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_END_HEADER

#endif /* __OPENTYPE_FTGLUE_H__ */