Commit 98d185c79428feb25c57fd187cd4f8d0e464527e
2013-12-07T09:26:55
[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.
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diff --git a/ChangeLog b/ChangeLog
index 4390639..df8f9ce 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -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.
diff --git a/src/truetype/ttgload.c b/src/truetype/ttgload.c
index 2c2bea5..0d74248 100644
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -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 )