src/freetype/freetype/internal/ftextend.h

   1 /***************************************************************************/
   2 /*                                                                         */
   3 /*  ftextend.h                                                             */
   4 /*                                                                         */
   5 /*    FreeType extensions implementation (specification).                  */
   6 /*                                                                         */
   7 /*  Copyright 1996-2000 by                                                 */
   8 /*  David Turner, Robert Wilhelm, and Werner Lemberg.                      */
   9 /*                                                                         */
  10 /*  This file is part of the FreeType project, and may only be used,       */
  11 /*  modified, and distributed under the terms of the FreeType project      */
  12 /*  license, LICENSE.TXT.  By continuing to use, modify, or distribute     */
  13 /*  this file you indicate that you have read the license and              */
  14 /*  understand and accept it fully.                                        */
  15 /*                                                                         */
  16 /***************************************************************************/
  17
  18
  19 #ifndef FTEXTEND_H
  20 #define FTEXTEND_H
  21
  22
  23 #include <freetype/internal/ftobjs.h>
  24
  25
  26 #ifdef __cplusplus
  27   extern "C" {
  28 #endif
  29
  30
  31   /*************************************************************************/
  32   /*                                                                       */
  33   /* The extensions don't need to be integrated at compile time into the   */
  34   /* engine, only at link time.                                            */
  35   /*                                                                       */
  36   /*************************************************************************/
  37
  38
  39   /*************************************************************************/
  40   /*                                                                       */
  41   /* <FuncType>                                                            */
  42   /*    FT_Extension_Initializer                                           */
  43   /*                                                                       */
  44   /* <Description>                                                         */
  45   /*    Each new face object can have several extensions associated with   */
  46   /*    it at creation time.  This function is used to initialize given    */
  47   /*    extension data for a given face.                                   */
  48   /*                                                                       */
  49   /* <InOut>                                                               */
  50   /*    ext  :: A typeless pointer to the extension data.                  */
  51   /*                                                                       */
  52   /*    face :: A handle to the source face object the extension is        */
  53   /*            associated with.                                           */
  54   /*                                                                       */
  55   /* <Return>                                                              */
  56   /*    FreeType error code.  0 means success.                             */
  57   /*                                                                       */
  58   /* <Note>                                                                */
  59   /*    In case of error, the initializer should not destroy the extension */
  60   /*    data, as the finalizer will get called later by the function's     */
  61   /*    caller.                                                            */
  62   /*                                                                       */
  63   typedef FT_Error  (*FT_Extension_Initializer)( void*    ext,
  64                                                  FT_Face  face );
  65
  66
  67   /*************************************************************************/
  68   /*                                                                       */
  69   /* <FuncType>                                                            */
  70   /*    FT_Extension_Finalizer                                             */
  71   /*                                                                       */
  72   /* <Description>                                                         */
  73   /*    Each new face object can have several extensions associated with   */
  74   /*    it at creation time.  This function is used to finalize given      */
  75   /*    extension data for a given face; it occurs before the face object  */
  76   /*    itself is finalized.                                               */
  77   /*                                                                       */
  78   /* <InOut>                                                               */
  79   /*   ext  :: A typeless pointer to the extension data.                   */
  80   /*                                                                       */
  81   /*   face :: A handle to the source face object the extension is         */
  82   /*           associated with.                                            */
  83   /*                                                                       */
  84   typedef void  (*FT_Extension_Finalizer)( void*    ext,
  85                                            FT_Face  face );
  86
  87
  88   /*************************************************************************/
  89   /*                                                                       */
  90   /* <Struct>                                                              */
  91   /*    FT_Extension_Class                                                 */
  92   /*                                                                       */
  93   /* <Description>                                                         */
  94   /*    A simple structure used to describe a given extension to the       */
  95   /*    FreeType base layer.  An FT_Extension_Class is used as a parameter */
  96   /*    for FT_Register_Extension().                                       */
  97   /*                                                                       */
  98   /* <Fields>                                                              */
  99   /*    id        :: The extension's ID.  This is a normal C string that   */
 100   /*                 is used to uniquely reference the extension's         */
 101   /*                 interface.                                            */
 102   /*                                                                       */
 103   /*    size      :: The size in bytes of the extension data that must be  */
 104   /*                 associated with each face object.                     */
 105   /*                                                                       */
 106   /*    init      :: A pointer to the extension data's initializer.        */
 107   /*                                                                       */
 108   /*    finalize  :: A pointer to the extension data's finalizer.          */
 109   /*                                                                       */
 110   /*    interface :: This pointer can be anything, but should usually      */
 111   /*                 point to a table of function pointers which implement */
 112   /*                 the extension's interface.                            */
 113   /*                                                                       */
 114   /*    offset    :: This field is set and used within the base layer and  */
 115   /*                 should be set to 0 when registering an extension      */
 116   /*                 through FT_Register_Extension().  It contains an      */
 117   /*                 offset within the face's extension block for the      */
 118   /*                 current extension's data.                             */
 119   /*                                                                       */
 120   typedef struct  FT_Extension_Class_
 121   {
 122     const char*               id;
 123     FT_ULong                  size;
 124     FT_Extension_Initializer  init;
 125     FT_Extension_Finalizer    finalize;
 126     void*                     interface;
 127
 128     FT_ULong                  offset;
 129
 130   } FT_Extension_Class;
 131
 132
 133   FT_EXPORT_DEF( FT_Error )  FT_Register_Extension(
 134                                FT_Driver            driver,
 135                                FT_Extension_Class*  clazz );
 136
 137
 138 #ifdef FT_CONFIG_OPTION_EXTEND_ENGINE
 139
 140
 141   /* Initialize the extension component */
 142   LOCAL_DEF
 143   FT_Error  FT_Init_Extensions( FT_Library  library );
 144
 145   /* Finalize the extension component */
 146   LOCAL_DEF
 147   FT_Error  FT_Done_Extensions( FT_Library  library );
 148
 149   /* Create an extension within a face object.  Called by the */
 150   /* face object constructor.                                 */
 151   LOCAL_DEF
 152   FT_Error  FT_Create_Extensions( FT_Face  face );
 153
 154   /* Destroy all extensions within a face object.  Called by the */
 155   /* face object destructor.                                     */
 156   LOCAL_DEF
 157   FT_Error  FT_Destroy_Extensions( FT_Face  face );
 158
 159
 160 #endif
 161
 162
 163   /* return an extension's data & interface according to its ID */
 164   FT_EXPORT_DEF( void* )  FT_Get_Extension(
 165                             FT_Face      face,
 166                             const char*  extension_id,
 167                             void**       extension_interface );
 168
 169
 170 #ifdef __cplusplus
 171   }
 172 #endif
 173
 174
 175 #endif /* FTEXTEND_H */
 176
 177
 178 /* END */