ftdriver.h (50570B)
1 /**************************************************************************** 2 * 3 * ftdriver.h 4 * 5 * FreeType API for controlling driver modules (specification only). 6 * 7 * Copyright (C) 2017-2025 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 FTDRIVER_H_ 20 #define FTDRIVER_H_ 21 22 #include <freetype/freetype.h> 23 #include <freetype/ftparams.h> 24 25 #ifdef FREETYPE_H 26 #error "freetype.h of FreeType 1 has been loaded!" 27 #error "Please fix the directory search order for header files" 28 #error "so that freetype.h of FreeType 2 is found first." 29 #endif 30 31 32 FT_BEGIN_HEADER 33 34 35 /************************************************************************** 36 * 37 * @section: 38 * auto_hinter 39 * 40 * @title: 41 * The auto-hinter 42 * 43 * @abstract: 44 * Controlling the auto-hinting module. 45 * 46 * @description: 47 * While FreeType's auto-hinter doesn't expose API functions by itself, 48 * it is possible to control its behaviour with @FT_Property_Set and 49 * @FT_Property_Get. The following lists the available properties 50 * together with the necessary macros and structures. 51 * 52 * Note that the auto-hinter's module name is 'autofitter' for historical 53 * reasons. 54 * 55 * Available properties are @increase-x-height, @no-stem-darkening 56 * (experimental), @darkening-parameters (experimental), 57 * @glyph-to-script-map (experimental), @fallback-script (experimental), 58 * and @default-script (experimental), as documented in the @properties 59 * section. 60 * 61 */ 62 63 64 /************************************************************************** 65 * 66 * @section: 67 * cff_driver 68 * 69 * @title: 70 * The CFF driver 71 * 72 * @abstract: 73 * Controlling the CFF driver module. 74 * 75 * @description: 76 * While FreeType's CFF driver doesn't expose API functions by itself, it 77 * is possible to control its behaviour with @FT_Property_Set and 78 * @FT_Property_Get. 79 * 80 * The CFF driver's module name is 'cff'. 81 * 82 * Available properties are @hinting-engine, @no-stem-darkening, 83 * @darkening-parameters, and @random-seed, as documented in the 84 * @properties section. 85 * 86 * 87 * **Hinting and anti-aliasing principles of the new engine** 88 * 89 * The rasterizer is positioning horizontal features (e.g., ascender 90 * height & x-height, or crossbars) on the pixel grid and minimizing the 91 * amount of anti-aliasing applied to them, while placing vertical 92 * features (vertical stems) on the pixel grid without hinting, thus 93 * representing the stem position and weight accurately. Sometimes the 94 * vertical stems may be only partially black. In this context, 95 * 'anti-aliasing' means that stems are not positioned exactly on pixel 96 * borders, causing a fuzzy appearance. 97 * 98 * There are two principles behind this approach. 99 * 100 * 1) No hinting in the horizontal direction: Unlike 'superhinted' 101 * TrueType, which changes glyph widths to accommodate regular 102 * inter-glyph spacing, Adobe's approach is 'faithful to the design' in 103 * representing both the glyph width and the inter-glyph spacing designed 104 * for the font. This makes the screen display as close as it can be to 105 * the result one would get with infinite resolution, while preserving 106 * what is considered the key characteristics of each glyph. Note that 107 * the distances between unhinted and grid-fitted positions at small 108 * sizes are comparable to kerning values and thus would be noticeable 109 * (and distracting) while reading if hinting were applied. 110 * 111 * One of the reasons to not hint horizontally is anti-aliasing for LCD 112 * screens: The pixel geometry of modern displays supplies three vertical 113 * subpixels as the eye moves horizontally across each visible pixel. On 114 * devices where we can be certain this characteristic is present a 115 * rasterizer can take advantage of the subpixels to add increments of 116 * weight. In Western writing systems this turns out to be the more 117 * critical direction anyway; the weights and spacing of vertical stems 118 * (see above) are central to Armenian, Cyrillic, Greek, and Latin type 119 * designs. Even when the rasterizer uses greyscale anti-aliasing instead 120 * of color (a necessary compromise when one doesn't know the screen 121 * characteristics), the unhinted vertical features preserve the design's 122 * weight and spacing much better than aliased type would. 123 * 124 * 2) Alignment in the vertical direction: Weights and spacing along the 125 * y~axis are less critical; what is much more important is the visual 126 * alignment of related features (like cap-height and x-height). The 127 * sense of alignment for these is enhanced by the sharpness of grid-fit 128 * edges, while the cruder vertical resolution (full pixels instead of 129 * 1/3 pixels) is less of a problem. 130 * 131 * On the technical side, horizontal alignment zones for ascender, 132 * x-height, and other important height values (traditionally called 133 * 'blue zones') as defined in the font are positioned independently, 134 * each being rounded to the nearest pixel edge, taking care of overshoot 135 * suppression at small sizes, stem darkening, and scaling. 136 * 137 * Hstems (that is, hint values defined in the font to help align 138 * horizontal features) that fall within a blue zone are said to be 139 * 'captured' and are aligned to that zone. Uncaptured stems are moved 140 * in one of four ways, top edge up or down, bottom edge up or down. 141 * Unless there are conflicting hstems, the smallest movement is taken to 142 * minimize distortion. 143 * 144 */ 145 146 147 /************************************************************************** 148 * 149 * @section: 150 * pcf_driver 151 * 152 * @title: 153 * The PCF driver 154 * 155 * @abstract: 156 * Controlling the PCF driver module. 157 * 158 * @description: 159 * While FreeType's PCF driver doesn't expose API functions by itself, it 160 * is possible to control its behaviour with @FT_Property_Set and 161 * @FT_Property_Get. Right now, there is a single property 162 * @no-long-family-names available if FreeType is compiled with 163 * PCF_CONFIG_OPTION_LONG_FAMILY_NAMES. 