0d94592942
This speeds up FreeType's handling of malformed fonts. * src/truetype/ttinterp.c (TT_RunIns): Set up limits for the number of twilight points, the total number of negative jumps, and the total number of loops in LOOPCALL opcodes. The values are based on the number of points and entries in the CVT table. (Ins_JMPR): Test negative jump counter. (Ins_LOOPCALL): Test loopcall counter. * src/truetype/ttinterp.h (TT_ExecContext): Updated. * docs/CHANGES: Updated.
524 lines
23 KiB
C
524 lines
23 KiB
C
/***************************************************************************/
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/* */
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/* ttinterp.h */
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/* */
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/* TrueType bytecode interpreter (specification). */
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/* */
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/* Copyright 1996-2016 by */
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/* David Turner, Robert Wilhelm, and Werner Lemberg. */
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/* */
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/* This file is part of the FreeType project, and may only be used, */
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/* modified, and distributed under the terms of the FreeType project */
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/* license, LICENSE.TXT. By continuing to use, modify, or distribute */
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/* this file you indicate that you have read the license and */
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/* understand and accept it fully. */
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/* */
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/***************************************************************************/
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#ifndef TTINTERP_H_
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#define TTINTERP_H_
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#include <ft2build.h>
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#include "ttobjs.h"
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FT_BEGIN_HEADER
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/*************************************************************************/
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/* */
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/* Rounding mode constants. */
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/* */
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#define TT_Round_Off 5
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#define TT_Round_To_Half_Grid 0
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#define TT_Round_To_Grid 1
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#define TT_Round_To_Double_Grid 2
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#define TT_Round_Up_To_Grid 4
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#define TT_Round_Down_To_Grid 3
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#define TT_Round_Super 6
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#define TT_Round_Super_45 7
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/*************************************************************************/
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/* */
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/* Function types used by the interpreter, depending on various modes */
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/* (e.g. the rounding mode, whether to render a vertical or horizontal */
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/* line etc). */
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/* */
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/*************************************************************************/
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/* Rounding function */
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typedef FT_F26Dot6
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(*TT_Round_Func)( TT_ExecContext exc,
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FT_F26Dot6 distance,
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FT_F26Dot6 compensation );
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/* Point displacement along the freedom vector routine */
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typedef void
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(*TT_Move_Func)( TT_ExecContext exc,
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TT_GlyphZone zone,
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FT_UShort point,
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FT_F26Dot6 distance );
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/* Distance projection along one of the projection vectors */
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typedef FT_F26Dot6
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(*TT_Project_Func)( TT_ExecContext exc,
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FT_Pos dx,
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FT_Pos dy );
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/* getting current ppem. Take care of non-square pixels if necessary */
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typedef FT_Long
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(*TT_Cur_Ppem_Func)( TT_ExecContext exc );
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/* reading a cvt value. Take care of non-square pixels if necessary */
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typedef FT_F26Dot6
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(*TT_Get_CVT_Func)( TT_ExecContext exc,
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FT_ULong idx );
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/* setting or moving a cvt value. Take care of non-square pixels */
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/* if necessary */
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typedef void
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(*TT_Set_CVT_Func)( TT_ExecContext exc,
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FT_ULong idx,
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FT_F26Dot6 value );
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/*************************************************************************/
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/* */
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/* This structure defines a call record, used to manage function calls. */
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/* */
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typedef struct TT_CallRec_
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{
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FT_Int Caller_Range;
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FT_Long Caller_IP;
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FT_Long Cur_Count;
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TT_DefRecord *Def; /* either FDEF or IDEF */
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} TT_CallRec, *TT_CallStack;
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#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
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/*************************************************************************/
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/* */
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/* These structures define rules used to tweak subpixel hinting for */
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/* various fonts. "", 0, "", NULL value indicates to match any value. */
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/* */
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#define SPH_MAX_NAME_SIZE 32
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#define SPH_MAX_CLASS_MEMBERS 100
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typedef struct SPH_TweakRule_
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{
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const char family[SPH_MAX_NAME_SIZE];
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const FT_UInt ppem;
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const char style[SPH_MAX_NAME_SIZE];
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const FT_ULong glyph;
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} SPH_TweakRule;
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typedef struct SPH_ScaleRule_
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{
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const char family[SPH_MAX_NAME_SIZE];
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const FT_UInt ppem;
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const char style[SPH_MAX_NAME_SIZE];
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const FT_ULong glyph;
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const FT_ULong scale;
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} SPH_ScaleRule;
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typedef struct SPH_Font_Class_
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{
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const char name[SPH_MAX_NAME_SIZE];
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const char member[SPH_MAX_CLASS_MEMBERS][SPH_MAX_NAME_SIZE];
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} SPH_Font_Class;
