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[truetype] Next round in phantom point handling.

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Greg Hitchcock provided very interesting insights into the
complicated history of the horizontal positions of the TSB and BSB
phantom points.

* src/truetype/ttgload.c (TT_LOADER_SET_PP)
[TT_CONFIG_OPTION_SUBPIXEL_HINTING]: Use `subpixel_hinting' and
`grayscale_hinting' flags as conditionals for the x position of TSB
and BSB.
This commit is contained in:
Werner Lemberg 2013-12-07 09:26:55 +01:00
parent fcdb784082
commit 98d185c794
2 changed files with 42 additions and 11 deletions
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13
ChangeLog
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@ -1,3 +1,16 @@
2013-12-07 Werner Lemberg <wl@gnu.org>
[truetype] Next round in phantom point handling.
Greg Hitchcock provided very interesting insights into the
complicated history of the horizontal positions of the TSB and BSB
phantom points.
* src/truetype/ttgload.c (TT_LOADER_SET_PP)
[TT_CONFIG_OPTION_SUBPIXEL_HINTING]: Use `subpixel_hinting' and
`grayscale_hinting' flags as conditionals for the x position of TSB
and BSB.
2013-12-05 Werner Lemberg <wl@gnu.org>
* builds/freetype.mk (FT_CC): Removed. Unused.

40
src/truetype/ttgload.c
View File

@ -1329,14 +1329,30 @@
*
* Usually we have
*
* x = aw / 2 ,
* x = aw / 2 , (1)
*
* but there is a compatibility case where it can be set to
* but there is one compatibility case where it can be set to
*
* x = -DefaultDescender -
* ((DefaultAscender - DefaultDescender - aw) / 2) .
* ((DefaultAscender - DefaultDescender - aw) / 2) . (2)
*
* For (old) non-ClearType hinting, `x' is set to zero.
* and another one with
*
* x = 0 . (3)
*
* In Windows, the history of those values is quite complicated,
* depending on the hinting engine (that is, the graphics framework).
*
* framework from to formula
* ----------------------------------------------------------
* GDI Windows 98 current (1)
* (Windows 2000 for NT)
* GDI+ Windows XP Windows 7 (2)
* GDI+ Windows 8 current (3)
* DWrite Windows 7 current (3)
*
* For simplicity, FreeType uses (1) for grayscale subpixel hinting and
* (3) for everything else.
*
*/
#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
@ -1344,20 +1360,22 @@
#define TT_LOADER_SET_PP( loader ) \
do \
{ \
TT_Face face_ = (TT_Face)(loader)->face; \
TT_Driver driver_ = (TT_Driver)FT_FACE_DRIVER( face_ ); \
FT_Bool is_ver_38_ = (FT_Bool) \
( driver_->interpreter_version == \
TT_INTERPRETER_VERSION_38 ); \
FT_Bool subpixel_ = loader->exec \
? loader->exec->subpixel_hinting \
: 0; \
FT_Bool grayscale_ = loader->exec \
? loader->exec->grayscale_hinting \
: 0; \
FT_Bool use_aw_2_ = (FT_Bool)( subpixel_ && grayscale_ ); \
\
\
(loader)->pp1.x = (loader)->bbox.xMin - (loader)->left_bearing; \
(loader)->pp1.y = 0; \
(loader)->pp2.x = (loader)->pp1.x + (loader)->advance; \
(loader)->pp2.y = 0; \
(loader)->pp3.x = is_ver_38_ ? (loader)->advance / 2 : 0; \
(loader)->pp3.x = use_aw_2_ ? (loader)->advance / 2 : 0; \
(loader)->pp3.y = (loader)->bbox.yMax + (loader)->top_bearing; \
(loader)->pp4.x = is_ver_38_ ? (loader)->advance / 2 : 0; \
(loader)->pp4.x = use_aw_2_ ? (loader)->advance / 2 : 0; \
(loader)->pp4.y = (loader)->pp3.y - (loader)->vadvance; \
} while ( 0 )