src/ftglue.h

/* ftglue.c: Glue code for compiling the OpenType code from
 *           FreeType 1 using only the public API of FreeType 2
 *
 * By David Turner, The FreeType Project (www.freetype.org)
 *
 * This code is explicitely put in the public domain
 *
 * ==========================================================================
 *
 * the OpenType parser codes was originally written as an extension to
 * FreeType 1.x. As such, its source code was embedded within the library,
 * and used many internal FreeType functions to deal with memory and
 * stream i/o.
 *
 * When it was 'salvaged' for Pango and Qt, the code was "ported" to FreeType 2,
 * which basically means that some macro tricks were performed in order to
 * directly access FT2 _internal_ functions.
 *
 * these functions were never part of FT2 public API, and _did_ change between
 * various releases. This created chaos for many users: when they upgraded the
 * FreeType library on their system, they couldn't run Gnome anymore since
 * Pango refused to link.
 *
 * Very fortunately, it's possible to completely avoid this problem because
 * the FT_StreamRec and FT_MemoryRec structure types, which describe how
 * memory and stream implementations interface with the rest of the font
 * library, have always been part of the public API, and never changed.
 *
 * What we do thus is re-implement, within the OpenType parser, the few
 * functions that depend on them. This only adds one or two kilobytes of
 * code, and ensures that the parser can work with _any_ version
 * of FreeType installed on your system. How sweet... !
 *
 * Note that we assume that Pango doesn't use any other internal functions
 * from FreeType. It used to in old versions, but this should no longer
 * be the case. (crossing my fingers).
 *
 *  - David Turner
 *  - The FreeType Project  (www.freetype.org)
 *
 * PS: This "glue" code is explicitely put in the public domain
 */
#ifndef __OPENTYPE_FTGLUE_H__
#define __OPENTYPE_FTGLUE_H__

#include "fcint.h"

#include <ft2build.h>
#include FT_FREETYPE_H

FT_BEGIN_HEADER

#define SET_ERR(c) ((error = (c)) != 0)

#ifndef FTGLUE_API
#  define FTGLUE_API(x) extern FcPrivate x
#endif

#ifndef FTGLUE_APIDEF
#  define FTGLUE_APIDEF(x) x
#endif

/* stream macros used by the OpenType parser */
#define FILE_Pos()         ftglue_stream_pos (stream)
#define FILE_Seek(pos)     SET_ERR (ftglue_stream_seek (stream, pos))
#define ACCESS_Frame(size) SET_ERR (ftglue_stream_frame_enter (stream, size))
#define FORGET_Frame()     ftglue_stream_frame_exit (stream)

#define GET_Byte()         (*stream->cursor++)
#define GET_Short()        (stream->cursor += 2, (FT_Short)(((FT_ULong) * (((FT_Byte *)stream->cursor) - 2) << 8) | \
                                                     (FT_ULong) * (((FT_Byte *)stream->cursor) - 1)))
#define GET_Long() (stream->cursor += 4, (FT_Long)(((FT_ULong) * (((FT_Byte *)stream->cursor) - 4) << 24) | \
                                                   ((FT_ULong) * (((FT_Byte *)stream->cursor) - 3) << 16) | \
                                                   ((FT_ULong) * (((FT_Byte *)stream->cursor) - 2) << 8) |  \
                                                   (FT_ULong) * (((FT_Byte *)stream->cursor) - 1)))

#define GET_Char()   ((FT_Char)GET_Byte())
#define GET_UShort() ((FT_UShort)GET_Short())
#define GET_ULong()  ((FT_ULong)GET_Long())
#define GET_Tag4()   GET_ULong()

#define FT_SET_ERROR(expression) \
    ((error = (expression)) != 0)

FTGLUE_API (FT_Long)
ftglue_stream_pos (FT_Stream stream);

FTGLUE_API (FT_Error)
ftglue_stream_seek (FT_Stream stream,
                    FT_Long   pos);

FTGLUE_API (FT_Error)
ftglue_stream_frame_enter (FT_Stream stream,
                           FT_ULong  size);

FTGLUE_API (void)
ftglue_stream_frame_exit (FT_Stream stream);

FTGLUE_API (FT_Error)
ftglue_face_goto_table (FT_Face   face,
                        FT_ULong  tag,
                        FT_Stream stream,
                        FT_ULong *table_size);

FT_END_HEADER

#endif /* __OPENTYPE_FTGLUE_H__ */