1 /**************************************************************************** 2 * 3 * ttinterp.h 4 * 5 * TrueType bytecode interpreter (specification). 6 * 7 * Copyright (C) 1996-2023 by 8 * David Turner, Robert Wilhelm, and Werner Lemberg. 9 * 10 * This file is part of the FreeType project, and may only be used, 11 * modified, and distributed under the terms of the FreeType project 12 * license, LICENSE.TXT. By continuing to use, modify, or distribute 13 * this file you indicate that you have read the license and 14 * understand and accept it fully. 15 * 16 */ 17 18 19 #ifndef TTINTERP_H_ 20 #define TTINTERP_H_ 21 22 #include "ttobjs.h" 23 24 25 FT_BEGIN_HEADER 26 27 28 /************************************************************************** 29 * 30 * Rounding mode constants. 31 */ 32 #define TT_Round_Off 5 33 #define TT_Round_To_Half_Grid 0 34 #define TT_Round_To_Grid 1 35 #define TT_Round_To_Double_Grid 2 36 #define TT_Round_Up_To_Grid 4 37 #define TT_Round_Down_To_Grid 3 38 #define TT_Round_Super 6 39 #define TT_Round_Super_45 7 40 41 42 /************************************************************************** 43 * 44 * Function types used by the interpreter, depending on various modes 45 * (e.g. the rounding mode, whether to render a vertical or horizontal 46 * line etc). 47 * 48 */ 49 50 /* Rounding function */ 51 typedef FT_F26Dot6 52 (*TT_Round_Func)( TT_ExecContext exc, 53 FT_F26Dot6 distance, 54 FT_Int color ); 55 56 /* Point displacement along the freedom vector routine */ 57 typedef void 58 (*TT_Move_Func)( TT_ExecContext exc, 59 TT_GlyphZone zone, 60 FT_UShort point, 61 FT_F26Dot6 distance ); 62 63 /* Distance projection along one of the projection vectors */ 64 typedef FT_F26Dot6 65 (*TT_Project_Func)( TT_ExecContext exc, 66 FT_Pos dx, 67 FT_Pos dy ); 68 69 /* getting current ppem. Take care of non-square pixels if necessary */ 70 typedef FT_Long 71 (*TT_Cur_Ppem_Func)( TT_ExecContext exc ); 72 73 /* reading a cvt value. Take care of non-square pixels if necessary */ 74 typedef FT_F26Dot6 75 (*TT_Get_CVT_Func)( TT_ExecContext exc, 76 FT_ULong idx ); 77 78 /* setting or moving a cvt value. Take care of non-square pixels */ 79 /* if necessary */ 80 typedef void 81 (*TT_Set_CVT_Func)( TT_ExecContext exc, 82 FT_ULong idx, 83 FT_F26Dot6 value ); 84 85 86 /************************************************************************** 87 * 88 * This structure defines a call record, used to manage function calls. 89 */ 90 typedef struct TT_CallRec_ 91 { 92 FT_Int Caller_Range; 93 FT_Long Caller_IP; 94 FT_Long Cur_Count; 95 96 TT_DefRecord *Def; /* either FDEF or IDEF */ 97 98 } TT_CallRec, *TT_CallStack; 99 100 101 #ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY 102 103 /************************************************************************** 104 * 105 * These structures define rules used to tweak subpixel hinting for 106 * various fonts. "", 0, "", NULL value indicates to match any value. 107 */ 108 109 #define SPH_MAX_NAME_SIZE 32 110 #define SPH_MAX_CLASS_MEMBERS 100 111 112 typedef struct SPH_TweakRule_ 113 { 114 const char family[SPH_MAX_NAME_SIZE]; 115 const FT_UInt ppem; 116 const char style[SPH_MAX_NAME_SIZE]; 117 const FT_ULong glyph; 118 119 } SPH_TweakRule; 120 121 122 typedef struct SPH_ScaleRule_ 123 { 124 const char family[SPH_MAX_NAME_SIZE]; 125 const FT_UInt ppem; 126 const char style[SPH_MAX_NAME_SIZE]; 127 const FT_ULong glyph; 128 const FT_ULong scale; 129 130 } SPH_ScaleRule; 131 132 133 typedef struct SPH_Font_Class_ 134 { 135 const char name[SPH_MAX_NAME_SIZE]; 136 const char member[SPH_MAX_CLASS_MEMBERS][SPH_MAX_NAME_SIZE]; 137 138 } SPH_Font_Class; 139 140 #endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */ 141 142 143 /************************************************************************** 144 * 145 * The main structure for the interpreter which collects all necessary 146 * variables and states. 