libass/ass_font.c

   1 /*
   2  * Copyright (C) 2006 Evgeniy Stepanov <eugeni.stepanov@gmail.com>
   3  *
   4  * This file is part of libass.
   5  *
   6  * Permission to use, copy, modify, and distribute this software for any
   7  * purpose with or without fee is hereby granted, provided that the above
   8  * copyright notice and this permission notice appear in all copies.
   9  *
  10  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  11  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  12  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  13  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  14  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  15  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  16  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  17  */
  18
  19 #include "config.h"
  20
  21 #include <inttypes.h>
  22 #include <ft2build.h>
  23 #include FT_FREETYPE_H
  24 #include FT_SYNTHESIS_H
  25 #include FT_GLYPH_H
  26 #include FT_TRUETYPE_TABLES_H
  27 #include FT_OUTLINE_H
  28 #include <strings.h>
  29
  30 #include "ass.h"
  31 #include "ass_library.h"
  32 #include "ass_font.h"
  33 #include "ass_fontconfig.h"
  34 #include "ass_utils.h"
  35 #include "ass_shaper.h"
  36
  37 #define VERTICAL_LOWER_BOUND 0x02f1
  38
  39 /**
  40  * Select a good charmap, prefer Microsoft Unicode charmaps.
  41  * Otherwise, let FreeType decide.
  42  */
  43 static void charmap_magic(ASS_Library *library, FT_Face face)
  44 {
  45     int i;
  46     int ms_cmap = -1;
  47
  48     // Search for a Microsoft Unicode cmap
  49     for (i = 0; i < face->num_charmaps; ++i) {
  50         FT_CharMap cmap = face->charmaps[i];
  51         unsigned pid = cmap->platform_id;
  52         unsigned eid = cmap->encoding_id;
  53         if (pid == 3 /*microsoft */
  54             && (eid == 1 /*unicode bmp */
  55                 || eid == 10 /*full unicode */ )) {
  56             FT_Set_Charmap(face, cmap);
  57             return;
  58         } else if (pid == 3 && ms_cmap < 0)
  59             ms_cmap = i;
  60     }
  61
  62     // Try the first Microsoft cmap if no Microsoft Unicode cmap was found
  63     if (ms_cmap >= 0) {
  64         FT_CharMap cmap = face->charmaps[ms_cmap];
  65         FT_Set_Charmap(face, cmap);
  66         return;
  67     }
  68
  69     if (!face->charmap) {
  70         if (face->num_charmaps == 0) {
  71             ass_msg(library, MSGL_WARN, "Font face with no charmaps");
  72             return;
  73         }
  74         ass_msg(library, MSGL_WARN,
  75                 "No charmap autodetected, trying the first one");
  76         FT_Set_Charmap(face, face->charmaps[0]);
  77         return;
  78     }
  79 }
  80
  81 /**
  82  * \brief find a memory font by name
  83  */
  84 static int find_font(ASS_Library *library, char *name)
  85 {
  86     int i;
  87     for (i = 0; i < library->num_fontdata; ++i)
  88         if (strcasecmp(name, library->fontdata[i].name) == 0)
  89             return i;
  90     return -1;
  91 }
  92
  93 static void buggy_font_workaround(FT_Face face)
  94 {
  95     // Some fonts have zero Ascender/Descender fields in 'hhea' table.
  96     // In this case, get the information from 'os2' table or, as
  97     // a last resort, from face.bbox.
