCALABLE( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_SCALABLE )

A macro that returns true whenever a face object contains a scalable font face (true for TrueType, Type 1, Type 42, CID, OpenType/CFF, and PFR font formats).


FT_IS_FIXED_WIDTH

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_FIXED_WIDTH( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_FIXED_WIDTH )

A macro that returns true whenever a face object contains a font face that contains fixed-width (or ‘monospace’, ‘fixed-pitch’, etc.) glyphs.


FT_IS_CID_KEYED

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_CID_KEYED( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_CID_KEYED )

A macro that returns true whenever a face object contains a CID-keyed font. See the discussion of FT_FACE_FLAG_CID_KEYED for more details.

If this macro is true, all functions defined in FT_CID_H are available.


FT_IS_TRICKY

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_TRICKY( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_TRICKY )

A macro that returns true whenever a face represents a ‘tricky’ font. See the discussion of FT_FACE_FLAG_TRICKY for more details.


FT_IS_NAMED_INSTANCE

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_NAMED_INSTANCE( face ) \
          ( (face)->face_index & 0x7FFF0000L )

A macro that returns true whenever a face object is a named instance of a GX or OpenType variation font.

[Since 2.9] Changing the design coordinates with FT_Set_Var_Design_Coordinates or FT_Set_Var_Blend_Coordinates does not influence the return value of this macro (only FT_Set_Named_Instance does that).

since

2.7


FT_IS_VARIATION

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_IS_VARIATION( face ) \
          ( (face)->face_flags & FT_FACE_FLAG_VARIATION )

A macro that returns true whenever a face object has been altered by FT_Set_MM_Design_Coordinates, FT_Set_Var_Design_Coordinates, or FT_Set_Var_Blend_Coordinates.

since

2.9


FT_SizeRec

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_SizeRec_
  {
    FT_Face           face;      /* parent face object              */
    FT_Generic        generic;   /* generic pointer for client uses */
    FT_Size_Metrics   metrics;   /* size metrics                    */
    FT_Size_Internal  internal;

  } FT_SizeRec;

FreeType root size class structure. A size object models a face object at a given size.

fields

face

Handle to the parent face object.

generic

A typeless pointer, unused by the FreeType library or any of its drivers. It can be used by client applications to link their own data to each size object.

metrics

Metrics for this size object. This field is read-only.


FT_Size_Metrics

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Size_Metrics_
  {
    FT_UShort  x_ppem;      /* horizontal pixels per EM               */
    FT_UShort  y_ppem;      /* vertical pixels per EM                 */

    FT_Fixed   x_scale;     /* scaling values used to convert font    */
    FT_Fixed   y_scale;     /* units to 26.6 fractional pixels        */

    FT_Pos     ascender;    /* ascender in 26.6 frac. pixels          */
    FT_Pos     descender;   /* descender in 26.6 frac. pixels         */
    FT_Pos     height;      /* text height in 26.6 frac. pixels       */
    FT_Pos     max_advance; /* max horizontal advance, in 26.6 pixels */

  } FT_Size_Metrics;

The size metrics structure gives the metrics of a size object.

fields

x_ppem

The width of the scaled EM square in pixels, hence the term ‘ppem’ (pixels per EM). It is also referred to as ‘nominal width’.

y_ppem

The height of the scaled EM square in pixels, hence the term ‘ppem’ (pixels per EM). It is also referred to as ‘nominal height’.

x_scale

A 16.16 fractional scaling value to convert horizontal metrics from font units to 26.6 fractional pixels. Only relevant for scalable font formats.

y_scale

A 16.16 fractional scaling value to convert vertical metrics from font units to 26.6 fractional pixels. Only relevant for scalable font formats.

ascender

The ascender in 26.6 fractional pixels, rounded up to an integer value. See FT_FaceRec for the details.

descender

The descender in 26.6 fractional pixels, rounded down to an integer value. See FT_FaceRec for the details.

height

The height in 26.6 fractional pixels, rounded to an integer value. See FT_FaceRec for the details.

max_advance

The maximum advance width in 26.6 fractional pixels, rounded to an integer value. See FT_FaceRec for the details.

note

The scaling values, if relevant, are determined first during a size changing operation. The remaining fields are then set by the driver. For scalable formats, they are usually set to scaled values of the corresponding fields in FT_FaceRec. Some values like ascender or descender are rounded for historical reasons; more precise values (for outline fonts) can be derived by scaling the corresponding FT_FaceRec values manually, with code similar to the following.

  scaled_ascender = FT_MulFix( face->ascender,
                               size_metrics->y_scale );

Note that due to glyph hinting and the selected rendering mode these values are usually not exact; consequently, they must be treated as unreliable with an error margin of at least one pixel!

Indeed, the only way to get the exact metrics is to render all glyphs. As this would be a definite performance hit, it is up to client applications to perform such computations.

The FT_Size_Metrics structure is valid for bitmap fonts also.

TrueType fonts with native bytecode hinting

All applications that handle TrueType fonts with native hinting must be aware that TTFs expect different rounding of vertical font dimensions. The application has to cater for this, especially if it wants to rely on a TTF's vertical data (for example, to properly align box characters vertically).

Only the application knows in advance that it is going to use native hinting for TTFs! FreeType, on the other hand, selects the hinting mode not at the time of creating an FT_Size object but much later, namely while calling FT_Load_Glyph.

Here is some pseudo code that illustrates a possible solution.

  font_format = FT_Get_Font_Format( face );

  if ( !strcmp( font_format, "TrueType" ) &&
       do_native_bytecode_hinting         )
  {
    ascender  = ROUND( FT_MulFix( face->ascender,
                                  size_metrics->y_scale ) );
    descender = ROUND( FT_MulFix( face->descender,
                                  size_metrics->y_scale ) );
  }
  else
  {
    ascender  = size_metrics->ascender;
    descender = size_metrics->descender;
  }

  height      = size_metrics->height;
  max_advance = size_metrics->max_advance;


FT_GlyphSlotRec

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_GlyphSlotRec_
  {
    FT_Library        library;
    FT_Face           face;
    FT_GlyphSlot      next;
    FT_UInt           glyph_index; /* new in 2.10; was reserved previously */
    FT_Generic        generic;

    FT_Glyph_Metrics  metrics;
    FT_Fixed          linearHoriAdvance;
    FT_Fixed          linearVertAdvance;
    FT_Vector         advance;

    FT_Glyph_Format   format;

    FT_Bitmap         bitmap;
    FT_Int            bitmap_left;
    FT_Int            bitmap_top;

    FT_Outline        outline;

    FT_UInt           num_subglyphs;
    FT_SubGlyph       subglyphs;

    void*             control_data;
    long              control_len;

    FT_Pos            lsb_delta;
    FT_Pos            rsb_delta;

    void*             other;

    FT_Slot_Internal  internal;

  } FT_GlyphSlotRec;

FreeType root glyph slot class structure. A glyph slot is a container where individual glyphs can be loaded, be they in outline or bitmap format.

fields

library

A handle to the FreeType library instance this slot belongs to.

face

A handle to the parent face object.

next

In some cases (like some font tools), several glyph slots per face object can be a good thing. As this is rare, the glyph slots are listed through a direct, single-linked list using its next field.

glyph_index

[Since 2.10] The glyph index passed as an argument to FT_Load_Glyph while initializing the glyph slot.

generic

A typeless pointer unused by the FreeType library or any of its drivers. It can be used by client applications to link their own data to each glyph slot object.

metrics

The metrics of the last loaded glyph in the slot. The returned values depend on the last load flags (see the FT_Load_Glyph API function) and can be expressed either in 26.6 fractional pixels or font units.

Note that even when the glyph image is transformed, the metrics are not.

linearHoriAdvance

The advance width of the unhinted glyph. Its value is expressed in 16.16 fractional pixels, unless FT_LOAD_LINEAR_DESIGN is set when loading the glyph. This field can be important to perform correct WYSIWYG layout. Only relevant for outline glyphs.

linearVertAdvance

The advance height of the unhinted glyph. Its value is expressed in 16.16 fractional pixels, unless FT_LOAD_LINEAR_DESIGN is set when loading the glyph. This field can be important to perform correct WYSIWYG layout. Only relevant for outline glyphs.

advance

This shorthand is, depending on FT_LOAD_IGNORE_TRANSFORM, the transformed (hinted) advance width for the glyph, in 26.6 fractional pixel format. As specified with FT_LOAD_VERTICAL_LAYOUT, it uses either the horiAdvance or the vertAdvance value of metrics field.

format

This field indicates the format of the image contained in the glyph slot. Typically FT_GLYPH_FORMAT_BITMAP, FT_GLYPH_FORMAT_OUTLINE, or FT_GLYPH_FORMAT_COMPOSITE, but other values are possible.

bitmap

This field is used as a bitmap descriptor. Note that the address and content of the bitmap buffer can change between calls of FT_Load_Glyph and a few other functions.

bitmap_left

The bitmap's left bearing expressed in integer pixels.

bitmap_top

The bitmap's top bearing expressed in integer pixels. This is the distance from the baseline to the top-most glyph scanline, upwards y coordinates being positive.

outline

The outline descriptor for the current glyph image if its format is FT_GLYPH_FORMAT_OUTLINE. Once a glyph is loaded, outline can be transformed, distorted, emboldened, etc. However, it must not be freed.

num_subglyphs

The number of subglyphs in a composite glyph. This field is only valid for the composite glyph format that should normally only be loaded with the FT_LOAD_NO_RECURSE flag.

subglyphs

An array of subglyph descriptors for composite glyphs. There are num_subglyphs elements in there. Currently internal to FreeType.

control_data

Certain font drivers can also return the control data for a given glyph image (e.g. TrueType bytecode, Type 1 charstrings, etc.). This field is a pointer to such data; it is currently internal to FreeType.

control_len

This is the length in bytes of the control data. Currently internal to FreeType.

other

Reserved.

lsb_delta

The difference between hinted and unhinted left side bearing while auto-hinting is active. Zero otherwise.

rsb_delta

The difference between hinted and unhinted right side bearing while auto-hinting is active. Zero otherwise.

note

If FT_Load_Glyph is called with default flags (see FT_LOAD_DEFAULT) the glyph image is loaded in the glyph slot in its native format (e.g., an outline glyph for TrueType and Type 1 formats). [Since 2.9] The prospective bitmap metrics are calculated according to FT_LOAD_TARGET_XXX and other flags even for the outline glyph, even if FT_LOAD_RENDER is not set.