164 * 165 * The PCF driver's module name is 'pcf'. 166 * 167 */ 168 169 170 /************************************************************************** 171 * 172 * @section: 173 * t1_cid_driver 174 * 175 * @title: 176 * The Type 1 and CID drivers 177 * 178 * @abstract: 179 * Controlling the Type~1 and CID driver modules. 180 * 181 * @description: 182 * It is possible to control the behaviour of FreeType's Type~1 and 183 * Type~1 CID drivers with @FT_Property_Set and @FT_Property_Get. 184 * 185 * Behind the scenes, both drivers use the Adobe CFF engine for hinting; 186 * however, the used properties must be specified separately. 187 * 188 * The Type~1 driver's module name is 'type1'; the CID driver's module 189 * name is 't1cid'. 190 * 191 * Available properties are @hinting-engine, @no-stem-darkening, 192 * @darkening-parameters, and @random-seed, as documented in the 193 * @properties section. 194 * 195 * Please see the @cff_driver section for more details on the new hinting 196 * engine. 197 * 198 */ 199 200 201 /************************************************************************** 202 * 203 * @section: 204 * tt_driver 205 * 206 * @title: 207 * The TrueType driver 208 * 209 * @abstract: 210 * Controlling the TrueType driver module. 211 * 212 * @description: 213 * While FreeType's TrueType driver doesn't expose API functions by 214 * itself, it is possible to control its behaviour with @FT_Property_Set 215 * and @FT_Property_Get. 216 * 217 * The TrueType driver's module name is 'truetype'; a single property 218 * @interpreter-version is available, as documented in the @properties 219 * section. 220 * 221 * To help understand the differences between interpreter versions, we 222 * introduce a list of definitions, kindly provided by Greg Hitchcock. 223 * 224 * _Bi-Level Rendering_ 225 * 226 * Monochromatic rendering, exclusively used in the early days of 227 * TrueType by both Apple and Microsoft. Microsoft's GDI interface 228 * supported hinting of the right-side bearing point, such that the 229 * advance width could be non-linear. Most often this was done to 230 * achieve some level of glyph symmetry. To enable reasonable 231 * performance (e.g., not having to run hinting on all glyphs just to get 232 * the widths) there was a bit in the head table indicating if the side 233 * bearing was hinted, and additional tables, 'hdmx' and 'LTSH', to cache 234 * hinting widths across multiple sizes and device aspect ratios. 235 * 236 * _Font Smoothing_ 237 * 238 * Microsoft's GDI implementation of anti-aliasing. Not traditional 239 * anti-aliasing as the outlines were hinted before the sampling. The 240 * widths matched the bi-level rendering. 241 * 242 * _ClearType Rendering_ 243 * 244 * Technique that uses physical subpixels to improve rendering on LCD 245 * (and other) displays. Because of the higher resolution, many methods 246 * of improving symmetry in glyphs through hinting the right-side bearing 247 * were no longer necessary. This lead to what GDI calls 'natural 248 * widths' ClearType, see 249 * http://rastertragedy.com/RTRCh4.htm#Sec21. Since hinting 250 * has extra resolution, most non-linearity went away, but it is still 251 * possible for hints to change the advance widths in this mode. 252 * 253 * _ClearType Compatible Widths_ 254 * 255 * One of the earliest challenges with ClearType was allowing the 256 * implementation in GDI to be selected without requiring all UI and 257 * documents to reflow. To address this, a compatible method of 258 * rendering ClearType was added where the font hints are executed once 259 * to determine the width in bi-level rendering, and then re-run in 260 * ClearType, with the difference in widths being absorbed in the font 261 * hints for ClearType (mostly in the white space of hints); see 262 * http://rastertragedy.com/RTRCh4.htm#Sec20. Somewhat by 263 * definition, compatible width ClearType allows for non-linear widths, 264 * but only when the bi-level version has non-linear widths. 265 * 266 * _ClearType Subpixel Positioning_ 267 * 268 * One of the nice benefits of ClearType is the ability to more crisply 269 * display fractional widths; unfortunately, the GDI model of integer 270 * bitmaps did not support this. However, the WPF and Direct Write 271 * frameworks do support fractional widths. DWrite calls this 'natural 272 * mode', not to be confused with GDI's 'natural widths'. Subpixel 273 * positioning, in the current implementation of Direct Write, 274 * unfortunately does not support hinted advance widths, see 275 * http://rastertragedy.com/RTRCh4.htm#Sec22. Note that the 276 * TrueType interpreter fully allows the advance width to be adjusted in 277 * this mode, just the DWrite client will ignore those changes. 278 * 279 * _ClearType Backward Compatibility_ 280 * 281 * This is a set of exceptions made in the TrueType interpreter to 282 * minimize hinting techniques that were problematic with the extra 283 * resolution of ClearType; see 284 * http://rastertragedy.com/RTRCh4.htm#Sec1 and 285 * https://learn.microsoft.com/typography/cleartype/truetypecleartype. 286 * This technique is not to be confused with ClearType compatible widths. 287 * ClearType backward compatibility has no direct impact on changing 288 * advance widths, but there might be an indirect impact on disabling 289 * some deltas. This could be worked around in backward compatibility 290 * mode. 291 * 292 * _Native ClearType Mode_ 293 * 294 * (Not to be confused with 'natural widths'.) This mode removes all the 295 * exceptions in the TrueType interpreter when running with ClearType. 296 * Any issues on widths would still apply, though. 297 * 298 */ 299 300 301 /************************************************************************** 302 * 303 * @section: 304 * ot_svg_driver 305 * 306 * @title: 307 * The SVG driver 308 * 309 * @abstract: 310 * Controlling the external rendering of OT-SVG glyphs. 