kc3-lang/freetype

diff --git a/ChangeLog b/ChangeLog
index d4ac785..a36547d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,47 @@
+2016-05-17  Nikolaus Waxweiler  <madigens@gmail.com>
+
+	[truetype] New implementation of v38 bytecode interpreter [1/3].
+
+	This patch prepares data structures and the like.
+
+	See added comments in `ttinterp.h' for more information on this and
+	the following commits in the series.
+
+	* devel/ftoption.h, include/freetype/config/ftoption.h
+	(TT_CONFIG_OPTION_SUBPIXEL_HINTING): Assign values to differentiate
+	between subpixel versions.
+	(TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY,
+	TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL): New macros.
+
+	* include/freetype/ftttdrv.h (TT_INTERPRETER_VERSION_40): New macro.
+
+	* include/freetype/internal/tttypes.h (TT_FaceRec): Updated.
+
+	* src/truetype/ttinterp.h (TT_ExecContextRec): Define new fields
+	`subpixel_hinting_lean', `vertical_lcd_lean',
+	`backwards_compatibility', `iupx_called', iupy_called', and
+	`grayscale_cleartype' for new hinting mode.
+
+	* src/truetype/ttdriver.c (tt_property_set): Handle v38 and v40
+	interpreters conditionally.
+
+	* src/truetype/ttgload.c (TT_Hint_Glyph): Save phantom points unless
+	in v38 backwards compatibility mode.
+	Updated.
+	(compute_glyph_metrics): Add v38 backwards compatibility mode
+	constraint for adjusting advance widths.
+	Updated.
+	(tt_loader_init): Handle new flags `subpixel_hinting_lean',
+	`grayscale_cleartype', and `vertical_lcd_lean'.
+	Updated.
+	(tt_get_metrics, TT_Process_Simple_Glyph, TT_LOADER_SET_PP):
+	Updated.
+
+	* src/truetype/ttobjs.c (tt_driver_init): Conditionally set
+	default interpreter version number.
+
+	* src/truetype/ttsubpix.c, src/truetype/ttsubpix.h: Updated.
+
 2016-05-17  Werner Lemberg  <wl@gnu.org>
 
 	[cff] Fix matrix scaling (#47848).
diff --git a/devel/ftoption.h b/devel/ftoption.h
index b354efd..2360ec6 100644
--- a/devel/ftoption.h
+++ b/devel/ftoption.h
@@ -586,23 +586,53 @@ FT_BEGIN_HEADER
   /*************************************************************************/
   /*                                                                       */
   /* Define TT_CONFIG_OPTION_SUBPIXEL_HINTING if you want to compile       */
-  /* EXPERIMENTAL subpixel hinting support into the TrueType driver.  This */
-  /* replaces the native TrueType hinting mechanism when anything but      */
-  /* FT_RENDER_MODE_MONO is requested.                                     */
+  /* subpixel hinting support into the TrueType driver.  This modifies the */
+  /* TrueType hinting mechanism when anything but FT_RENDER_MODE_MONO is   */
+  /* requested.                                                            */
   /*                                                                       */
-  /* Enabling this causes the TrueType driver to ignore instructions under */
-  /* certain conditions.  This is done in accordance with the guide here,  */
-  /* with some minor differences:                                          */
+  /* In particular, it modifies the bytecode interpreter to interpret (or  */
+  /* not) instructions in a certain way so that all TrueType fonts look    */
+  /* like they do in a Windows ClearType (DirectWrite) environment.  See   */
+  /* [1] for a technical overview on what this means.  See `ttinterp.h'    */
+  /* for more details on the LEAN option.                                  */
   /*                                                                       */
-  /*  http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx */
+  /* There are three options.                                              */
   /*                                                                       */
-  /* By undefining this, you only compile the code necessary to hint       */
-  /* TrueType glyphs with native TT hinting.                               */
+  /* 1. This option is associated with the `Infinality' moniker.           */
+  /*    Contributed by an individual nicknamed Infinality with the goal of */
+  /*    making TrueType fonts render better than on Windows.  A high       */
+  /*    amount of configurability and flexibility, down to rules for       */
+  /*    single glyphs in fonts, but also very slow.  Its experimental and  */
+  /*    slow nature and the original developer losing interest meant that  */
+  /*    this option was never enabled in default builds.                   */
   /*                                                                       */
-  /*   This option requires TT_CONFIG_OPTION_BYTECODE_INTERPRETER to be    */
-  /*   defined.                                                            */
+  /* 2. The new default mode for the TrueType driver.  The Infinality code */
+  /*    base was stripped to the bare minimum and all configurability      */
+  /*    removed in the name of speed and simplicity.  The configurability  */
+  /*    was mainly aimed at legacy fonts like Arial, Times New Roman, or   */
+  /*    Courier.  Legacy fonts are fonts that modify vertical stems to     */
+  /*    achieve clean black-and-white bitmaps.  The new mode focuses on    */
+  /*    applying a minimal set of rules to all fonts indiscriminately so   */
+  /*    that modern and web fonts render well while legacy fonts render    */
+  /*    okay.                                                              */
   /*                                                                       */
-#define TT_CONFIG_OPTION_SUBPIXEL_HINTING
+  /* 3. Compile both.                                                      */
+  /*                                                                       */
+  /* By undefining these, you get rendering behavior like on Windows       */
+  /* without ClearType, i.e., Windows XP without ClearType enabled and     */
+  /* Win9x (interpreter version v35).  Or not, depending on how much       */
+  /* hinting blood and testing tears the font designer put into a given    */
+  /* font.  If you define one or both subpixel hinting options, you can    */
+  /* switch between between v35 and the ones you define.                   */
+  /*                                                                       */
+  /* This option requires TT_CONFIG_OPTION_BYTECODE_INTERPRETER to be      */
+  /* defined.                                                              */
+  /*                                                                       */
+  /* [1] http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx */
+  /*                                                                       */
+/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING  1     */
+/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING  2     */
+#define TT_CONFIG_OPTION_SUBPIXEL_HINTING     1 | 2
 
