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Diffstat (limited to 'modules/freetype2/include/freetype/internal/autohint.h')
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1 files changed, 234 insertions, 0 deletions
diff --git a/modules/freetype2/include/freetype/internal/autohint.h b/modules/freetype2/include/freetype/internal/autohint.h new file mode 100644 index 0000000000..bf9c8b7cf2 --- /dev/null +++ b/modules/freetype2/include/freetype/internal/autohint.h @@ -0,0 +1,234 @@ +/**************************************************************************** + * + * 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 + + + typedef struct FT_AutoHinterRec_ *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. + */ + typedef void + (*FT_AutoHinter_GlobalGetFunc)( FT_AutoHinter hinter, + FT_Face face, + void** global_hints, + long* global_len ); + + + /************************************************************************** + * + * @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. + */ + typedef void + (*FT_AutoHinter_GlobalDoneFunc)( FT_AutoHinter hinter, + void* global ); + + + /************************************************************************** + * + * @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. + */ + typedef void + (*FT_AutoHinter_GlobalResetFunc)( FT_AutoHinter hinter, + FT_Face face ); + + + /************************************************************************** + * + * @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. + */ + typedef FT_Error + (*FT_AutoHinter_GlyphLoadFunc)( FT_AutoHinter hinter, + FT_GlyphSlot slot, + FT_Size size, + FT_UInt glyph_index, + FT_Int32 load_flags ); + + + /************************************************************************** + * + * @struct: + * FT_AutoHinter_InterfaceRec + * + * @description: + * The auto-hinter module's interface. + */ + typedef struct FT_AutoHinter_InterfaceRec_ + { + FT_AutoHinter_GlobalResetFunc reset_face; + FT_AutoHinter_GlobalGetFunc get_global_hints; + FT_AutoHinter_GlobalDoneFunc done_global_hints; + FT_AutoHinter_GlyphLoadFunc load_glyph; + + } FT_AutoHinter_InterfaceRec, *FT_AutoHinter_Interface; + + +#define FT_DECLARE_AUTOHINTER_INTERFACE( class_ ) \ + FT_CALLBACK_TABLE const FT_AutoHinter_InterfaceRec class_; + +#define FT_DEFINE_AUTOHINTER_INTERFACE( \ + class_, \ + reset_face_, \ + get_global_hints_, \ + done_global_hints_, \ + load_glyph_ ) \ + FT_CALLBACK_TABLE_DEF \ + const FT_AutoHinter_InterfaceRec class_ = \ + { \ + reset_face_, \ + get_global_hints_, \ + done_global_hints_, \ + load_glyph_ \ + }; + + +FT_END_HEADER + +#endif /* AUTOHINT_H_ */ + + +/* END */ |