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Diffstat (limited to 'modules/freetype2/src/truetype/ttinterp.h')
| -rw-r--r-- | modules/freetype2/src/truetype/ttinterp.h | 547 |
1 files changed, 547 insertions, 0 deletions
diff --git a/modules/freetype2/src/truetype/ttinterp.h b/modules/freetype2/src/truetype/ttinterp.h new file mode 100644 index 0000000000..c54c053b29 --- /dev/null +++ b/modules/freetype2/src/truetype/ttinterp.h @@ -0,0 +1,547 @@ +/**************************************************************************** + * + * ttinterp.h + * + * TrueType bytecode interpreter (specification). + * + * Copyright (C) 1996-2023 by + * David Turner, Robert Wilhelm, and Werner Lemberg. + * + * This file is part of the FreeType project, and may only be used, + * modified, and distributed under the terms of the FreeType project + * license, LICENSE.TXT. By continuing to use, modify, or distribute + * this file you indicate that you have read the license and + * understand and accept it fully. + * + */ + + +#ifndef TTINTERP_H_ +#define TTINTERP_H_ + +#include "ttobjs.h" + + +FT_BEGIN_HEADER + + + /************************************************************************** + * + * Rounding mode constants. + */ +#define TT_Round_Off 5 +#define TT_Round_To_Half_Grid 0 +#define TT_Round_To_Grid 1 +#define TT_Round_To_Double_Grid 2 +#define TT_Round_Up_To_Grid 4 +#define TT_Round_Down_To_Grid 3 +#define TT_Round_Super 6 +#define TT_Round_Super_45 7 + + + /************************************************************************** + * + * Function types used by the interpreter, depending on various modes + * (e.g. the rounding mode, whether to render a vertical or horizontal + * line etc). + * + */ + + /* Rounding function */ + typedef FT_F26Dot6 + (*TT_Round_Func)( TT_ExecContext exc, + FT_F26Dot6 distance, + FT_Int color ); + + /* Point displacement along the freedom vector routine */ + typedef void + (*TT_Move_Func)( TT_ExecContext exc, + TT_GlyphZone zone, + FT_UShort point, + FT_F26Dot6 distance ); + + /* Distance projection along one of the projection vectors */ + typedef FT_F26Dot6 + (*TT_Project_Func)( TT_ExecContext exc, + FT_Pos dx, + FT_Pos dy ); + + /* getting current ppem. Take care of non-square pixels if necessary */ + typedef FT_Long + (*TT_Cur_Ppem_Func)( TT_ExecContext exc ); + + /* reading a cvt value. Take care of non-square pixels if necessary */ + typedef FT_F26Dot6 + (*TT_Get_CVT_Func)( TT_ExecContext exc, + FT_ULong idx ); + + /* setting or moving a cvt value. Take care of non-square pixels */ + /* if necessary */ + typedef void + (*TT_Set_CVT_Func)( TT_ExecContext exc, + FT_ULong idx, + FT_F26Dot6 value ); + + + /************************************************************************** + * + * This structure defines a call record, used to manage function calls. + */ + typedef struct TT_CallRec_ + { + FT_Int Caller_Range; + FT_Long Caller_IP; + FT_Long Cur_Count; + + TT_DefRecord *Def; /* either FDEF or IDEF */ + + } TT_CallRec, *TT_CallStack; + + +#ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY + + /************************************************************************** + * + * These structures define rules used to tweak subpixel hinting for + * various fonts. "", 0, "", NULL value indicates to match any value. + */ + +#define SPH_MAX_NAME_SIZE 32 +#define SPH_MAX_CLASS_MEMBERS 100 + + typedef struct SPH_TweakRule_ + { + const char family[SPH_MAX_NAME_SIZE]; + const FT_UInt ppem; + const char style[SPH_MAX_NAME_SIZE]; + const FT_ULong glyph; + + } SPH_TweakRule; + + + typedef struct SPH_ScaleRule_ + { + const char family[SPH_MAX_NAME_SIZE]; + const FT_UInt ppem; + const char style[SPH_MAX_NAME_SIZE]; + const FT_ULong glyph; + const FT_ULong scale; + + } SPH_ScaleRule; + + + typedef struct SPH_Font_Class_ + { + const char name[SPH_MAX_NAME_SIZE]; + const char member[SPH_MAX_CLASS_MEMBERS][SPH_MAX_NAME_SIZE]; + + } SPH_Font_Class; + +#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */ + + + /************************************************************************** + * + * The main structure for the interpreter which collects all necessary + * variables and states. + * + * Members that are initialized by `TT_Load_Context` are marked with '!'