This image can later be converted into a bitmap by calling FT_Render_Glyph. This function searches the current renderer for the native image's format, then invokes it.

The renderer is in charge of transforming the native image through the slot's face transformation fields, then converting it into a bitmap that is returned in slot->bitmap.

Note that slot->bitmap_left and slot->bitmap_top are also used to specify the position of the bitmap relative to the current pen position (e.g., coordinates (0,0) on the baseline). Of course, slot->format is also changed to FT_GLYPH_FORMAT_BITMAP.

Here is a small pseudo code fragment that shows how to use lsb_delta and rsb_delta to do fractional positioning of glyphs:

  FT_GlyphSlot  slot     = face->glyph;
  FT_Pos        origin_x = 0;


  for all glyphs do
    <load glyph with `FT_Load_Glyph'>

    FT_Outline_Translate( slot->outline, origin_x & 63, 0 );

    <save glyph image, or render glyph, or ...>

    <compute kern between current and next glyph
     and add it to `origin_x'>

    origin_x += slot->advance.x;
    origin_x += slot->lsb_delta - slot->rsb_delta;
  endfor

Here is another small pseudo code fragment that shows how to use lsb_delta and rsb_delta to improve integer positioning of glyphs:

  FT_GlyphSlot  slot           = face->glyph;
  FT_Pos        origin_x       = 0;
  FT_Pos        prev_rsb_delta = 0;


  for all glyphs do
    <compute kern between current and previous glyph
     and add it to `origin_x'>

    <load glyph with `FT_Load_Glyph'>

    if ( prev_rsb_delta - slot->lsb_delta >  32 )
      origin_x -= 64;
    else if ( prev_rsb_delta - slot->lsb_delta < -31 )
      origin_x += 64;

    prev_rsb_delta = slot->rsb_delta;

    <save glyph image, or render glyph, or ...>

    origin_x += slot->advance.x;
  endfor

If you use strong auto-hinting, you must apply these delta values! Otherwise you will experience far too large inter-glyph spacing at small rendering sizes in most cases. Note that it doesn't harm to use the above code for other hinting modes also, since the delta values are zero then.


FT_Glyph_Metrics

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Glyph_Metrics_
  {
    FT_Pos  width;
    FT_Pos  height;

    FT_Pos  horiBearingX;
    FT_Pos  horiBearingY;
    FT_Pos  horiAdvance;

    FT_Pos  vertBearingX;
    FT_Pos  vertBearingY;
    FT_Pos  vertAdvance;

  } FT_Glyph_Metrics;

A structure to model the metrics of a single glyph. The values are expressed in 26.6 fractional pixel format; if the flag FT_LOAD_NO_SCALE has been used while loading the glyph, values are expressed in font units instead.

fields

width

The glyph's width.

height

The glyph's height.

horiBearingX

Left side bearing for horizontal layout.

horiBearingY

Top side bearing for horizontal layout.

horiAdvance

Advance width for horizontal layout.

vertBearingX

Left side bearing for vertical layout.

vertBearingY

Top side bearing for vertical layout. Larger positive values mean further below the vertical glyph origin.

vertAdvance

Advance height for vertical layout. Positive values mean the glyph has a positive advance downward.

note

If not disabled with FT_LOAD_NO_HINTING, the values represent dimensions of the hinted glyph (in case hinting is applicable).

Stroking a glyph with an outside border does not increase horiAdvance or vertAdvance; you have to manually adjust these values to account for the added width and height.

FreeType doesn't use the ‘VORG’ table data for CFF fonts because it doesn't have an interface to quickly retrieve the glyph height. The y coordinate of the vertical origin can be simply computed as vertBearingY + height after loading a glyph.


FT_SubGlyph

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_SubGlyphRec_*  FT_SubGlyph;

The subglyph structure is an internal object used to describe subglyphs (for example, in the case of composites).

note

The subglyph implementation is not part of the high-level API, hence the forward structure declaration.

You can however retrieve subglyph information with FT_Get_SubGlyph_Info.


FT_Bitmap_Size

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Bitmap_Size_
  {
    FT_Short  height;
    FT_Short  width;

    FT_Pos    size;

    FT_Pos    x_ppem;
    FT_Pos    y_ppem;

  } FT_Bitmap_Size;

This structure models the metrics of a bitmap strike (i.e., a set of glyphs for a given point size and resolution) in a bitmap font. It is used for the available_sizes field of FT_Face.

fields

height

The vertical distance, in pixels, between two consecutive baselines. It is always positive.

width

The average width, in pixels, of all glyphs in the strike.

size

The nominal size of the strike in 26.6 fractional points. This field is not very useful.

x_ppem

The horizontal ppem (nominal width) in 26.6 fractional pixels.

y_ppem

The vertical ppem (nominal height) in 26.6 fractional pixels.

note

Windows FNT: The nominal size given in a FNT font is not reliable. If the driver finds it incorrect, it sets size to some calculated values, and x_ppem and y_ppem to the pixel width and height given in the font, respectively.

TrueType embedded bitmaps: size, width, and height values are not contained in the bitmap strike itself. They are computed from the global font parameters.


FT_Init_FreeType

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Init_FreeType( FT_Library  *alibrary );

Initialize a new FreeType library object. The set of modules that are registered by this function is determined at build time.

output

alibrary

A handle to a new library object.

return

FreeType error code. 0 means success.

note

In case you want to provide your own memory allocating routines, use FT_New_Library instead, followed by a call to FT_Add_Default_Modules (or a series of calls to FT_Add_Module) and FT_Set_Default_Properties.

See the documentation of FT_Library and FT_Face for multi-threading issues.

If you need reference-counting (cf. FT_Reference_Library), use FT_New_Library and FT_Done_Library.

If compilation option FT_CONFIG_OPTION_ENVIRONMENT_PROPERTIES is set, this function reads the FREETYPE_PROPERTIES environment variable to control driver properties. See section ‘Driver properties’ for more.


FT_Done_FreeType

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Done_FreeType( FT_Library  library );

Destroy a given FreeType library object and all of its children, including resources, drivers, faces, sizes, etc.

input

library

A handle to the target library object.

return

FreeType error code. 0 means success.


FT_New_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_New_Face( FT_Library   library,
               const char*  filepathname,
               FT_Long      face_index,
               FT_Face     *aface );

Call FT_Open_Face to open a font by its pathname.

inout

library

A handle to the library resource.

input

pathname

A path to the font file.

face_index

See FT_Open_Face for a detailed description of this parameter.

output

aface

A handle to a new face object. If face_index is greater than or equal to zero, it must be non-NULL.

return

FreeType error code. 0 means success.

note

Use FT_Done_Face to destroy the created FT_Face object (along with its slot and sizes).


FT_Done_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Done_Face( FT_Face  face );

Discard a given face object, as well as all of its child slots and sizes.

input

face

A handle to a target face object.

return

FreeType error code. 0 means success.

note

See the discussion of reference counters in the description of FT_Reference_Face.


FT_Reference_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Reference_Face( FT_Face  face );

A counter gets initialized to 1 at the time an FT_Face structure is created. This function increments the counter. FT_Done_Face then only destroys a face if the counter is 1, otherwise it simply decrements the counter.

This function helps in managing life-cycles of structures that reference FT_Face objects.

input

face

A handle to a target face object.

return

FreeType error code. 0 means success.

since

2.4.2


FT_New_Memory_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_New_Memory_Face( FT_Library      library,
                      const FT_Byte*  file_base,
                      FT_Long         file_size,
                      FT_Long         face_index,
                      FT_Face        *aface );

Call FT_Open_Face to open a font that has been loaded into memory.

inout

library

A handle to the library resource.

input

file_base

A pointer to the beginning of the font data.

file_size

The size of the memory chunk used by the font data.

face_index

See FT_Open_Face for a detailed description of this parameter.

output

aface

A handle to a new face object. If face_index is greater than or equal to zero, it must be non-NULL.

return

FreeType error code. 0 means success.

note

You must not deallocate the memory before calling FT_Done_Face.


FT_Face_Properties

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Face_Properties( FT_Face        face,
                      FT_UInt        num_properties,
                      FT_Parameter*  properties );

Set or override certain (library or module-wide) properties on a face-by-face basis. Useful for finer-grained control and avoiding locks on shared structures (threads can modify their own faces as they see fit).

Contrary to FT_Property_Set, this function uses FT_Parameter so that you can pass multiple properties to the target face in one call. Note that only a subset of the available properties can be controlled.

Pass NULL as data in FT_Parameter for a given tag to reset the option and use the library or module default again.

input

face

A handle to the source face object.

num_properties

The number of properties that follow.

properties

A handle to an FT_Parameter array with num_properties elements.

return

FreeType error code. 0 means success.

example

Here is an example that sets three properties. You must define FT_CONFIG_OPTION_SUBPIXEL_RENDERING to make the LCD filter examples work.