  98     if (face->ascender + face->descender == 0 || face->height == 0) {
  99         TT_OS2 *os2 = FT_Get_Sfnt_Table(face, ft_sfnt_os2);
 100         if (os2) {
 101             face->ascender = os2->sTypoAscender;
 102             face->descender = os2->sTypoDescender;
 103             face->height = face->ascender - face->descender;
 104         } else {
 105             face->ascender = face->bbox.yMax;
 106             face->descender = face->bbox.yMin;
 107             face->height = face->ascender - face->descender;
 108         }
 109     }
 110 }
 111
 112 /**
 113  * \brief Select a face with the given charcode and add it to ASS_Font
 114  * \return index of the new face in font->faces, -1 if failed
 115  */
 116 static int add_face(void *fc_priv, ASS_Font *font, uint32_t ch)
 117 {
 118     char *path;
 119     int index;
 120     FT_Face face;
 121     int error;
 122     int mem_idx;
 123
 124     if (font->n_faces == ASS_FONT_MAX_FACES)
 125         return -1;
 126
 127     path =
 128         fontconfig_select(font->library, fc_priv, font->desc.family,
 129                           font->desc.treat_family_as_pattern,
 130                           font->desc.bold, font->desc.italic, &index, ch);
 131     if (!path)
 132         return -1;
 133
 134     mem_idx = find_font(font->library, path);
 135     if (mem_idx >= 0) {
 136         error =
 137             FT_New_Memory_Face(font->ftlibrary,
 138                                (unsigned char *) font->library->
 139                                fontdata[mem_idx].data,
 140                                font->library->fontdata[mem_idx].size, index,
 141                                &face);
 142         if (error) {
 143             ass_msg(font->library, MSGL_WARN,
 144                     "Error opening memory font: '%s'", path);
 145             free(path);
 146             return -1;
 147         }
 148     } else {
 149         error = FT_New_Face(font->ftlibrary, path, index, &face);
 150         if (error) {
 151             ass_msg(font->library, MSGL_WARN,
 152                     "Error opening font: '%s', %d", path, index);
 153             free(path);
 154             return -1;
 155         }
 156     }
 157     charmap_magic(font->library, face);
 158     buggy_font_workaround(face);
 159
 160     font->faces[font->n_faces++] = face;
 161     ass_face_set_size(face, font->size);
 162     free(path);
 163     return font->n_faces - 1;
 164 }
 165
 166 /**
 167  * \brief Create a new ASS_Font according to "desc" argument
 168  */
 169 ASS_Font *ass_font_new(Cache *font_cache, ASS_Library *library,
 170                        FT_Library ftlibrary, void *fc_priv,
 171                        ASS_FontDesc *desc)
 172 {
 173     int error;
 174     ASS_Font *fontp;
 175     ASS_Font font;
 176
 177     fontp = ass_cache_get(font_cache, desc);
 178     if (fontp)
 179         return fontp;
 180
 181     font.library = library;
 182     font.ftlibrary = ftlibrary;
 183     font.shaper_priv = NULL;
 184     font.n_faces = 0;
 185     font.desc.family = strdup(desc->family);
 186     font.desc.treat_family_as_pattern = desc->treat_family_as_pattern;
 187     font.desc.bold = desc->bold;
 188     font.desc.italic = desc->italic;
 189     font.desc.vertical = desc->vertical;
 190
 191     font.scale_x = font.scale_y = 1.;
 192     font.v.x = font.v.y = 0;
 193     font.size = 0.;
 194
 195     error = add_face(fc_priv, &font, 0);
 196     if (error == -1) {
 197         free(font.desc.family);
 198         return 0;
 199     } else
 200         return ass_cache_put(font_cache, &font.desc, &font);
 201 }
 202
 203 /**
 204  * \brief Set font transformation matrix and shift vector
 205  **/
 206 void ass_font_set_transform(ASS_Font *font, double scale_x,
 207                             double scale_y, FT_Vector *v)
 208 {
 209     font->scale_x = scale_x;
 210     font->scale_y = scale_y;
 211     if (v) {
 212         font->v.x = v->x;
 213         font->v.y = v->y;
 214     }
 215 }
 216
 217 void ass_face_set_size(FT_Face face, double size)
 218 {
 219     TT_HoriHeader *hori = FT_Get_Sfnt_Table(face, ft_sfnt_hhea);
 220     TT_OS2 *os2 = FT_Get_Sfnt_Table(face, ft_sfnt_os2);
 221     double mscale = 1.;
 222     FT_Size_RequestRec rq;
 223     FT_Size_Metrics *m = &face->size->metrics;
 224     // VSFilter uses metrics from TrueType OS/2 table
 225     // The idea was borrowed from asa (http://asa.diac24.net)
 226     if (hori && os2) {
 227         int hori_height = hori->Ascender - hori->Descender;
 228         int os2_height = os2->usWinAscent + os2->usWinDescent;
 229         if (hori_height && os2_height)
 230             mscale = (double) hori_height / os2_height;
 231     }
 232     memset(&rq, 0, sizeof(rq));
 233     rq.type = FT_SIZE_REQUEST_TYPE_REAL_DIM;
 234     rq.width = 0;
 235     rq.height = double_to_d6(size * mscale);
 236     rq.horiResolution = rq.vertResolution = 0;
 237     FT_Request_Size(face, &rq);
 238     m->ascender /= mscale;
 239     m->descender /= mscale;
 240     m->height /= mscale;
 241 }
 242
 243 /**
 244  * \brief Set font size
 245  **/
 246 void ass_font_set_size(ASS_Font *font, double size)
 247 {
 248     int i;
 249     if (font->size != size) {
 250         font->size = size;
 251         for (i = 0; i < font->n_faces; ++i)
 252             ass_face_set_size(font->faces[i], size);
 253     }
 254 }
 255
 256 /**
 257  * \brief Get maximal font ascender and descender.
