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[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.
This commit is contained in:
Nikolaus Waxweiler 2016-05-18 06:57:59 +02:00 committed by Werner Lemberg
parent 119e8e41ef
commit 596157365a
12 changed files with 453 additions and 106 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

44
ChangeLog
View File

@ -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).

62
devel/ftoption.h
View File

@ -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

62
include/freetype/config/ftoption.h
View File

@ -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

8
include/freetype/ftcffdrv.h
View File

@ -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 ::

61
include/freetype/ftttdrv.h
View File

@ -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
/* */

4
include/freetype/internal/tttypes.h
View File

@ -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;

5
src/truetype/ttdriver.c
View File

@ -73,8 +73,11 @@
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;

159
src/truetype/ttgload.c
View File

@ -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

136
src/truetype/ttinterp.h
View File

@ -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? */
FT_Bool grayscale; /* bi-level hinting and */
/* grayscale rendering */
#ifdef TT_CONFIG_OPTION_SUBPIXEL_HINTING
#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;

8
src/truetype/ttobjs.c
View File

@ -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 */

6
src/truetype/ttsubpix.c
View File

@ -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 */

4
src/truetype/ttsubpix.h
View File

@ -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