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@ -2,7 +2,7 @@ |
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/* */ |
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/* autohint.h */ |
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/* */ |
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/* High-level `autohint" module-specific interface (specification) */ |
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/* High-level `autohint' module-specific interface (specification). */ |
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/* */ |
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/* Copyright 1996-2000 by */ |
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */ |
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@ -13,159 +13,172 @@ |
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/* this file you indicate that you have read the license and */ |
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/* understand and accept it fully. */ |
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/* */ |
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/* */ |
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/* The auto-hinter is used to load and automatically hint glyphs */ |
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/* when a format-specific hinter isn't available.. */ |
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/* */ |
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/***************************************************************************/ |
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/*************************************************************************/ |
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/* */ |
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/* The auto-hinter is used to load and automatically hint glyphs if a */ |
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/* format-specific hinter isn't available. */ |
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/* */ |
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/*************************************************************************/ |
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#ifndef AUTOHINT_H |
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#define AUTOHINT_H |
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/***************************************************************************
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* |
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* A small technical note regarding automatic hinting in order to clarify |
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* this module interface. |
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* |
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* An automatic hinter might compute two kinds of data for a given face: |
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* |
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* - global hints: usually some metrics that describe global properties |
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* of the face. It is computed by scanning more or less |
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* agressively the glyphs in the face, and thus can be |
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* very slow to compute (even if the size of global hints |
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* is really small) |
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* |
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* - glyph hints: these describe some important features of the glyph |
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* outline, as well as how to align them. They are generally |
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* much faster to compute than global hints. |
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* |
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* The current FreeType auto-hinter does a pretty good job while performing |
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* fast computations for both global and glyph hints. However, we might be |
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* interested in introducing more complex and powerful algorithms in the |
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* future, like the one described in the John D. Hobby paper, which |
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* unfortunately require a lot more horsepower. |
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* |
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* Because a sufficiently sophisticated font management system would |
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* typically implement a LRU cache of opened face objects to reduce memory |
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* usage, it is a good idea to be able to avoid recomputing global hints |
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* every time the same face is re-opened. |
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* |
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* We thus provide the ability to cache global hints outside of the face |
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* object, in order to speed up font re-opening time. Of course, this |
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* feature is purely optional, so most client programs won't even notice |
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* it :o) |
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* |
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* I initially though that it'd be a good idea to cache the glyph hints too, |
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* however, if my general idea now is that if you really need to cache these |
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* too, you're simply in need of a new font format, where all this information |
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* could be stored within the font file and decoded on the fly :-) |
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* |
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*/ |
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/*************************************************************************/ |
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/* */ |
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/* A small technical note regarding automatic hinting in order to */ |
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/* clarify this module interface. */ |
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/* */ |
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/* An automatic hinter might compute two kinds of data for a given face: */ |
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/* */ |
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/* - global hints: Usually some metrics that describe global properties */ |
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/* of the face. It is computed by scanning more or less */ |
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/* agressively the glyphs in the face, and thus can be */ |
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/* very slow to compute (even if the size of global */ |
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/* hints is really small). */ |
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/* */ |
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/* - glyph hints: These describe some important features of the glyph */ |
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/* outline, as well as how to align them. They are */ |
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/* generally much faster to compute than global hints. */ |
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/* */ |
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/* The current FreeType auto-hinter does a pretty good job while */ |
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/* performing fast computations for both global and glyph hints. */ |
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/* However, we might be interested in introducing more complex and */ |
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/* powerful algorithms in the future, like the one described in the John */ |
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/* D. Hobby paper, which unfortunately requires a lot more horsepower. */ |
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/* */ |
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/* Because a sufficiently sophisticated font management system would */ |
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/* typically implement an LRU cache of opened face objects to reduce */ |
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/* memory usage, it is a good idea to be able to avoid recomputing */ |
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/* global hints every time the same face is re-opened. */ |