 258  * \param ch character code
 259  * The values are extracted from the font face that provides glyphs for the given character
 260  **/
 261 void ass_font_get_asc_desc(ASS_Font *font, uint32_t ch, int *asc,
 262                            int *desc)
 263 {
 264     int i;
 265     for (i = 0; i < font->n_faces; ++i) {
 266         FT_Face face = font->faces[i];
 267         TT_OS2 *os2 = FT_Get_Sfnt_Table(face, ft_sfnt_os2);
 268         if (FT_Get_Char_Index(face, ch)) {
 269             int y_scale = face->size->metrics.y_scale;
 270             if (os2) {
 271                 *asc = FT_MulFix(os2->usWinAscent, y_scale);
 272                 *desc = FT_MulFix(os2->usWinDescent, y_scale);
 273             } else {
 274                 *asc = FT_MulFix(face->ascender, y_scale);
 275                 *desc = FT_MulFix(-face->descender, y_scale);
 276             }
 277             return;
 278         }
 279     }
 280
 281     *asc = *desc = 0;
 282 }
 283
 284 /*
 285  * Strike a glyph with a horizontal line; it's possible to underline it
 286  * and/or strike through it.  For the line's position and size, truetype
 287  * tables are consulted.  Obviously this relies on the data in the tables
 288  * being accurate.
 289  *
 290  */
 291 static int ass_strike_outline_glyph(FT_Face face, ASS_Font *font,
 292                                     FT_Glyph glyph, int under, int through)
 293 {
 294     TT_OS2 *os2 = FT_Get_Sfnt_Table(face, ft_sfnt_os2);
 295     TT_Postscript *ps = FT_Get_Sfnt_Table(face, ft_sfnt_post);
 296     FT_Outline *ol = &((FT_OutlineGlyph) glyph)->outline;
 297     int bear, advance, y_scale, i, dir;
 298
 299     if (!under && !through)
 300         return 0;
 301
 302     // Grow outline
 303     i = (under ? 4 : 0) + (through ? 4 : 0);
 304     ol->points = realloc(ol->points, sizeof(FT_Vector) *
 305                          (ol->n_points + i));
 306     ol->tags = realloc(ol->tags, ol->n_points + i);
 307     i = !!under + !!through;
 308     ol->contours = realloc(ol->contours, sizeof(short) *
 309                            (ol->n_contours + i));
 310
 311     // If the bearing is negative, the glyph starts left of the current
 312     // pen position
 313     bear = FFMIN(face->glyph->metrics.horiBearingX, 0);
 314     // We're adding half a pixel to avoid small gaps
 315     advance = d16_to_d6(glyph->advance.x) + 32;
 316     y_scale = face->size->metrics.y_scale;
 317
 318     // Reverse drawing direction for non-truetype fonts
 319     dir = FT_Outline_Get_Orientation(ol);
 320
 321     // Add points to the outline
 322     if (under && ps) {
 323         int pos, size;
 324         pos = FT_MulFix(ps->underlinePosition, y_scale * font->scale_y);
 325         size = FT_MulFix(ps->underlineThickness,
 326                          y_scale * font->scale_y / 2);
 327
 328         if (pos > 0 || size <= 0)
 329             return 1;
 330
 331         FT_Vector points[4] = {