311 * 312 * @description: 313 * By default, FreeType can only load the 'SVG~' table of OpenType fonts 314 * if configuration macro `FT_CONFIG_OPTION_SVG` is defined. To make it 315 * render SVG glyphs, an external SVG rendering library is needed. All 316 * details on the interface between FreeType and the external library 317 * via function hooks can be found in section @svg_fonts. 318 * 319 * The OT-SVG driver's module name is 'ot-svg'; it supports a single 320 * property called @svg-hooks, documented below in the @properties 321 * section. 322 * 323 */ 324 325 326 /************************************************************************** 327 * 328 * @section: 329 * properties 330 * 331 * @title: 332 * Driver properties 333 * 334 * @abstract: 335 * Controlling driver modules. 336 * 337 * @description: 338 * Driver modules can be controlled by setting and unsetting properties, 339 * using the functions @FT_Property_Set and @FT_Property_Get. This 340 * section documents the available properties, together with auxiliary 341 * macros and structures. 342 * 343 */ 344 345 346 /************************************************************************** 347 * 348 * @enum: 349 * FT_HINTING_XXX 350 * 351 * @description: 352 * A list of constants used for the @hinting-engine property to select 353 * the hinting engine for CFF, Type~1, and CID fonts. 354 * 355 * @values: 356 * FT_HINTING_FREETYPE :: 357 * Use the old FreeType hinting engine. 358 * 359 * FT_HINTING_ADOBE :: 360 * Use the hinting engine contributed by Adobe. 361 * 362 * @since: 363 * 2.9 364 * 365 */ 366 #define FT_HINTING_FREETYPE 0 367 #define FT_HINTING_ADOBE 1 368 369 /* these constants (introduced in 2.4.12) are deprecated */ 370 #define FT_CFF_HINTING_FREETYPE FT_HINTING_FREETYPE 371 #define FT_CFF_HINTING_ADOBE FT_HINTING_ADOBE 372 373 374 /************************************************************************** 375 * 376 * @property: 377 * hinting-engine 378 * 379 * @description: 380 * Thanks to Adobe, which contributed a new hinting (and parsing) engine, 381 * an application can select between 'freetype' and 'adobe' if compiled 382 * with `CFF_CONFIG_OPTION_OLD_ENGINE`. If this configuration macro 383 * isn't defined, 'hinting-engine' does nothing. 384 * 385 * The same holds for the Type~1 and CID modules if compiled with 386 * `T1_CONFIG_OPTION_OLD_ENGINE`. 387 * 388 * For the 'cff' module, the default engine is 'adobe'. For both the 389 * 'type1' and 't1cid' modules, the default engine is 'adobe', too. 390 * 391 * @note: 392 * This property can be used with @FT_Property_Get also. 393 * 394 * This property can be set via the `FREETYPE_PROPERTIES` environment 395 * variable (using values 'adobe' or 'freetype'). 396 * 397 * @example: 398 * The following example code demonstrates how to select Adobe's hinting 399 * engine for the 'cff' module (omitting the error handling). 400 * 401 * ``` 402 * FT_Library library; 403 * FT_UInt hinting_engine = FT_HINTING_ADOBE; 404 * 405 * 406 * FT_Init_FreeType( &library ); 407 * 408 * FT_Property_Set( library, "cff", 409 * "hinting-engine", &hinting_engine ); 410 * ``` 411 * 412 * @since: 413 * 2.4.12 (for 'cff' module) 414 * 415 * 2.9 (for 'type1' and 't1cid' modules) 416 * 417 */ 418 419 420 /************************************************************************** 421 * 422 * @property: 423 * no-stem-darkening 424 * 425 * @description: 426 * All glyphs that pass through the auto-hinter will be emboldened unless 427 * this property is set to TRUE. The same is true for the CFF, Type~1, 428 * and CID font modules if the 'Adobe' engine is selected (which is the 429 * default). 430 * 431 * Stem darkening emboldens glyphs at smaller sizes to make them more 432 * readable on common low-DPI screens when using linear alpha blending 433 * and gamma correction, see @FT_Render_Glyph. When not using linear 434 * alpha blending and gamma correction, glyphs will appear heavy and 435 * fuzzy! 436 * 437 * Gamma correction essentially lightens fonts since shades of grey are 438 * shifted to higher pixel values (=~higher brightness) to match the 439 * original intention to the reality of our screens. The side-effect is 440 * that glyphs 'thin out'. Mac OS~X and Adobe's proprietary font 441 * rendering library implement a counter-measure: stem darkening at 442 * smaller sizes where shades of gray dominate. By emboldening a glyph 443 * slightly in relation to its pixel size, individual pixels get higher 444 * coverage of filled-in outlines and are therefore 'blacker'. This 445 * counteracts the 'thinning out' of glyphs, making text remain readable 446 * at smaller sizes. 447 * 448 * For the auto-hinter, stem-darkening is experimental currently and thus 449 * switched off by default (that is, `no-stem-darkening` is set to TRUE 450 * by default). Total consistency with the CFF driver is not achieved 451 * right now because the emboldening method differs and glyphs must be 452 * scaled down on the Y-axis to keep outline points inside their 453 * precomputed blue zones. The smaller the size (especially 9ppem and 454 * down), the higher the loss of emboldening versus the CFF driver. 455 * 456 * Note that stem darkening is never applied if @FT_LOAD_NO_SCALE is set. 457 * 458 * @note: 459 * This property can be used with @FT_Property_Get also. 460 * 461 * This property can be set via the `FREETYPE_PROPERTIES` environment 462 * variable (using values 1 and 0 for 'on' and 'off', respectively). It 463 * can also be set per face using @FT_Face_Properties with 464 * @FT_PARAM_TAG_STEM_DARKENING. 