  FT_Parameter         property1;
  FT_Bool              darken_stems = 1;

  FT_Parameter         property2;
  FT_LcdFiveTapFilter  custom_weight =
                         { 0x11, 0x44, 0x56, 0x44, 0x11 };

  FT_Parameter         property3;
  FT_Int32             random_seed = 314159265;

  FT_Parameter         properties[3] = { property1,
                                         property2,
                                         property3 };


  property1.tag  = FT_PARAM_TAG_STEM_DARKENING;
  property1.data = &darken_stems;

  property2.tag  = FT_PARAM_TAG_LCD_FILTER_WEIGHTS;
  property2.data = custom_weight;

  property3.tag  = FT_PARAM_TAG_RANDOM_SEED;
  property3.data = &random_seed;

  FT_Face_Properties( face, 3, properties );

The next example resets a single property to its default value.

  FT_Parameter  property;


  property.tag  = FT_PARAM_TAG_LCD_FILTER_WEIGHTS;
  property.data = NULL;

  FT_Face_Properties( face, 1, &property );

since

2.8


FT_Open_Face

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Open_Face( FT_Library           library,
                const FT_Open_Args*  args,
                FT_Long              face_index,
                FT_Face             *aface );

Create a face object from a given resource described by FT_Open_Args.

inout

library

A handle to the library resource.

input

args

A pointer to an FT_Open_Args structure that must be filled by the caller.

face_index

This field holds two different values. Bits 0-15 are the index of the face in the font file (starting with value 0). Set it to 0 if there is only one face in the font file.

[Since 2.6.1] Bits 16-30 are relevant to GX and OpenType variation fonts only, specifying the named instance index for the current face index (starting with value 1; value 0 makes FreeType ignore named instances). For non-variation fonts, bits 16-30 are ignored. Assuming that you want to access the third named instance in face 4, face_index should be set to 0x00030004. If you want to access face 4 without variation handling, simply set face_index to value 4.

FT_Open_Face and its siblings can be used to quickly check whether the font format of a given font resource is supported by FreeType. In general, if the face_index argument is negative, the function's return value is 0 if the font format is recognized, or non-zero otherwise. The function allocates a more or less empty face handle in *aface (if aface isn't NULL); the only two useful fields in this special case are face->num_faces and face->style_flags. For any negative value of face_index, face->num_faces gives the number of faces within the font file. For the negative value ‘-(N+1)’ (with ‘N’ a non-negative 16-bit value), bits 16-30 in face->style_flags give the number of named instances in face ‘N’ if we have a variation font (or zero otherwise). After examination, the returned FT_Face structure should be deallocated with a call to FT_Done_Face.

output

aface

A handle to a new face object. If face_index is greater than or equal to zero, it must be non-NULL.

return

FreeType error code. 0 means success.

note

Unlike FreeType 1.x, this function automatically creates a glyph slot for the face object that can be accessed directly through face->glyph.

Each new face object created with this function also owns a default FT_Size object, accessible as face->size.

One FT_Library instance can have multiple face objects, this is, FT_Open_Face and its siblings can be called multiple times using the same library argument.

See the discussion of reference counters in the description of FT_Reference_Face.

example

To loop over all faces, use code similar to the following snippet (omitting the error handling).

  ...
  FT_Face  face;
  FT_Long  i, num_faces;


  error = FT_Open_Face( library, args, -1, &face );
  if ( error ) { ... }

  num_faces = face->num_faces;
  FT_Done_Face( face );

  for ( i = 0; i < num_faces; i++ )
  {
    ...
    error = FT_Open_Face( library, args, i, &face );
    ...
    FT_Done_Face( face );
    ...
  }

To loop over all valid values for face_index, use something similar to the following snippet, again without error handling. The code accesses all faces immediately (thus only a single call of FT_Open_Face within the do-loop), with and without named instances.

  ...
  FT_Face  face;

  FT_Long  num_faces     = 0;
  FT_Long  num_instances = 0;

  FT_Long  face_idx     = 0;
  FT_Long  instance_idx = 0;


  do
  {
    FT_Long  id = ( instance_idx << 16 ) + face_idx;


    error = FT_Open_Face( library, args, id, &face );
    if ( error ) { ... }

    num_faces     = face->num_faces;
    num_instances = face->style_flags >> 16;

    ...

    FT_Done_Face( face );

    if ( instance_idx < num_instances )
      instance_idx++;
    else
    {
      face_idx++;
      instance_idx = 0;
    }

  } while ( face_idx < num_faces )


FT_Open_Args

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Open_Args_
  {
    FT_UInt         flags;
    const FT_Byte*  memory_base;
    FT_Long         memory_size;
    FT_String*      pathname;
    FT_Stream       stream;
    FT_Module       driver;
    FT_Int          num_params;
    FT_Parameter*   params;

  } FT_Open_Args;

A structure to indicate how to open a new font file or stream. A pointer to such a structure can be used as a parameter for the functions FT_Open_Face and FT_Attach_Stream.

fields

flags

A set of bit flags indicating how to use the structure.

memory_base

The first byte of the file in memory.

memory_size

The size in bytes of the file in memory.

pathname

A pointer to an 8-bit file pathname.

stream

A handle to a source stream object.

driver

This field is exclusively used by FT_Open_Face; it simply specifies the font driver to use for opening the face. If set to NULL, FreeType tries to load the face with each one of the drivers in its list.

num_params

The number of extra parameters.

params

Extra parameters passed to the font driver when opening a new face.

note

The stream type is determined by the contents of flags that are tested in the following order by FT_Open_Face:

If the FT_OPEN_MEMORY bit is set, assume that this is a memory file of memory_size bytes, located at memory_address. The data are not copied, and the client is responsible for releasing and destroying them after the corresponding call to FT_Done_Face.

Otherwise, if the FT_OPEN_STREAM bit is set, assume that a custom input stream stream is used.

Otherwise, if the FT_OPEN_PATHNAME bit is set, assume that this is a normal file and use pathname to open it.

If the FT_OPEN_DRIVER bit is set, FT_Open_Face only tries to open the file with the driver whose handler is in driver.

If the FT_OPEN_PARAMS bit is set, the parameters given by num_params and params is used. They are ignored otherwise.

Ideally, both the pathname and params fields should be tagged as ‘const’; this is missing for API backward compatibility. In other words, applications should treat them as read-only.


FT_Parameter

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Parameter_
  {
    FT_ULong    tag;
    FT_Pointer  data;

  } FT_Parameter;

A simple structure to pass more or less generic parameters to FT_Open_Face and FT_Face_Properties.

fields

tag

A four-byte identification tag.

data

A pointer to the parameter data.

note

The ID and function of parameters are driver-specific. See section ‘Parameter Tags’ for more information.


FT_Attach_File

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Attach_File( FT_Face      face,
                  const char*  filepathname );

Call FT_Attach_Stream to attach a file.

inout

face

The target face object.

input

filepathname

The pathname.

return

FreeType error code. 0 means success.


FT_Attach_Stream

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Attach_Stream( FT_Face        face,
                    FT_Open_Args*  parameters );

‘Attach’ data to a face object. Normally, this is used to read additional information for the face object. For example, you can attach an AFM file that comes with a Type 1 font to get the kerning values and other metrics.

inout

face

The target face object.

input

parameters

A pointer to FT_Open_Args that must be filled by the caller.

return

FreeType error code. 0 means success.

note

The meaning of the ‘attach’ (i.e., what really happens when the new file is read) is not fixed by FreeType itself. It really depends on the font format (and thus the font driver).

Client applications are expected to know what they are doing when invoking this function. Most drivers simply do not implement file or stream attachments.


FT_Set_Char_Size

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Set_Char_Size( FT_Face     face,
                    FT_F26Dot6  char_width,
                    FT_F26Dot6  char_height,
                    FT_UInt     horz_resolution,
                    FT_UInt     vert_resolution );

Call FT_Request_Size to request the nominal size (in points).

inout

face

A handle to a target face object.

input

char_width

The nominal width, in 26.6 fractional points.

char_height

The nominal height, in 26.6 fractional points.

horz_resolution

The horizontal resolution in dpi.

vert_resolution

The vertical resolution in dpi.

return

FreeType error code. 0 means success.

note

While this function allows fractional points as input values, the resulting ppem value for the given resolution is always rounded to the nearest integer.

If either the character width or height is zero, it is set equal to the other value.

If either the horizontal or vertical resolution is zero, it is set equal to the other value.

A character width or height smaller than 1pt is set to 1pt; if both resolution values are zero, they are set to 72dpi.

Don't use this function if you are using the FreeType cache API.


FT_Set_Pixel_Sizes

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Set_Pixel_Sizes( FT_Face  face,
                      FT_UInt  pixel_width,
                      FT_UInt  pixel_height );

Call FT_Request_Size to request the nominal size (in pixels).

inout

face

A handle to the target face object.

input

pixel_width

The nominal width, in pixels.

pixel_height

The nominal height, in pixels.

return

FreeType error code. 0 means success.

note

You should not rely on the resulting glyphs matching or being constrained to this pixel size. Refer to FT_Request_Size to understand how requested sizes relate to actual sizes.

Don't use this function if you are using the FreeType cache API.


FT_Request_Size

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Request_Size( FT_Face          face,
                   FT_Size_Request  req );

Resize the scale of the active FT_Size object in a face.

inout

face

A handle to a target face object.

input

req

A pointer to a FT_Size_RequestRec.

return

FreeType error code. 0 means success.

note

Although drivers may select the bitmap strike matching the request, you should not rely on this if you intend to select a particular bitmap strike. Use FT_Select_Size instead in that case.

The relation between the requested size and the resulting glyph size is dependent entirely on how the size is defined in the source face. The font designer chooses the final size of each glyph relative to this size. For more information refer to ‘https://www.freetype.org/freetype2/docs/glyphs/glyphs-2.html’.

Contrary to FT_Set_Char_Size, this function doesn't have special code to normalize zero-valued widths, heights, or resolutions (which lead to errors in most cases).