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/* */ |
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/* We thus provide the ability to cache global hints outside of the face */ |
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/* object, in order to speed up font re-opening time. Of course, this */ |
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/* feature is purely optional, so most client programs won't even notice */ |
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/* it. */ |
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/* */ |
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/* I initially thought that it would be a good idea to cache the glyph */ |
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/* hints too. However, my general idea now is that if you really need */ |
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/* to cache these too, you are simply in need of a new font format, */ |
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/* where all this information could be stored within the font file and */
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/* decoded on the fly. */ |
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/* */ |
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/*************************************************************************/ |
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#include <freetype/freetype.h> |
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typedef struct FT_AutoHinterRec_ *FT_AutoHinter; |
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/***********************************************************************
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* |
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* <FuncType> |
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* FT_AutoHinter_Get_Global_Func |
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* |
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* <Description> |
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* Retrieve the global hints computed for a given face object |
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* the resulting data is dissociated from the face and will survive |
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* a call to FT_Done_Face. It must be discarded through the API |
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* FT_AutoHinter_Done_Global_Func. |
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* |
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* <Input> |
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* hinter :: handle to source auto-hinter |
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* face :: handle to source face object |
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* |
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* <Output> |
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* global_hints :: typeless pointer to the global hints |
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* global_len :: size in bytes of global hints |
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* |
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*/ |
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typedef void (*FT_AutoHinter_Get_Global_Func)( FT_AutoHinter hinter, |
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FT_Face face, |
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void* *global_hints, |
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long *global_len ); |
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/***********************************************************************
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* |
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* <FuncType> |
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* FT_AutoHinter_Done_Global_Func |
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* |
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* <Description> |
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* Discards the global hints retrieved through |
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* FT_AutoHinter_Get_Global_Func. This is the only way these hints |
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* are freed from memory. |
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* |
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* <Input> |
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* hinter :: handle to auto-hinter module |
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* global :: pointer to retrieved global hints to discard |
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*/ |
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typedef void (*FT_AutoHinter_Done_Global_Func)( FT_AutoHinter hinter, |
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void* global ); |
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/***********************************************************************
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* |
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* <FuncType> |
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* FT_AutoHinter_Reset_Func |
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* |
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* <Description> |
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* This function is used to recompute the global metrics in a given
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* font. This is useful when global font data changes (e.g. multiple |
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* masters fonts where blend coordinates change..) |
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* |
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* <Input> |
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* hinter :: handle to source auto-hinter |
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* face :: handle to the face. |
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* |
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* |
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*/ |
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typedef void (*FT_AutoHinter_Reset_Func)( FT_AutoHinter hinter, |
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FT_Face face ); |
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/***********************************************************************
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* |
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* <FuncType> |
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* FT_AutoHinter_Load_Func |
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* |
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* <Description> |
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* This function is used to load, scale and automatically hint a glyph |
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* from a given face. |
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* |
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* <Input> |
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* face :: handle to the face. |
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* glyph_index :: glyph index |
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* load_flags :: load flags |
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* |
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* <Note> |
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* This function is capable of loading composite glyphs by hinting |
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* each sub-glyph independently (which improves quality). |
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* |
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* It will call the font driver with FT_Load_Glyph, with FT_LOAD_NO_SCALE |
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* set.. |
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* |
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*/ |
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typedef FT_Error (*FT_AutoHinter_Load_Func)( |
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FT_AutoHinter hinter, |
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FT_GlyphSlot slot, |
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FT_Size size, |
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FT_UInt glyph_index, |
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FT_ULong load_flags ); |
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/***********************************************************************
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* |
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* <Struct> |
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* FT_AutoHinter_Interface |
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* |
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* <Description> |