147 * 148 * Members that are initialized by `TT_Load_Context` are marked with '!'. 149 * Members that are initialized by `TT_Run_Context` are marked with '@'. 150 */ 151 typedef struct TT_ExecContextRec_ 152 { 153 TT_Face face; /* ! */ 154 TT_Size size; /* ! */ 155 FT_Memory memory; 156 157 /* instructions state */ 158 159 FT_Error error; /* last execution error */ 160 161 FT_Long top; /* @ top of exec. stack */ 162 163 FT_Long stackSize; /* ! size of exec. stack */ 164 FT_Long* stack; /* ! current exec. stack */ 165 166 FT_Long args; 167 FT_Long new_top; /* new top after exec. */ 168 169 TT_GlyphZoneRec zp0, /* @! zone records */ 170 zp1, /* @! */ 171 zp2, /* @! */ 172 pts, /* ! */ 173 twilight; /* ! */ 174 175 FT_Long pointSize; /* ! in 26.6 format */ 176 FT_Size_Metrics metrics; /* ! */ 177 TT_Size_Metrics tt_metrics; /* ! size metrics */ 178 179 TT_GraphicsState GS; /* !@ current graphics state */ 180 181 FT_Int iniRange; /* initial code range number */ 182 FT_Int curRange; /* current code range number */ 183 FT_Byte* code; /* current code range */ 184 FT_Long IP; /* current instruction pointer */ 185 FT_Long codeSize; /* size of current range */ 186 187 FT_Byte opcode; /* current opcode */ 188 FT_Int length; /* length of current opcode */ 189 190 FT_Bool step_ins; /* true if the interpreter must */ 191 /* increment IP after ins. exec */ 192 FT_ULong cvtSize; /* ! */ 193 FT_Long* cvt; /* ! */ 194 FT_ULong glyfCvtSize; 195 FT_Long* glyfCvt; /* cvt working copy for glyph */ 196 197 FT_UInt glyphSize; /* ! glyph instructions buffer size */ 198 FT_Byte* glyphIns; /* ! glyph instructions buffer */ 199 200 FT_UInt numFDefs; /* ! number of function defs */ 201 FT_UInt maxFDefs; /* ! maximum number of function defs */ 202 TT_DefArray FDefs; /* table of FDefs entries */ 203 204 FT_UInt numIDefs; /* ! number of instruction defs */ 205 FT_UInt maxIDefs; /* ! maximum number of ins defs */ 206 TT_DefArray IDefs; /* table of IDefs entries */ 207 208 FT_UInt maxFunc; /* ! maximum function index */ 209 FT_UInt maxIns; /* ! maximum instruction index */ 210 211 FT_Int callTop, /* @ top of call stack during execution */ 212 callSize; /* size of call stack */ 213 TT_CallStack callStack; /* call stack */ 214 215 FT_UShort maxPoints; /* capacity of this context's `pts' */ 216 FT_Short maxContours; /* record, expressed in points and */ 217 /* contours. */ 218 219 TT_CodeRangeTable codeRangeTable; /* ! table of valid code ranges */ 220 /* useful for the debugger */ 221 222 FT_UShort storeSize; /* ! size of current storage */ 223 FT_Long* storage; /* ! storage area */ 224 FT_UShort glyfStoreSize; 225 FT_Long* glyfStorage; /* storage working copy for glyph */ 226 227 FT_F26Dot6 period; /* values used for the */ 228 FT_F26Dot6 phase; /* `SuperRounding' */ 229 FT_F26Dot6 threshold; 230 231 FT_Bool instruction_trap; /* ! If `True', the interpreter */ 232 /* exits after each instruction */ 233 234 TT_GraphicsState default_GS; /* graphics state resulting from */ 235 /* the prep program */ 236 FT_Bool is_composite; /* true if the glyph is composite */ 237 FT_Bool pedantic_hinting; /* true if pedantic interpretation */ 238 239 /* latest interpreter additions */ 240 241 FT_Long F_dot_P; /* dot product of freedom and projection */ 242 /* vectors */ 243 TT_Round_Func func_round; /* current rounding function */ 244 245 TT_Project_Func func_project, /* current projection function */ 246 func_dualproj, /* current dual proj. function */ 247 func_freeProj; /* current freedom proj. func */ 248 249 TT_Move_Func func_move; /* current point move function */ 250 TT_Move_Func func_move_orig; /* move original position function */ 251 252 TT_Cur_Ppem_Func func_cur_ppem; /* get current proj. ppem value */ 253 254 TT_Get_CVT_Func func_read_cvt; /* read a cvt entry */ 255 TT_Set_CVT_Func func_write_cvt; /* write a cvt entry (in pixels) */ 256 TT_Set_CVT_Func func_move_cvt; /* incr a cvt entry (in pixels) */ 257 258 FT_Bool grayscale; /* bi-level hinting and */ 259 /* grayscale rendering */ 260 261 #ifdef TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL 262 /* 263 * FreeType supports ClearType-like hinting of TrueType fonts through 264 * the version 40 interpreter. This is achieved through several hacks 265 * in the base (v35) interpreter, as detailed below. 