src/base/ftextend.h

/***************************************************************************/
/*                                                                         */
/*  ftextend.h                                                             */
/*                                                                         */
/*  FreeType extensions implementation (specification).                    */
/*                                                                         */
/*  Copyright 1996-2000 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.                                        */
/*                                                                         */
/***************************************************************************/

#ifndef FTEXTEND_H
#define FTEXTEND_H

#include <ftobjs.h>


#ifdef __cplusplus
  extern "C" {
#endif

  /*************************************************************************/
  /*                                                                       */
  /* The extensions don't need to be integrated at compile time into the   */
  /* engine, only at link time.                                            */
  /*                                                                       */
  /*************************************************************************/

  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Extension_Initializer                                           */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Each new face object can have several extensions associated with   */
  /*    it at creation time.  This function is used to initialize given    */
  /*    extension data for a given face.                                   */
  /*                                                                       */
  /* <InOut>                                                               */
  /*    ext  :: A typeless pointer to the extension data.                  */
  /*    face :: A handle to the source face object the extension is        */
  /*            associated with.                                           */
  /*                                                                       */
  /* <Return>                                                              */
  /*    FreeType error code.  0 means success.                             */
  /*                                                                       */
  /* <Note>                                                                */
  /*    In case of error, the initializer should not destroy the extension */
  /*    data, as the finalizer will get called later by the function's     */
  /*    caller.                                                            */
  /*                                                                       */
  typedef FT_Error (*FT_Extension_Initializer)( void*    ext, 
                                                FT_Face  face );


  /*************************************************************************/
  /*                                                                       */
  /* <FuncType>                                                            */
  /*    FT_Extension_Finalizer                                             */
  /*                                                                       */
  /* <Description>                                                         */
  /*    Each new face object can have several extensions associated with   */
  /*    it at creation time.  This function is used to finalize given      */
  /*    extension data for a given face; it occurs before the face object  */
  /*    itself is finalized.                                               */
  /*                                                                       */
  /* <InOut>                                                               */
  /*   ext  :: A typeless pointer to the extension data.                   */
  /*   face :: A handle to the source face object the extension is         */
  /*           associated with.                                            */
  /*                                                                       */
  typedef void  (*FT_Extension_Finalizer)( void*    ext,
                                           FT_Face  face );


  /*************************************************************************/
  /*                                                                       */
  /* <Struct>                                                              */
  /*    FT_Extension_Class                                                 */
  /*                                                                       */
  /* <Description>                                                         */
  /*    A simple structure used to describe a given extension to the       */
  /*    FreeType base layer.  An FT_Extension_Class is used as a parameter */
  /*    for FT_Register_Extension().                                       */
  /*                                                                       */
  /* <Fields>                                                              */
  /*    id        :: The extension's ID.  This is a normal C string that   */
  /*                 is used to uniquely reference the extension's         */
  /*                 interface.                                            */
  /*    size      :: The size in bytes of the extension data that must be  */
  /*                 associated with each face object.                     */
  /*    init      :: A pointer to the extension data's initializer.        */
  /*    finalize  :: A pointer to the extension data's finalizer.          */
  /*    interface :: This pointer can be anything, but should usually      */
  /*                 point to a table of function pointers which implement */
  /*                 the extension's interface.                            */
  /*                                                                       */
  /*    offset    :: This field is set and used within the base layer and  */
  /*                 should be set to 0 when registering an extension      */
  /*                 through FT_Register_Extension().  It contains an      */
  /*                 offset within the face's extension block for the      */
  /*                 current extension's data.                             */
  /*                                                                       */
  typedef struct  FT_Extension_Class_
  {
    const char*               id;
    FT_ULong                  size;
    FT_Extension_Initializer  init;
    FT_Extension_Finalizer    finalize;
    void*                     interface;
    
    FT_ULong                  offset;
    
  } FT_Extension_Class;
  

  EXPORT_DEF
  FT_Error  FT_Register_Extension( FT_Driver            driver,
                                   FT_Extension_Class*  clazz );


#ifdef FT_CONFIG_OPTION_EXTEND_ENGINE


  /* Initialize the extension component */
  LOCAL_DEF
  FT_Error  FT_Init_Extensions( FT_Library  library );

  /* Finalize the extension component */
  LOCAL_DEF
  FT_Error  FT_Done_Extensions( FT_Library  library );

  /* Create an extension within a face object.  Called by the */
  /* face object constructor.                                 */
  LOCAL_DEF
  FT_Error  FT_Create_Extensions( FT_Face  face );

  /* Destroy all extensions within a face object.  Called by the */
  /* face object destructor.                                     */
  LOCAL_DEF
  FT_Error  FT_Destroy_Extensions( FT_Face  face );


#endif


  /* Returns an extension's data & interface according to its ID */
  EXPORT_DEF
  void*     FT_Get_Extension( FT_Face      face,
                              const char*  extension_id,
                              void*       *extension_interface );

#ifdef __cplusplus
  }
#endif


#endif /* FTEXTEND_H */


/* END */