 
   /*************************************************************************/
@@ -811,6 +841,14 @@ FT_BEGIN_HEADER
    */
 #ifdef TT_CONFIG_OPTION_BYTECODE_INTERPRETER
 #define  TT_USE_BYTECODE_INTERPRETER
+
+#if TT_CONFIG_OPTION_SUBPIXEL_HINTING & 1
+#define  TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
+#endif
+
+#if TT_CONFIG_OPTION_SUBPIXEL_HINTING & 2
+#define  TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+#endif
 #endif
 
 
diff --git a/include/freetype/config/ftoption.h b/include/freetype/config/ftoption.h
index a8097fe..1447908 100644
--- a/include/freetype/config/ftoption.h
+++ b/include/freetype/config/ftoption.h
@@ -586,23 +586,53 @@ FT_BEGIN_HEADER
   /*************************************************************************/
   /*                                                                       */
   /* Define TT_CONFIG_OPTION_SUBPIXEL_HINTING if you want to compile       */
-  /* EXPERIMENTAL subpixel hinting support into the TrueType driver.  This */
-  /* replaces the native TrueType hinting mechanism when anything but      */
-  /* FT_RENDER_MODE_MONO is requested.                                     */
+  /* subpixel hinting support into the TrueType driver.  This modifies the */
+  /* TrueType hinting mechanism when anything but FT_RENDER_MODE_MONO is   */
+  /* requested.                                                            */
   /*                                                                       */
-  /* Enabling this causes the TrueType driver to ignore instructions under */
-  /* certain conditions.  This is done in accordance with the guide here,  */
-  /* with some minor differences:                                          */
+  /* In particular, it modifies the bytecode interpreter to interpret (or  */
+  /* not) instructions in a certain way so that all TrueType fonts look    */
+  /* like they do in a Windows ClearType (DirectWrite) environment.  See   */
+  /* [1] for a technical overview on what this means.  See `ttinterp.h'    */
+  /* for more details on the LEAN option.                                  */
   /*                                                                       */
-  /*  http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx */
+  /* There are three options.                                              */
   /*                                                                       */
-  /* By undefining this, you only compile the code necessary to hint       */
-  /* TrueType glyphs with native TT hinting.                               */
+  /* 1. This option is associated with the `Infinality' moniker.           */
+  /*    Contributed by an individual nicknamed Infinality with the goal of */
+  /*    making TrueType fonts render better than on Windows.  A high       */
+  /*    amount of configurability and flexibility, down to rules for       */
+  /*    single glyphs in fonts, but also very slow.  Its experimental and  */
+  /*    slow nature and the original developer losing interest meant that  */
+  /*    this option was never enabled in default builds.                   */
   /*                                                                       */
-  /*   This option requires TT_CONFIG_OPTION_BYTECODE_INTERPRETER to be    */
-  /*   defined.                                                            */
+  /* 2. The new default mode for the TrueType driver.  The Infinality code */
+  /*    base was stripped to the bare minimum and all configurability      */
+  /*    removed in the name of speed and simplicity.  The configurability  */
+  /*    was mainly aimed at legacy fonts like Arial, Times New Roman, or   */
+  /*    Courier.  Legacy fonts are fonts that modify vertical stems to     */
+  /*    achieve clean black-and-white bitmaps.  The new mode focuses on    */
+  /*    applying a minimal set of rules to all fonts indiscriminately so   */
+  /*    that modern and web fonts render well while legacy fonts render    */
+  /*    okay.                                                              */
   /*                                                                       */
-/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+  /* 3. Compile both.                                                      */
+  /*                                                                       */
+  /* By undefining these, you get rendering behavior like on Windows       */
+  /* without ClearType, i.e., Windows XP without ClearType enabled and     */
+  /* Win9x (interpreter version v35).  Or not, depending on how much       */
+  /* hinting blood and testing tears the font designer put into a given    */
+  /* font.  If you define one or both subpixel hinting options, you can    */
+  /* switch between between v35 and the ones you define.                   */
+  /*                                                                       */
+  /* This option requires TT_CONFIG_OPTION_BYTECODE_INTERPRETER to be      */
+  /* defined.                                                              */
+  /*                                                                       */
+  /* [1] http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx */
+  /*                                                                       */
+/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING  1     */
+#define TT_CONFIG_OPTION_SUBPIXEL_HINTING     2
+/* #define TT_CONFIG_OPTION_SUBPIXEL_HINTING  1 | 2 */
 
