ftincrem.h
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- /***************************************************************************/
- /* */
- /* ftincrem.h */
- /* */
- /* FreeType incremental loading (specification). */
- /* */
- /* Copyright 2002, 2003, 2006, 2007 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 __FTINCREM_H__
- #define __FTINCREM_H__
- #include <ft2build.h>
- #include FT_FREETYPE_H
- #ifdef FREETYPE_H
- #error "freetype.h of FreeType 1 has been loaded!"
- #error "Please fix the directory search order for header files"
- #error "so that freetype.h of FreeType 2 is found first."
- #endif
- FT_BEGIN_HEADER
- /***************************************************************************
- *
- * @section:
- * incremental
- *
- * @title:
- * Incremental Loading
- *
- * @abstract:
- * Custom Glyph Loading.
- *
- * @description:
- * This section contains various functions used to perform so-called
- * `incremental' glyph loading. This is a mode where all glyphs loaded
- * from a given @FT_Face are provided by the client application,
- *
- * Apart from that, all other tables are loaded normally from the font
- * file. This mode is useful when FreeType is used within another
- * engine, e.g., a Postscript Imaging Processor.
- *
- * To enable this mode, you must use @FT_Open_Face, passing an
- * @FT_Parameter with the @FT_PARAM_TAG_INCREMENTAL tag and an
- * @FT_Incremental_Interface value. See the comments for
- * @FT_Incremental_InterfaceRec for an example.
- *
- */
- /***************************************************************************
- *
- * @type:
- * FT_Incremental
- *
- * @description:
- * An opaque type describing a user-provided object used to implement
- * `incremental' glyph loading within FreeType. This is used to support
- * embedded fonts in certain environments (e.g., Postscript interpreters),
- * where the glyph data isn't in the font file, or must be overridden by
- * different values.
- *
- * @note:
- * It is up to client applications to create and implement @FT_Incremental
- * objects, as long as they provide implementations for the methods
- * @FT_Incremental_GetGlyphDataFunc, @FT_Incremental_FreeGlyphDataFunc
- * and @FT_Incremental_GetGlyphMetricsFunc.
- *
- * See the description of @FT_Incremental_InterfaceRec to understand how
- * to use incremental objects with FreeType.
- */
- typedef struct FT_IncrementalRec_* FT_Incremental;
- /***************************************************************************
- *
- * @struct:
- * FT_Incremental_Metrics
- *
- * @description:
- * A small structure used to contain the basic glyph metrics returned
- * by the @FT_Incremental_GetGlyphMetricsFunc method.
- *
- * @fields:
- * bearing_x ::
- * Left bearing, in font units.
- *
- * bearing_y ::
- * Top bearing, in font units.
- *
- * advance ::
- * Glyph advance, in font units.
- *
- * @note:
- * These correspond to horizontal or vertical metrics depending on the
- * value of the `vertical' argument to the function
- * @FT_Incremental_GetGlyphMetricsFunc.
- */
- typedef struct FT_Incremental_MetricsRec_
- {
- FT_Long bearing_x;
- FT_Long bearing_y;
- FT_Long advance;
- } FT_Incremental_MetricsRec, *FT_Incremental_Metrics;
- /***************************************************************************
- *
- * @type:
- * FT_Incremental_GetGlyphDataFunc
- *
- * @description:
- * A function called by FreeType to access a given glyph's data bytes
- * during @FT_Load_Glyph or @FT_Load_Char if incremental loading is
- * enabled.
- *
- * Note that the format of the glyph's data bytes depends on the font
- * file format. For TrueType, it must correspond to the raw bytes within
- * the `glyf' table. For Postscript formats, it must correspond to the
- * *unencrypted* charstring bytes, without any `lenIV' header. It is
- * undefined for any other format.
- *
- * @input:
- * incremental ::
- * Handle to an opaque @FT_Incremental handle provided by the client
- * application.
- *
- * glyph_index ::
- * Index of relevant glyph.
- *
- * @output:
- * adata ::
- * A structure describing the returned glyph data bytes (which will be
- * accessed as a read-only byte block).
- *
- * @return:
- * FreeType error code. 0 means success.
- *
- * @note:
- * If this function returns successfully the method
- * @FT_Incremental_FreeGlyphDataFunc will be called later to release
- * the data bytes.
- *
- * Nested calls to @FT_Incremental_GetGlyphDataFunc can happen for
- * compound glyphs.
- */
- typedef FT_Error
- (*FT_Incremental_GetGlyphDataFunc)( FT_Incremental incremental,
- FT_UInt glyph_index,
- FT_Data* adata );
- /***************************************************************************
- *
- * @type:
- * FT_Incremental_FreeGlyphDataFunc
- *
- * @description:
- * A function used to release the glyph data bytes returned by a
- * successful call to @FT_Incremental_GetGlyphDataFunc.
