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Rev	Author	Line No.	Line
5496	leency	1	/*******************************************************************
		2	*
		3	* ttextend.h 2.0
		4	*
		5	* Extensions Interface.
		6	*
		7	* Copyright 1996-1999 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	* This is an updated version of the extension component, now
		17	* located in the main library's source directory. It allows
		18	* the dynamic registration/use of various face object extensions
		19	* through a simple API.
		20	*
		21	******************************************************************/
		22
		23	#ifndef TTEXTEND_H
		24	#define TTEXTEND_H
		25
		26	#include "ttconfig.h"
		27	#include "tttypes.h"
		28	#include "ttobjs.h"
		29
		30
		31	#ifdef __cplusplus
		32	extern "C" {
		33	#endif
		34
		35	/* The extensions don't need to be integrated at compile time into */
		36	/* the engine, only at link time. */
		37
		38
		39	/* When a new face object is created, the face constructor calls */
		40	/* the extension constructor with the following arguments: */
		41	/* */
		42	/* ext : typeless pointer to the face's extension block. */
		43	/* Its size is the one given at registration time */
		44	/* in the extension class's 'size' field. */
		45	/* */
		46	/* face : the parent face object. Note that the extension */
		47	/* constructor is called when the face object is */
		48	/* built. */
		49
		50	typedef TT_Error TExt_Constructor( void* ext, PFace face );
		51
		52
		53	/* When a face object is destroyed, the face destructor calls */
		54	/* the extension destructor with the following arguments. */
		55	/* */
		56	/* ext : typeless pointer to the face's extension block. */
		57	/* Its size is the one given at registration time */
		58	/* in the extension class's 'size' field. */
		59	/* */
		60	/* face : the parent face object. Note that the extension */
		61	/* destructor is called before the actual face object */
		62	/* is destroyed. */
		63
		64	typedef TT_Error TExt_Destructor ( void* ext, PFace face );
		65
		66	typedef TExt_Constructor* PExt_Constructor;
		67	typedef TExt_Destructor* PExt_Destructor;
		68
		69
		70	struct TExtension_Class_
		71	{
		72	Long id; /* extension id */
		73	Long size; /* size in bytes of extension record */
		74	PExt_Constructor build; /* the extension's class constructor */
		75	PExt_Destructor destroy; /* the extension's class destructor */
		76
		77	Long offset; /* offset of ext. record in face obj */
		78	/* (set by the engine) */
		79	};
		80
		81	typedef struct TExtension_Class_ TExtension_Class;
		82	typedef TExtension_Class* PExtension_Class;
		83
		84
		85	#define Build_Extension_ID( a, b, c, d ) \
		86	( ((ULong)(a) << 24) \| \
		87	((ULong)(b) << 16) \| \
		88	((ULong)(c) << 8 ) \| \
		89	(ULong)(d) )
		90
		91	/* A note regarding extensions and the single-object compilation */
		92	/* mode : */
		93	/* */
		94	/* When the engine is compiled as a single object file, extensions */
		95	/* must remain linkable after compile time. In order to do this, */
		96	/* we need to export the functions that an extension may need. */
		97	/* Fortunately, we can limit ourselves to : */
		98	/* */
		99	/* o TT_Register_Extension (previously called Extension_Register) */
		100	/* which is to be called by each extension on within */
		101	/* it TT_Init_XXXX_Extension initializer. */
		102	/* */
		103	/* o File and frame access functions. Fortunately, these already */
		104	/* have their names prefixed by "TT_", so no change was needed */
		105	/* except replacing the LOCAL_DEF keyword with EXPORT_DEF */
		106	/* */
		107	/* o Memory access functions, i.e. TT_Alloc and TT_Free. Again, */
		108	/* the change is minimal */
		109	/* */
		110	/* o the table-lookup function : TT_LookUp_Table, formerly known */
		111	/* as Load_TrueType_Table in ttload.c. */
		112	/* */
		113	/* */
		114	/* Other than that, an extension should be able to #include all */
		115	/* relevant header files to get access to internal types, but */
		116	/* should not call engine internal functions.. */
		117	/* */
		118	/* If there is a need for a specific internal function call, let */
		119	/* me known to see if we need to export it by default.. */
		120	/* - DavidT */
		121	/* */
		122
		123	/* Register a new extension. Called by extension */
		124	/* service initializers. */
		125	EXPORT_DEF
		126	TT_Error TT_Register_Extension( PEngine_Instance engine,
		127	Long id,
		128	Long size,
		129	PExt_Constructor create,
		130	PExt_Destructor destroy );
		131
		132
		133	#ifdef TT_CONFIG_OPTION_EXTEND_ENGINE
		134	/* Initialize the extension component */
		135	LOCAL_DEF
		136	TT_Error TTExtend_Init( PEngine_Instance engine );
		137
		138	/* Finalize the extension component */
		139	LOCAL_DEF
		140	TT_Error TTExtend_Done( PEngine_Instance engine );
		141
		142	/* Create an extension within a face object. Called by the */
		143	/* face object constructor. */
		144	LOCAL_DEF
		145	TT_Error Extension_Create( PFace face );
		146
		147	/* Destroy all extensions within a face object. Called by the */
		148	/* face object destructor. */
		149	LOCAL_DEF
		150	TT_Error Extension_Destroy( PFace face );
		151	#endif
		152
		153	/* Query an extension block by extension_ID. Called by extension */
		154	/* service routines. */
		155	EXPORT_DEF
		156	TT_Error TT_Extension_Get( PFace face,
		157	Long extension_id,
		158	void** extension_block );
		159
		160	#ifdef __cplusplus
		161	}
		162	#endif
		163
		164
		165	#endif /* TTEXTEND_H */
		166
		167
		168	/* END */

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