 332             {.x = bear,      .y = pos + size},
 333             {.x = advance,   .y = pos + size},
 334             {.x = advance,   .y = pos - size},
 335             {.x = bear,      .y = pos - size},
 336         };
 337
 338         if (dir == FT_ORIENTATION_TRUETYPE) {
 339             for (i = 0; i < 4; i++) {
 340                 ol->points[ol->n_points] = points[i];
 341                 ol->tags[ol->n_points++] = 1;
 342             }
 343         } else {
 344             for (i = 3; i >= 0; i--) {
 345                 ol->points[ol->n_points] = points[i];
 346                 ol->tags[ol->n_points++] = 1;
 347             }
 348         }
 349
 350         ol->contours[ol->n_contours++] = ol->n_points - 1;
 351     }
 352
 353     if (through && os2) {
 354         int pos, size;
 355         pos = FT_MulFix(os2->yStrikeoutPosition, y_scale * font->scale_y);
 356         size = FT_MulFix(os2->yStrikeoutSize, y_scale * font->scale_y / 2);
 357
 358         if (pos < 0 || size <= 0)
 359             return 1;
 360
 361         FT_Vector points[4] = {
 362             {.x = bear,      .y = pos + size},
 363             {.x = advance,   .y = pos + size},
 364             {.x = advance,   .y = pos - size},
 365             {.x = bear,      .y = pos - size},
 366         };
 367
 368         if (dir == FT_ORIENTATION_TRUETYPE) {
 369             for (i = 0; i < 4; i++) {
 370                 ol->points[ol->n_points] = points[i];
 371                 ol->tags[ol->n_points++] = 1;
 372             }
 373         } else {
 374             for (i = 3; i >= 0; i--) {
 375                 ol->points[ol->n_points] = points[i];
 376                 ol->tags[ol->n_points++] = 1;
 377             }
 378         }
 379
 380         ol->contours[ol->n_contours++] = ol->n_points - 1;
 381     }
 382
 383     return 0;
 384 }
 385
 386 void outline_copy(FT_Library lib, FT_Outline *source, FT_Outline **dest)
 387 {
 388     if (source == NULL) {
 389         *dest = NULL;
 390         return;
 391     }
 392     *dest = calloc(1, sizeof(**dest));
 393
 394     FT_Outline_New(lib, source->n_points, source->n_contours, *dest);
 395     FT_Outline_Copy(source, *dest);
 396 }
 397
 398 void outline_free(FT_Library lib, FT_Outline *outline)
 399 {
 400     if (outline)
 401         FT_Outline_Done(lib, outline);
 402     free(outline);
 403 }
 404
 405 /**
 406  * Slightly embold a glyph without touching its metrics
 407  */
 408 static void ass_glyph_embolden(FT_GlyphSlot slot)
 409 {
 410     int str;
 411
 412     if (slot->format != FT_GLYPH_FORMAT_OUTLINE)
 413         return;
 414
 415     str = FT_MulFix(slot->face->units_per_EM,
 416                     slot->face->size->metrics.y_scale) / 64;
 417
 418     FT_Outline_Embolden(&slot->outline, str);
 419 }
 420
 421 /**
 422  * \brief Get glyph and face index
 423  * Finds a face that has the requested codepoint and returns both face
 424  * and glyph index.