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#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
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/*************************************************************************/
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/* */
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/* The main structure for the interpreter which collects all necessary */
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/* variables and states. */
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/* */
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typedef struct TT_ExecContextRec_
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{
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TT_Face face;
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TT_Size size;
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FT_Memory memory;
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/* instructions state */
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FT_Error error; /* last execution error */
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FT_Long top; /* top of exec. stack */
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FT_Long stackSize; /* size of exec. stack */
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FT_Long* stack; /* current exec. stack */
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FT_Long args;
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FT_Long new_top; /* new top after exec. */
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TT_GlyphZoneRec zp0, /* zone records */
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zp1,
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zp2,
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pts,
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twilight;
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FT_Long pointSize; /* in 26.6 format */
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FT_Size_Metrics metrics;
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TT_Size_Metrics tt_metrics; /* size metrics */
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TT_GraphicsState GS; /* current graphics state */
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FT_Int curRange; /* current code range number */
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FT_Byte* code; /* current code range */
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FT_Long IP; /* current instruction pointer */
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FT_Long codeSize; /* size of current range */
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FT_Byte opcode; /* current opcode */
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FT_Int length; /* length of current opcode */
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FT_Bool step_ins; /* true if the interpreter must */
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/* increment IP after ins. exec */
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FT_ULong cvtSize;
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FT_Long* cvt;
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FT_UInt glyphSize; /* glyph instructions buffer size */
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FT_Byte* glyphIns; /* glyph instructions buffer */
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FT_UInt numFDefs; /* number of function defs */
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FT_UInt maxFDefs; /* maximum number of function defs */
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TT_DefArray FDefs; /* table of FDefs entries */
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FT_UInt numIDefs; /* number of instruction defs */
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FT_UInt maxIDefs; /* maximum number of ins defs */
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TT_DefArray IDefs; /* table of IDefs entries */
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FT_UInt maxFunc; /* maximum function index */
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FT_UInt maxIns; /* maximum instruction index */
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FT_Int callTop, /* top of call stack during execution */
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callSize; /* size of call stack */
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TT_CallStack callStack; /* call stack */
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FT_UShort maxPoints; /* capacity of this context's `pts' */
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FT_Short maxContours; /* record, expressed in points and */
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/* contours. */
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TT_CodeRangeTable codeRangeTable; /* table of valid code ranges */
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/* useful for the debugger */
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FT_UShort storeSize; /* size of current storage */
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FT_Long* storage; /* storage area */
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FT_F26Dot6 period; /* values used for the */
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FT_F26Dot6 phase; /* `SuperRounding' */
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FT_F26Dot6 threshold;
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FT_Bool instruction_trap; /* If `True', the interpreter will */
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/* exit after each instruction */
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TT_GraphicsState default_GS; /* graphics state resulting from */
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/* the prep program */
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FT_Bool is_composite; /* true if the glyph is composite */
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FT_Bool pedantic_hinting; /* true if pedantic interpretation */
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/* latest interpreter additions */
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FT_Long F_dot_P; /* dot product of freedom and projection */
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/* vectors */
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TT_Round_Func func_round; /* current rounding function */
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TT_Project_Func func_project, /* current projection function */
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func_dualproj, /* current dual proj. function */
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func_freeProj; /* current freedom proj. func */
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TT_Move_Func func_move; /* current point move function */
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TT_Move_Func func_move_orig; /* move original position function */
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TT_Cur_Ppem_Func func_cur_ppem; /* get current proj. ppem value */
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TT_Get_CVT_Func func_read_cvt; /* read a cvt entry */
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TT_Set_CVT_Func func_write_cvt; /* write a cvt entry (in pixels) */
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TT_Set_CVT_Func func_move_cvt; /* incr a cvt entry (in pixels) */
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FT_Bool grayscale; /* bi-level hinting and */
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/* grayscale rendering */
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#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL
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/*
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* Modern TrueType fonts are usually rendered through Microsoft's
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* collection of rendering techniques called ClearType (e.g., subpixel
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* rendering and subpixel hinting). When ClearType was introduced, most
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* fonts were not ready. Microsoft decided to implement a backwards
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* compatibility mode that employed several simple to complicated
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* assumptions and tricks that modified the interpretation of the
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* bytecode contained in these fonts to make them look ClearType-y
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* somehow. Most (web)fonts that were released since then have come to
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* rely on these hacks to render correctly, even some of Microsoft's
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* flagship ClearType fonts (Calibri, Cambria, Segoe UI).
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*
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* The minimal subpixel hinting code (interpreter version 40) employs a
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* small list of font-agnostic hacks to bludgeon non-native-ClearType
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* fonts (except tricky ones[1]) into submission. It will not try to
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* toggle hacks for specific fonts for performance and complexity
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* reasons. The focus is on modern (web)fonts rather than legacy fonts
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* that were made for black-and-white rendering.