Don't use this function if you are using the FreeType cache API.


FT_Select_Size

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Select_Size( FT_Face  face,
                  FT_Int   strike_index );

Select a bitmap strike. To be more precise, this function sets the scaling factors of the active FT_Size object in a face so that bitmaps from this particular strike are taken by FT_Load_Glyph and friends.

inout

face

A handle to a target face object.

input

strike_index

The index of the bitmap strike in the available_sizes field of FT_FaceRec structure.

return

FreeType error code. 0 means success.

note

For bitmaps embedded in outline fonts it is common that only a subset of the available glyphs at a given ppem value is available. FreeType silently uses outlines if there is no bitmap for a given glyph index.

For GX and OpenType variation fonts, a bitmap strike makes sense only if the default instance is active (this is, no glyph variation takes place); otherwise, FreeType simply ignores bitmap strikes. The same is true for all named instances that are different from the default instance.

Don't use this function if you are using the FreeType cache API.


FT_Size_Request_Type

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef enum  FT_Size_Request_Type_
  {
    FT_SIZE_REQUEST_TYPE_NOMINAL,
    FT_SIZE_REQUEST_TYPE_REAL_DIM,
    FT_SIZE_REQUEST_TYPE_BBOX,
    FT_SIZE_REQUEST_TYPE_CELL,
    FT_SIZE_REQUEST_TYPE_SCALES,

    FT_SIZE_REQUEST_TYPE_MAX

  } FT_Size_Request_Type;

An enumeration type that lists the supported size request types, i.e., what input size (in font units) maps to the requested output size (in pixels, as computed from the arguments of FT_Size_Request).

values

FT_SIZE_REQUEST_TYPE_NOMINAL

The nominal size. The units_per_EM field of FT_FaceRec is used to determine both scaling values.

This is the standard scaling found in most applications. In particular, use this size request type for TrueType fonts if they provide optical scaling or something similar. Note, however, that units_per_EM is a rather abstract value which bears no relation to the actual size of the glyphs in a font.

FT_SIZE_REQUEST_TYPE_REAL_DIM

The real dimension. The sum of the ascender and (minus of) the descender fields of FT_FaceRec is used to determine both scaling values.

FT_SIZE_REQUEST_TYPE_BBOX

The font bounding box. The width and height of the bbox field of FT_FaceRec are used to determine the horizontal and vertical scaling value, respectively.

FT_SIZE_REQUEST_TYPE_CELL

The max_advance_width field of FT_FaceRec is used to determine the horizontal scaling value; the vertical scaling value is determined the same way as FT_SIZE_REQUEST_TYPE_REAL_DIM does. Finally, both scaling values are set to the smaller one. This type is useful if you want to specify the font size for, say, a window of a given dimension and 80x24 cells.

FT_SIZE_REQUEST_TYPE_SCALES

Specify the scaling values directly.

note

The above descriptions only apply to scalable formats. For bitmap formats, the behaviour is up to the driver.

See the note section of FT_Size_Metrics if you wonder how size requesting relates to scaling values.


FT_Size_RequestRec

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_Size_RequestRec_
  {
    FT_Size_Request_Type  type;
    FT_Long               width;
    FT_Long               height;
    FT_UInt               horiResolution;
    FT_UInt               vertResolution;

  } FT_Size_RequestRec;

A structure to model a size request.

fields

type

See FT_Size_Request_Type.

width

The desired width, given as a 26.6 fractional point value (with 72pt = 1in).

height

The desired height, given as a 26.6 fractional point value (with 72pt = 1in).

horiResolution

The horizontal resolution (dpi, i.e., pixels per inch). If set to zero, width is treated as a 26.6 fractional pixel value, which gets internally rounded to an integer.

vertResolution

The vertical resolution (dpi, i.e., pixels per inch). If set to zero, height is treated as a 26.6 fractional pixel value, which gets internally rounded to an integer.

note

If width is zero, the horizontal scaling value is set equal to the vertical scaling value, and vice versa.

If type is FT_SIZE_REQUEST_TYPE_SCALES, width and height are interpreted directly as 16.16 fractional scaling values, without any further modification, and both horiResolution and vertResolution are ignored.


FT_Size_Request

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_Size_RequestRec_  *FT_Size_Request;

A handle to a size request structure.


FT_Set_Transform

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( void )
  FT_Set_Transform( FT_Face     face,
                    FT_Matrix*  matrix,
                    FT_Vector*  delta );

Set the transformation that is applied to glyph images when they are loaded into a glyph slot through FT_Load_Glyph.

inout

face

A handle to the source face object.

input

matrix

A pointer to the transformation's 2x2 matrix. Use NULL for the identity matrix.

delta

A pointer to the translation vector. Use NULL for the null vector.

note

The transformation is only applied to scalable image formats after the glyph has been loaded. It means that hinting is unaltered by the transformation and is performed on the character size given in the last call to FT_Set_Char_Size or FT_Set_Pixel_Sizes.

Note that this also transforms the face.glyph.advance field, but not the values in face.glyph.metrics.


FT_Load_Glyph

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Load_Glyph( FT_Face   face,
                 FT_UInt   glyph_index,
                 FT_Int32  load_flags );

Load a glyph into the glyph slot of a face object.

inout

face

A handle to the target face object where the glyph is loaded.

input

glyph_index

The index of the glyph in the font file. For CID-keyed fonts (either in PS or in CFF format) this argument specifies the CID value.

load_flags

A flag indicating what to load for this glyph. The FT_LOAD_XXX constants can be used to control the glyph loading process (e.g., whether the outline should be scaled, whether to load bitmaps or not, whether to hint the outline, etc).

return

FreeType error code. 0 means success.

note

The loaded glyph may be transformed. See FT_Set_Transform for the details.

For subsetted CID-keyed fonts, FT_Err_Invalid_Argument is returned for invalid CID values (this is, for CID values that don't have a corresponding glyph in the font). See the discussion of the FT_FACE_FLAG_CID_KEYED flag for more details.

If you receive FT_Err_Glyph_Too_Big, try getting the glyph outline at EM size, then scale it manually and fill it as a graphics operation.


FT_Get_Char_Index

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_UInt )
  FT_Get_Char_Index( FT_Face   face,
                     FT_ULong  charcode );

Return the glyph index of a given character code. This function uses the currently selected charmap to do the mapping.

input

face

A handle to the source face object.

charcode

The character code.

return

The glyph index. 0 means ‘undefined character code’.

note

If you use FreeType to manipulate the contents of font files directly, be aware that the glyph index returned by this function doesn't always correspond to the internal indices used within the file. This is done to ensure that value 0 always corresponds to the ‘missing glyph’. If the first glyph is not named ‘.notdef’, then for Type 1 and Type 42 fonts, ‘.notdef’ will be moved into the glyph ID 0 position, and whatever was there will be moved to the position ‘.notdef’ had. For Type 1 fonts, if there is no ‘.notdef’ glyph at all, then one will be created at index 0 and whatever was there will be moved to the last index -- Type 42 fonts are considered invalid under this condition.


FT_Get_First_Char

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_ULong )
  FT_Get_First_Char( FT_Face   face,
                     FT_UInt  *agindex );

Return the first character code in the current charmap of a given face, together with its corresponding glyph index.

input

face

A handle to the source face object.

output

agindex

Glyph index of first character code. 0 if charmap is empty.

return

The charmap's first character code.

note

You should use this function together with FT_Get_Next_Char to parse all character codes available in a given charmap. The code should look like this:

  FT_ULong  charcode;
  FT_UInt   gindex;


  charcode = FT_Get_First_Char( face, &gindex );
  while ( gindex != 0 )
  {
    ... do something with (charcode,gindex) pair ...

    charcode = FT_Get_Next_Char( face, charcode, &gindex );
  }

Be aware that character codes can have values up to 0xFFFFFFFF; this might happen for non-Unicode or malformed cmaps. However, even with regular Unicode encoding, so-called ‘last resort fonts’ (using SFNT cmap format 13, see function FT_Get_CMap_Format) normally have entries for all Unicode characters up to 0x1FFFFF, which can cause a lot of iterations.

Note that *agindex is set to 0 if the charmap is empty. The result itself can be 0 in two cases: if the charmap is empty or if the value 0 is the first valid character code.


FT_Get_Next_Char

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_ULong )
  FT_Get_Next_Char( FT_Face    face,
                    FT_ULong   char_code,
                    FT_UInt   *agindex );

Return the next character code in the current charmap of a given face following the value char_code, as well as the corresponding glyph index.

input

face

A handle to the source face object.

char_code

The starting character code.

output

agindex

Glyph index of next character code. 0 if charmap is empty.

return

The charmap's next character code.

note

You should use this function with FT_Get_First_Char to walk over all character codes available in a given charmap. See the note for that function for a simple code example.

Note that *agindex is set to 0 when there are no more codes in the charmap.


FT_Get_Name_Index

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_UInt )
  FT_Get_Name_Index( FT_Face     face,
                     FT_String*  glyph_name );

Return the glyph index of a given glyph name.

input

face

A handle to the source face object.

glyph_name

The glyph name.

return

The glyph index. 0 means ‘undefined character code’.


FT_Load_Char

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Load_Char( FT_Face   face,
                FT_ULong  char_code,
                FT_Int32  load_flags );

Load a glyph into the glyph slot of a face object, accessed by its character code.

inout

face

A handle to a target face object where the glyph is loaded.

input

char_code

The glyph's character code, according to the current charmap used in the face.

load_flags

A flag indicating what to load for this glyph. The FT_LOAD_XXX constants can be used to control the glyph loading process (e.g., whether the outline should be scaled, whether to load bitmaps or not, whether to hint the outline, etc).

return

FreeType error code. 0 means success.

note

This function simply calls FT_Get_Char_Index and FT_Load_Glyph.