465 * 466 * @example: 467 * ``` 468 * FT_Library library; 469 * FT_Bool no_stem_darkening = TRUE; 470 * 471 * 472 * FT_Init_FreeType( &library ); 473 * 474 * FT_Property_Set( library, "cff", 475 * "no-stem-darkening", &no_stem_darkening ); 476 * ``` 477 * 478 * @since: 479 * 2.4.12 (for 'cff' module) 480 * 481 * 2.6.2 (for 'autofitter' module) 482 * 483 * 2.9 (for 'type1' and 't1cid' modules) 484 * 485 */ 486 487 488 /************************************************************************** 489 * 490 * @property: 491 * darkening-parameters 492 * 493 * @description: 494 * By default, the Adobe hinting engine, as used by the CFF, Type~1, and 495 * CID font drivers, darkens stems as follows (if the `no-stem-darkening` 496 * property isn't set): 497 * 498 * ``` 499 * stem width <= 0.5px: darkening amount = 0.4px 500 * stem width = 1px: darkening amount = 0.275px 501 * stem width = 1.667px: darkening amount = 0.275px 502 * stem width >= 2.333px: darkening amount = 0px 503 * ``` 504 * 505 * and piecewise linear in-between. At configuration time, these four 506 * control points can be set with the macro 507 * `CFF_CONFIG_OPTION_DARKENING_PARAMETERS`; the CFF, Type~1, and CID 508 * drivers share these values. At runtime, the control points can be 509 * changed using the `darkening-parameters` property (see the example 510 * below that demonstrates this for the Type~1 driver). 511 * 512 * The x~values give the stem width, and the y~values the darkening 513 * amount. The unit is 1000th of pixels. All coordinate values must be 514 * positive; the x~values must be monotonically increasing; the y~values 515 * must be monotonically decreasing and smaller than or equal to 500 516 * (corresponding to half a pixel); the slope of each linear piece must 517 * be shallower than -1 (e.g., -.4). 518 * 519 * The auto-hinter provides this property, too, as an experimental 520 * feature. See @no-stem-darkening for more. 521 * 522 * @note: 523 * This property can be used with @FT_Property_Get also. 524 * 525 * This property can be set via the `FREETYPE_PROPERTIES` environment 526 * variable, using eight comma-separated integers without spaces. Here 527 * the above example, using `\` to break the line for readability. 528 * 529 * ``` 530 * FREETYPE_PROPERTIES=\ 531 * type1:darkening-parameters=500,300,1000,200,1500,100,2000,0 532 * ``` 533 * 534 * @example: 535 * ``` 536 * FT_Library library; 537 * FT_Int darken_params[8] = { 500, 300, // x1, y1 538 * 1000, 200, // x2, y2 539 * 1500, 100, // x3, y3 540 * 2000, 0 }; // x4, y4 541 * 542 * 543 * FT_Init_FreeType( &library ); 544 * 545 * FT_Property_Set( library, "type1", 546 * "darkening-parameters", darken_params ); 547 * ``` 548 * 549 * @since: 550 * 2.5.1 (for 'cff' module) 551 * 552 * 2.6.2 (for 'autofitter' module) 553 * 554 * 2.9 (for 'type1' and 't1cid' modules) 555 * 556 */ 557 558 559 /************************************************************************** 560 * 561 * @property: 562 * random-seed 563 * 564 * @description: 565 * By default, the seed value for the CFF 'random' operator and the 566 * similar '0 28 callothersubr pop' command for the Type~1 and CID 567 * drivers is set to a random value. However, mainly for debugging 568 * purposes, it is often necessary to use a known value as a seed so that 569 * the pseudo-random number sequences generated by 'random' are 570 * repeatable. 571 * 572 * The `random-seed` property does that. Its argument is a signed 32bit 573 * integer; if the value is zero or negative, the seed given by the 574 * `intitialRandomSeed` private DICT operator in a CFF file gets used (or 575 * a default value if there is no such operator). If the value is 576 * positive, use it instead of `initialRandomSeed`, which is consequently 577 * ignored. 578 * 579 * @note: 580 * This property can be set via the `FREETYPE_PROPERTIES` environment 581 * variable. It can also be set per face using @FT_Face_Properties with 582 * @FT_PARAM_TAG_RANDOM_SEED. 583 * 584 * @since: 585 * 2.8 (for 'cff' module) 586 * 587 * 2.9 (for 'type1' and 't1cid' modules) 588 * 589 */ 590 591 592 /************************************************************************** 593 * 594 * @property: 595 * no-long-family-names 596 * 597 * @description: 598 * If `PCF_CONFIG_OPTION_LONG_FAMILY_NAMES` is active while compiling 599 * FreeType, the PCF driver constructs long family names. 600 * 601 * There are many PCF fonts just called 'Fixed' which look completely 602 * different, and which have nothing to do with each other. When 603 * selecting 'Fixed' in KDE or Gnome one gets results that appear rather 604 * random, the style changes often if one changes the size and one cannot 605 * select some fonts at all. The improve this situation, the PCF module 606 * prepends the foundry name (plus a space) to the family name. It also 607 * checks whether there are 'wide' characters; all put together, family 608 * names like 'Sony Fixed' or 'Misc Fixed Wide' are constructed. 609 * 610 * If `no-long-family-names` is set, this feature gets switched off. 611 * 612 * @note: 613 * This property can be used with @FT_Property_Get also. 614 * 615 * This property can be set via the `FREETYPE_PROPERTIES` environment 616 * variable (using values 1 and 0 for 'on' and 'off', respectively). 617 * 618 * @example: 619 * ``` 620 * FT_Library library; 621 * FT_Bool no_long_family_names = TRUE; 622 * 623 * 624 * FT_Init_FreeType( &library ); 625 * 626 * FT_Property_Set( library, "pcf", 627 * "no-long-family-names", 628 * &no_long_family_names ); 629 * ``` 630 * 631 * @since: 632 * 2.8 633 */ 634 635 636 /************************************************************************** 637 * 638 * @enum: 639 * TT_INTERPRETER_VERSION_XXX 640 * 641 * @description: 642 * A list of constants used for the @interpreter-version property to 643 * select the hinting engine for Truetype fonts. 644 * 645 * The numeric value in the constant names represents the version number 646 * as returned by the 'GETINFO' bytecode instruction. 647 * 648 * @values: 649 * TT_INTERPRETER_VERSION_35 :: 650 * Version~35 corresponds to MS rasterizer v.1.7 as used e.g. in 651 * Windows~98; only grayscale and B/W rasterizing is supported. 652 * 653 * TT_INTERPRETER_VERSION_38 :: 654 * Version~38 is the same Version~40. The original 'Infinality' code is 655 * no longer available. 656 * 657 * TT_INTERPRETER_VERSION_40 :: 658 * Version~40 corresponds to MS rasterizer v.2.1; it is roughly 659 * equivalent to the hinting provided by DirectWrite ClearType (as can 660 * be found, for example, in Microsoft's Edge Browser on Windows~10). 