 
   /*************************************************************************/
@@ -811,6 +841,14 @@ FT_BEGIN_HEADER
    */
 #ifdef TT_CONFIG_OPTION_BYTECODE_INTERPRETER
 #define  TT_USE_BYTECODE_INTERPRETER
+
+#if TT_CONFIG_OPTION_SUBPIXEL_HINTING & 1
+#define  TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
+#endif
+
+#if TT_CONFIG_OPTION_SUBPIXEL_HINTING & 2
+#define  TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+#endif
 #endif
 
 
diff --git a/include/freetype/ftcffdrv.h b/include/freetype/ftcffdrv.h
index b0b4299..ad34541 100644
--- a/include/freetype/ftcffdrv.h
+++ b/include/freetype/ftcffdrv.h
@@ -110,7 +110,7 @@ FT_BEGIN_HEADER
    *   to minimize distortion.
    *
    * @order:
-   *   hinting-engine
+   *   hinting-engine[cff]
    *   no-stem-darkening[cff]
    *   darkening-parameters[cff]
    *
@@ -120,7 +120,7 @@ FT_BEGIN_HEADER
   /**************************************************************************
    *
    * @property:
-   *   hinting-engine
+   *   hinting-engine[cff]
    *
    * @description:
    *   Thanks to Adobe, which contributed a new hinting (and parsing)
@@ -157,8 +157,8 @@ FT_BEGIN_HEADER
    *   FT_CFF_HINTING_XXX
    *
    * @description:
-   *   A list of constants used for the @hinting-engine property to select
-   *   the hinting engine for CFF fonts.
+   *   A list of constants used for the @hinting-engine[cff] property to
+   *   select the hinting engine for CFF fonts.
    *
    * @values:
    *   FT_CFF_HINTING_FREETYPE ::
diff --git a/include/freetype/ftttdrv.h b/include/freetype/ftttdrv.h
index 6c02e65..0d868bc 100644
--- a/include/freetype/ftttdrv.h
+++ b/include/freetype/ftttdrv.h
@@ -138,31 +138,37 @@ FT_BEGIN_HEADER
    *   interpreter-version
    *
    * @description:
-   *   Currently, two versions are available, representing the bytecode
-   *   interpreter with and without subpixel hinting support,
-   *   respectively.  The default is subpixel support if
-   *   TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel
-   *   support otherwise (since it isn't available then).
+
+   *   Currently, three versions are available, two representing the
+   *   bytecode interpreter with subpixel hinting support (old `Infinality'
+   *   code and new stripped-down and higher performance `minimal' code) and
+   *   one without, respectively.  The default is subpixel support if
+   *   TT_CONFIG_OPTION_SUBPIXEL_HINTING is defined, and no subpixel support
+   *   otherwise (since it isn't available then).
    *
    *   If subpixel hinting is on, many TrueType bytecode instructions behave
    *   differently compared to B/W or grayscale rendering (except if `native
-   *   ClearType' is selected by the font).  The main idea is to render at a
-   *   much increased horizontal resolution, then sampling down the created
-   *   output to subpixel precision.  However, many older fonts are not
-   *   suited to this and must be specially taken care of by applying
-   *   (hardcoded) font-specific tweaks.
+   *   ClearType' is selected by the font).  Microsoft's main idea is to
+   *   render at a much increased horizontal resolution, then sampling down
+   *   the created output to subpixel precision.  However, many older fonts
+   *   are not suited to this and must be specially taken care of by
+   *   applying (hardcoded) tweaks in Microsoft's interpreter.
    *
    *   Details on subpixel hinting and some of the necessary tweaks can be
    *   found in Greg Hitchcock's whitepaper at
-   *   `http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'.
+   *   `http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx'. 
+   *   Note that FreeType currently doesn't really `subpixel hint' (6x1, 6x2,
+   *   or 6x5 supersampling) like discussed in the paper.  Depending on the
+   *   chosen interpreter, it simply ignores instructions on vertical stems
+   *   to arrive at very similar results.
    *
-   *   The following example code demonstrates how to activate subpixel
+   *   The following example code demonstrates how to deactivate subpixel
    *   hinting (omitting the error handling).
    *
    *   {
    *     FT_Library  library;
    *     FT_Face     face;
-   *     FT_UInt     interpreter_version = TT_INTERPRETER_VERSION_38;
+   *     FT_UInt     interpreter_version = TT_INTERPRETER_VERSION_35;
    *
    *
    *     FT_Init_FreeType( &library );
@@ -197,9 +203,19 @@ FT_BEGIN_HEADER
    *
    *   TT_INTERPRETER_VERSION_38 ::
    *     Version~38 corresponds to MS rasterizer v.1.9; it is roughly
-   *     equivalent to the hinting provided by DirectWrite ClearType (as
-   *     can be found, for example, in the Internet Explorer~9 running on
-   *     Windows~7).
+   *     equivalent to the hinting provided by DirectWrite ClearType (as can
+   *     be found, for example, in the Internet Explorer~9 running on
+   *     Windows~7).  It is used in FreeType to select the `Infinality'
+   *     subpixel hinting code.  The code may be removed in a future
+   *     version.
+   *
+   *   TT_INTERPRETER_VERSION_40 ::
+   *     Version~40 corresponds to MS rasterizer v.2.1; it is roughly
+   *     equivalent to the hinting provided by DirectWrite ClearType (as can
+   *     be found, for example, in Microsoft's Edge Browser on Windows~10). 
+   *     It is used in FreeType to select the `minimal' subpixel hinting
+   *     code, a stripped-down and higher performance version of the
+   *     `Infinality' code.
    *
    * @note:
    *   This property controls the behaviour of the bytecode interpreter
@@ -207,9 +223,9 @@ FT_BEGIN_HEADER
    *   get rasterized!  In particular, it does not control subpixel color
    *   filtering.
    *
-   *   If FreeType has not been compiled with configuration option
-   *   FT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 causes an
-   *   `FT_Err_Unimplemented_Feature' error.
+   *   If FreeType has not been compiled with the configuration option
+   *   FT_CONFIG_OPTION_SUBPIXEL_HINTING, selecting version~38 or~40 causes
+   *   an `FT_Err_Unimplemented_Feature' error.
    *
    *   Depending on the graphics framework, Microsoft uses different
    *   bytecode and rendering engines.  As a consequence, the version
@@ -290,13 +306,14 @@ FT_BEGIN_HEADER
    *   the version~1 gasp table exclusively (like Color ClearType), while
    *   v1.6 only respects the values of version~0 (bits 0 and~1).
    *
-   *   FreeType doesn't provide all capabilities of the most recent
-   *   ClearType incarnation, thus we identify our subpixel support as
-   *   version~38.
+   *   Keep in mind that the features of the above interpreter versions
+   *   might not map exactly to FreeType features or behavior because it is
+   *   a fundamentally different library with different internals.
    *
    */
 #define TT_INTERPRETER_VERSION_35  35
 #define TT_INTERPRETER_VERSION_38  38
+#define TT_INTERPRETER_VERSION_40  40
 