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* The auto-hinter module's interface. |
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* |
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*/ |
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typedef struct FT_AutoHinter_Interface |
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/*************************************************************************/ |
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/* */ |
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/* <FuncType> */ |
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/* FT_AutoHinter_Get_Global_Func */ |
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/* */ |
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/* <Description> */ |
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/* Retrieves the global hints computed for a given face object the */ |
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/* resulting data is dissociated from the face and will survive a */ |
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/* call to FT_Done_Face(). It must be discarded through the API */ |
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/* FT_AutoHinter_Done_Global_Func(). */ |
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/* */ |
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/* <Input> */ |
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/* hinter :: A handle to the source auto-hinter. */ |
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/* */ |
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/* face :: A handle to the source face object. */ |
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/* */ |
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/* <Output> */ |
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/* global_hints :: A typeless pointer to the global hints. */ |
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/* */ |
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/* global_len :: The size in bytes of the global hints. */ |
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/* */ |
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typedef void (*FT_AutoHinter_Get_Global_Func)( |
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FT_AutoHinter hinter, |
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FT_Face face, |
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void** global_hints, |
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long* global_len ); |
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/*************************************************************************/ |
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/* */ |
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/* <FuncType> */ |
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/* FT_AutoHinter_Done_Global_Func */ |
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/* */ |
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/* <Description> */ |
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/* Discards the global hints retrieved through */ |
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/* FT_AutoHinter_Get_Global_Func(). This is the only way these hints */ |
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/* are freed from memory. */ |
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/* */ |
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/* <Input> */ |
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/* hinter :: A handle to the auto-hinter module. */ |
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/* */ |
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/* global :: A pointer to retrieved global hints to discard. */ |
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/* */ |
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typedef void (*FT_AutoHinter_Done_Global_Func)( FT_AutoHinter hinter, |
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void* global ); |
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/*************************************************************************/ |
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/* */ |
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/* <FuncType> */ |
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/* FT_AutoHinter_Reset_Func */ |
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/* */ |
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/* <Description> */ |
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/* This function is used to recompute the global metrics in a given */ |
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/* font. This is useful when global font data changes (e.g. Multiple */ |
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/* Masters fonts where blend coordinates change). */ |
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/* */ |
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/* <Input> */ |
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/* hinter :: A handle to the source auto-hinter. */ |
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/* */ |
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/* face :: A handle to the face. */ |
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/* */ |
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typedef void (*FT_AutoHinter_Reset_Func)( FT_AutoHinter hinter, |
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FT_Face face ); |
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/*************************************************************************/ |
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/* */ |
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/* <FuncType> */ |
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/* FT_AutoHinter_Load_Func */ |
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/* */ |
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/* <Description> */ |
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/* This function is used to load, scale, and automatically hint a */ |
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/* glyph from a given face. */ |
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/* */ |
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/* <Input> */ |
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/* face :: A handle to the face. */ |
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/* glyph_index :: The glyph index. */ |
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/* load_flags :: The load flags. */ |
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/* */ |
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/* <Note> */ |
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/* This function is capable of loading composite glyphs by hinting */ |
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/* each sub-glyph independently (which improves quality). */ |
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/* */ |
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/* It will call the font driver with FT_Load_Glyph(), with */ |
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/* FT_LOAD_NO_SCALE set. */ |
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/* */ |
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typedef FT_Error (*FT_AutoHinter_Load_Func)( FT_AutoHinter hinter, |
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FT_GlyphSlot slot, |
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FT_Size size, |
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FT_UInt glyph_index, |
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FT_ULong load_flags ); |
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/*************************************************************************/ |
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/* */ |
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/* <Struct> */ |
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/* FT_AutoHinter_Interface */ |
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/* */ |
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/* <Description> */ |
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/* The auto-hinter module's interface. */ |
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/* */ |
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typedef struct FT_AutoHinter_Interface |
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{ |
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FT_AutoHinter_Reset_Func reset_face; |
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FT_AutoHinter_Load_Func load_glyph; |
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@ -175,5 +188,8 @@ |
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} FT_AutoHinter_Interface; |
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#endif /* AUTOHINT_H */ |
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/* END */ |
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Werner Lemberg
25 years ago