661 * It is used in FreeType to select the 'minimal' subpixel hinting 662 * code, a stripped-down and higher performance version of the 663 * 'Infinality' code. 664 * 665 * @note: 666 * This property controls the behaviour of the bytecode interpreter and 667 * thus how outlines get hinted. It does **not** control how glyph get 668 * rasterized! In particular, it does not control subpixel color 669 * filtering. 670 * 671 * If FreeType has not been compiled with the configuration option 672 * `TT_CONFIG_OPTION_SUBPIXEL_HINTING`, selecting version~38 or~40 causes 673 * an `FT_Err_Unimplemented_Feature` error. 674 * 675 * Depending on the graphics framework, Microsoft uses different bytecode 676 * and rendering engines. As a consequence, the version numbers returned 677 * by a call to the 'GETINFO' bytecode instruction are more convoluted 678 * than desired. 679 * 680 * Here are two tables that try to shed some light on the possible values 681 * for the MS rasterizer engine, together with the additional features 682 * introduced by it. 683 * 684 * ``` 685 * GETINFO framework version feature 686 * ------------------------------------------------------------------- 687 * 3 GDI (Win 3.1), v1.0 16-bit, first version 688 * TrueImage 689 * 33 GDI (Win NT 3.1), v1.5 32-bit 690 * HP Laserjet 691 * 34 GDI (Win 95) v1.6 font smoothing, 692 * new SCANTYPE opcode 693 * 35 GDI (Win 98/2000) v1.7 (UN)SCALED_COMPONENT_OFFSET 694 * bits in composite glyphs 695 * 36 MGDI (Win CE 2) v1.6+ classic ClearType 696 * 37 GDI (XP and later), v1.8 ClearType 697 * GDI+ old (before Vista) 698 * 38 GDI+ old (Vista, Win 7), v1.9 subpixel ClearType, 699 * WPF Y-direction ClearType, 700 * additional error checking 701 * 39 DWrite (before Win 8) v2.0 subpixel ClearType flags 702 * in GETINFO opcode, 703 * bug fixes 704 * 40 GDI+ (after Win 7), v2.1 Y-direction ClearType flag 705 * DWrite (Win 8) in GETINFO opcode, 706 * Gray ClearType 707 * ``` 708 * 709 * The 'version' field gives a rough orientation only, since some 710 * applications provided certain features much earlier (as an example, 711 * Microsoft Reader used subpixel and Y-direction ClearType already in 712 * Windows 2000). Similarly, updates to a given framework might include 713 * improved hinting support. 714 * 715 * ``` 716 * version sampling rendering comment 717 * x y x y 718 * -------------------------------------------------------------- 719 * v1.0 normal normal B/W B/W bi-level 720 * v1.6 high high gray gray grayscale 721 * v1.8 high normal color-filter B/W (GDI) ClearType 722 * v1.9 high high color-filter gray Color ClearType 723 * v2.1 high normal gray B/W Gray ClearType 724 * v2.1 high high gray gray Gray ClearType 725 * ``` 726 * 727 * Color and Gray ClearType are the two available variants of 728 * 'Y-direction ClearType', meaning grayscale rasterization along the 729 * Y-direction; the name used in the TrueType specification for this 730 * feature is 'symmetric smoothing'. 'Classic ClearType' is the original 731 * algorithm used before introducing a modified version in Win~XP. 732 * Another name for v1.6's grayscale rendering is 'font smoothing', and 733 * 'Color ClearType' is sometimes also called 'DWrite ClearType'. To 734 * differentiate between today's Color ClearType and the earlier 735 * ClearType variant with B/W rendering along the vertical axis, the 736 * latter is sometimes called 'GDI ClearType'. 737 * 738 * 'Normal' and 'high' sampling describe the (virtual) resolution to 739 * access the rasterized outline after the hinting process. 'Normal' 740 * means 1 sample per grid line (i.e., B/W). In the current Microsoft 741 * implementation, 'high' means an extra virtual resolution of 16x16 (or 742 * 16x1) grid lines per pixel for bytecode instructions like 'MIRP'. 743 * After hinting, these 16 grid lines are mapped to 6x5 (or 6x1) grid 744 * lines for color filtering if Color ClearType is activated. 745 * 746 * Note that 'Gray ClearType' is essentially the same as v1.6's grayscale 747 * rendering. However, the GETINFO instruction handles it differently: 748 * v1.6 returns bit~12 (hinting for grayscale), while v2.1 returns 749 * bits~13 (hinting for ClearType), 18 (symmetrical smoothing), and~19 750 * (Gray ClearType). Also, this mode respects bits 2 and~3 for the 751 * version~1 gasp table exclusively (like Color ClearType), while v1.6 752 * only respects the values of version~0 (bits 0 and~1). 753 * 754 * Keep in mind that the features of the above interpreter versions might 755 * not map exactly to FreeType features or behavior because it is a 756 * fundamentally different library with different internals. 757 * 758 */ 759 #define TT_INTERPRETER_VERSION_35 35 760 #define TT_INTERPRETER_VERSION_38 38 761 #define TT_INTERPRETER_VERSION_40 40 762 763 764 /************************************************************************** 765 * 766 * @property: 767 * interpreter-version 768 * 769 * @description: 770 * Currently, three versions are available, two representing the bytecode 771 * interpreter with subpixel hinting support (old 'Infinality' code and 772 * new stripped-down and higher performance 'minimal' code) and one 773 * without, respectively. The default is subpixel support if 774 * `TT_CONFIG_OPTION_SUBPIXEL_HINTING` is defined, and no subpixel 775 * support otherwise (since it isn't available then). 776 * 777 * If subpixel hinting is on, many TrueType bytecode instructions behave 778 * differently compared to B/W or grayscale rendering (except if 'native 779 * ClearType' is selected by the font). Microsoft's main idea is to 780 * render at a much increased horizontal resolution, then sampling down 781 * the created output to subpixel precision. However, many older fonts 782 * are not suited to this and must be specially taken care of by applying 783 * (hardcoded) tweaks in Microsoft's interpreter. 784 * 785 * Details on subpixel hinting and some of the necessary tweaks can be 786 * found in Greg Hitchcock's whitepaper at 787 * 'https://learn.microsoft.com/typography/cleartype/truetypecleartype'. 