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Diffstat (limited to 'modules/freetype2/include/freetype/ftincrem.h')
| -rw-r--r-- | modules/freetype2/include/freetype/ftincrem.h | 348 |
1 files changed, 348 insertions, 0 deletions
diff --git a/modules/freetype2/include/freetype/ftincrem.h b/modules/freetype2/include/freetype/ftincrem.h new file mode 100644 index 0000000000..2d4f5def24 --- /dev/null +++ b/modules/freetype2/include/freetype/ftincrem.h @@ -0,0 +1,348 @@ +/**************************************************************************** + * + * ftincrem.h + * + * FreeType incremental loading (specification). + * + * Copyright (C) 2002-2023 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 <freetype/freetype.h> +#include <freetype/ftparams.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_MetricsRec + * + * @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 :: + * Horizontal component of glyph advance, in font units. + * + * advance_v :: + * Vertical component of 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_Long advance_v; /* since 2.3.12 */ + + } FT_Incremental_MetricsRec; + + + /************************************************************************** + * + * @struct: + * FT_Incremental_Metrics + * + * @description: + * A handle to an @FT_Incremental_MetricsRec structure. + * + */ + typedef struct 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 allows for handling font types such + * as PCL~XL Format~1, Class~2 downloaded TrueType fonts, where the glyph + * metrics (`hmtx` and `vmtx` tables) are permitted to be omitted from + * the font, and the relevant metrics included in the header of the glyph + * outline data. Importantly, this is not intended to allow custom glyph + * metrics (for example, Postscript Metrics dictionaries), because that + * conflicts with the requirements of outline hinting. Such custom + * metrics must be handled separately, by the calling application. + * + * @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 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 + * require it. + * + */ + 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; + + + /* */ + + +FT_END_HEADER + +#endif /* FTINCREM_H_ */ + + +/* END */ |