/**************************************************************************** * * aftypes.h * * Auto-fitter types (specification only). * * Copyright (C) 2003-2023 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. * */ /************************************************************************* * * The auto-fitter is a complete rewrite of the old auto-hinter. * Its main feature is the ability to differentiate between different * writing systems and scripts in order to apply specific rules. * * The code has also been compartmentalized into several entities that * should make algorithmic experimentation easier than with the old * code. * *************************************************************************/ #ifndef AFTYPES_H_ #define AFTYPES_H_ #include <freetype/freetype.h> #include <freetype/ftoutln.h> #include <freetype/internal/ftobjs.h> #include <freetype/internal/ftdebug.h> #include "afblue.h" #ifdef FT_DEBUG_AUTOFIT #include FT_CONFIG_STANDARD_LIBRARY_H #endif FT_BEGIN_HEADER /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** D E B U G G I N G *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ #ifdef FT_DEBUG_AUTOFIT extern int af_debug_disable_horz_hints_; extern int af_debug_disable_vert_hints_; extern int af_debug_disable_blue_hints_; extern void* af_debug_hints_; #endif /* FT_DEBUG_AUTOFIT */ /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** U T I L I T Y S T U F F *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ AF_Width; FT_LOCAL( void ) af_sort_pos( FT_UInt count, FT_Pos* table ); FT_LOCAL( void ) af_sort_and_quantize_widths( FT_UInt* count, AF_Width widths, FT_Pos threshold ); /* * opaque handle to glyph-specific hints -- see `afhints.h' for more * details */ AF_GlyphHints; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** S C A L E R S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ /* * A scaler models the target pixel device that will receive the * auto-hinted glyph image. */ #define AF_SCALER_FLAG_NO_HORIZONTAL … #define AF_SCALER_FLAG_NO_VERTICAL … #define AF_SCALER_FLAG_NO_ADVANCE … AF_Scaler; #define AF_SCALER_EQUAL_SCALES( a, b ) … AF_StyleMetrics; /* * This function parses an FT_Face to compute global metrics for * a specific style. */ AF_WritingSystem_InitMetricsFunc; AF_WritingSystem_ScaleMetricsFunc; AF_WritingSystem_DoneMetricsFunc; AF_WritingSystem_GetStdWidthsFunc; AF_WritingSystem_InitHintsFunc; AF_WritingSystem_ApplyHintsFunc; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** W R I T I N G S Y S T E M S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ /* * For the auto-hinter, a writing system consists of multiple scripts that * can be handled similarly *in a typographical way*; the relationship is * not based on history. For example, both the Greek and the unrelated * Armenian scripts share the same features like ascender, descender, * x-height, etc. Essentially, a writing system is covered by a * submodule of the auto-fitter; it contains * * - a specific global analyzer that computes global metrics specific to * the script (based on script-specific characters to identify ascender * height, x-height, etc.), * * - a specific glyph analyzer that computes segments and edges for each * glyph covered by the script, * * - a specific grid-fitting algorithm that distorts the scaled glyph * outline according to the results of the glyph analyzer. */ #undef WRITING_SYSTEM #define WRITING_SYSTEM( ws, WS ) … /* The list of known writing systems. */ AF_WritingSystem; AF_WritingSystemClassRec; AF_WritingSystemClass; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** S C R I P T S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ /* * Each script is associated with two sets of Unicode ranges to test * whether the font face supports the script, and which non-base * characters the script contains. * * We use four-letter script tags from the OpenType specification, * extended by `NONE', which indicates `no script'. */ #undef SCRIPT #define SCRIPT( s, S, d, h, H, ss ) … /* The list of known scripts. */ AF_Script; AF_Script_UniRangeRec; #define AF_UNIRANGE_REC( a, b ) … AF_Script_UniRange; AF_ScriptClassRec; AF_ScriptClass; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** C O V E R A G E S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ /* * Usually, a font contains more glyphs than can be addressed by its * character map. * * In the PostScript font world, encoding vectors specific to a given * task are used to select such glyphs, and these glyphs can be often * recognized by having a suffix in its glyph names. For example, a * superscript glyph `A' might be called `A.sup'. Unfortunately, this * naming scheme is not standardized and thus unusable for us. * * In the OpenType world, a better solution was invented, namely * `features', which cleanly separate a character's input encoding from * the corresponding glyph's appearance, and which don't use glyph names * at all. For our purposes, and slightly generalized, an OpenType * feature is a name of a mapping that maps character codes to * non-standard glyph indices (features get used for other things also). * For example, the `sups' feature provides superscript glyphs, thus * mapping character codes like `A' or `B' to superscript glyph * representation forms. How this mapping happens is completely * uninteresting to us. * * For the auto-hinter, a `coverage' represents all glyphs of an OpenType * feature collected in a set (as listed below) that can be hinted * together. To continue the above example, superscript glyphs must not * be hinted together with normal glyphs because the blue zones * completely differ. * * Note that FreeType itself doesn't compute coverages; it only provides * the glyphs addressable by the default Unicode character map. Instead, * we use the HarfBuzz library (if available), which has many functions * exactly for this purpose. * * AF_COVERAGE_DEFAULT is special: It should cover everything that isn't * listed separately (including the glyphs addressable by the character * map). In case HarfBuzz isn't available, it exactly covers the glyphs * addressable by the character map. * */ #undef COVERAGE #define COVERAGE( name, NAME, description, \ tag1, tag2, tag3, tag4 ) … AF_Coverage; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** S T Y L E S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ /* * The topmost structure for modelling the auto-hinter glyph input data * is a `style class', grouping everything together. */ #undef STYLE #define STYLE( s, S, d, ws, sc, ss, c ) … /* The list of known styles. */ AF_Style; AF_StyleClassRec; AF_StyleClass; /*************************************************************************/ /*************************************************************************/ /***** *****/ /***** S T Y L E M E T R I C S *****/ /***** *****/ /*************************************************************************/ /*************************************************************************/ AF_FaceGlobals; /* This is the main structure that combines everything. Autofit modules */ /* specific to writing systems derive their structures from it, for */ /* example `AF_LatinMetrics'. */ AF_StyleMetricsRec; #define AF_HINTING_BOTTOM_TO_TOP … #define AF_HINTING_TOP_TO_BOTTOM … /* Declare and define vtables for classes */ #define AF_DECLARE_WRITING_SYSTEM_CLASS( writing_system_class ) … #define AF_DEFINE_WRITING_SYSTEM_CLASS( \ writing_system_class, \ system, \ m_size, \ m_init, \ m_scale, \ m_done, \ m_stdw, \ h_init, \ h_apply ) … #define AF_DECLARE_SCRIPT_CLASS( script_class ) … #define AF_DEFINE_SCRIPT_CLASS( \ script_class, \ script, \ ranges, \ nonbase_ranges, \ top_to_bottom, \ std_charstring ) … #define AF_DECLARE_STYLE_CLASS( style_class ) … #define AF_DEFINE_STYLE_CLASS( \ style_class, \ style, \ writing_system, \ script, \ blue_stringset, \ coverage ) … /* */ FT_END_HEADER #endif /* AFTYPES_H_ */ /* END */
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