Many fonts contain glyphs that can't be loaded by this function since its glyph indices are not listed in any of the font's charmaps.

If no active cmap is set up (i.e., face->charmap is zero), the call to FT_Get_Char_Index is omitted, and the function behaves identically to FT_Load_Glyph.


FT_LOAD_TARGET_MODE

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_LOAD_TARGET_MODE( x )  ( (FT_Render_Mode)( ( (x) >> 16 ) & 15 ) )

Return the FT_Render_Mode corresponding to a given FT_LOAD_TARGET_XXX value.


FT_Render_Glyph

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Render_Glyph( FT_GlyphSlot    slot,
                   FT_Render_Mode  render_mode );

Convert a given glyph image to a bitmap. It does so by inspecting the glyph image format, finding the relevant renderer, and invoking it.

inout

slot

A handle to the glyph slot containing the image to convert.

input

render_mode

The render mode used to render the glyph image into a bitmap. See FT_Render_Mode for a list of possible values.

If FT_RENDER_MODE_NORMAL is used, a previous call of FT_Load_Glyph with flag FT_LOAD_COLOR makes FT_Render_Glyph provide a default blending of colored glyph layers associated with the current glyph slot (provided the font contains such layers) instead of rendering the glyph slot's outline. This is an experimental feature; see FT_LOAD_COLOR for more information.

return

FreeType error code. 0 means success.

note

To get meaningful results, font scaling values must be set with functions like FT_Set_Char_Size before calling FT_Render_Glyph.

When FreeType outputs a bitmap of a glyph, it really outputs an alpha coverage map. If a pixel is completely covered by a filled-in outline, the bitmap contains 0xFF at that pixel, meaning that 0xFF/0xFF fraction of that pixel is covered, meaning the pixel is 100% black (or 0% bright). If a pixel is only 50% covered (value 0x80), the pixel is made 50% black (50% bright or a middle shade of grey). 0% covered means 0% black (100% bright or white).

On high-DPI screens like on smartphones and tablets, the pixels are so small that their chance of being completely covered and therefore completely black are fairly good. On the low-DPI screens, however, the situation is different. The pixels are too large for most of the details of a glyph and shades of gray are the norm rather than the exception.

This is relevant because all our screens have a second problem: they are not linear. 1 + 1 is not 2. Twice the value does not result in twice the brightness. When a pixel is only 50% covered, the coverage map says 50% black, and this translates to a pixel value of 128 when you use 8 bits per channel (0-255). However, this does not translate to 50% brightness for that pixel on our sRGB and gamma 2.2 screens. Due to their non-linearity, they dwell longer in the darks and only a pixel value of about 186 results in 50% brightness -- 128 ends up too dark on both bright and dark backgrounds. The net result is that dark text looks burnt-out, pixely and blotchy on bright background, bright text too frail on dark backgrounds, and colored text on colored background (for example, red on green) seems to have dark halos or ‘dirt’ around it. The situation is especially ugly for diagonal stems like in ‘w’ glyph shapes where the quality of FreeType's anti-aliasing depends on the correct display of grays. On high-DPI screens where smaller, fully black pixels reign supreme, this doesn't matter, but on our low-DPI screens with all the gray shades, it does. 0% and 100% brightness are the same things in linear and non-linear space, just all the shades in-between aren't.

The blending function for placing text over a background is

  dst = alpha * src + (1 - alpha) * dst    ,

which is known as the OVER operator.

To correctly composite an antialiased pixel of a glyph onto a surface,

  1. take the foreground and background colors (e.g., in sRGB space) and apply gamma to get them in a linear space,

  2. use OVER to blend the two linear colors using the glyph pixel as the alpha value (remember, the glyph bitmap is an alpha coverage bitmap), and

  3. apply inverse gamma to the blended pixel and write it back to the image.

Internal testing at Adobe found that a target inverse gamma of 1.8 for step 3 gives good results across a wide range of displays with an sRGB gamma curve or a similar one.

This process can cost performance. There is an approximation that does not need to know about the background color; see https://bel.fi/alankila/lcd/ and https://bel.fi/alankila/lcd/alpcor.html for details.

ATTENTION: Linear blending is even more important when dealing with subpixel-rendered glyphs to prevent color-fringing! A subpixel-rendered glyph must first be filtered with a filter that gives equal weight to the three color primaries and does not exceed a sum of 0x100, see section ‘Subpixel Rendering’. Then the only difference to gray linear blending is that subpixel-rendered linear blending is done 3 times per pixel: red foreground subpixel to red background subpixel and so on for green and blue.


FT_Render_Mode

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef enum  FT_Render_Mode_
  {
    FT_RENDER_MODE_NORMAL = 0,
    FT_RENDER_MODE_LIGHT,
    FT_RENDER_MODE_MONO,
    FT_RENDER_MODE_LCD,
    FT_RENDER_MODE_LCD_V,

    FT_RENDER_MODE_MAX

  } FT_Render_Mode;


  /* these constants are deprecated; use the corresponding */
  /* `FT_Render_Mode` values instead                       */
#define ft_render_mode_normal  FT_RENDER_MODE_NORMAL
#define ft_render_mode_mono    FT_RENDER_MODE_MONO

Render modes supported by FreeType 2. Each mode corresponds to a specific type of scanline conversion performed on the outline.

For bitmap fonts and embedded bitmaps the bitmap->pixel_mode field in the FT_GlyphSlotRec structure gives the format of the returned bitmap.

All modes except FT_RENDER_MODE_MONO use 256 levels of opacity, indicating pixel coverage. Use linear alpha blending and gamma correction to correctly render non-monochrome glyph bitmaps onto a surface; see FT_Render_Glyph.

values

FT_RENDER_MODE_NORMAL

Default render mode; it corresponds to 8-bit anti-aliased bitmaps.

FT_RENDER_MODE_LIGHT

This is equivalent to FT_RENDER_MODE_NORMAL. It is only defined as a separate value because render modes are also used indirectly to define hinting algorithm selectors. See FT_LOAD_TARGET_XXX for details.

FT_RENDER_MODE_MONO

This mode corresponds to 1-bit bitmaps (with 2 levels of opacity).

FT_RENDER_MODE_LCD

This mode corresponds to horizontal RGB and BGR subpixel displays like LCD screens. It produces 8-bit bitmaps that are 3 times the width of the original glyph outline in pixels, and which use the FT_PIXEL_MODE_LCD mode.

FT_RENDER_MODE_LCD_V

This mode corresponds to vertical RGB and BGR subpixel displays (like PDA screens, rotated LCD displays, etc.). It produces 8-bit bitmaps that are 3 times the height of the original glyph outline in pixels and use the FT_PIXEL_MODE_LCD_V mode.

note

Should you define FT_CONFIG_OPTION_SUBPIXEL_RENDERING in your ftoption.h, which enables patented ClearType-style rendering, the LCD-optimized glyph bitmaps should be filtered to reduce color fringes inherent to this technology. You can either set up LCD filtering with FT_Library_SetLcdFilter or FT_Face_Properties, or do the filtering yourself. The default FreeType LCD rendering technology does not require filtering.

The selected render mode only affects vector glyphs of a font. Embedded bitmaps often have a different pixel mode like FT_PIXEL_MODE_MONO. You can use FT_Bitmap_Convert to transform them into 8-bit pixmaps.


FT_Get_Kerning

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Get_Kerning( FT_Face     face,
                  FT_UInt     left_glyph,
                  FT_UInt     right_glyph,
                  FT_UInt     kern_mode,
                  FT_Vector  *akerning );

Return the kerning vector between two glyphs of the same face.

input

face

A handle to a source face object.

left_glyph

The index of the left glyph in the kern pair.

right_glyph

The index of the right glyph in the kern pair.

kern_mode

See FT_Kerning_Mode for more information. Determines the scale and dimension of the returned kerning vector.

output

akerning

The kerning vector. This is either in font units, fractional pixels (26.6 format), or pixels for scalable formats, and in pixels for fixed-sizes formats.

return

FreeType error code. 0 means success.

note

Only horizontal layouts (left-to-right & right-to-left) are supported by this method. Other layouts, or more sophisticated kernings, are out of the scope of this API function -- they can be implemented through format-specific interfaces.

Kerning for OpenType fonts implemented in a ‘GPOS’ table is not supported; use FT_HAS_KERNING to find out whether a font has data that can be extracted with FT_Get_Kerning.


FT_Kerning_Mode

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef enum  FT_Kerning_Mode_
  {
    FT_KERNING_DEFAULT = 0,
    FT_KERNING_UNFITTED,
    FT_KERNING_UNSCALED

  } FT_Kerning_Mode;


  /* these constants are deprecated; use the corresponding */
  /* `FT_Kerning_Mode` values instead                      */
#define ft_kerning_default   FT_KERNING_DEFAULT
#define ft_kerning_unfitted  FT_KERNING_UNFITTED
#define ft_kerning_unscaled  FT_KERNING_UNSCALED

An enumeration to specify the format of kerning values returned by FT_Get_Kerning.

values

FT_KERNING_DEFAULT

Return grid-fitted kerning distances in 26.6 fractional pixels.

FT_KERNING_UNFITTED

Return un-grid-fitted kerning distances in 26.6 fractional pixels.

FT_KERNING_UNSCALED

Return the kerning vector in original font units.

note

FT_KERNING_DEFAULT returns full pixel values; it also makes FreeType heuristically scale down kerning distances at small ppem values so that they don't become too big.

Both FT_KERNING_DEFAULT and FT_KERNING_UNFITTED use the current horizontal scaling factor (as set e.g. with FT_Set_Char_Size) to convert font units to pixels.


