145 lines
4.1 KiB
C
145 lines
4.1 KiB
C
/****************************************************************************
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*
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* ftgasp.h
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*
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* Access of TrueType's `gasp` table (specification).
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*
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* Copyright 2007-2018 by
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* David Turner, Robert Wilhelm, and Werner Lemberg.
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*
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* This file is part of the FreeType project, and may only be used,
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* modified, and distributed under the terms of the FreeType project
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* license, LICENSE.TXT. By continuing to use, modify, or distribute
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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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#ifndef FTGASP_H_
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#define FTGASP_H_
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#include <ft2build.h>
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#include FT_FREETYPE_H
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#ifdef FREETYPE_H
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#error "freetype.h of FreeType 1 has been loaded!"
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#error "Please fix the directory search order for header files"
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#error "so that freetype.h of FreeType 2 is found first."
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#endif
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FT_BEGIN_HEADER
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/**************************************************************************
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*
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* @section:
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* gasp_table
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*
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* @title:
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* Gasp Table
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*
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* @abstract:
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* Retrieving TrueType `gasp` table entries.
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*
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* @description:
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* The function @FT_Get_Gasp can be used to query a TrueType or OpenType
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* font for specific entries in its `gasp` table, if any. This is mainly
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* useful when implementing native TrueType hinting with the bytecode
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* interpreter to duplicate the Windows text rendering results.
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*/
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/**************************************************************************
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*
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* @enum:
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* FT_GASP_XXX
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*
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* @description:
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* A list of values and/or bit-flags returned by the @FT_Get_Gasp
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* function.
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*
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* @values:
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* FT_GASP_NO_TABLE ::
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* This special value means that there is no GASP table in this face.
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* It is up to the client to decide what to do.
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*
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* FT_GASP_DO_GRIDFIT ::
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* Grid-fitting and hinting should be performed at the specified ppem.
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* This **really** means TrueType bytecode interpretation. If this bit
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* is not set, no hinting gets applied.
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*
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* FT_GASP_DO_GRAY ::
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* Anti-aliased rendering should be performed at the specified ppem.
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* If not set, do monochrome rendering.
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*
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* FT_GASP_SYMMETRIC_SMOOTHING ::
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* If set, smoothing along multiple axes must be used with ClearType.
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*
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* FT_GASP_SYMMETRIC_GRIDFIT ::
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* Grid-fitting must be used with ClearType's symmetric smoothing.
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*
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* @note:
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* The bit-flags `FT_GASP_DO_GRIDFIT` and `FT_GASP_DO_GRAY` are to be
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* used for standard font rasterization only. Independently of that,
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* `FT_GASP_SYMMETRIC_SMOOTHING` and `FT_GASP_SYMMETRIC_GRIDFIT` are to
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* be used if ClearType is enabled (and `FT_GASP_DO_GRIDFIT` and
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* `FT_GASP_DO_GRAY` are consequently ignored).
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*
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* 'ClearType' is Microsoft's implementation of LCD rendering, partly
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* protected by patents.
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*
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* @since:
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* 2.3.0
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*/
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#define FT_GASP_NO_TABLE -1
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#define FT_GASP_DO_GRIDFIT 0x01
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#define FT_GASP_DO_GRAY 0x02
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#define FT_GASP_SYMMETRIC_GRIDFIT 0x04
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#define FT_GASP_SYMMETRIC_SMOOTHING 0x08
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/**************************************************************************
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*
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* @function:
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* FT_Get_Gasp
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*
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* @description:
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* For a TrueType or OpenType font file, return the rasterizer behaviour
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* flags from the font's `gasp` table corresponding to a given character
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* pixel size.
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*
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* @input:
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* face ::
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* The source face handle.
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*
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* ppem ::
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* The vertical character pixel size.
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*
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* @return:
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* Bit flags (see @FT_GASP_XXX), or @FT_GASP_NO_TABLE if there is no
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* `gasp` table in the face.
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*
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* @note:
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* If you want to use the MM functionality of OpenType variation fonts
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* (i.e., using @FT_Set_Var_Design_Coordinates and friends), call this
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* function **after** setting an instance since the return values can
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* change.
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*
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* @since:
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* 2.3.0
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*/
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FT_EXPORT( FT_Int )
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FT_Get_Gasp( FT_Face face,
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FT_UInt ppem );
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/* */
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FT_END_HEADER
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#endif /* FTGASP_H_ */
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/* END */
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