 425  */
 426 int ass_font_get_index(void *fcpriv, ASS_Font *font, uint32_t symbol,
 427                        int *face_index, int *glyph_index)
 428 {
 429     int index = 0;
 430     int i;
 431     FT_Face face = 0;
 432
 433     *glyph_index = 0;
 434
 435     if (symbol < 0x20) {
 436         *face_index = 0;
 437         return 0;
 438     }
 439     // Handle NBSP like a regular space when rendering the glyph
 440     if (symbol == 0xa0)
 441         symbol = ' ';
 442     if (font->n_faces == 0) {
 443         *face_index = 0;
 444         return 0;
 445     }
 446
 447     // try with the requested face
 448     if (*face_index < font->n_faces) {
 449         face = font->faces[*face_index];
 450         index = FT_Get_Char_Index(face, symbol);
 451     }
 452
 453     // not found in requested face, try all others
 454     for (i = 0; i < font->n_faces && index == 0; ++i) {
 455         face = font->faces[i];
 456         index = FT_Get_Char_Index(face, symbol);
 457         if (index)
 458             *face_index = i;
 459     }
 460
 461 #ifdef CONFIG_FONTCONFIG
 462     if (index == 0) {
 463         int face_idx;
 464         ass_msg(font->library, MSGL_INFO,
 465                 "Glyph 0x%X not found, selecting one more "
 466                 "font for (%s, %d, %d)", symbol, font->desc.family,
 467                 font->desc.bold, font->desc.italic);
 468         face_idx = *face_index = add_face(fcpriv, font, symbol);
 469         if (face_idx >= 0) {
 470             face = font->faces[face_idx];
 471             index = FT_Get_Char_Index(face, symbol);
 472             if (index == 0 && face->num_charmaps > 0) {
 473                 int i;
 474                 ass_msg(font->library, MSGL_WARN,
 475                     "Glyph 0x%X not found, broken font? Trying all charmaps", symbol);
 476                 for (i = 0; i < face->num_charmaps; i++) {
 477                     FT_Set_Charmap(face, face->charmaps[i]);
 478                     if ((index = FT_Get_Char_Index(face, symbol)) != 0) break;
 479                 }
 480             }
 481             if (index == 0) {
 482                 ass_msg(font->library, MSGL_ERR,
 483                         "Glyph 0x%X not found in font for (%s, %d, %d)",
 484                         symbol, font->desc.family, font->desc.bold,
 485                         font->desc.italic);
 486             }
 487         }
 488     }
 489 #endif
 490     *glyph_index = index;
 491
 492     return 1;
 493 }
 494
 495 /**
 496  * \brief Get a glyph
 497  * \param ch character code
 498  **/
 499 FT_Glyph ass_font_get_glyph(void *fontconfig_priv, ASS_Font *font,
 500                             uint32_t ch, int face_index, int index,
 501                             ASS_Hinting hinting, int deco)
 502 {
 503     int error;
 504     FT_Glyph glyph;
 505     FT_Face face = font->faces[face_index];
 506     int flags = 0;
 507     int vertical = font->desc.vertical;
 508
 509     flags = FT_LOAD_NO_BITMAP | FT_LOAD_IGNORE_GLOBAL_ADVANCE_WIDTH
 510             | FT_LOAD_IGNORE_TRANSFORM;
 511     switch (hinting) {
 512     case ASS_HINTING_NONE:
 513         flags |= FT_LOAD_NO_HINTING;
 514         break;
 515     case ASS_HINTING_LIGHT:
 516         flags |= FT_LOAD_FORCE_AUTOHINT | FT_LOAD_TARGET_LIGHT;
 517         break;
 518     case ASS_HINTING_NORMAL:
 519         flags |= FT_LOAD_FORCE_AUTOHINT;
 520         break;
 521     case ASS_HINTING_NATIVE:
 522         break;
 523     }
 524
 525     error = FT_Load_Glyph(face, index, flags);
 526     if (error) {
 527         ass_msg(font->library, MSGL_WARN, "Error loading glyph, index %d",
 528                 index);
 529         return 0;
 530     }
 531     if (!(face->style_flags & FT_STYLE_FLAG_ITALIC) &&
