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Document that some FT_Size_Metrics values are always rounded.

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Werner Lemberg 2017-04-26 09:58:28 +02:00
parent ba86636b14
commit 69da54cacc
1 changed files with 18 additions and 11 deletions
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29
include/freetype/freetype.h
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@ -1506,27 +1506,34 @@ FT_BEGIN_HEADER
/* fractional pixels. Only relevant for scalable */
/* font formats. */
/* */
/* ascender :: The ascender in 26.6 fractional pixels. See */
/* @FT_FaceRec for the details. */
/* ascender :: The ascender in 26.6 fractional pixels, rounded up */
/* to an integer value. See @FT_FaceRec for the */
/* details. */
/* */
/* descender :: The descender in 26.6 fractional pixels. See */
/* @FT_FaceRec for the details. */
/* descender :: The descender in 26.6 fractional pixels, rounded */
/* down to an integer value. See @FT_FaceRec for the */
/* details. */
/* */
/* height :: The height in 26.6 fractional pixels. See */
/* @FT_FaceRec for the details. */
/* height :: The height in 26.6 fractional pixels, rounded to */
/* an integer value. See @FT_FaceRec for the */
/* details. */
/* */
/* max_advance :: The maximum advance width in 26.6 fractional */
/* pixels. See @FT_FaceRec for the details. */
/* pixels, rounded to an integer value. See */
/* @FT_FaceRec for the details. */
/* */
/* <Note> */
/* The scaling values, if relevant, are determined first during a */
/* size changing operation. The remaining fields are then set by the */
/* driver. For scalable formats, they are usually set to scaled */
/* values of the corresponding fields in @FT_FaceRec. */
/* values of the corresponding fields in @FT_FaceRec. Some values */
/* like ascender or descender are rounded for historical reasons; */
/* more precise values (for outline fonts) can be derived by scaling */
/* the corresponding @FT_FaceRec values manually. */
/* */
/* Note that due to glyph hinting, these values might not be exact */
/* for certain fonts. Thus they must be treated as unreliable */
/* with an error margin of at least one pixel! */
/* Note that due to glyph hinting and the selected rendering mode */
/* these values are usually not exact; consequently, they must be */
/* treated as unreliable with an error margin of at least one pixel! */
/* */
/* Indeed, the only way to get the exact metrics is to render _all_ */
/* glyphs. As this would be a definite performance hit, it is up to */