  /* */
 
diff --git a/include/freetype/internal/tttypes.h b/include/freetype/internal/tttypes.h
index 8f1a642..4110d50 100644
--- a/include/freetype/internal/tttypes.h
+++ b/include/freetype/internal/tttypes.h
@@ -1386,12 +1386,12 @@ FT_BEGIN_HEADER
     FT_ULong              horz_metrics_offset;
     FT_ULong              vert_metrics_offset;
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
     /* since 2.4.12 */
     FT_ULong              sph_found_func_flags; /* special functions found */
                                                 /* for this face           */
     FT_Bool               sph_compatibility_mode;
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
   } TT_FaceRec;
 
diff --git a/src/truetype/ttdriver.c b/src/truetype/ttdriver.c
index abbd127..c9d4081 100644
--- a/src/truetype/ttdriver.c
+++ b/src/truetype/ttdriver.c
@@ -73,9 +73,12 @@
 
 
       if ( *interpreter_version == TT_INTERPRETER_VERSION_35
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
            || *interpreter_version == TT_INTERPRETER_VERSION_38
 #endif
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+           || *interpreter_version == TT_INTERPRETER_VERSION_40
+#endif
          )
         driver->interpreter_version = *interpreter_version;
       else
diff --git a/src/truetype/ttgload.c b/src/truetype/ttgload.c
index 90828ea..b02bd10 100644
--- a/src/truetype/ttgload.c
+++ b/src/truetype/ttgload.c
@@ -122,7 +122,7 @@
                   FT_UInt    glyph_index )
   {
     TT_Face    face   = loader->face;
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
     TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( face );
 #endif
 
@@ -153,7 +153,7 @@
     loader->top_bearing  = top_bearing;
     loader->vadvance     = advance_height;
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
     if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 &&
          loader->exec                                             )
     {
@@ -165,7 +165,7 @@
       /* backwards compatibility mode on and off.                   */
       sph_set_tweaks( loader, glyph_index );
     }
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
     if ( !loader->linear_def )
     {
@@ -733,7 +733,8 @@
   TT_Hint_Glyph( TT_Loader  loader,
                  FT_Bool    is_composite )
   {
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#if defined TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY || \
+    defined TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
     TT_Face    face   = loader->face;
     TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( face );
 #endif
@@ -816,13 +817,23 @@
 