- *
- * @input:
- * incremental ::
- * A handle to an opaque @FT_Incremental handle provided by the client
- * application.
- *
- * data ::
- * A structure describing the glyph data bytes (which will be accessed
- * as a read-only byte block).
- */
- typedef void
- (*FT_Incremental_FreeGlyphDataFunc)( FT_Incremental incremental,
- FT_Data* data );
- /***************************************************************************
- *
- * @type:
- * FT_Incremental_GetGlyphMetricsFunc
- *
- * @description:
- * A function used to retrieve the basic metrics of a given glyph index
- * before accessing its data. This is necessary because, in certain
- * formats like TrueType, the metrics are stored in a different place from
- * the glyph images proper.
- *
- * @input:
- * incremental ::
- * A handle to an opaque @FT_Incremental handle provided by the client
- * application.
- *
- * glyph_index ::
- * Index of relevant glyph.
- *
- * vertical ::
- * If true, return vertical metrics.
- *
- * ametrics ::
- * This parameter is used for both input and output.
- * The original glyph metrics, if any, in font units. If metrics are
- * not available all the values must be set to zero.
- *
- * @output:
- * ametrics ::
- * The replacement glyph metrics in font units.
- *
- */
- typedef FT_Error
- (*FT_Incremental_GetGlyphMetricsFunc)
- ( FT_Incremental incremental,
- FT_UInt glyph_index,
- FT_Bool vertical,
- FT_Incremental_MetricsRec *ametrics );
- /**************************************************************************
- *
- * @struct:
- * FT_Incremental_FuncsRec
- *
- * @description:
- * A table of functions for accessing fonts that load data
- * incrementally. Used in @FT_Incremental_InterfaceRec.
- *
- * @fields:
- * get_glyph_data ::
- * The function to get glyph data. Must not be null.
- *
- * free_glyph_data ::
- * The function to release glyph data. Must not be null.
- *
- * get_glyph_metrics ::
- * The function to get glyph metrics. May be null if the font does
- * not provide overriding glyph metrics.
- */
- typedef struct FT_Incremental_FuncsRec_
- {
- FT_Incremental_GetGlyphDataFunc get_glyph_data;
- FT_Incremental_FreeGlyphDataFunc free_glyph_data;
- FT_Incremental_GetGlyphMetricsFunc get_glyph_metrics;
- } FT_Incremental_FuncsRec;
- /***************************************************************************
- *
- * @struct:
- * FT_Incremental_InterfaceRec
- *
- * @description:
- * A structure to be used with @FT_Open_Face to indicate that the user
- * wants to support incremental glyph loading. You should use it with
- * @FT_PARAM_TAG_INCREMENTAL as in the following example:
- *
- * {
- * FT_Incremental_InterfaceRec inc_int;
- * FT_Parameter parameter;
- * FT_Open_Args open_args;
- *
- *
- * // set up incremental descriptor
- * inc_int.funcs = my_funcs;
- * inc_int.object = my_object;
- *
- * // set up optional parameter
- * parameter.tag = FT_PARAM_TAG_INCREMENTAL;
- * parameter.data = &inc_int;
- *
- * // set up FT_Open_Args structure
- * open_args.flags = FT_OPEN_PATHNAME | FT_OPEN_PARAMS;
- * open_args.pathname = my_font_pathname;
- * open_args.num_params = 1;
- * open_args.params = ¶meter; // we use one optional argument
- *
- * // open the font
- * error = FT_Open_Face( library, &open_args, index, &face );
- * ...
- * }
- */
- typedef struct FT_Incremental_InterfaceRec_
- {
- const FT_Incremental_FuncsRec* funcs;
- FT_Incremental object;
- } FT_Incremental_InterfaceRec;
- /***************************************************************************
- *
- * @type:
- * FT_Incremental_Interface
- *
- * @description:
- * A pointer to an @FT_Incremental_InterfaceRec structure.
- *
- */
- typedef FT_Incremental_InterfaceRec* FT_Incremental_Interface;
- /***************************************************************************
- *
- * @constant:
- * FT_PARAM_TAG_INCREMENTAL
- *
- * @description:
- * A constant used as the tag of @FT_Parameter structures to indicate
- * an incremental loading object to be used by FreeType.
- *
- */
- #define FT_PARAM_TAG_INCREMENTAL FT_MAKE_TAG( 'i', 'n', 'c', 'r' )
- /* */
- FT_END_HEADER
- #endif /* __FTINCREM_H__ */
- /* END */