266 * 267 * ClearType is an umbrella term for several rendering techniques 268 * employed by Microsoft's various GUI and rendering toolkit 269 * implementations, most importantly: subpixel rendering for using the 270 * RGB subpixels of LCDs to approximately triple the perceived 271 * resolution on the x-axis and subpixel hinting for positioning stems 272 * on subpixel borders. TrueType programming is explicit, i.e., fonts 273 * must be programmed to take advantage of ClearType's possibilities. 274 * 275 * When ClearType was introduced, it seemed unlikely that all fonts 276 * would be reprogrammed, so Microsoft decided to implement a backward 277 * compatibility mode. It employs several simple to complicated 278 * assumptions and tricks, many of them font-dependent, that modify the 279 * interpretation of the bytecode contained in these fonts to retrofit 280 * them into a ClearType-y look. The quality of the results varies. 281 * Most (web)fonts that were released since then have come to rely on 282 * these hacks to render correctly, even some of Microsoft's flagship 283 * fonts (e.g., Calibri, Cambria, Segoe UI). 284 * 285 * FreeType's minimal subpixel hinting code (interpreter version 40) 286 * employs a small list of font-agnostic hacks loosely based on the 287 * public information available on Microsoft's compatibility mode[2]. 288 * The focus is on modern (web)fonts rather than legacy fonts that were 289 * made for monochrome rendering. It will not match ClearType rendering 290 * exactly. Unlike the `Infinality' code (interpreter version 38) that 291 * came before, it will not try to toggle hacks for specific fonts for 292 * performance and complexity reasons. It will fall back to version 35 293 * behavior for tricky fonts[1] or when monochrome rendering is 294 * requested. 295 * 296 * Major hacks 297 * 298 * - Any point movement on the x axis is ignored (cf. `Direct_Move' and 299 * `Direct_Move_X'). This has the smallest code footprint and single 300 * biggest effect. The ClearType way to increase resolution is 301 * supersampling the x axis, the FreeType way is ignoring instructions 302 * on the x axis, which gives the same result in the majority of 303 * cases. 304 * 305 * - Points are not moved post-IUP (neither on the x nor on the y axis), 306 * except the x component of diagonal moves post-IUP (cf. 307 * `Direct_Move', `Direct_Move_Y', `Move_Zp2_Point'). Post-IUP 308 * changes are commonly used to `fix' pixel patterns which has little 309 * use outside monochrome rendering. 310 * 311 * - SHPIX and DELTAP don't execute unless moving a composite on the 312 * y axis or moving a previously y touched point. SHPIX additionally 313 * denies movement on the x axis (cf. `Ins_SHPIX' and `Ins_DELTAP'). 314 * Both instructions are commonly used to `fix' pixel patterns for 315 * monochrome or Windows's GDI rendering but make little sense for 316 * FreeType rendering. Both can distort the outline. See [2] for 317 * details. 318 * 319 * - The hdmx table and modifications to phantom points are ignored. 320 * Bearings and advance widths remain unchanged (except rounding them 321 * outside the interpreter!), cf. `compute_glyph_metrics' and 322 * `TT_Hint_Glyph'. Letting non-native-ClearType fonts modify spacing 323 * might mess up spacing. 