 #endif
 
-    /* save glyph phantom points */
-    loader->pp1 = zone->cur[zone->n_points - 4];
-    loader->pp2 = zone->cur[zone->n_points - 3];
-    loader->pp3 = zone->cur[zone->n_points - 2];
-    loader->pp4 = zone->cur[zone->n_points - 1];
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+    /* Save possibly modified glyph phantom points unless in v40 backwards */
+    /* compatibility mode, where no movement on the x axis means no reason */
+    /* to change bearings or advance widths.                               */
+    if ( !( driver->interpreter_version == TT_INTERPRETER_VERSION_40 &&
+            !loader->exec->backwards_compatibility ) )
+    {
+#endif
+      loader->pp1 = zone->cur[zone->n_points - 4];
+      loader->pp2 = zone->cur[zone->n_points - 3];
+      loader->pp3 = zone->cur[zone->n_points - 2];
+      loader->pp4 = zone->cur[zone->n_points - 1];
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+    }
+#endif
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
     if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 )
     {
       if ( loader->exec->sph_tweak_flags & SPH_TWEAK_DEEMBOLDEN )
@@ -831,7 +842,7 @@
       else if ( loader->exec->sph_tweak_flags & SPH_TWEAK_EMBOLDEN )
         FT_Outline_EmboldenXY( &loader->gloader->current.outline, 24, 0 );
     }
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
     return FT_Err_Ok;
   }
@@ -897,7 +908,7 @@
     }
 
     {
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
       TT_Face    face   = loader->face;
       TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( face );
 
@@ -916,7 +927,7 @@
       FT_Bool  do_scale = FALSE;
 
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
       if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 )
       {
@@ -947,7 +958,7 @@
       }
       else
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
       {
         /* scale the glyph */
@@ -1078,7 +1089,7 @@
                                             : -subglyph->transform.yx;
         int  c = subglyph->transform.xy > 0 ?  subglyph->transform.xy
                                             : -subglyph->transform.xy;
-        int  d = subglyph->transform.yy > 0 ? subglyph->transform.yy
+        int  d = subglyph->transform.yy > 0 ?  subglyph->transform.yy
                                             : -subglyph->transform.yy;
         int  m = a > b ? a : b;
         int  n = c > d ? c : d;
@@ -1324,7 +1335,8 @@
    * (3) for everything else.
    *
    */
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+   /* XXX merge infinality + lean datafields? */
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
 #define TT_LOADER_SET_PP( loader )                                          \
           do                                                                \
@@ -1350,7 +1362,7 @@
             (loader)->pp4.y = (loader)->pp3.y - (loader)->vadvance;         \
           } while ( 0 )
 
-#else /* !TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#else /* !TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
 #define TT_LOADER_SET_PP( loader )                                          \
           do                                                                \
@@ -1366,7 +1378,7 @@
             (loader)->pp4.y = (loader)->pp3.y - (loader)->vadvance;         \
           } while ( 0 )
 
-#endif /* !TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* !TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
 
   /* a utility function to retrieve i-th node from given FT_List */
@@ -1978,7 +1990,8 @@
                          FT_UInt    glyph_index )
   {
     TT_Face    face   = loader->face;
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#if defined TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY || \
+    defined TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
     TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( face );
 #endif
 
@@ -2005,11 +2018,18 @@
     glyph->metrics.horiBearingY = bbox.yMax;
     glyph->metrics.horiAdvance  = loader->pp2.x - loader->pp1.x;
 
-    /* adjust advance width to the value contained in the hdmx table */
-    /* unless FT_LOAD_COMPUTE_METRICS is set                         */
-    if ( !face->postscript.isFixedPitch                    &&
-         IS_HINTED( loader->load_flags )                   &&
-         !( loader->load_flags & FT_LOAD_COMPUTE_METRICS ) )
+    /* Adjust advance width to the value contained in the hdmx table    */
+    /* unless FT_LOAD_COMPUTE_METRICS is set or backwards compatibility */
+    /* mode of the v40 interpreter is active.  See `ttinterp.h' for     */
+    /* details on backwards compatibility mode.                         */
+    if (
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+         !( driver->interpreter_version == TT_INTERPRETER_VERSION_40 &&
+            ( loader->exec && loader->exec->backwards_compatibility  ) ) &&
+#endif
+         !face->postscript.isFixedPitch                                  &&
+         IS_HINTED( loader->load_flags )                                 &&
+         !( loader->load_flags & FT_LOAD_COMPUTE_METRICS )               )
     {
       FT_Byte*  widthp;
 
