/**************************************************************************** * * autohint.h * * High-level 'autohint' module-specific interface (specification). * * Copyright (C) 1996-2023 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-hinter is used to load and automatically hint glyphs if a * format-specific hinter isn't available. * */ #ifndef AUTOHINT_H_ #define AUTOHINT_H_ /************************************************************************** * * A small technical note regarding automatic hinting in order to clarify * this module interface. * * An automatic hinter might compute two kinds of data for a given face: * * - global hints: Usually some metrics that describe global properties * of the face. It is computed by scanning more or less * aggressively the glyphs in the face, and thus can be * very slow to compute (even if the size of global hints * is really small). * * - glyph hints: These describe some important features of the glyph * outline, as well as how to align them. They are * generally much faster to compute than global hints. * * The current FreeType auto-hinter does a pretty good job while performing * fast computations for both global and glyph hints. However, we might be * interested in introducing more complex and powerful algorithms in the * future, like the one described in the John D. Hobby paper, which * unfortunately requires a lot more horsepower. * * Because a sufficiently sophisticated font management system would * typically implement an LRU cache of opened face objects to reduce memory * usage, it is a good idea to be able to avoid recomputing global hints * every time the same face is re-opened. * * We thus provide the ability to cache global hints outside of the face * object, in order to speed up font re-opening time. Of course, this * feature is purely optional, so most client programs won't even notice * it. * * I initially thought that it would be a good idea to cache the glyph * hints too. However, my general idea now is that if you really need to * cache these too, you are simply in need of a new font format, where all * this information could be stored within the font file and decoded on the * fly. * */ #include <freetype/freetype.h> FT_BEGIN_HEADER FT_AutoHinter; /************************************************************************** * * @functype: * FT_AutoHinter_GlobalGetFunc * * @description: * Retrieve the global hints computed for a given face object. The * resulting data is dissociated from the face and will survive a call to * FT_Done_Face(). It must be discarded through the API * FT_AutoHinter_GlobalDoneFunc(). * * @input: * hinter :: * A handle to the source auto-hinter. * * face :: * A handle to the source face object. * * @output: * global_hints :: * A typeless pointer to the global hints. * * global_len :: * The size in bytes of the global hints. */ FT_AutoHinter_GlobalGetFunc; /************************************************************************** * * @functype: * FT_AutoHinter_GlobalDoneFunc * * @description: * Discard the global hints retrieved through * FT_AutoHinter_GlobalGetFunc(). This is the only way these hints are * freed from memory. * * @input: * hinter :: * A handle to the auto-hinter module. * * global :: * A pointer to retrieved global hints to discard. */ FT_AutoHinter_GlobalDoneFunc; /************************************************************************** * * @functype: * FT_AutoHinter_GlobalResetFunc * * @description: * This function is used to recompute the global metrics in a given font. * This is useful when global font data changes (e.g. Multiple Masters * fonts where blend coordinates change). * * @input: * hinter :: * A handle to the source auto-hinter. * * face :: * A handle to the face. */ FT_AutoHinter_GlobalResetFunc; /************************************************************************** * * @functype: * FT_AutoHinter_GlyphLoadFunc * * @description: * This function is used to load, scale, and automatically hint a glyph * from a given face. * * @input: * face :: * A handle to the face. * * glyph_index :: * The glyph index. * * load_flags :: * The load flags. * * @note: * This function is capable of loading composite glyphs by hinting each * sub-glyph independently (which improves quality). * * It will call the font driver with @FT_Load_Glyph, with * @FT_LOAD_NO_SCALE set. */ FT_AutoHinter_GlyphLoadFunc; /************************************************************************** * * @struct: * FT_AutoHinter_InterfaceRec * * @description: * The auto-hinter module's interface. */ FT_AutoHinter_Interface; #define FT_DECLARE_AUTOHINTER_INTERFACE( class_ ) … #define FT_DEFINE_AUTOHINTER_INTERFACE( \ class_, \ reset_face_, \ get_global_hints_, \ done_global_hints_, \ load_glyph_ ) … FT_END_HEADER #endif /* AUTOHINT_H_ */ /* END */
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