. + * Members that are initialized by `TT_Run_Context` are marked with '@'. + */ + typedef struct TT_ExecContextRec_ + { + TT_Face face; /* ! */ + TT_Size size; /* ! */ + FT_Memory memory; + + /* instructions state */ + + FT_Error error; /* last execution error */ + + FT_Long top; /* @ top of exec. stack */ + + FT_Long stackSize; /* ! size of exec. stack */ + FT_Long* stack; /* ! current exec. stack */ + + FT_Long args; + FT_Long new_top; /* new top after exec. */ + + TT_GlyphZoneRec zp0, /* @! zone records */ + zp1, /* @! */ + zp2, /* @! */ + pts, /* ! */ + twilight; /* ! */ + + FT_Long pointSize; /* ! in 26.6 format */ + FT_Size_Metrics metrics; /* ! */ + TT_Size_Metrics tt_metrics; /* ! size metrics */ + + TT_GraphicsState GS; /* !@ current graphics state */ + + FT_Int iniRange; /* initial code range number */ + FT_Int curRange; /* current code range number */ + FT_Byte* code; /* current code range */ + FT_Long IP; /* current instruction pointer */ + FT_Long codeSize; /* size of current range */ + + FT_Byte opcode; /* current opcode */ + FT_Int length; /* length of current opcode */ + + FT_Bool step_ins; /* true if the interpreter must */ + /* increment IP after ins. exec */ + FT_ULong cvtSize; /* ! */ + FT_Long* cvt; /* ! */ + FT_ULong glyfCvtSize; + FT_Long* glyfCvt; /* cvt working copy for glyph */ + + FT_UInt glyphSize; /* ! glyph instructions buffer size */ + FT_Byte* glyphIns; /* ! glyph instructions buffer */ + + FT_UInt numFDefs; /* ! number of function defs */ + FT_UInt maxFDefs; /* ! maximum number of function defs */ + TT_DefArray FDefs; /* table of FDefs entries */ + + FT_UInt numIDefs; /* ! number of instruction defs */ + FT_UInt maxIDefs; /* ! maximum number of ins defs */ + TT_DefArray IDefs; /* table of IDefs entries */ + + FT_UInt maxFunc; /* ! maximum function index */ + FT_UInt maxIns; /* ! maximum instruction index */ + + FT_Int callTop, /* @ top of call stack during execution */ + callSize; /* size of call stack */ + TT_CallStack callStack; /* call stack */ + + FT_UShort maxPoints; /* capacity of this context's `pts' */ + FT_Short maxContours; /* record, expressed in points and */ + /* contours. */ + + TT_CodeRangeTable codeRangeTable; /* ! table of valid code ranges */ + /* useful for the debugger */ + + FT_UShort storeSize; /* ! size of current storage */ + FT_Long* storage; /* ! storage area */ + FT_UShort glyfStoreSize; + FT_Long* glyfStorage; /* storage working copy for glyph */ + + FT_F26Dot6 period; /* values used for the */ + FT_F26Dot6 phase; /* `SuperRounding' */ + FT_F26Dot6 threshold; + + FT_Bool instruction_trap; /* ! If `True', the interpreter */ + /* exits after each instruction */ + + TT_GraphicsState default_GS; /* graphics state resulting from */ + /* the prep program */ + FT_Bool is_composite; /* true if the glyph is composite */ + FT_Bool pedantic_hinting; /* true if pedantic interpretation */ + + /* latest interpreter additions */ + + FT_Long F_dot_P; /* dot product of freedom and projection */ + /* vectors */ + TT_Round_Func func_round; /* current rounding function */ + + TT_Project_Func func_project, /* current projection function */ + func_dualproj, /* current dual proj. function */ + func_freeProj; /* current freedom proj. func */ + + TT_Move_Func func_move; /* current point move function */ + TT_Move_Func func_move_orig; /* move original position function */ + + TT_Cur_Ppem_Func func_cur_ppem; /* get current proj. ppem value */ + + TT_Get_CVT_Func func_read_cvt; /* read a cvt entry */ + 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; /* bi-level hinting and */ + /* grayscale rendering */ + +#ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL + /* + * FreeType supports ClearType-like hinting of TrueType fonts through + * the version 40 interpreter. This is achieved through several hacks + * in the base (v35) interpreter, as detailed below. + * + * ClearType is an umbrella term for several rendering techniques + * employed by Microsoft's various GUI and rendering toolkit + * implementations, most importantly: subpixel rendering for using the + * RGB subpixels of LCDs to approximately triple the perceived + * resolution on the x-axis and subpixel hinting for positioning stems + * on subpixel borders. TrueType programming is explicit, i.e., fonts + * must be programmed to take advantage of ClearType's possibilities. + * + * When ClearType was introduced, it seemed unlikely that all fonts + * would be reprogrammed, so Microsoft decided to implement a backward + * compatibility mode. It employs several simple to complicated + * assumptions and tricks, many of them font-dependent, that modify the + * interpretation of the bytecode contained in these fonts to retrofit + * them into a ClearType-y look. The quality of the results varies. + * Most (web)fonts that were released since then have come to rely on + * these hacks to render correctly, even some of Microsoft's flagship + * fonts (e.g., Calibri, Cambria, Segoe