@@ -2018,7 +2038,7 @@
                                            size->root.metrics.x_ppem,
                                            glyph_index );
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
       if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 )
       {
@@ -2036,7 +2056,7 @@
       }
       else
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
       {
         if ( widthp )
@@ -2225,6 +2245,10 @@
 #ifdef TT_USE_BYTECODE_INTERPRETER
     FT_Bool    pedantic = FT_BOOL( load_flags & FT_LOAD_PEDANTIC );
 #endif
+#if defined TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY || \
+    defined TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+    TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( (TT_Face)glyph->face );
+#endif
 
 
     face   = (TT_Face)glyph->face;
@@ -2238,11 +2262,13 @@
     if ( IS_HINTED( load_flags ) && !glyf_table_only )
     {
       TT_ExecContext  exec;
-      FT_Bool         grayscale;
-
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
-      TT_Driver  driver = (TT_Driver)FT_FACE_DRIVER( face );
+      FT_Bool         grayscale = TRUE;
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+      FT_Bool         subpixel_hinting_lean;
+      FT_Bool         grayscale_cleartype;
+#endif
 
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
       FT_Bool  subpixel_hinting = FALSE;
 
 #if 0
@@ -2254,7 +2280,7 @@
       FT_Bool  subpixel_positioned;
       FT_Bool  gray_cleartype;
 #endif
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
       FT_Bool  reexecute = FALSE;
 
@@ -2275,7 +2301,26 @@
       if ( !exec )
         return FT_THROW( Could_Not_Find_Context );
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+      if ( driver->interpreter_version == TT_INTERPRETER_VERSION_40 )
+      {
+        subpixel_hinting_lean   = TRUE;
+        grayscale_cleartype     = !FT_BOOL( load_flags         &
+                                            FT_LOAD_TARGET_LCD     ||
+                                            load_flags           &
+                                            FT_LOAD_TARGET_LCD_V   );
+        exec->vertical_lcd_lean = FT_BOOL( load_flags           &
+                                           FT_LOAD_TARGET_LCD_V );
+      }
+      else
+      {
+        subpixel_hinting_lean   = FALSE;
+        grayscale_cleartype     = FALSE;
+        exec->vertical_lcd_lean = FALSE;
+      }
+#endif
+
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
       if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 )
       {
@@ -2332,18 +2377,23 @@
       }
       else
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
-      {
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+      if ( driver->interpreter_version == TT_INTERPRETER_VERSION_40 )
+        grayscale = FT_BOOL( !subpixel_hinting_lean               &&
+                             FT_LOAD_TARGET_MODE( load_flags ) !=
+                               FT_RENDER_MODE_MONO                );
+      else
+#endif
         grayscale = FT_BOOL( FT_LOAD_TARGET_MODE( load_flags ) !=
-                             FT_RENDER_MODE_MONO );
-      }
+                               FT_RENDER_MODE_MONO             );
 
       error = TT_Load_Context( exec, face, size );
       if ( error )
         return error;
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
       if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 )
       {
@@ -2371,9 +2421,37 @@
       }
       else
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
       {
+
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+        if ( driver->interpreter_version == TT_INTERPRETER_VERSION_40 )
+        {
+          /* a change from mono to subpixel rendering (and vice versa) */
+          /* requires a re-execution of the CVT program                */
+          if ( subpixel_hinting_lean != exec->subpixel_hinting_lean )
+          {
+            FT_TRACE4(( "tt_loader_init: subpixel hinting change,"
+                        " re-executing `prep' table\n" ));
+
+            exec->subpixel_hinting_lean = subpixel_hinting_lean;
+            reexecute                   = TRUE;
+          }
+
+          /* a change from colored to grayscale subpixel rendering (and */
+          /* vice versa) requires a re-execution of the CVT program     */
+          if ( grayscale_cleartype != exec->grayscale_cleartype )
+          {
+            FT_TRACE4(( "tt_loader_init: grayscale subpixel hinting change,"
+                        " re-executing `prep' table\n" ));
+
+            exec->grayscale_cleartype = grayscale_cleartype;
+            reexecute                 = TRUE;
+          }
+        }
+#endif
+
         /* a change from mono to grayscale rendering (and vice versa) */
         /* requires a re-execution of the CVT program                 */
         if ( grayscale != exec->grayscale )
@@ -2406,10 +2484,11 @@
       if ( exec->GS.instruct_control & 2 )
         exec->GS = tt_default_graphics_state;
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
       /* check whether we have a font hinted for ClearType --           */
       /* note that this flag can also be modified in a glyph's bytecode */
-      if ( exec->GS.instruct_control & 4 )
+      if ( driver->interpreter_version == TT_INTERPRETER_VERSION_38 &&
+           exec->GS.instruct_control & 4                            )
         exec->ignore_x_mode = 0;
 #endif
 
diff --git a/src/truetype/ttinterp.h b/src/truetype/ttinterp.h
index e5a02b9..df7ce51 100644
--- a/src/truetype/ttinterp.h
+++ b/src/truetype/ttinterp.h
@@ -99,7 +99,7 @@ FT_BEGIN_HEADER
   } TT_CallRec, *TT_CallStack;
 