FT_Get_Track_Kerning

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Get_Track_Kerning( FT_Face    face,
                        FT_Fixed   point_size,
                        FT_Int     degree,
                        FT_Fixed*  akerning );

Return the track kerning for a given face object at a given size.

input

face

A handle to a source face object.

point_size

The point size in 16.16 fractional points.

degree

The degree of tightness. Increasingly negative values represent tighter track kerning, while increasingly positive values represent looser track kerning. Value zero means no track kerning.

output

akerning

The kerning in 16.16 fractional points, to be uniformly applied between all glyphs.

return

FreeType error code. 0 means success.

note

Currently, only the Type 1 font driver supports track kerning, using data from AFM files (if attached with FT_Attach_File or FT_Attach_Stream).

Only very few AFM files come with track kerning data; please refer to Adobe's AFM specification for more details.


FT_Get_Glyph_Name

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Get_Glyph_Name( FT_Face     face,
                     FT_UInt     glyph_index,
                     FT_Pointer  buffer,
                     FT_UInt     buffer_max );

Retrieve the ASCII name of a given glyph in a face. This only works for those faces where FT_HAS_GLYPH_NAMES(face) returns 1.

input

face

A handle to a source face object.

glyph_index

The glyph index.

buffer_max

The maximum number of bytes available in the buffer.

output

buffer

A pointer to a target buffer where the name is copied to.

return

FreeType error code. 0 means success.

note

An error is returned if the face doesn't provide glyph names or if the glyph index is invalid. In all cases of failure, the first byte of buffer is set to 0 to indicate an empty name.

The glyph name is truncated to fit within the buffer if it is too long. The returned string is always zero-terminated.

Be aware that FreeType reorders glyph indices internally so that glyph index 0 always corresponds to the ‘missing glyph’ (called ‘.notdef’).

This function always returns an error if the config macro FT_CONFIG_OPTION_NO_GLYPH_NAMES is not defined in ftoption.h.


FT_Get_Postscript_Name

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( const char* )
  FT_Get_Postscript_Name( FT_Face  face );

Retrieve the ASCII PostScript name of a given face, if available. This only works with PostScript, TrueType, and OpenType fonts.

input

face

A handle to the source face object.

return

A pointer to the face's PostScript name. NULL if unavailable.

note

The returned pointer is owned by the face and is destroyed with it.

For variation fonts, this string changes if you select a different instance, and you have to call FT_Get_PostScript_Name again to retrieve it. FreeType follows Adobe TechNote #5902, ‘Generating PostScript Names for Fonts Using OpenType Font Variations’.

https://download.macromedia.com/pub/developer/opentype/tech-notes/5902.AdobePSNameGeneration.html

[Since 2.9] Special PostScript names for named instances are only returned if the named instance is set with FT_Set_Named_Instance (and the font has corresponding entries in its ‘fvar’ table). If FT_IS_VARIATION returns true, the algorithmically derived PostScript name is provided, not looking up special entries for named instances.


FT_CharMapRec

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct  FT_CharMapRec_
  {
    FT_Face      face;
    FT_Encoding  encoding;
    FT_UShort    platform_id;
    FT_UShort    encoding_id;

  } FT_CharMapRec;

The base charmap structure.

fields

face

A handle to the parent face object.

encoding

An FT_Encoding tag identifying the charmap. Use this with FT_Select_Charmap.

platform_id

An ID number describing the platform for the following encoding ID. This comes directly from the TrueType specification and gets emulated for other formats.

encoding_id

A platform-specific encoding number. This also comes from the TrueType specification and gets emulated similarly.


FT_Select_Charmap

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Select_Charmap( FT_Face      face,
                     FT_Encoding  encoding );

Select a given charmap by its encoding tag (as listed in freetype.h).

inout

face

A handle to the source face object.

input

encoding

A handle to the selected encoding.

return

FreeType error code. 0 means success.

note

This function returns an error if no charmap in the face corresponds to the encoding queried here.

Because many fonts contain more than a single cmap for Unicode encoding, this function has some special code to select the one that covers Unicode best (‘best’ in the sense that a UCS-4 cmap is preferred to a UCS-2 cmap). It is thus preferable to FT_Set_Charmap in this case.


FT_Set_Charmap

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Set_Charmap( FT_Face     face,
                  FT_CharMap  charmap );

Select a given charmap for character code to glyph index mapping.

inout

face

A handle to the source face object.

input

charmap

A handle to the selected charmap.

return

FreeType error code. 0 means success.

note

This function returns an error if the charmap is not part of the face (i.e., if it is not listed in the face->charmaps table).

It also fails if an OpenType type 14 charmap is selected (which doesn't map character codes to glyph indices at all).


FT_Get_Charmap_Index

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Int )
  FT_Get_Charmap_Index( FT_CharMap  charmap );

Retrieve index of a given charmap.

input

charmap

A handle to a charmap.

return

The index into the array of character maps within the face to which charmap belongs. If an error occurs, -1 is returned.


FT_Get_FSType_Flags

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_UShort )
  FT_Get_FSType_Flags( FT_Face  face );

Return the fsType flags for a font.

input

face

A handle to the source face object.

return

The fsType flags, see FT_FSTYPE_XXX.

note

Use this function rather than directly reading the fs_type field in the PS_FontInfoRec structure, which is only guaranteed to return the correct results for Type 1 fonts.

since

2.3.8


FT_Get_SubGlyph_Info

Defined in FT_FREETYPE_H (freetype/freetype.h).

  FT_EXPORT( FT_Error )
  FT_Get_SubGlyph_Info( FT_GlyphSlot  glyph,
                        FT_UInt       sub_index,
                        FT_Int       *p_index,
                        FT_UInt      *p_flags,
                        FT_Int       *p_arg1,
                        FT_Int       *p_arg2,
                        FT_Matrix    *p_transform );

Retrieve a description of a given subglyph. Only use it if glyph->format is FT_GLYPH_FORMAT_COMPOSITE; an error is returned otherwise.

input

glyph

The source glyph slot.

sub_index

The index of the subglyph. Must be less than glyph->num_subglyphs.

output

p_index

The glyph index of the subglyph.

p_flags

The subglyph flags, see FT_SUBGLYPH_FLAG_XXX.

p_arg1

The subglyph's first argument (if any).

p_arg2

The subglyph's second argument (if any).

p_transform

The subglyph transformation (if any).

return

FreeType error code. 0 means success.

note

The values of *p_arg1, *p_arg2, and *p_transform must be interpreted depending on the flags returned in *p_flags. See the OpenType specification for details.

https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#composite-glyph-description


FT_Face_Internal

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_Face_InternalRec_*  FT_Face_Internal;

An opaque handle to an FT_Face_InternalRec structure that models the private data of a given FT_Face object.

This structure might change between releases of FreeType 2 and is not generally available to client applications.


FT_Size_Internal

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_Size_InternalRec_*  FT_Size_Internal;

An opaque handle to an FT_Size_InternalRec structure, used to model private data of a given FT_Size object.


FT_Slot_Internal

Defined in FT_FREETYPE_H (freetype/freetype.h).

  typedef struct FT_Slot_InternalRec_*  FT_Slot_Internal;

An opaque handle to an FT_Slot_InternalRec structure, used to model private data of a given FT_GlyphSlot object.


FT_FACE_FLAG_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_FACE_FLAG_SCALABLE          ( 1L <<  0 )
#define FT_FACE_FLAG_FIXED_SIZES       ( 1L <<  1 )
#define FT_FACE_FLAG_FIXED_WIDTH       ( 1L <<  2 )
#define FT_FACE_FLAG_SFNT              ( 1L <<  3 )
#define FT_FACE_FLAG_HORIZONTAL        ( 1L <<  4 )
#define FT_FACE_FLAG_VERTICAL          ( 1L <<  5 )
#define FT_FACE_FLAG_KERNING           ( 1L <<  6 )
#define FT_FACE_FLAG_FAST_GLYPHS       ( 1L <<  7 )
#define FT_FACE_FLAG_MULTIPLE_MASTERS  ( 1L <<  8 )
#define FT_FACE_FLAG_GLYPH_NAMES       ( 1L <<  9 )
#define FT_FACE_FLAG_EXTERNAL_STREAM   ( 1L << 10 )
#define FT_FACE_FLAG_HINTER            ( 1L << 11 )
#define FT_FACE_FLAG_CID_KEYED         ( 1L << 12 )
#define FT_FACE_FLAG_TRICKY            ( 1L << 13 )
#define FT_FACE_FLAG_COLOR             ( 1L << 14 )
#define FT_FACE_FLAG_VARIATION         ( 1L << 15 )

A list of bit flags used in the face_flags field of the FT_FaceRec structure. They inform client applications of properties of the corresponding face.

values

FT_FACE_FLAG_SCALABLE

The face contains outline glyphs. Note that a face can contain bitmap strikes also, i.e., a face can have both this flag and FT_FACE_FLAG_FIXED_SIZES set.

FT_FACE_FLAG_FIXED_SIZES

The face contains bitmap strikes. See also the num_fixed_sizes and available_sizes fields of FT_FaceRec.

FT_FACE_FLAG_FIXED_WIDTH

The face contains fixed-width characters (like Courier, Lucida, MonoType, etc.).

FT_FACE_FLAG_SFNT

The face uses the SFNT storage scheme. For now, this means TrueType and OpenType.

FT_FACE_FLAG_HORIZONTAL

The face contains horizontal glyph metrics. This should be set for all common formats.

FT_FACE_FLAG_VERTICAL

The face contains vertical glyph metrics. This is only available in some formats, not all of them.

FT_FACE_FLAG_KERNING

The face contains kerning information. If set, the kerning distance can be retrieved using the function FT_Get_Kerning. Otherwise the function always return the vector (0,0). Note that FreeType doesn't handle kerning data from the SFNT ‘GPOS’ table (as present in many OpenType fonts).

