kc3-lang/freetype/devel

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  • Hash : 79e36bae
    Author : Infinality
    Date : 2012-06-18T10:36:06

    [truetype] Support subpixel hinting. This is the large, famous `Infinality' patch to support ClearType bytecode which has been available from http://www.infinality.net/blog/ for some time, and which has been refined over the last years. While still experimental, it is now mature enough to be included directly into FreeType. Most of the code is based on the ClearType whitepaper written by Greg Hitchcock http://www.microsoft.com/typography/cleartype/truetypecleartype.aspx which gives a detailed overview of the necessary changes to the Microsoft rasterizer so that older fonts are supported. However, a lot of details are still missing, and this patches provides a framework to easily handle rendering issues down to the glyph level of certain fonts. Note that ClearType support is not completely implemented! In particular, full support for the options `compatible_widths', `symmetrical_smoothing, and `bgr' (via the GETINFO bytecode instruction) is missing. * src/truetype/ttsubpix.c: New file, providing code to handle `tweaks', this is, rules for certain glyphs in certain fonts (including wildcards) which need a special treatment. * src/truetype/ttsubpix.h: New file, holding the tweaking rules. * include/freetype/config/ftoption.h, src/devel/ftoption.h (TT_CONFIG_OPTION_SUBPIXEL_HINTING): New macro. * include/freetype/internal/ftobjs.h (FT_PIX_FLOOR_GRID, FT_PIX_ROUND_GRID, FT_PIX_CEIL_GRID): New macros. * src/truetype/truetype.c [TT_USE_BYTECODE_INTERPRETER]: Include `ttsubpix.c'. * src/truetype/ttgload.c: Include `ttsubpix.h'. [All changes below are guarded by TT_CONFIG_OPTION_SUBPIXEL_HINTING.] (tt_get_metrics): Set tweak flags. (TT_Hint_Glyph): Call `FT_Outline_EmboldenXY' if necessary. (TT_Process_Simple_Glyph): Compensate emboldening if necessary. (compute_glyph_metrics): Handle `compatible widths' option. (tt_loader_init): Handle ClearType GETINFO information bits. * src/truetype/rules.mk (TT_DRC_SRC): Updated. * src/truetype/ttinterp.c: Include `ttsubpix.h'. [Where necessary, changes below are guarded by TT_CONFIG_OPTION_SUBPIXEL_HINTING.] (Direct_Move, Direct_Move_X): Extended. (Round_None, Round_To_Grid, Round_To_Half_Grid, Round_Down_To_Grid, Round_Up_To_Grid, Round_To_Double_Grid, Round_Super, Round_Super_45, SetSuperRound): Add parameter to handle the number of grid lines per pixel. (SET_SuperRound, ROUND_None, CUR_Func_round): Updated. (DO_SROUND, DOS45ROUND, DO_ODD, DO_EVEN): Updated. (DO_ROUND, DO_NROUND): Updated. (DO_RS): Take care of `Typeman' bytecode patterns. (Ins_FDEF): Add some debugging code. Commented out. (Ins_ENDF): Restore state. (Ins_CALL, Ins_LOOPCALL): Handle inline delta functions. (Ins_MD): Handle `Vacuform' rounds. (Move_Zp2_Point, Ins_SHPIX, Ins_MSIRP, Ins_MDAP, Ins_MIAP, Ins_MDRP, Ins_MIRP): Handle tweaks. (Ins_ALIGNRP): Add tweak guard. (Ins_IUP, Ins_DELTAP): Handle tweaks. (Ins_GETINFO): Handle new ClearType bits. (TT_RunIns): Handle tweaks. * src/truetype/ttinterp.h: Updated. (SPH_TweakRule, SPH_ScaleRule): New structures for tweaks. (TT_ExecContextRec): Add members for subpixel hinting support. * src/truetype/ttobjs.h (TT_DefRecord): Add `inline_delta' member.

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