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
   /*************************************************************************/
   /*                                                                       */
@@ -138,7 +138,7 @@ FT_BEGIN_HEADER
 
   } SPH_Font_Class;
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
 
   /*************************************************************************/
@@ -247,9 +247,135 @@ FT_BEGIN_HEADER
     TT_Set_CVT_Func    func_write_cvt; /* write a cvt entry (in pixels) */
     TT_Set_CVT_Func    func_move_cvt;  /* incr a cvt entry (in pixels)  */
 
-    FT_Bool            grayscale;      /* are we hinting for grayscale? */
-
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+    FT_Bool            grayscale;      /* bi-level hinting and */
+                                       /* grayscale rendering  */
+
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+    /*
+     * Modern TrueType fonts are usually rendered through Microsoft's
+     * collection of rendering techniques called ClearType (e.g., subpixel
+     * rendering and subpixel hinting).  When ClearType was introduced, most
+     * fonts were not ready.  Microsoft decided to implement a backwards
+     * compatibility mode that employed several simple to complicated
+     * assumptions and tricks that modified the interpretation of the
+     * bytecode contained in these fonts to make them look ClearType-y
+     * somehow.  Most (web)fonts that were released since then have come to
+     * rely on these hacks to render correctly, even some of Microsoft's
+     * flagship ClearType fonts (Calibri, Cambria, Segoe UI).
+     *
+     * The minimal subpixel hinting code (interpreter version 40) employs a
+     * small list of font-agnostic hacks to bludgeon non-native-ClearType
+     * fonts (except tricky ones[1]) into submission.  It will not try to
+     * toggle hacks for specific fonts for performance and complexity
+     * reasons.  The focus is on modern (web)fonts rather than legacy fonts
+     * that were made for black-and-white rendering.
+     *
+     * Major hacks
+     *
+     * - Any point movement on the x axis is ignored (cf. `Direct_Move' and
+     *   `Direct_Move_X').  This has the smallest code footprint and single
+     *   biggest effect.  The ClearType way to increase resolution is
+     *   supersampling the x axis, the FreeType way is ignoring instructions
+     *   on the x axis, which gives the same result in the majority of
+     *   cases.
+     *
+     * - Points are not moved post-IUP (neither on the x nor on the y axis),
+     *   except the x component of diagonal moves post-IUP (cf.
+     *   `Direct_Move', `Direct_Move_Y', `Move_Zp2_Point').  Post-IUP
+     *   changes are commonly used to `fix' pixel patterns which has little
+     *   use outside monochrome rendering.
+     *
+     * - SHPIX and DELTAP don't execute unless moving a composite on the
+     *   y axis or moving a previously y touched point.  SHPIX additionally
+     *   denies movement on the x axis (cf. `Ins_SHPIX' and `Ins_DELTAP').
+     *   Both instructions are commonly used to `fix' pixel patterns for
+     *   monochrome or Windows's GDI rendering but make little sense for
+     *   FreeType rendering.  Both can distort the outline.  See [2] for
+     *   details.
+     *
+     * - The hdmx table and modifications to phantom points are ignored.
+     *   Bearings and advance widths remain unchanged (except rounding them
+     *   outside the interpreter!), cf. `compute_glyph_metrics' and
+     *   `TT_Hint_Glyph'.  Letting non-native-ClearType fonts modify spacing
+     *   might mess up spacing.
+     *
+     * Minor hacks
+     *
+     * - FLIPRGON, FLIPRGOFF, and FLIPPT don't execute post-IUP.  This
+     *   prevents dents in e.g. Arial-Regular's `D' and `G' glyphs at
+     *   various sizes.
+     *
+     * (Post-IUP is the state after both IUP[x] and IUP[y] have been
+     * executed.)
+     *
+     * The best results are achieved for fonts that were from the outset
+     * designed with ClearType in mind, meaning they leave the x axis mostly
+     * alone and don't mess with the `final' outline to produce more
+     * pleasing pixel patterns.  The harder the designer tried to produce
+     * very specific patterns (`superhinting') for pre-ClearType-displays,
+     * the worse the results.
+     *
+     * Microsoft defines a way to turn off backwards compatibility and
+     * interpret instructions as before (called `native ClearType')[2][3].
+     * The font designer then regains full control and is responsible for
+     * making the font work correctly with ClearType without any
+     * hand-holding by the interpreter or rasterizer[4].  The v40
+     * interpreter assumes backwards compatibility by default, which can be
+     * turned off the same way by executing the following in the control
+     * program (cf. `Ins_INSTCTRL').
+     *
+     *   #PUSH 4,3
+     *   INSTCTRL[]
+     *
+     * [1] Tricky fonts as FreeType defines them rely on the bytecode
+     *     interpreter to display correctly.  Hacks can interfere with them,
+     *     so they get treated like native ClearType fonts (v40 with
+     *     backwards compatibility turned off).  Cf. `TT_RunIns'.
+     *
+     * [2] Proposed by Microsoft's Greg Hitchcock in
+     *     https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx
+     *
+     * [3] Beat Stamm describes it in more detail:
+     *     http://www.beatstamm.com/typography/RTRCh4.htm#Sec12
+     *
+     * [4] The list of `native ClearType' fonts is small at the time of this
+     *     writing; I found the following on a Windows 10 Update 1511
+     *     installation: Constantia, Corbel, Sitka, Malgun Gothic, Microsoft
+     *     JhengHei (Bold and UI Bold), Microsoft YaHei (Bold and UI Bold),
+     *     SimSun, NSimSun, and Yu Gothic.
+     *
+     */
+
+    /* Using v40 implies subpixel hinting.  Used to detect interpreter */
+    /* version switches.  `_lean' to differentiate from the Infinality */
+    /* `subpixel_hinting', which is managed differently.               */
+    FT_Bool            subpixel_hinting_lean;
+
+    /* Long side of a LCD subpixel is vertical (e.g., screen is rotated). */
+    /* `_lean' to differentiate from the Infinality `vertical_lcd', which */
+    /* is managed differently.                                            */
+    FT_Bool            vertical_lcd_lean;
+
+    /* Default to backwards compatibility mode in v40 interpreter.  If  */
+    /* this is false, it implies the interpreter is in v35 or in native */
+    /* ClearType mode.                                                  */
+    FT_Bool            backwards_compatibility;
+
+    /* Useful for detecting and denying post-IUP trickery that is usually */
+    /* used to fix pixel patterns (`superhinting').                       */
+    FT_Bool            iupx_called;
+    FT_Bool            iupy_called;
+
+    /* ClearType hinting and grayscale rendering, as used by Universal */
+    /* Windows Platform apps (Windows 8 and above).  Like the standard */
+    /* colorful ClearType mode, it utilizes a vastly increased virtual */
+    /* resolution on the x axis.  Different from bi-level hinting and  */
+    /* grayscale rendering, the old mode from Win9x days that roughly  */
+    /* adheres to the physical pixel grid on both axes.                */
+    FT_Bool            grayscale_cleartype;
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL */
+
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
     TT_Round_Func      func_round_sphn;   /* subpixel rounding function */
 