FT_FACE_FLAG_FAST_GLYPHS

THIS FLAG IS DEPRECATED. DO NOT USE OR TEST IT.

FT_FACE_FLAG_MULTIPLE_MASTERS

The face contains multiple masters and is capable of interpolating between them. Supported formats are Adobe MM, TrueType GX, and OpenType variation fonts.

See section ‘Multiple Masters’ for API details.

FT_FACE_FLAG_GLYPH_NAMES

The face contains glyph names, which can be retrieved using FT_Get_Glyph_Name. Note that some TrueType fonts contain broken glyph name tables. Use the function FT_Has_PS_Glyph_Names when needed.

FT_FACE_FLAG_EXTERNAL_STREAM

Used internally by FreeType to indicate that a face's stream was provided by the client application and should not be destroyed when FT_Done_Face is called. Don't read or test this flag.

FT_FACE_FLAG_HINTER

The font driver has a hinting machine of its own. For example, with TrueType fonts, it makes sense to use data from the SFNT ‘gasp’ table only if the native TrueType hinting engine (with the bytecode interpreter) is available and active.

FT_FACE_FLAG_CID_KEYED

The face is CID-keyed. In that case, the face is not accessed by glyph indices but by CID values. For subsetted CID-keyed fonts this has the consequence that not all index values are a valid argument to FT_Load_Glyph. Only the CID values for which corresponding glyphs in the subsetted font exist make FT_Load_Glyph return successfully; in all other cases you get an FT_Err_Invalid_Argument error.

Note that CID-keyed fonts that are in an SFNT wrapper (this is, all OpenType/CFF fonts) don't have this flag set since the glyphs are accessed in the normal way (using contiguous indices); the ‘CID-ness’ isn't visible to the application.

FT_FACE_FLAG_TRICKY

The face is ‘tricky’, this is, it always needs the font format's native hinting engine to get a reasonable result. A typical example is the old Chinese font mingli.ttf (but not mingliu.ttc) that uses TrueType bytecode instructions to move and scale all of its subglyphs.

It is not possible to auto-hint such fonts using FT_LOAD_FORCE_AUTOHINT; it will also ignore FT_LOAD_NO_HINTING. You have to set both FT_LOAD_NO_HINTING and FT_LOAD_NO_AUTOHINT to really disable hinting; however, you probably never want this except for demonstration purposes.

Currently, there are about a dozen TrueType fonts in the list of tricky fonts; they are hard-coded in file ttobjs.c.

FT_FACE_FLAG_COLOR

[Since 2.5.1] The face has color glyph tables. See FT_LOAD_COLOR for more information.

FT_FACE_FLAG_VARIATION

[Since 2.9] Set if the current face (or named instance) has been altered with FT_Set_MM_Design_Coordinates, FT_Set_Var_Design_Coordinates, or FT_Set_Var_Blend_Coordinates. This flag is unset by a call to FT_Set_Named_Instance.


FT_STYLE_FLAG_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_STYLE_FLAG_ITALIC  ( 1 << 0 )
#define FT_STYLE_FLAG_BOLD    ( 1 << 1 )

A list of bit flags to indicate the style of a given face. These are used in the style_flags field of FT_FaceRec.

values

FT_STYLE_FLAG_ITALIC

The face style is italic or oblique.

FT_STYLE_FLAG_BOLD

The face is bold.

note

The style information as provided by FreeType is very basic. More details are beyond the scope and should be done on a higher level (for example, by analyzing various fields of the ‘OS/2’ table in SFNT based fonts).


FT_OPEN_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_OPEN_MEMORY    0x1
#define FT_OPEN_STREAM    0x2
#define FT_OPEN_PATHNAME  0x4
#define FT_OPEN_DRIVER    0x8
#define FT_OPEN_PARAMS    0x10

  /* these constants are deprecated; use the corresponding `FT_OPEN_XXX` */
  /* values instead                                                      */
#define ft_open_memory    FT_OPEN_MEMORY
#define ft_open_stream    FT_OPEN_STREAM
#define ft_open_pathname  FT_OPEN_PATHNAME
#define ft_open_driver    FT_OPEN_DRIVER
#define ft_open_params    FT_OPEN_PARAMS

A list of bit field constants used within the flags field of the FT_Open_Args structure.

values

FT_OPEN_MEMORY

This is a memory-based stream.

FT_OPEN_STREAM

Copy the stream from the stream field.

FT_OPEN_PATHNAME

Create a new input stream from a C path name.

FT_OPEN_DRIVER

Use the driver field.

FT_OPEN_PARAMS

Use the num_params and params fields.

note

The FT_OPEN_MEMORY, FT_OPEN_STREAM, and FT_OPEN_PATHNAME flags are mutually exclusive.


FT_LOAD_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_LOAD_DEFAULT                      0x0
#define FT_LOAD_NO_SCALE                     ( 1L << 0 )
#define FT_LOAD_NO_HINTING                   ( 1L << 1 )
#define FT_LOAD_RENDER                       ( 1L << 2 )
#define FT_LOAD_NO_BITMAP                    ( 1L << 3 )
#define FT_LOAD_VERTICAL_LAYOUT              ( 1L << 4 )
#define FT_LOAD_FORCE_AUTOHINT               ( 1L << 5 )
#define FT_LOAD_CROP_BITMAP                  ( 1L << 6 )
#define FT_LOAD_PEDANTIC                     ( 1L << 7 )
#define FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH  ( 1L << 9 )
#define FT_LOAD_NO_RECURSE                   ( 1L << 10 )
#define FT_LOAD_IGNORE_TRANSFORM             ( 1L << 11 )
#define FT_LOAD_MONOCHROME                   ( 1L << 12 )
#define FT_LOAD_LINEAR_DESIGN                ( 1L << 13 )
#define FT_LOAD_NO_AUTOHINT                  ( 1L << 15 )
  /* Bits 16-19 are used by `FT_LOAD_TARGET_` */
#define FT_LOAD_COLOR                        ( 1L << 20 )
#define FT_LOAD_COMPUTE_METRICS              ( 1L << 21 )
#define FT_LOAD_BITMAP_METRICS_ONLY          ( 1L << 22 )

A list of bit field constants for FT_Load_Glyph to indicate what kind of operations to perform during glyph loading.

values

FT_LOAD_DEFAULT

Corresponding to 0, this value is used as the default glyph load operation. In this case, the following happens:

  1. FreeType looks for a bitmap for the glyph corresponding to the face's current size. If one is found, the function returns. The bitmap data can be accessed from the glyph slot (see note below).

  2. If no embedded bitmap is searched for or found, FreeType looks for a scalable outline. If one is found, it is loaded from the font file, scaled to device pixels, then ‘hinted’ to the pixel grid in order to optimize it. The outline data can be accessed from the glyph slot (see note below).

Note that by default the glyph loader doesn't render outlines into bitmaps. The following flags are used to modify this default behaviour to more specific and useful cases.

FT_LOAD_NO_SCALE

Don't scale the loaded outline glyph but keep it in font units.

This flag implies FT_LOAD_NO_HINTING and FT_LOAD_NO_BITMAP, and unsets FT_LOAD_RENDER.

If the font is ‘tricky’ (see FT_FACE_FLAG_TRICKY for more), using FT_LOAD_NO_SCALE usually yields meaningless outlines because the subglyphs must be scaled and positioned with hinting instructions. This can be solved by loading the font without FT_LOAD_NO_SCALE and setting the character size to font->units_per_EM.

FT_LOAD_NO_HINTING

Disable hinting. This generally generates ‘blurrier’ bitmap glyphs when the glyph are rendered in any of the anti-aliased modes. See also the note below.

This flag is implied by FT_LOAD_NO_SCALE.

FT_LOAD_RENDER

Call FT_Render_Glyph after the glyph is loaded. By default, the glyph is rendered in FT_RENDER_MODE_NORMAL mode. This can be overridden by FT_LOAD_TARGET_XXX or FT_LOAD_MONOCHROME.

This flag is unset by FT_LOAD_NO_SCALE.

FT_LOAD_NO_BITMAP

Ignore bitmap strikes when loading. Bitmap-only fonts ignore this flag.

FT_LOAD_NO_SCALE always sets this flag.

FT_LOAD_VERTICAL_LAYOUT

Load the glyph for vertical text layout. In particular, the advance value in the FT_GlyphSlotRec structure is set to the vertAdvance value of the metrics field.

In case FT_HAS_VERTICAL doesn't return true, you shouldn't use this flag currently. Reason is that in this case vertical metrics get synthesized, and those values are not always consistent across various font formats.

FT_LOAD_FORCE_AUTOHINT

Prefer the auto-hinter over the font's native hinter. See also the note below.

FT_LOAD_PEDANTIC

Make the font driver perform pedantic verifications during glyph loading and hinting. This is mostly used to detect broken glyphs in fonts. By default, FreeType tries to handle broken fonts also.

In particular, errors from the TrueType bytecode engine are not passed to the application if this flag is not set; this might result in partially hinted or distorted glyphs in case a glyph's bytecode is buggy.

FT_LOAD_NO_RECURSE

Don't load composite glyphs recursively. Instead, the font driver fills the num_subglyph and subglyphs values of the glyph slot; it also sets glyph->format to FT_GLYPH_FORMAT_COMPOSITE. The description of subglyphs can then be accessed with FT_Get_SubGlyph_Info.

Don't use this flag for retrieving metrics information since some font drivers only return rudimentary data.

This flag implies FT_LOAD_NO_SCALE and FT_LOAD_IGNORE_TRANSFORM.

FT_LOAD_IGNORE_TRANSFORM

Ignore the transform matrix set by FT_Set_Transform.

FT_LOAD_MONOCHROME

This flag is used with FT_LOAD_RENDER to indicate that you want to render an outline glyph to a 1-bit monochrome bitmap glyph, with 8 pixels packed into each byte of the bitmap data.