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*
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* Major hacks
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*
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* - Any point movement on the x axis is ignored (cf. `Direct_Move' and
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* `Direct_Move_X'). This has the smallest code footprint and single
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* biggest effect. The ClearType way to increase resolution is
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* supersampling the x axis, the FreeType way is ignoring instructions
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* on the x axis, which gives the same result in the majority of
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* cases.
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*
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* - Points are not moved post-IUP (neither on the x nor on the y axis),
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* except the x component of diagonal moves post-IUP (cf.
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* `Direct_Move', `Direct_Move_Y', `Move_Zp2_Point'). Post-IUP
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* changes are commonly used to `fix' pixel patterns which has little
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* use outside monochrome rendering.
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*
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* - SHPIX and DELTAP don't execute unless moving a composite on the
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* y axis or moving a previously y touched point. SHPIX additionally
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* denies movement on the x axis (cf. `Ins_SHPIX' and `Ins_DELTAP').
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* Both instructions are commonly used to `fix' pixel patterns for
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* monochrome or Windows's GDI rendering but make little sense for
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* FreeType rendering. Both can distort the outline. See [2] for
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* details.
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*
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* - The hdmx table and modifications to phantom points are ignored.
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* Bearings and advance widths remain unchanged (except rounding them
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* outside the interpreter!), cf. `compute_glyph_metrics' and
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* `TT_Hint_Glyph'. Letting non-native-ClearType fonts modify spacing
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* might mess up spacing.
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*
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* Minor hacks
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*
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* - FLIPRGON, FLIPRGOFF, and FLIPPT don't execute post-IUP. This
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* prevents dents in e.g. Arial-Regular's `D' and `G' glyphs at
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* various sizes.
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*
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* (Post-IUP is the state after both IUP[x] and IUP[y] have been
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* executed.)
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*
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* The best results are achieved for fonts that were from the outset
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* designed with ClearType in mind, meaning they leave the x axis mostly
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* alone and don't mess with the `final' outline to produce more
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* pleasing pixel patterns. The harder the designer tried to produce
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* very specific patterns (`superhinting') for pre-ClearType-displays,
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* the worse the results.
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*
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* Microsoft defines a way to turn off backwards compatibility and
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* interpret instructions as before (called `native ClearType')[2][3].
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* The font designer then regains full control and is responsible for
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* making the font work correctly with ClearType without any
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* hand-holding by the interpreter or rasterizer[4]. The v40
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* interpreter assumes backwards compatibility by default, which can be
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* turned off the same way by executing the following in the control
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* program (cf. `Ins_INSTCTRL').
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*
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* #PUSH 4,3
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* INSTCTRL[]
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*
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* [1] Tricky fonts as FreeType defines them rely on the bytecode
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* interpreter to display correctly. Hacks can interfere with them,
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* so they get treated like native ClearType fonts (v40 with
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* backwards compatibility turned off). Cf. `TT_RunIns'.
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*
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* [2] Proposed by Microsoft's Greg Hitchcock in
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* https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx
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*
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* [3] Beat Stamm describes it in more detail:
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* http://www.beatstamm.com/typography/RTRCh4.htm#Sec12
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*
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* [4] The list of `native ClearType' fonts is small at the time of this
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* writing; I found the following on a Windows 10 Update 1511
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* installation: Constantia, Corbel, Sitka, Malgun Gothic, Microsoft
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* JhengHei (Bold and UI Bold), Microsoft YaHei (Bold and UI Bold),
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* SimSun, NSimSun, and Yu Gothic.
