Extra bitmap padding for LCD filtering depends on the filter. The
default 5-tap filter needs 2 extra subpixels. The light 3-tap filter
needs only 1 extra subpixel. This space could be already available
due to rounding. In order to optimize the padding, we now expand
CBox for the given filter weights before rounding.
This change breakes current Skia (and Firefox).
* include/freetype/internal/ftobjs.h (FT_LibraryRec)
[FT_CONFIG_OPTION_SUBPIXEL_RENDERING]: Remove `lcd_extra' field.
* src/base/ftlcdfil.c (FT_Library_SetLcdFilterWeights,
FT_Library_SetLcdFilter): Remove `lcd_extra' initializations.
* src/smooth/ftsmooth.c (ft_smooth_render_generic): Implement dymanic
LCD padding.
* src/base/ftlcdfil.c (FT_Library_SetLcdFilterWeights): Enable filter
in addition to setting weights.
(FT_Library_SetLcdFilter): Clean out FT_FORCE_LIGHT_LCD_FILTER and
FT_FORCE_LEGACY_LCD_FILTER.
* include/freetype/ftlcdfil.h: Documentation update.
This does the same as `FT_LCD_FILTER_LEGACY'.
See
https://bugs.freedesktop.org/show_bug.cgi?id=92981
for the reasoning.
* include/freetype/ftlcdfil.h (FT_LcdFilter): New value
`FT_LCD_FILTER_LEGACY1'.
* src/base/ftlcdfil.c (FT_Library_SetLcdFilter): Use it.
This is essentially a mechanical conversion, adding inclusion of
`FT_INTERNAL_DEBUG_H' where necessary, and providing the macros for
stand-alone compiling modes of the rasterizer modules.
To convert the remaining occurrences of FT_Err_XXX and friends it is
necessary to rewrite the code. Note, however, that it doesn't harm
if some cases are not handled since FT_THROW is a no-op.
This is based on code written by Lifter
<http://unixforum.org/index.php?showuser=11691>. It fixes
FreeDesktop bug #27386.
* src/base/ftlcdfil.c (FT_Library_SetLcdFilterWeights): New
function.
* include/freetype/ftlcdfil.h: Updated.
* docs/CHANGES: Updated.
and FT_FORCE_LEGACY_LCD_FILTER at compile time. Define these macros
when building the library to change the default LCD filter to be
used. This is only useful for experimentation
src/base/ftlcdfilt.c, src/smooth/ftsmooth.c: API change for
the LCD filter, the FT_LcdFilter value is a enum describing
which filter to apply, new values FT_LCD_FILTER_LIGHT and
FT_LCD_FILTER_LEGACY (the latter implements the LibXft original
algorithm which produces incredible color fringes for everything
except very-well hinted text)
* src/autofit/aflatin.c: various tiny improvements that drastically
improve the handling of serif fonts and of LCD/LCD_V hinting modes.
Alexei Podtelezhnikov