| /**************************************************************************** |
| * |
| * ttinterp.h |
| * |
| * TrueType bytecode interpreter (specification). |
| * |
| * Copyright (C) 1996-2021 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_Long* origCvt; |
| |
| 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_Long* origStorage; |
| |
| 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 */ |