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*
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*/
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/* Using v40 implies subpixel hinting. Used to detect interpreter */
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/* version switches. `_lean' to differentiate from the Infinality */
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/* `subpixel_hinting', which is managed differently. */
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FT_Bool subpixel_hinting_lean;
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/* Long side of a LCD subpixel is vertical (e.g., screen is rotated). */
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/* `_lean' to differentiate from the Infinality `vertical_lcd', which */
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/* is managed differently. */
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FT_Bool vertical_lcd_lean;
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/* Default to backwards compatibility mode in v40 interpreter. If */
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/* this is false, it implies the interpreter is in v35 or in native */
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/* ClearType mode. */
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FT_Bool backwards_compatibility;
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/* Useful for detecting and denying post-IUP trickery that is usually */
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/* used to fix pixel patterns (`superhinting'). */
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FT_Bool iupx_called;
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FT_Bool iupy_called;
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/* ClearType hinting and grayscale rendering, as used by Universal */
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/* Windows Platform apps (Windows 8 and above). Like the standard */
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/* colorful ClearType mode, it utilizes a vastly increased virtual */
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/* resolution on the x axis. Different from bi-level hinting and */
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/* grayscale rendering, the old mode from Win9x days that roughly */
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/* adheres to the physical pixel grid on both axes. */
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FT_Bool grayscale_cleartype;
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#endif /* TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL */
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#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY
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TT_Round_Func func_round_sphn; /* subpixel rounding function */
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FT_Bool subpixel_hinting; /* Using subpixel hinting? */
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FT_Bool ignore_x_mode; /* Standard rendering mode for */
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/* subpixel hinting. On if gray */
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/* or subpixel hinting is on. */
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/* The following 6 aren't fully implemented but here for MS rasterizer */
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/* compatibility. */
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FT_Bool compatible_widths; /* compatible widths? */
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FT_Bool symmetrical_smoothing; /* symmetrical_smoothing? */
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FT_Bool bgr; /* bgr instead of rgb? */
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FT_Bool vertical_lcd; /* long side of LCD subpixel */
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/* rectangles is horizontal */
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FT_Bool subpixel_positioned; /* subpixel positioned */
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/* (DirectWrite ClearType)? */
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FT_Bool gray_cleartype; /* ClearType hinting but */
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/* grayscale rendering */
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FT_Int rasterizer_version; /* MS rasterizer version */
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FT_Bool iup_called; /* IUP called for glyph? */
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FT_ULong sph_tweak_flags; /* flags to control */
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/* hint tweaks */
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FT_ULong sph_in_func_flags; /* flags to indicate if in */
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/* special functions */
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#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */
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/* We maintain two counters (in addition to the instruction counter) */
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/* that act as loop detectors for LOOPCALL and jump opcodes with */
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/* negative arguments. */
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FT_Long loopcall_counter;
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FT_Long loopcall_counter_max;
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FT_Long neg_jump_counter;
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FT_Long neg_jump_counter_max;
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} TT_ExecContextRec;
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extern const TT_GraphicsState tt_default_graphics_state;
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#ifdef TT_USE_BYTECODE_INTERPRETER
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FT_LOCAL( void )
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TT_Goto_CodeRange( TT_ExecContext exec,
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FT_Int range,
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FT_Long IP );
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FT_LOCAL( void )
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TT_Set_CodeRange( TT_ExecContext exec,
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FT_Int range,
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void* base,
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FT_Long length );
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FT_LOCAL( void )
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TT_Clear_CodeRange( TT_ExecContext exec,
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FT_Int range );
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FT_LOCAL( FT_Error )
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Update_Max( FT_Memory memory,
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FT_ULong* size,
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FT_ULong multiplier,
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void* _pbuff,
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FT_ULong new_max );
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#endif /* TT_USE_BYTECODE_INTERPRETER */
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/*************************************************************************/
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/* */
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/* <Function> */
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/* TT_New_Context */
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/* */
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/* <Description> */
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/* Queries the face context for a given font. Note that there is */
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/* now a _single_ execution context in the TrueType driver which is */
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/* shared among faces. */
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/* */
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/* <Input> */
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/* face :: A handle to the source face object. */
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/* */
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/* <Return> */
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/* A handle to the execution context. Initialized for `face'. */
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/* */
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/* <Note> */
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/* Only the glyph loader and debugger should call this function. */
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/* (And right now only the glyph loader uses it.) */
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/* */
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FT_EXPORT( TT_ExecContext )
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TT_New_Context( TT_Driver driver );
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#ifdef TT_USE_BYTECODE_INTERPRETER
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FT_LOCAL( void )
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TT_Done_Context( TT_ExecContext exec );
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FT_LOCAL( FT_Error )
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TT_Load_Context( TT_ExecContext exec,
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TT_Face face,
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TT_Size size );
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FT_LOCAL( void )
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TT_Save_Context( TT_ExecContext exec,
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TT_Size ins );
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FT_LOCAL( FT_Error )
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TT_Run_Context( TT_ExecContext exec );
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#endif /* TT_USE_BYTECODE_INTERPRETER */
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/*************************************************************************/
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/* */
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/* <Function> */
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/* TT_RunIns */
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/* */
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/* <Description> */
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/* Executes one or more instruction in the execution context. This */
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/* is the main function of the TrueType opcode interpreter. */
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/* */
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/* <Input> */
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/* exec :: A handle to the target execution context. */
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/* */
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/* <Return> */
|
|
/* FreeType error code. 0 means success. */
|
|
/* */
|
|
/* <Note> */
|
|
/* Only the object manager and debugger should call this function. */
|
|
/* */
|
|
/* This function is publicly exported because it is directly */
|
|
/* invoked by the TrueType debugger. */
|
|
/* */
|
|
FT_EXPORT( FT_Error )
|
|
TT_RunIns( TT_ExecContext exec );
|
|
|
|
|
|
FT_END_HEADER
|
|
|
|
#endif /* TTINTERP_H_ */
|
|
|
|
|
|
/* END */
|