From 1ff88d285d9ed00c43f1e3aca66d9a965cfd2226 Mon Sep 17 00:00:00 2001 From: David Turner Date: Tue, 30 Jul 2002 18:42:29 +0000 Subject: [PATCH] * include/freetype/ftincrem.h: adding new experimental header file to demonstrate a "cleaner" API to support incremental font loading. comments appreciated... --- ChangeLog | 6 ++ include/freetype/ftincrem.h | 203 ++++++++++++++++++++++++++++++++++++ 2 files changed, 209 insertions(+) create mode 100644 include/freetype/ftincrem.h diff --git a/ChangeLog b/ChangeLog index d9c21725c..c4654f94e 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,9 @@ +2002-07-30 David Turner + + * include/freetype/ftincrem.h: adding new experimental header file + to demonstrate a "cleaner" API to support incremental font loading. + comments appreciated... + 2002-07-28 Werner Lemberg s/ft_memset/FT_MEM_SET/. diff --git a/include/freetype/ftincrem.h b/include/freetype/ftincrem.h new file mode 100644 index 000000000..fdc4dcdcf --- /dev/null +++ b/include/freetype/ftincrem.h @@ -0,0 +1,203 @@ +#ifndef __FT_INCREMENTAL_H__ +#define __FT_INCREMENTAL_H__ + +#include +#include FT_FREETYPE_H + +FT_BEGIN_HEADER + + /************************************************************************* + * + * @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 over-ridden by + * different values. + * + * @note: + * it's 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_ServiceRec 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 model the basic glyph metrics returned + * by the @FT_Incremental_GetGlyphMetricsFunc method + * + * @fields: + * bearing_x :: left-most bearing, in font units. + * bearing_y :: top-most 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' parameter of the method + * @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, when incremental loading is + * enable. + * + * 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* charstrings 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 succesfully, the method + * @FT_Incremental_FreeGlyphDataFunc will be called later to "release" + * the se bytes. + * + * nested @FT_Incremental_GetGlyphDataFunc can happen, in the case of + * compound glyphs !! + */ + typedef FT_Error (*FT_Incremental_GetGlyphDataFunc) + ( FT_Incremental incremental, + FT_UInt glyph_index, + FT_DataRec *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 :: handle to an opaque @FT_Incremental handle provided + * by the client application + * + * data :: glyph_index :: index of relevant glyph + */ + typedef void (*FT_Incremental_FreeGlyphDataFunc) + ( FT_Incremental incremental, + FT_DataRec* 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 than the + * glyph images proper. + * + * @input: + * incremental :: handle to an opaque @FT_Incremental handle provided + * by the client application + * + */ + typedef FT_Error (*FT_Incremental_GetGlyphMetricsFunc) + ( FT_Incremental incremental, + FT_UInt glyph_index, + FT_Bool vertical, + FT_Incremental_MetricsRec *ametrics, + FT_Bool *afound ); + + + /************************************************************************** + * + * @struct: FT_Incremental_ServiceRec + * + * @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_ServiceRec incr_service; + * FT_Parameter parameter; + * FT_Open_Args open_args; + * + * // set up incremental descriptor + * incr_service.incremental = my_object; + * incr_service.get_glyph_metrics = my_get_glyph_metrics; + * incr_service.get_glyph_data = my_get_glyph_data; + * incr_service.free_glyph_data = my_free_glyph_data; + * + * // set up optional parameter + * parameter.tag = FT_PARAM_TAG_INCREMENTAL; + * parameter.data = &incr_service; + * + * // set up FT_Open_Args structure + * open_args.flags = ft_open_flag_pathname; + * open_args.pathname = my_font_pathname; + * open_args.num_params = 1; + * open_args.params = ¶meter; // we use one optional argument + * + * // open the + * error = FT_Open_Face( library, &open_args, index, &face ); + * .... + * } + */ + typedef struct FT_IncrementalParamsRec_ + { + FT_Incremental incremental; + FT_Incremental_GetGlyphMetricsFunc get_glyph_metrics; + FT_Incremental_GetGlyphDataFunc get_glyph_data; + FT_Incremental_FreeGlyphDataFunc free_glyph_data; + + } FT_IncrementalParamsRec, *FT_IncrementalParams; + + + /************************************************************************** + * + * @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 + * + * see the node for @FT_IncrementalParamsRec + */ +#define FT_PARAM_TAG_INCREMENTAL FT_MAKE_TAG('i','n','c','r') + + /* */ + +FT_END_HEADER + +#endif /* __FT_INCREMENTAL_H__ */