We used to split large glyphs into horizontal bands and continue
bisecting them still horizontally if that was not enough. This is
guaranteed to fail when a single scanline cannot fit into the
rendering memory pool. Now we bisect the bands vertically so that
the smallest unit is a column of the band height, which is guranteed
to fit into memory.
* src/smooth/ftgrays.c (gray_convert_glyph): Implement it.
At large sizes almost but not exactly horizontal segments can quickly
drain the rendering pool. This patch at least avoids filling the pool
with trivial cells. Beyond this, we can only increase the pool size.
Reported, analyzed, and tested by Colin Fahey.
* src/smooth/ftgrays.c (gray_set_cell): Do not record trivial cells.
* src/raster/ftrend1.c (ft_raster1_render): Clean up the exit.
* src/smooth/ftsmooth.c (ft_smooth_render_generic): Reduce
translations and clean up the exit.
(ft_smooth_render_lcd, ft_smooth_render_lcd): Remove unused `error'..
This mainly just extracts the code for presetting the bitmap metrics
from the monochrome, grayscale, and LCD renderers into a separate
function.
* src/base/ftobjs.c (ft_glyphslot_preset_bitmap): New function that
calculates prespective bitmap metrics for the given rendering mode.
* include/freetype/internal/ftobjs.h (ft_glyphslot_preset_bitmap):
Declare it.
* src/base/ftlcdfil.c (ft_lcd_padding): New helper function that adds
padding to CBox taking into account pecularities of LCD rendering.
* include/freetype/ftlcdfil.h (ft_lcd_padding): Declare it.
* src/raster/ftrend1.c (ft_raster1_render): Reworked to use
`ft_glyphslot_preset_bitmap'.
* src/smooth/ftsmooth.c (ft_smooth_render_generic): Ditto.
(ft_smooth_render_lcd, ft_smooth_render_lcd): The pixel_mode setting
is moved to `ft_glyphslot_preset_bitmap'.
Thing are simpler with a NULL-function pointer.
* include/freetype/internal/ftobjs.h (FT_Face_InternalRec): New
pointer to the filter function.
(FT_LibraryRec): Remove unused `lcd_filter'.
(FT_Bitmap_LcdFilterFunc, ft_lcd_filter_fir): Move from here...
* include/freetype/ftlcdfil.h (FT_Bitmap_LcdFilterFunc,
ft_lcd_filter_fir): ... to here.
* src/base/ftobjs.c (ft_open_face_internal): NULL-initialize the
per-face filter.
(FT_Face_Properties): Set it.
* src/smooth/ftsmooth.c (ft_smooth_render_generic): Simplify.
* src/base/ftlcdfil.c (ft_lcd_filter_fir, FT_Libary_SetLcdFilter):
Minor.
This is a new technology for LCD-optimized rendering. It capitalizes
on the fact that each color channel grid is shifted by a third of a
pixel. Therefore it is logical to render 3 separate monochrome
bitmaps shifting the outline by 1/3 pixel, and then combine them.
Importantly, the resulting output does not require additional LCD
filtering.
* src/smooth/ftsmooth.c (ft_smooth_render_generic)
[!FT_CONFIG_OPTION_SUBPIXEL_RENDERING]: Implement new LCD-optimized
rendering.
* include/freetype/ftlcdfil.h, include/freetype/freetype.h,
include/freetype/config/ftoption.h, devel/ftoption.h: Updated
documentation.
* src/smooth/ftgrays.c [STANDALONE] (OVERFLOW_ADD_LONG,
OVERFLOW_SUB_LONG, OVERFLOW_MUL_LONG, NEG_LONG): New macros.
[!STANDALONE]: Include FT_INTERNAL_CALC_H.
(gray_render_cubic): Use those macros where appropriate.
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.
This mode uses fractional advance widths and doesn't scale glyphs
horizontally, only applying vertical scaling and hinting.
At the same time, the behaviour of the `light' auto-hinter gets
restored for backwards compatibility: Both vertical and horizontal
scaling is again based on rounded metrics values (this was changed
in a commit from 2017-03-30 as a side effect). To be more precise,
the behaviour is restored for TrueType fonts only; for other font
formats like Type 1, this is a new feature of the `light' hinting
mode.
* include/freetype/freetype.h (FT_LOAD_TARGET_SLIGHT): New macro.
(FT_RENDER_MODE_SLIGHT): New render mode.
* include/freetype/internal/ftobjs.h (FT_Size_InternalRec): Add
`autohint_mode' and `autohint_metrics' fields.
* src/autofit/afcjk.c (af_cjk_hints_init), src/autofit/aflatin.c
(af_latin_hints_init), src/autofit/aflatin2 (af_latin2_hints_init):
Updated.
* src/autofit/afloader.c (af_loader_embolden_glyph_in_slot): Use
`autohint_metrics'.
(af_loader_load_glyph): s/internal/slot_internal/.
Initialize `autohint_metrics' and `autohint_mode' depending on
current auto-hint mode.
Use `autohint_metrics'.
Updated.
* src/base/ftadvanc.c (LOAD_ADVANCE_FAST_CHECK): Updated.
* src/base/ftobjs.c (FT_Load_Glyph): Updated.
(FT_New_Size): Allocate `internal' object.
* src/pshinter/pshalgo.c (ps_hints_apply): Updated.
* src/smooth/ftsmooth.c (ft_smooth_render): Updated.
We don't need some divisions if a line segments stays within a single
row or a single column of pixels.
* src/smooth/ftgrays.c (gray_render_line) [FT_LONG64]: Make divisions
conditional.
The algorithm calls `gray_set_cell' at the start of each new contour
or when the contours cross the cell boundaries. Double-checking for
that is wasteful.
* src/smooth/ftgrays.c (gray_set_cell): Remove check for a new cell.
(gray_convert_glyph): Remove initialization introduced by 44b172e88.
* src/smooth/ftgrays.c (gray_move_to): Call `gray_set_cell' directly
instead of...
(gray_start_cell): ... this function, which is removed.
(gray_convert_glyph): Make initial y-coordinate invalid.