324 * 325 * Minor hacks 326 * 327 * - FLIPRGON, FLIPRGOFF, and FLIPPT don't execute post-IUP. This 328 * prevents dents in e.g. Arial-Regular's `D' and `G' glyphs at 329 * various sizes. 330 * 331 * (Post-IUP is the state after both IUP[x] and IUP[y] have been 332 * executed.) 333 * 334 * The best results are achieved for fonts that were from the outset 335 * designed with ClearType in mind, meaning they leave the x axis mostly 336 * alone and don't mess with the `final' outline to produce more 337 * pleasing pixel patterns. The harder the designer tried to produce 338 * very specific patterns (`superhinting') for pre-ClearType-displays, 339 * the worse the results. 340 * 341 * Microsoft defines a way to turn off backward compatibility and 342 * interpret instructions as before (called `native ClearType')[2][3]. 343 * The font designer then regains full control and is responsible for 344 * making the font work correctly with ClearType without any 345 * hand-holding by the interpreter or rasterizer[4]. The v40 346 * interpreter assumes backward compatibility by default, which can be 347 * turned off the same way by executing the following in the control 348 * program (cf. `Ins_INSTCTRL'). 349 * 350 * #PUSH 4,3 351 * INSTCTRL[] 352 * 353 * [1] Tricky fonts as FreeType defines them rely on the bytecode 354 * interpreter to display correctly. Hacks can interfere with them, 355 * so they get treated like native ClearType fonts (v40 with 356 * backward compatibility turned off). Cf. `TT_RunIns'. 357 * 358 * [2] Proposed by Microsoft's Greg Hitchcock in 359 * https://www.microsoft.com/typography/cleartype/truetypecleartype.aspx 360 * 361 * [3] Beat Stamm describes it in more detail: 362 * http://rastertragedy.com/RTRCh4.htm#Sec12. 363 * 364 * [4] The list of `native ClearType' fonts is small at the time of this 365 * writing; I found the following on a Windows 10 Update 1511 366 * installation: Constantia, Corbel, Sitka, Malgun Gothic, Microsoft 367 * JhengHei (Bold and UI Bold), Microsoft YaHei (Bold and UI Bold), 368 * SimSun, NSimSun, and Yu Gothic. 369 * 370 */ 371 372 /* Using v40 implies subpixel hinting, unless FT_RENDER_MODE_MONO has been 373 * requested. Used to detect interpreter */ 374 /* version switches. `_lean' to differentiate from the Infinality */ 375 /* `subpixel_hinting', which is managed differently. */ 376 FT_Bool subpixel_hinting_lean; 377 378 /* Long side of a LCD subpixel is vertical (e.g., screen is rotated). */ 379 /* `_lean' to differentiate from the Infinality `vertical_lcd', which */ 380 /* is managed differently. */ 381 FT_Bool vertical_lcd_lean; 382 383 /* Default to backward compatibility mode in v40 interpreter. If */ 384 /* this is false, it implies the interpreter is in v35 or in native */ 385 /* ClearType mode. */ 386 FT_Bool backward_compatibility; 387 388 /* Useful for detecting and denying post-IUP trickery that is usually */ 389 /* used to fix pixel patterns (`superhinting'). */ 390 FT_Bool iupx_called; 391 FT_Bool iupy_called; 392 393 /* ClearType hinting and grayscale rendering, as used by Universal */ 394 /* Windows Platform apps (Windows 8 and above). Like the standard */ 395 /* colorful ClearType mode, it utilizes a vastly increased virtual */ 396 /* resolution on the x axis. Different from bi-level hinting and */ 397 /* grayscale rendering, the old mode from Win9x days that roughly */ 398 /* adheres to the physical pixel grid on both axes. */ 399 FT_Bool grayscale_cleartype; 400 #endif /* TT_SUPPORT_SUBPIXEL_HINTING_MINIMAL */ 401 402 #ifdef TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY 403 TT_Round_Func func_round_sphn; /* subpixel rounding function */ 404 405 FT_Bool subpixel_hinting; /* Using subpixel hinting? */ 406 FT_Bool ignore_x_mode; /* Standard rendering mode for */ 