788 * Note that FreeType currently doesn't really 'subpixel hint' (6x1, 6x2, 789 * or 6x5 supersampling) like discussed in the paper. Depending on the 790 * chosen interpreter, it simply ignores instructions on vertical stems 791 * to arrive at very similar results. 792 * 793 * @note: 794 * This property can be used with @FT_Property_Get also. 795 * 796 * This property can be set via the `FREETYPE_PROPERTIES` environment 797 * variable (using values '35', '38', or '40'). 798 * 799 * @example: 800 * The following example code demonstrates how to deactivate subpixel 801 * hinting (omitting the error handling). 802 * 803 * ``` 804 * FT_Library library; 805 * FT_Face face; 806 * FT_UInt interpreter_version = TT_INTERPRETER_VERSION_35; 807 * 808 * 809 * FT_Init_FreeType( &library ); 810 * 811 * FT_Property_Set( library, "truetype", 812 * "interpreter-version", 813 * &interpreter_version ); 814 * ``` 815 * 816 * @since: 817 * 2.5 818 */ 819 820 821 /************************************************************************** 822 * 823 * @property: 824 * spread 825 * 826 * @description: 827 * This property of the 'sdf' and 'bsdf' renderers defines how the signed 828 * distance field (SDF) is represented in the output bitmap. The output 829 * values are calculated as follows, '128 * ( SDF / spread + 1 )', with 830 * the result clamped to the 8-bit range [0..255]. Therefore, 'spread' 831 * is also the maximum euclidean distance from the edge after which the 832 * values are clamped. The spread is specified in pixels with the 833 * default value of 8. For accurate SDF texture mapping (interpolation), 834 * the spread should be large enough to accommodate the target grid unit. 835 * 836 * @example: 837 * The following example code demonstrates how to set the SDF spread 838 * (omitting the error handling). 839 * 840 * ``` 841 * FT_Library library; 842 * FT_Int spread = 2; 843 * 844 * 845 * FT_Init_FreeType( &library ); 846 * 847 * FT_Property_Set( library, "sdf", "spread", &spread ); 848 * ``` 849 * 850 * @note: 851 * FreeType has two rasterizers for generating SDF, namely: 852 * 853 * 1. `sdf` for generating SDF directly from glyph's outline, and 854 * 855 * 2. `bsdf` for generating SDF from rasterized bitmaps. 856 * 857 * Depending on the glyph type (i.e., outline or bitmap), one of the two 858 * rasterizers is chosen at runtime and used for generating SDFs. To 859 * force the use of `bsdf` you should render the glyph with any of the 860 * FreeType's other rendering modes (e.g., `FT_RENDER_MODE_NORMAL`) and 861 * then re-render with `FT_RENDER_MODE_SDF`. 862 * 863 * There are some issues with stability and possible failures of the SDF 864 * renderers (specifically `sdf`). 865 * 866 * 1. The `sdf` rasterizer is sensitive to really small features (e.g., 867 * sharp turns that are less than 1~pixel) and imperfections in the 868 * glyph's outline, causing artifacts in the final output. 869 * 870 * 2. The `sdf` rasterizer has limited support for handling intersecting 871 * contours and *cannot* handle self-intersecting contours whatsoever. 872 * Self-intersection happens when a single connected contour 873 * intersects itself at some point; having these in your font 874 * definitely poses a problem to the rasterizer and cause artifacts, 875 * too. 876 * 877 * 3. Generating SDF for really small glyphs may result in undesirable 878 * output; the pixel grid (which stores distance information) becomes 879 * too coarse. 880 * 881 * 4. Since the output buffer is normalized, precision at smaller spreads 882 * is greater than precision at larger spread values because the 883 * output range of [0..255] gets mapped to a smaller SDF range. A 884 * spread of~2 should be sufficient in most cases. 885 * 886 * Points (1) and (2) can be avoided by using the `bsdf` rasterizer, 887 * which is more stable than the `sdf` rasterizer in general. 888 * 889 * @since: 890 * 2.11 891 */ 892 893 894 /************************************************************************** 895 * 896 * @property: 897 * svg-hooks 898 * 899 * @description: 900 * Set up the interface between FreeType and an extern SVG rendering 901 * library like 'librsvg'. All details on the function hooks can be 902 * found in section @svg_fonts. 903 * 904 * @example: 905 * The following example code expects that the four hook functions 906 * `svg_*` are defined elsewhere. Error handling is omitted, too. 907 * 908 * ``` 909 * FT_Library library; 910 * SVG_RendererHooks hooks = { 911 * (SVG_Lib_Init_Func)svg_init, 912 * (SVG_Lib_Free_Func)svg_free, 913 * (SVG_Lib_Render_Func)svg_render, 914 * (SVG_Lib_Preset_Slot_Func)svg_preset_slot }; 915 * 916 * 917 * FT_Init_FreeType( &library ); 918 * 919 * FT_Property_Set( library, "ot-svg", 920 * "svg-hooks", &hooks ); 921 * ``` 922 * 923 * @since: 924 * 2.12 925 */ 926 927 928 /************************************************************************** 929 * 930 * @property: 931 * glyph-to-script-map 932 * 933 * @description: 934 * **Experimental only** 935 * 936 * The auto-hinter provides various script modules to hint glyphs. 937 * Examples of supported scripts are Latin or CJK. Before a glyph is 938 * auto-hinted, the Unicode character map of the font gets examined, and 939 * the script is then determined based on Unicode character ranges, see 940 * below. 941 * 942 * OpenType fonts, however, often provide much more glyphs than character 943 * codes (small caps, superscripts, ligatures, swashes, etc.), to be 944 * controlled by so-called 'features'. Handling OpenType features can be 945 * quite complicated and thus needs a separate library on top of 946 * FreeType. 947 * 948 * The mapping between glyph indices and scripts (in the auto-hinter 949 * sense, see the @FT_AUTOHINTER_SCRIPT_XXX values) is stored as an array 950 * with `num_glyphs` elements, as found in the font's @FT_Face structure. 