     FT_Bool            subpixel_hinting;  /* Using subpixel hinting?       */
@@ -279,7 +405,7 @@ FT_BEGIN_HEADER
     FT_ULong           sph_in_func_flags;     /* flags to indicate if in   */
                                               /* special functions         */
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
   } TT_ExecContextRec;
 
diff --git a/src/truetype/ttobjs.c b/src/truetype/ttobjs.c
index a05f216..ed3be2d 100644
--- a/src/truetype/ttobjs.c
+++ b/src/truetype/ttobjs.c
@@ -1287,10 +1287,12 @@
 
     TT_Driver  driver = (TT_Driver)ttdriver;
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
-    driver->interpreter_version = TT_INTERPRETER_VERSION_38;
-#else
     driver->interpreter_version = TT_INTERPRETER_VERSION_35;
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
+    driver->interpreter_version = TT_INTERPRETER_VERSION_38;
+#endif
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
+    driver->interpreter_version = TT_INTERPRETER_VERSION_40;
 #endif
 
 #else /* !TT_USE_BYTECODE_INTERPRETER */
diff --git a/src/truetype/ttsubpix.c b/src/truetype/ttsubpix.c
index 5a8f262..0395096 100644
--- a/src/truetype/ttsubpix.c
+++ b/src/truetype/ttsubpix.c
@@ -27,7 +27,7 @@
 #include "ttsubpix.h"
 
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
   /*************************************************************************/
   /*                                                                       */
@@ -1000,12 +1000,12 @@
     }
   }
 
-#else /* !TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#else /* !TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
   /* ANSI C doesn't like empty source files */
   typedef int  _tt_subpix_dummy;
 
-#endif /* !TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* !TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
 
 /* END */
diff --git a/src/truetype/ttsubpix.h b/src/truetype/ttsubpix.h
index 6313baa..86844da 100644
--- a/src/truetype/ttsubpix.h
+++ b/src/truetype/ttsubpix.h
@@ -27,7 +27,7 @@
 FT_BEGIN_HEADER
 
 
-#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
+#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
 
   /*************************************************************************/
   /*                                                                       */
@@ -100,7 +100,7 @@ FT_BEGIN_HEADER
 #define SPH_OPTION_SET_COMPATIBLE_WIDTHS   FALSE
 #define SPH_OPTION_SET_RASTERIZER_VERSION  38
 
-#endif /* TT_CONFIG_OPTION_SUBPIXEL_HINTING */
+#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
 
 
 FT_END_HEADER