Commit 706f752b5ec9e65e01c63adde6609857a1cd3544
2014-11-03T07:20:57
* src/truetype/ttinterp.c (Ins_DELTAP): Fix subpixel hinting. Before this patch, it was impossible to ever call DELTAP[123] in subpixel hinting mode as described in the ClearType whitepaper; it only worked if in `compatibility mode'. However, compatibility mode essentially disables SHPIX, completely ruining hinting of ttfautohint output, for example. We now follow the whitepaper more closely so that DELTAP[123] instructions for touched points in the non-subpixel direction are executed.
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diff --git a/ChangeLog b/ChangeLog
index cc7ff45..bdc3fb9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,17 @@
+2014-11-03 Werner Lemberg <wl@gnu.org>
+
+ * src/truetype/ttinterp.c (Ins_DELTAP): Fix subpixel hinting.
+
+ Before this patch, it was impossible to ever call DELTAP[123] in
+ subpixel hinting mode as described in the ClearType whitepaper; it
+ only worked if in `compatibility mode'. However, compatibility mode
+ essentially disables SHPIX, completely ruining hinting of
+ ttfautohint output, for example.
+
+ We now follow the whitepaper more closely so that DELTAP[123]
+ instructions for touched points in the non-subpixel direction are
+ executed.
+
2014-10-31 Alexei Podtelezhnikov <apodtele@gmail.com>
[smooth] Improve code readability.
diff --git a/src/truetype/ttinterp.c b/src/truetype/ttinterp.c
index 43d88fd..75c67ef 100644
--- a/src/truetype/ttinterp.c
+++ b/src/truetype/ttinterp.c
@@ -7581,42 +7581,33 @@
/*
* Allow delta move if
*
- * - not using ignore_x_mode rendering
- * - glyph is specifically set to allow it
- * - glyph is composite and freedom vector is not subpixel
- * vector
+ * - not using ignore_x_mode rendering,
+ * - glyph is specifically set to allow it, or
+ * - glyph is composite and freedom vector is not in subpixel
+ * direction.
*/
if ( !CUR.ignore_x_mode ||
( CUR.sph_tweak_flags & SPH_TWEAK_ALWAYS_DO_DELTAP ) ||
( CUR.is_composite && CUR.GS.freeVector.y != 0 ) )
CUR_Func_move( &CUR.zp0, A, B );
- /* Otherwise apply subpixel hinting and */
- /* compatibility mode rules */
- else if ( CUR.ignore_x_mode )
+ /* Otherwise, apply subpixel hinting and compatibility mode */
+ /* rules, always skipping deltas in subpixel direction. */
+ else if ( CUR.ignore_x_mode && CUR.GS.freeVector.y != 0 )
{
- if ( CUR.GS.freeVector.y != 0 )
- B1 = (FT_UShort)CUR.zp0.cur[A].y;
- else
- B1 = (FT_UShort)CUR.zp0.cur[A].x;
+ /* save the y value of the point now; compare after move */
+ B1 = (FT_UShort)CUR.zp0.cur[A].y;
-#if 0
- /* Standard Subpixel Hinting: Allow y move. */
- /* This messes up dejavu and may not be needed... */
- if ( !CUR.face->sph_compatibility_mode &&
- CUR.GS.freeVector.y != 0 )
+ /* Standard subpixel hinting: Allow y move for y-touched */
+ /* points. This messes up DejaVu ... */
+ if ( !CUR.face->sph_compatibility_mode &&
+ ( CUR.zp0.tags[A] & FT_CURVE_TAG_TOUCH_Y ) )
CUR_Func_move( &CUR.zp0, A, B );
- else
-#endif /* 0 */
- /* Compatibility Mode: Allow x or y move if point touched in */
- /* Y direction. */
- if ( CUR.face->sph_compatibility_mode &&
- !( CUR.sph_tweak_flags & SPH_TWEAK_ALWAYS_SKIP_DELTAP ) )
+ /* compatibility mode */
+ else if ( CUR.face->sph_compatibility_mode &&
+ !( CUR.sph_tweak_flags & SPH_TWEAK_ALWAYS_SKIP_DELTAP ) )
{
- /* save the y value of the point now; compare after move */
- B1 = (FT_UShort)CUR.zp0.cur[A].y;
-
if ( CUR.sph_tweak_flags & SPH_TWEAK_ROUND_NONPIXEL_Y_MOVES )
B = FT_PIX_ROUND( B1 + B ) - B1;