951 * The `glyph-to-script-map` property returns a pointer to this array, 952 * which can be modified as needed. Note that the modification should 953 * happen before the first glyph gets processed by the auto-hinter so 954 * that the global analysis of the font shapes actually uses the modified 955 * mapping. 956 * 957 * @example: 958 * The following example code demonstrates how to access it (omitting the 959 * error handling). 960 * 961 * ``` 962 * FT_Library library; 963 * FT_Face face; 964 * FT_Prop_GlyphToScriptMap prop; 965 * 966 * 967 * FT_Init_FreeType( &library ); 968 * FT_New_Face( library, "foo.ttf", 0, &face ); 969 * 970 * prop.face = face; 971 * 972 * FT_Property_Get( library, "autofitter", 973 * "glyph-to-script-map", &prop ); 974 * 975 * // adjust `prop.map' as needed right here 976 * 977 * FT_Load_Glyph( face, ..., FT_LOAD_FORCE_AUTOHINT ); 978 * ``` 979 * 980 * @since: 981 * 2.4.11 982 * 983 */ 984 985 986 /************************************************************************** 987 * 988 * @enum: 989 * FT_AUTOHINTER_SCRIPT_XXX 990 * 991 * @description: 992 * **Experimental only** 993 * 994 * A list of constants used for the @glyph-to-script-map property to 995 * specify the script submodule the auto-hinter should use for hinting a 996 * particular glyph. 997 * 998 * @values: 999 * FT_AUTOHINTER_SCRIPT_NONE :: 1000 * Don't auto-hint this glyph. 1001 * 1002 * FT_AUTOHINTER_SCRIPT_LATIN :: 1003 * Apply the latin auto-hinter. For the auto-hinter, 'latin' is a very 1004 * broad term, including Cyrillic and Greek also since characters from 1005 * those scripts share the same design constraints. 1006 * 1007 * By default, characters from the following Unicode ranges are 1008 * assigned to this submodule. 1009 * 1010 * ``` 1011 * U+0020 - U+007F // Basic Latin (no control characters) 1012 * U+00A0 - U+00FF // Latin-1 Supplement (no control characters) 1013 * U+0100 - U+017F // Latin Extended-A 1014 * U+0180 - U+024F // Latin Extended-B 1015 * U+0250 - U+02AF // IPA Extensions 1016 * U+02B0 - U+02FF // Spacing Modifier Letters 1017 * U+0300 - U+036F // Combining Diacritical Marks 1018 * U+0370 - U+03FF // Greek and Coptic 1019 * U+0400 - U+04FF // Cyrillic 1020 * U+0500 - U+052F // Cyrillic Supplement 1021 * U+1D00 - U+1D7F // Phonetic Extensions 1022 * U+1D80 - U+1DBF // Phonetic Extensions Supplement 1023 * U+1DC0 - U+1DFF // Combining Diacritical Marks Supplement 1024 * U+1E00 - U+1EFF // Latin Extended Additional 1025 * U+1F00 - U+1FFF // Greek Extended 1026 * U+2000 - U+206F // General Punctuation 1027 * U+2070 - U+209F // Superscripts and Subscripts 1028 * U+20A0 - U+20CF // Currency Symbols 1029 * U+2150 - U+218F // Number Forms 1030 * U+2460 - U+24FF // Enclosed Alphanumerics 1031 * U+2C60 - U+2C7F // Latin Extended-C 1032 * U+2DE0 - U+2DFF // Cyrillic Extended-A 1033 * U+2E00 - U+2E7F // Supplemental Punctuation 1034 * U+A640 - U+A69F // Cyrillic Extended-B 1035 * U+A720 - U+A7FF // Latin Extended-D 1036 * U+FB00 - U+FB06 // Alphab. Present. Forms (Latin Ligatures) 1037 * U+1D400 - U+1D7FF // Mathematical Alphanumeric Symbols 1038 * U+1F100 - U+1F1FF // Enclosed Alphanumeric Supplement 1039 * ``` 1040 * 1041 * FT_AUTOHINTER_SCRIPT_CJK :: 1042 * Apply the CJK auto-hinter, covering Chinese, Japanese, Korean, old 1043 * Vietnamese, and some other scripts. 1044 * 1045 * By default, characters from the following Unicode ranges are 1046 * assigned to this submodule. 1047 * 1048 * ``` 1049 * U+1100 - U+11FF // Hangul Jamo 1050 * U+2E80 - U+2EFF // CJK Radicals Supplement 1051 * U+2F00 - U+2FDF // Kangxi Radicals 1052 * U+2FF0 - U+2FFF // Ideographic Description Characters 1053 * U+3000 - U+303F // CJK Symbols and Punctuation 1054 * U+3040 - U+309F // Hiragana 1055 * U+30A0 - U+30FF // Katakana 1056 * U+3100 - U+312F // Bopomofo 1057 * U+3130 - U+318F // Hangul Compatibility Jamo 1058 * U+3190 - U+319F // Kanbun 1059 * U+31A0 - U+31BF // Bopomofo Extended 1060 * U+31C0 - U+31EF // CJK Strokes 1061 * U+31F0 - U+31FF // Katakana Phonetic Extensions 1062 * U+3200 - U+32FF // Enclosed CJK Letters and Months 1063 * U+3300 - U+33FF // CJK Compatibility 1064 * U+3400 - U+4DBF // CJK Unified Ideographs Extension A 1065 * U+4DC0 - U+4DFF // Yijing Hexagram Symbols 1066 * U+4E00 - U+9FFF // CJK Unified Ideographs 1067 * U+A960 - U+A97F // Hangul Jamo Extended-A 1068 * U+AC00 - U+D7AF // Hangul Syllables 1069 * U+D7B0 - U+D7FF // Hangul Jamo Extended-B 1070 * U+F900 - U+FAFF // CJK Compatibility Ideographs 1071 * U+FE10 - U+FE1F // Vertical forms 1072 * U+FE30 - U+FE4F // CJK Compatibility Forms 1073 * U+FF00 - U+FFEF // Halfwidth and Fullwidth Forms 1074 * U+1B000 - U+1B0FF // Kana Supplement 1075 * U+1D300 - U+1D35F // Tai Xuan Hing Symbols 1076 * U+1F200 - U+1F2FF // Enclosed Ideographic Supplement 1077 * U+20000 - U+2A6DF // CJK Unified Ideographs Extension B 1078 * U+2A700 - U+2B73F // CJK Unified Ideographs Extension C 1079 * U+2B740 - U+2B81F // CJK Unified Ideographs Extension D 1080 * U+2F800 - U+2FA1F // CJK Compatibility Ideographs Supplement 1081 * ``` 1082 * 1083 * FT_AUTOHINTER_SCRIPT_INDIC :: 1084 * Apply the indic auto-hinter, covering all major scripts from the 1085 * Indian sub-continent and some other related scripts like Thai, Lao, 1086 * or Tibetan. 1087 * 1088 * By default, characters from the following Unicode ranges are 1089 * assigned to this submodule. 1090 * 1091 * ``` 1092 * U+0900 - U+0DFF // Indic Range 1093 * U+0F00 - U+0FFF // Tibetan 1094 * U+1900 - U+194F // Limbu 1095 * U+1B80 - U+1BBF // Sundanese 1096 * U+A800 - U+A82F // Syloti Nagri 1097 * U+ABC0 - U+ABFF // Meetei Mayek 1098 * U+11800 - U+118DF // Sharada 1099 * ``` 1100 * 1101 * Note that currently Indic support is rudimentary only, missing blue 1102 * zone support. 1103 * 1104 * @since: 1105 * 2.4.11 1106 * 1107 */ 1108 #define FT_AUTOHINTER_SCRIPT_NONE 0 1109 #define FT_AUTOHINTER_SCRIPT_LATIN 1 1110 #define FT_AUTOHINTER_SCRIPT_CJK 2 1111 #define FT_AUTOHINTER_SCRIPT_INDIC 3 1112 1113 1114 /************************************************************************** 1115 * 1116 * @struct: 1117 * FT_Prop_GlyphToScriptMap 1118 * 1119 * @description: 1120 * **Experimental only** 1121 * 1122 * The data exchange structure for the @glyph-to-script-map property. 