Note that this has no effect on the hinting algorithm used. You should rather use FT_LOAD_TARGET_MONO so that the monochrome-optimized hinting algorithm is used.

FT_LOAD_LINEAR_DESIGN

Keep linearHoriAdvance and linearVertAdvance fields of FT_GlyphSlotRec in font units. See FT_GlyphSlotRec for details.

FT_LOAD_NO_AUTOHINT

Disable the auto-hinter. See also the note below.

FT_LOAD_COLOR

Load colored glyphs. There are slight differences depending on the font format.

[Since 2.5] Load embedded color bitmap images. The resulting color bitmaps, if available, will have the FT_PIXEL_MODE_BGRA format, with pre-multiplied color channels. If the flag is not set and color bitmaps are found, they are converted to 256-level gray bitmaps, using the FT_PIXEL_MODE_GRAY format.

[Since 2.10, experimental] If the glyph index contains an entry in the face's ‘COLR’ table with a ‘CPAL’ palette table (as defined in the OpenType specification), make FT_Render_Glyph provide a default blending of the color glyph layers associated with the glyph index, using the same bitmap format as embedded color bitmap images. This is mainly for convenience; for full control of color layers use FT_Get_Color_Glyph_Layer and FreeType's color functions like FT_Palette_Select instead of setting FT_LOAD_COLOR for rendering so that the client application can handle blending by itself.

FT_LOAD_COMPUTE_METRICS

[Since 2.6.1] Compute glyph metrics from the glyph data, without the use of bundled metrics tables (for example, the ‘hdmx’ table in TrueType fonts). This flag is mainly used by font validating or font editing applications, which need to ignore, verify, or edit those tables.

Currently, this flag is only implemented for TrueType fonts.

FT_LOAD_BITMAP_METRICS_ONLY

[Since 2.7.1] Request loading of the metrics and bitmap image information of a (possibly embedded) bitmap glyph without allocating or copying the bitmap image data itself. No effect if the target glyph is not a bitmap image.

This flag unsets FT_LOAD_RENDER.

FT_LOAD_CROP_BITMAP

Ignored. Deprecated.

FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH

Ignored. Deprecated.

note

By default, hinting is enabled and the font's native hinter (see FT_FACE_FLAG_HINTER) is preferred over the auto-hinter. You can disable hinting by setting FT_LOAD_NO_HINTING or change the precedence by setting FT_LOAD_FORCE_AUTOHINT. You can also set FT_LOAD_NO_AUTOHINT in case you don't want the auto-hinter to be used at all.

See the description of FT_FACE_FLAG_TRICKY for a special exception (affecting only a handful of Asian fonts).

Besides deciding which hinter to use, you can also decide which hinting algorithm to use. See FT_LOAD_TARGET_XXX for details.

Note that the auto-hinter needs a valid Unicode cmap (either a native one or synthesized by FreeType) for producing correct results. If a font provides an incorrect mapping (for example, assigning the character code U+005A, LATIN CAPITAL LETTER Z, to a glyph depicting a mathematical integral sign), the auto-hinter might produce useless results.


FT_LOAD_TARGET_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_LOAD_TARGET_( x )   ( (FT_Int32)( (x) & 15 ) << 16 )

#define FT_LOAD_TARGET_NORMAL  FT_LOAD_TARGET_( FT_RENDER_MODE_NORMAL )
#define FT_LOAD_TARGET_LIGHT   FT_LOAD_TARGET_( FT_RENDER_MODE_LIGHT  )
#define FT_LOAD_TARGET_MONO    FT_LOAD_TARGET_( FT_RENDER_MODE_MONO   )
#define FT_LOAD_TARGET_LCD     FT_LOAD_TARGET_( FT_RENDER_MODE_LCD    )
#define FT_LOAD_TARGET_LCD_V   FT_LOAD_TARGET_( FT_RENDER_MODE_LCD_V  )

A list of values to select a specific hinting algorithm for the hinter. You should OR one of these values to your load_flags when calling FT_Load_Glyph.

Note that a font's native hinters may ignore the hinting algorithm you have specified (e.g., the TrueType bytecode interpreter). You can set FT_LOAD_FORCE_AUTOHINT to ensure that the auto-hinter is used.

values

FT_LOAD_TARGET_NORMAL

The default hinting algorithm, optimized for standard gray-level rendering. For monochrome output, use FT_LOAD_TARGET_MONO instead.

FT_LOAD_TARGET_LIGHT

A lighter hinting algorithm for gray-level modes. Many generated glyphs are fuzzier but better resemble their original shape. This is achieved by snapping glyphs to the pixel grid only vertically (Y-axis), as is done by FreeType's new CFF engine or Microsoft's ClearType font renderer. This preserves inter-glyph spacing in horizontal text. The snapping is done either by the native font driver, if the driver itself and the font support it, or by the auto-hinter.

Advance widths are rounded to integer values; however, using the lsb_delta and rsb_delta fields of FT_GlyphSlotRec, it is possible to get fractional advance widths for subpixel positioning (which is recommended to use).

If configuration option AF_CONFIG_OPTION_TT_SIZE_METRICS is active, TrueType-like metrics are used to make this mode behave similarly as in unpatched FreeType versions between 2.4.6 and 2.7.1 (inclusive).

FT_LOAD_TARGET_MONO

Strong hinting algorithm that should only be used for monochrome output. The result is probably unpleasant if the glyph is rendered in non-monochrome modes.

Note that for outline fonts only the TrueType font driver has proper monochrome hinting support, provided the TTFs contain hints for B/W rendering (which most fonts no longer provide). If these conditions are not met it is very likely that you get ugly results at smaller sizes.

FT_LOAD_TARGET_LCD

A variant of FT_LOAD_TARGET_LIGHT optimized for horizontally decimated LCD displays.

FT_LOAD_TARGET_LCD_V

A variant of FT_LOAD_TARGET_NORMAL optimized for vertically decimated LCD displays.

note

You should use only one of the FT_LOAD_TARGET_XXX values in your load_flags. They can't be ORed.

If FT_LOAD_RENDER is also set, the glyph is rendered in the corresponding mode (i.e., the mode that matches the used algorithm best). An exception is FT_LOAD_TARGET_MONO since it implies FT_LOAD_MONOCHROME.

You can use a hinting algorithm that doesn't correspond to the same rendering mode. As an example, it is possible to use the ‘light’ hinting algorithm and have the results rendered in horizontal LCD pixel mode, with code like

  FT_Load_Glyph( face, glyph_index,
                 load_flags | FT_LOAD_TARGET_LIGHT );

  FT_Render_Glyph( face->glyph, FT_RENDER_MODE_LCD );

In general, you should stick with one rendering mode. For example, switching between FT_LOAD_TARGET_NORMAL and FT_LOAD_TARGET_MONO enforces a lot of recomputation for TrueType fonts, which is slow. Another reason is caching: Selecting a different mode usually causes changes in both the outlines and the rasterized bitmaps; it is thus necessary to empty the cache after a mode switch to avoid false hits.


FT_SUBGLYPH_FLAG_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

A list of constants describing subglyphs. Please refer to the ‘glyf’ table description in the OpenType specification for the meaning of the various flags (which get synthesized for non-OpenType subglyphs).

https://docs.microsoft.com/en-us/typography/opentype/spec/glyf#composite-glyph-description

values

FT_SUBGLYPH_FLAG_ARGS_ARE_WORDS
FT_SUBGLYPH_FLAG_ARGS_ARE_XY_VALUES
FT_SUBGLYPH_FLAG_ROUND_XY_TO_GRID
FT_SUBGLYPH_FLAG_SCALE
FT_SUBGLYPH_FLAG_XY_SCALE
FT_SUBGLYPH_FLAG_2X2
FT_SUBGLYPH_FLAG_USE_MY_METRICS

FT_FSTYPE_XXX

Defined in FT_FREETYPE_H (freetype/freetype.h).

A list of bit flags used in the fsType field of the OS/2 table in a TrueType or OpenType font and the FSType entry in a PostScript font. These bit flags are returned by FT_Get_FSType_Flags; they inform client applications of embedding and subsetting restrictions associated with a font.

See https://www.adobe.com/content/dam/Adobe/en/devnet/acrobat/pdfs/FontPolicies.pdf for more details.

values

FT_FSTYPE_INSTALLABLE_EMBEDDING

Fonts with no fsType bit set may be embedded and permanently installed on the remote system by an application.

FT_FSTYPE_RESTRICTED_LICENSE_EMBEDDING

Fonts that have only this bit set must not be modified, embedded or exchanged in any manner without first obtaining permission of the font software copyright owner.

FT_FSTYPE_PREVIEW_AND_PRINT_EMBEDDING

The font may be embedded and temporarily loaded on the remote system. Documents containing Preview & Print fonts must be opened ‘read-only’; no edits can be applied to the document.

FT_FSTYPE_EDITABLE_EMBEDDING

The font may be embedded but must only be installed temporarily on other systems. In contrast to Preview & Print fonts, documents containing editable fonts may be opened for reading, editing is permitted, and changes may be saved.

FT_FSTYPE_NO_SUBSETTING

The font may not be subsetted prior to embedding.

FT_FSTYPE_BITMAP_EMBEDDING_ONLY

Only bitmaps contained in the font may be embedded; no outline data may be embedded. If there are no bitmaps available in the font, then the font is unembeddable.

note

The flags are ORed together, thus more than a single value can be returned.

While the fsType flags can indicate that a font may be embedded, a license with the font vendor may be separately required to use the font in this way.


FT_HAS_FAST_GLYPHS

Defined in FT_FREETYPE_H (freetype/freetype.h).

#define FT_HAS_FAST_GLYPHS( face )  0

Deprecated.