UI). + * + * FreeType's minimal subpixel hinting code (interpreter version 40) + * employs a small list of font-agnostic hacks loosely based on the + * public information available on Microsoft's compatibility mode[2]. + * The focus is on modern (web)fonts rather than legacy fonts that were + * made for monochrome rendering. It will not match ClearType rendering + * exactly. Unlike the `Infinality' code (interpreter version 38) that + * came before, it will not try to toggle hacks for specific fonts for + * performance and complexity reasons. It will fall back to version 35 + * behavior for tricky fonts[1] or when monochrome rendering is + * requested. + * + * 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 backward 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 backward 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 + * backward 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://rastertragedy.com/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, unless FT_RENDER_MODE_MONO has been + * requested. 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 backward compatibility mode in v40 interpreter. If */ + /* this is false, it implies the interpreter is in v35 or in native */ + /* ClearType mode. */ + FT_Bool backward_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? */ + FT_Bool ignore_x_mode; /* Standard rendering mode for */ + /* subpixel hinting. On if gray */ + /* or subpixel hinting is on. */ + + /* The following 6 aren't fully implemented but here for MS rasterizer */ + /* compatibility. */ + FT_Bool compatible_widths; /* compatible widths? */ + FT_Bool symmetrical_smoothing; /* symmetrical_smoothing? */ + FT_Bool bgr; /* bgr instead of rgb? */ + FT_Bool vertical_lcd; /* long side of LCD subpixel */ + /* rectangles is horizontal */ + FT_Bool subpixel_positioned; /* subpixel positioned */ + /* (DirectWrite ClearType)? */ + FT_Bool gray_cleartype; /* ClearType hinting but */ + /* grayscale rendering */ + + FT_Int rasterizer_version; /* MS rasterizer version */ + + FT_Bool iup_called; /* IUP called for glyph? */ + + FT_ULong sph_tweak_flags; /* flags to control */ + /* hint tweaks */ + + FT_ULong sph_in_func_flags; /* flags to indicate if in */ + /* special functions */ + +#endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */ + + /* We maintain two counters (in addition to the instruction counter) */ + /* that act as loop detectors for LOOPCALL and jump opcodes with */ + /* negative arguments. */ + FT_ULong loopcall_counter; + FT_ULong loopcall_counter_max; + FT_ULong neg_jump_counter; + FT_ULong neg_jump_counter_max; + + } TT_ExecContextRec; + + + extern const TT_GraphicsState tt_default_graphics_state; + + +#ifdef TT_USE_BYTECODE_INTERPRETER + FT_LOCAL( void ) + TT_Goto_CodeRange( TT_ExecContext exec, + FT_Int range, + FT_Long IP ); + + FT_LOCAL( void ) + TT_Set_CodeRange( TT_ExecContext exec, + FT_Int range, + void* base, + FT_Long length ); + + FT_LOCAL( void ) + TT_Clear_CodeRange( TT_ExecContext exec, + FT_Int range ); + + + FT_LOCAL( FT_Error ) + Update_Max( FT_Memory memory, + FT_ULong* size, + FT_ULong multiplier, + void* _pbuff, + FT_ULong new_max ); +#endif /* TT_USE_BYTECODE_INTERPRETER */ + + + /************************************************************************** + * + * @Function: + * TT_New_Context + * + * @Description: + * Create a `TT_ExecContext`. Note that there is now an execution + * context per `TT_Size` that is not shared among faces. + * + * @Input: + * driver :: + * A handle to the driver, used for memory allocation. + * + * @Return: + * A handle to a new empty execution context. + * + * @Note: + * Only the glyph loader and debugger should call this function. + * (And right now only the glyph loader uses it.) + */ + FT_EXPORT( TT_ExecContext ) + TT_New_Context( TT_Driver driver ); + + +#ifdef TT_USE_BYTECODE_INTERPRETER + FT_LOCAL( void ) + TT_Done_Context( TT_ExecContext exec ); + + FT_LOCAL( FT_Error ) + TT_Load_Context( TT_ExecContext exec, + TT_Face face, + TT_Size size ); + + FT_LOCAL( void ) + TT_Save_Context( TT_ExecContext exec, + TT_Size ins ); + + FT_LOCAL( FT_Error ) + TT_Run_Context( TT_ExecContext exec ); +#endif /* TT_USE_BYTECODE_INTERPRETER */ + + + /************************************************************************** + * + * @Function: + * TT_RunIns + * + * @Description: + * Executes one or more instruction in the execution context. This + * is the main function of the TrueType opcode interpreter. + * + * @Input: + * exec :: + * A handle to the target execution context. + * + * @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 */ |