1123 * 1124 * @since: 1125 * 2.4.11 1126 * 1127 */ 1128 typedef struct FT_Prop_GlyphToScriptMap_ 1129 { 1130 FT_Face face; 1131 FT_UShort* map; 1132 1133 } FT_Prop_GlyphToScriptMap; 1134 1135 1136 /************************************************************************** 1137 * 1138 * @property: 1139 * fallback-script 1140 * 1141 * @description: 1142 * **Experimental only** 1143 * 1144 * If no auto-hinter script module can be assigned to a glyph, a fallback 1145 * script gets assigned to it (see also the @glyph-to-script-map 1146 * property). By default, this is @FT_AUTOHINTER_SCRIPT_CJK. Using the 1147 * `fallback-script` property, this fallback value can be changed. 1148 * 1149 * @note: 1150 * This property can be used with @FT_Property_Get also. 1151 * 1152 * It's important to use the right timing for changing this value: The 1153 * creation of the glyph-to-script map that eventually uses the fallback 1154 * script value gets triggered either by setting or reading a 1155 * face-specific property like @glyph-to-script-map, or by auto-hinting 1156 * any glyph from that face. In particular, if you have already created 1157 * an @FT_Face structure but not loaded any glyph (using the 1158 * auto-hinter), a change of the fallback script will affect this face. 1159 * 1160 * @example: 1161 * ``` 1162 * FT_Library library; 1163 * FT_UInt fallback_script = FT_AUTOHINTER_SCRIPT_NONE; 1164 * 1165 * 1166 * FT_Init_FreeType( &library ); 1167 * 1168 * FT_Property_Set( library, "autofitter", 1169 * "fallback-script", &fallback_script ); 1170 * ``` 1171 * 1172 * @since: 1173 * 2.4.11 1174 * 1175 */ 1176 1177 1178 /************************************************************************** 1179 * 1180 * @property: 1181 * default-script 1182 * 1183 * @description: 1184 * **Experimental only** 1185 * 1186 * If FreeType gets compiled with `FT_CONFIG_OPTION_USE_HARFBUZZ` to make 1187 * the HarfBuzz library access OpenType features for getting better glyph 1188 * coverages, this property sets the (auto-fitter) script to be used for 1189 * the default (OpenType) script data of a font's GSUB table. Features 1190 * for the default script are intended for all scripts not explicitly 1191 * handled in GSUB; an example is a 'dlig' feature, containing the 1192 * combination of the characters 'T', 'E', and 'L' to form a 'TEL' 1193 * ligature. 1194 * 1195 * By default, this is @FT_AUTOHINTER_SCRIPT_LATIN. Using the 1196 * `default-script` property, this default value can be changed. 1197 * 1198 * @note: 1199 * This property can be used with @FT_Property_Get also. 1200 * 1201 * It's important to use the right timing for changing this value: The 1202 * creation of the glyph-to-script map that eventually uses the default 1203 * script value gets triggered either by setting or reading a 1204 * face-specific property like @glyph-to-script-map, or by auto-hinting 1205 * any glyph from that face. In particular, if you have already created 1206 * an @FT_Face structure but not loaded any glyph (using the 1207 * auto-hinter), a change of the default script will affect this face. 1208 * 1209 * @example: 1210 * ``` 1211 * FT_Library library; 1212 * FT_UInt default_script = FT_AUTOHINTER_SCRIPT_NONE; 1213 * 1214 * 1215 * FT_Init_FreeType( &library ); 1216 * 1217 * FT_Property_Set( library, "autofitter", 1218 * "default-script", &default_script ); 1219 * ``` 1220 * 1221 * @since: 1222 * 2.5.3 1223 * 1224 */ 1225 1226 1227 /************************************************************************** 1228 * 1229 * @property: 1230 * increase-x-height 1231 * 1232 * @description: 1233 * For ppem values in the range 6~<= ppem <= `increase-x-height`, round 1234 * up the font's x~height much more often than normally. If the value is 1235 * set to~0, which is the default, this feature is switched off. Use 1236 * this property to improve the legibility of small font sizes if 1237 * necessary. 1238 * 1239 * @note: 1240 * This property can be used with @FT_Property_Get also. 1241 * 1242 * Set this value right after calling @FT_Set_Char_Size, but before 1243 * loading any glyph (using the auto-hinter). 1244 * 1245 * @example: 1246 * ``` 1247 * FT_Library library; 1248 * FT_Face face; 1249 * FT_Prop_IncreaseXHeight prop; 1250 * 1251 * 1252 * FT_Init_FreeType( &library ); 1253 * FT_New_Face( library, "foo.ttf", 0, &face ); 1254 * FT_Set_Char_Size( face, 10 * 64, 0, 72, 0 ); 1255 * 1256 * prop.face = face; 1257 * prop.limit = 14; 1258 * 1259 * FT_Property_Set( library, "autofitter", 1260 * "increase-x-height", &prop ); 1261 * ``` 1262 * 1263 * @since: 1264 * 2.4.11 1265 * 1266 */ 1267 1268 1269 /************************************************************************** 1270 * 1271 * @struct: 1272 * FT_Prop_IncreaseXHeight 1273 * 1274 * @description: 1275 * The data exchange structure for the @increase-x-height property. 1276 * 1277 */ 1278 typedef struct FT_Prop_IncreaseXHeight_ 1279 { 1280 FT_Face face; 1281 FT_UInt limit; 1282 1283 } FT_Prop_IncreaseXHeight; 1284 1285 1286 /************************************************************************** 1287 * 1288 * @property: 1289 * warping 1290 * 1291 * @description: 1292 * **Obsolete** 1293 * 1294 * This property was always experimental and probably never worked 1295 * correctly. It was entirely removed from the FreeType~2 sources. This 1296 * entry is only here for historical reference. 1297 * 1298 * Warping only worked in 'normal' auto-hinting mode replacing it. The 1299 * idea of the code was to slightly scale and shift a glyph along the 1300 * non-hinted dimension (which is usually the horizontal axis) so that as 1301 * much of its segments were aligned (more or less) to the grid. To find 1302 * out a glyph's optimal scaling and shifting value, various parameter 1303 * combinations were tried and scored. 1304 * 1305 * @since: 1306 * 2.6 1307 * 1308 */ 1309 1310 1311 /* */ 1312 1313 1314 FT_END_HEADER 1315 1316 1317 #endif /* FTDRIVER_H_ */ 1318 1319 1320 /* END */