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/*******************************************************************
*
* ftxkern.h 1.0
*
* High-Level API Kerning extension
*
* Copyright 1996-1999 by
* David Turner, Robert Wilhelm, and Werner Lemberg.
*
* This file is part of the FreeType project, and may only be used
* modified and distributed under the terms of the FreeType project
* license, LICENSE.TXT. By continuing to use, modify, or distribute
* this file you indicate that you have read the license and
* understand and accept it fully.
*
*
* The kerning support is currently part of the engine extensions.
*
* This file should _not_ depend on engine internal types.
*
******************************************************************/
#ifndef FTXKERN_H
#define FTXKERN_H
#include "freetype.h"
#ifdef __cplusplus
extern "C" {
#endif
/* The kerning support in FreeType is minimal. This means that */
/* we do not try to interpret the kerning data in any way to */
/* `cook' it for a user application. This API lets you access */
/* directly the kerning tables found in the TrueType file; it's */
/* up to the client application to apply its own processing on */
/* these. */
/* The reason for this is that we generally do not encourage */
/* feature-bloat of the core engine. Moreover, not all */
/* libraries or font servers really need kerning data, or all */
/* formats of this data. */
/************** kerning error codes *****************************/
/* we choose the class 0x0A for our errors, this should not */
/* match with any error code class used in any other extension */
#define TT_Err_Invalid_Kerning_Table_Format 0x0A00
#define TT_Err_Invalid_Kerning_Table 0x0A01
/********** structures definitions ******************************/
/* Remember that all types and function are accessible by client */
/* applications in this section, and thus should have the `TT_' */
/* prefix. */
/* format 0 kerning pair */
struct TT_Kern_0_Pair_
{
TT_UShort left; /* index of left glyph in pair */
TT_UShort right; /* index of right glyph in pair */
TT_FWord value; /* kerning value */
};
typedef struct TT_Kern_0_Pair_ TT_Kern_0_Pair;
/* format 0 kerning subtable */
struct TT_Kern_0_
{
TT_UShort nPairs; /* number of kerning pairs */
TT_UShort searchRange; /* these values are defined by the TT spec */
TT_UShort entrySelector; /* for table searchs. */
TT_UShort rangeShift;
TT_Kern_0_Pair* pairs; /* a table of nPairs `pairs' */
};
typedef struct TT_Kern_0_ TT_Kern_0;
/* format 2 kerning glyph class */
struct TT_Kern_2_Class_
{
TT_UShort firstGlyph; /* first glyph in range */
TT_UShort nGlyphs; /* number of glyphs in range */
TT_UShort* classes; /* a table giving for each ranged glyph */
/* its class offset in the subtable pairs */
/* two-dimensional array */
};
typedef struct TT_Kern_2_Class_ TT_Kern_2_Class;
/* format 2 kerning subtable */
struct TT_Kern_2_
{
TT_UShort rowWidth; /* length of one row in bytes */
TT_Kern_2_Class leftClass; /* left class table */
TT_Kern_2_Class rightClass; /* right class table */
TT_FWord* array; /* 2-dimensional kerning values array */
};
typedef struct TT_Kern_2_ TT_Kern_2;
/* kerning subtable */
struct TT_Kern_Subtable_
{
TT_Bool loaded; /* boolean; indicates whether the table is */
/* loaded */
TT_UShort version; /* table version number */
TT_Long offset; /* file offset of table */
TT_UShort length; /* length of table, _excluding_ header */
TT_Byte coverage; /* lower 8 bit of the coverage table entry */
TT_Byte format; /* the subtable format, as found in the */
/* higher 8 bits of the coverage table entry */
union
{
TT_Kern_0 kern0;
TT_Kern_2 kern2;
} t;
};
typedef struct TT_Kern_Subtable_ TT_Kern_Subtable;
struct TT_Kerning_
{
TT_UShort version; /* kern table version number. starts at 0 */
TT_UShort nTables; /* number of tables */
TT_Kern_Subtable* tables; /* the kerning sub-tables */
};
typedef struct TT_Kerning_ TT_Kerning;
/***************** high-level API extension **************************/
/* Initialize Kerning extension, must be called after */
/* TT_Init_FreeType(). There is no need for a finalizer */
EXPORT_DEF
TT_Error TT_Init_Kerning_Extension( TT_Engine engine );
/* Note on the implemented mechanism: */
/* The kerning table directory is loaded with the face through the */
/* extension constructor. However, the tables will only be loaded */
/* on demand, as they may represent a lot of data, unnecessary to */
/* most applications. */
/* Queries a pointer to the kerning directory for the face object */
EXPORT_DEF
TT_Error TT_Get_Kerning_Directory( TT_Face face,
TT_Kerning* directory );
/* Load the kerning table number `kern_index' in the kerning */
/* directory. The table will stay in memory until the `face' */
/* face is destroyed. */
EXPORT_DEF
TT_Error TT_Load_Kerning_Table( TT_Face face,
TT_UShort kern_index );
#ifdef __cplusplus
}
#endif
#endif /* FTXKERN_H */
/* END */
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