www.pudn.com > freetype.rar > autohint.h

/***************************************************************************/ 
/*                                                                         */ 
/*  autohint.h                                                             */ 
/*                                                                         */ 
/*    High-level `autohint' module-specific interface (specification).     */ 
/*                                                                         */ 
/*  Copyright 1996-2001, 2002 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 auto-hinter is used to load and automatically hint glyphs if a    */ 
  /* format-specific hinter isn't available.                               */ 
  /*                                                                       */ 
  /*************************************************************************/ 
 
 
#ifndef __AUTOHINT_H__ 
#define __AUTOHINT_H__ 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /* A small technical note regarding automatic hinting in order to        */ 
  /* clarify this module interface.                                        */ 
  /*                                                                       */ 
  /* An automatic hinter might compute two kinds of data for a given face: */ 
  /*                                                                       */ 
  /* - global hints: Usually some metrics that describe global properties  */ 
  /*                 of the face.  It is computed by scanning more or less */ 
  /*                 agressively the glyphs in the face, and thus can be   */ 
  /*                 very slow to compute (even if the size of global      */ 
  /*                 hints is really small).                               */ 
  /*                                                                       */ 
  /* - glyph hints:  These describe some important features of the glyph   */ 
  /*                 outline, as well as how to align them.  They are      */ 
  /*                 generally much faster to compute than global hints.   */ 
  /*                                                                       */ 
  /* The current FreeType auto-hinter does a pretty good job while         */ 
  /* performing fast computations for both global and glyph hints.         */ 
  /* However, we might be interested in introducing more complex and       */ 
  /* powerful algorithms in the future, like the one described in the John */ 
  /* D. Hobby paper, which unfortunately requires a lot more horsepower.   */ 
  /*                                                                       */ 
  /* Because a sufficiently sophisticated font management system would     */ 
  /* typically implement an LRU cache of opened face objects to reduce     */ 
  /* memory usage, it is a good idea to be able to avoid recomputing       */ 
  /* global hints every time the same face is re-opened.                   */ 
  /*                                                                       */ 
  /* We thus provide the ability to cache global hints outside of the face */ 
  /* object, in order to speed up font re-opening time.  Of course, this   */ 
  /* feature is purely optional, so most client programs won't even notice */ 
  /* it.                                                                   */ 
  /*                                                                       */ 
  /* I initially thought that it would be a good idea to cache the glyph   */ 
  /* hints too.  However, my general idea now is that if you really need   */ 
  /* to cache these too, you are simply in need of a new font format,      */ 
  /* where all this information could be stored within the font file and   */ 
  /* decoded on the fly.                                                   */ 
  /*                                                                       */ 
  /*************************************************************************/ 
 
 
#include "ft2build.h" 
#include "freetype/freetype.h" 
 
 
FT_BEGIN_HEADER 
 
 
  typedef struct FT_AutoHinterRec_  *FT_AutoHinter; 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /*                                                             */ 
  /*    FT_AutoHinter_GlobalGetFunc                                        */ 
  /*                                                                       */ 
  /*                                                          */ 
  /*    Retrieves the global hints computed for a given face object the    */ 
  /*    resulting data is dissociated from the face and will survive a     */ 
  /*    call to FT_Done_Face().  It must be discarded through the API      */ 
  /*    FT_AutoHinter_GlobalDoneFunc().                                    */ 
  /*                                                                       */ 
  /*                                                                */ 
  /*    hinter        :: A handle to the source auto-hinter.               */ 
  /*                                                                       */ 
  /*    face          :: A handle to the source face object.               */ 
  /*                                                                       */ 
  /* 
                                                              */ 
  /*    global_hints  :: A typeless pointer to the global hints.           */ 
  /*                                                                       */ 
  /*    global_len    :: The size in bytes of the global hints.            */ 
  /*                                                                       */ 
  typedef void 
  (*FT_AutoHinter_GlobalGetFunc)( FT_AutoHinter  hinter, 
                                  FT_Face        face, 
                                  void**         global_hints, 
                                  long*          global_len ); 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /*                                                             */ 
  /*    FT_AutoHinter_GlobalDoneFunc                                       */ 
  /*                                                                       */ 
  /*                                                          */ 
  /*    Discards the global hints retrieved through                        */ 
  /*    FT_AutoHinter_GlobalGetFunc().  This is the only way these hints   */ 
  /*    are freed from memory.                                             */ 
  /*                                                                       */ 
  /*                                                                */ 
  /*    hinter :: A handle to the auto-hinter module.                      */ 
  /*                                                                       */ 
  /*    global :: A pointer to retrieved global hints to discard.          */ 
  /*                                                                       */ 
  typedef void 
  (*FT_AutoHinter_GlobalDoneFunc)( FT_AutoHinter  hinter, 
                                   void*          global ); 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /*                                                             */ 
  /*    FT_AutoHinter_GlobalResetFunc                                      */ 
  /*                                                                       */ 
  /*                                                          */ 
  /*    This function is used to recompute the global metrics in a given   */ 
  /*    font.  This is useful when global font data changes (e.g. Multiple */ 
  /*    Masters fonts where blend coordinates change).                     */ 
  /*                                                                       */ 
  /*                                                                */ 
  /*    hinter :: A handle to the source auto-hinter.                      */ 
  /*                                                                       */ 
  /*    face   :: A handle to the face.                                    */ 
  /*                                                                       */ 
  typedef void 
  (*FT_AutoHinter_GlobalResetFunc)( FT_AutoHinter  hinter, 
                                    FT_Face        face ); 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /*                                                             */ 
  /*    FT_AutoHinter_GlyphLoadFunc                                        */ 
  /*                                                                       */ 
  /*                                                          */ 
  /*    This function is used to load, scale, and automatically hint a     */ 
  /*    glyph from a given face.                                           */ 
  /*                                                                       */ 
  /*                                                                */ 
  /*    face        :: A handle to the face.                               */ 
  /*                                                                       */ 
  /*    glyph_index :: The glyph index.                                    */ 
  /*                                                                       */ 
  /*    load_flags  :: The load flags.                                     */ 
  /*                                                                       */ 
  /*                                                                 */ 
  /*    This function is capable of loading composite glyphs by hinting    */ 
  /*    each sub-glyph independently (which improves quality).             */ 
  /*                                                                       */ 
  /*    It will call the font driver with FT_Load_Glyph(), with            */ 
  /*    FT_LOAD_NO_SCALE set.                                              */ 
  /*                                                                       */ 
  typedef FT_Error 
  (*FT_AutoHinter_GlyphLoadFunc)( FT_AutoHinter  hinter, 
                                  FT_GlyphSlot   slot, 
                                  FT_Size        size, 
                                  FT_UInt        glyph_index, 
                                  FT_Int32       load_flags ); 
 
 
  /*************************************************************************/ 
  /*                                                                       */ 
  /*                                                               */ 
  /*    FT_AutoHinter_ServiceRec                                           */ 
  /*                                                                       */ 
  /*                                                          */ 
  /*    The auto-hinter module's interface.                                */ 
  /*                                                                       */ 
  typedef struct  FT_AutoHinter_ServiceRec_ 
  { 
    FT_AutoHinter_GlobalResetFunc  reset_face; 
    FT_AutoHinter_GlobalGetFunc    get_global_hints; 
    FT_AutoHinter_GlobalDoneFunc   done_global_hints; 
    FT_AutoHinter_GlyphLoadFunc    load_glyph; 
 
  } FT_AutoHinter_ServiceRec, *FT_AutoHinter_Service; 
 
 
FT_END_HEADER 
 
#endif /* __AUTOHINT_H__ */ 
 
 
/* END */