407 /* subpixel hinting. On if gray */ 408 /* or subpixel hinting is on. */ 409 410 /* The following 6 aren't fully implemented but here for MS rasterizer */ 411 /* compatibility. */ 412 FT_Bool compatible_widths; /* compatible widths? */ 413 FT_Bool symmetrical_smoothing; /* symmetrical_smoothing? */ 414 FT_Bool bgr; /* bgr instead of rgb? */ 415 FT_Bool vertical_lcd; /* long side of LCD subpixel */ 416 /* rectangles is horizontal */ 417 FT_Bool subpixel_positioned; /* subpixel positioned */ 418 /* (DirectWrite ClearType)? */ 419 FT_Bool gray_cleartype; /* ClearType hinting but */ 420 /* grayscale rendering */ 421 422 FT_Int rasterizer_version; /* MS rasterizer version */ 423 424 FT_Bool iup_called; /* IUP called for glyph? */ 425 426 FT_ULong sph_tweak_flags; /* flags to control */ 427 /* hint tweaks */ 428 429 FT_ULong sph_in_func_flags; /* flags to indicate if in */ 430 /* special functions */ 431 432 #endif /* TT_SUPPORT_SUBPIXEL_HINTING_INFINALITY */ 433 434 /* We maintain two counters (in addition to the instruction counter) */ 435 /* that act as loop detectors for LOOPCALL and jump opcodes with */ 436 /* negative arguments. */ 437 FT_ULong loopcall_counter; 438 FT_ULong loopcall_counter_max; 439 FT_ULong neg_jump_counter; 440 FT_ULong neg_jump_counter_max; 441 442 } TT_ExecContextRec; 443 444 445 extern const TT_GraphicsState tt_default_graphics_state; 446 447 448 #ifdef TT_USE_BYTECODE_INTERPRETER 449 FT_LOCAL( void ) 450 TT_Goto_CodeRange( TT_ExecContext exec, 451 FT_Int range, 452 FT_Long IP ); 453 454 FT_LOCAL( void ) 455 TT_Set_CodeRange( TT_ExecContext exec, 456 FT_Int range, 457 void* base, 458 FT_Long length ); 459 460 FT_LOCAL( void ) 461 TT_Clear_CodeRange( TT_ExecContext exec, 462 FT_Int range ); 463 464 465 FT_LOCAL( FT_Error ) 466 Update_Max( FT_Memory memory, 467 FT_ULong* size, 468 FT_ULong multiplier, 469 void* _pbuff, 470 FT_ULong new_max ); 471 #endif /* TT_USE_BYTECODE_INTERPRETER */ 472 473 474 /************************************************************************** 475 * 476 * @Function: 477 * TT_New_Context 478 * 479 * @Description: 480 * Create a `TT_ExecContext`. Note that there is now an execution 481 * context per `TT_Size` that is not shared among faces. 482 * 483 * @Input: 484 * driver :: 485 * A handle to the driver, used for memory allocation. 486 * 487 * @Return: 488 * A handle to a new empty execution context. 489 * 490 * @Note: 491 * Only the glyph loader and debugger should call this function. 492 * (And right now only the glyph loader uses it.) 493 */ 494 FT_EXPORT( TT_ExecContext ) 495 TT_New_Context( TT_Driver driver ); 496 497 498 #ifdef TT_USE_BYTECODE_INTERPRETER 499 FT_LOCAL( void ) 500 TT_Done_Context( TT_ExecContext exec ); 501 502 FT_LOCAL( FT_Error ) 503 TT_Load_Context( TT_ExecContext exec, 504 TT_Face face, 505 TT_Size size ); 506 507 FT_LOCAL( void ) 508 TT_Save_Context( TT_ExecContext exec, 509 TT_Size ins ); 510 511 FT_LOCAL( FT_Error ) 512 TT_Run_Context( TT_ExecContext exec ); 513 #endif /* TT_USE_BYTECODE_INTERPRETER */ 514 515 516 /************************************************************************** 517 * 518 * @Function: 519 * TT_RunIns 520 * 521 * @Description: 522 * Executes one or more instruction in the execution context. This 523 * is the main function of the TrueType opcode interpreter. 524 * 525 * @Input: 526 * exec :: 527 * A handle to the target execution context. 528 * 529 * @Return: 530 * FreeType error code. 0 means success. 531 * 532 * @Note: 533 * Only the object manager and debugger should call this function. 534 * 535 * This function is publicly exported because it is directly 536 * invoked by the TrueType debugger. 537 */ 538 FT_EXPORT( FT_Error ) 539 TT_RunIns( TT_ExecContext exec ); 540 541 542 FT_END_HEADER 543 544 #endif /* TTINTERP_H_ */ 545 546 547 /* END */ 548