 532         (font->desc.italic > 55)) {
 533         FT_GlyphSlot_Oblique(face->glyph);
 534     }
 535
 536     if (!(face->style_flags & FT_STYLE_FLAG_BOLD) &&
 537         (font->desc.bold > 80)) {
 538         ass_glyph_embolden(face->glyph);
 539     }
 540     error = FT_Get_Glyph(face->glyph, &glyph);
 541     if (error) {
 542         ass_msg(font->library, MSGL_WARN, "Error loading glyph, index %d",
 543                 index);
 544         return 0;
 545     }
 546
 547     // Rotate glyph, if needed
 548     if (vertical && ch >= VERTICAL_LOWER_BOUND) {
 549         FT_Matrix m = { 0, double_to_d16(-1.0), double_to_d16(1.0), 0 };
 550         FT_Outline_Transform(&((FT_OutlineGlyph) glyph)->outline, &m);
 551         FT_Outline_Translate(&((FT_OutlineGlyph) glyph)->outline,
 552                              face->glyph->metrics.vertAdvance,
 553                              0);
 554         glyph->advance.x = face->glyph->linearVertAdvance;
 555     }
 556
 557     // Apply scaling and shift
 558     FT_Matrix scale = { double_to_d16(font->scale_x), 0, 0,
 559                         double_to_d16(font->scale_y) };
 560     FT_Outline *outl = &((FT_OutlineGlyph) glyph)->outline;
 561     FT_Outline_Transform(outl, &scale);
 562     FT_Outline_Translate(outl, font->v.x, font->v.y);
 563     glyph->advance.x *= font->scale_x;
 564
 565     ass_strike_outline_glyph(face, font, glyph, deco & DECO_UNDERLINE,
 566                              deco & DECO_STRIKETHROUGH);
 567
 568     return glyph;
 569 }
 570
 571 /**
 572  * \brief Get kerning for the pair of glyphs.
 573  **/
 574 FT_Vector ass_font_get_kerning(ASS_Font *font, uint32_t c1, uint32_t c2)
 575 {
 576     FT_Vector v = { 0, 0 };
 577     int i;
 578
 579     if (font->desc.vertical)
 580         return v;
 581
 582     for (i = 0; i < font->n_faces; ++i) {
 583         FT_Face face = font->faces[i];
 584         int i1 = FT_Get_Char_Index(face, c1);
 585         int i2 = FT_Get_Char_Index(face, c2);
 586         if (i1 && i2) {
 587             if (FT_HAS_KERNING(face))
 588                 FT_Get_Kerning(face, i1, i2, FT_KERNING_DEFAULT, &v);
 589             return v;
 590         }
 591         if (i1 || i2)           // these glyphs are from different font faces, no kerning information
 592             return v;
 593     }
 594     return v;
 595 }
 596
 597 /**
 598  * \brief Deallocate ASS_Font
 599  **/
 600 void ass_font_free(ASS_Font *font)
 601 {
 602     int i;
 603     for (i = 0; i < font->n_faces; ++i)
 604         if (font->faces[i])
 605             FT_Done_Face(font->faces[i]);
 606     if (font->shaper_priv)
 607         ass_shaper_font_data_free(font->shaper_priv);
 608     free(font->desc.family);
 609     free(font);
 610 }
 611
 612 /**
 613  * \brief Calculate the cbox of a series of points
 614  */
 615 static void
 616 get_contour_cbox(FT_BBox *box, FT_Vector *points, int start, int end)
 617 {
 618     box->xMin = box->yMin = INT_MAX;
 619     box->xMax = box->yMax = INT_MIN;
 620     int i;
 621
 622     for (i = start; i <= end; i++) {
 623         box->xMin = (points[i].x < box->xMin) ? points[i].x : box->xMin;
 624         box->xMax = (points[i].x > box->xMax) ? points[i].x : box->xMax;
 625         box->yMin = (points[i].y < box->yMin) ? points[i].y : box->yMin;
 626         box->yMax = (points[i].y > box->yMax) ? points[i].y : box->yMax;
 627     }
 628 }
 629
 630 /**
 631  * \brief Determine winding direction of a contour
 632  * \return direction; 0 = clockwise
 633  */
 634 static int get_contour_direction(FT_Vector *points, int start, int end)
 635 {
 636     int i;
 637     long long sum = 0;
 638     int x = points[start].x;
 639     int y = points[start].y;
 640     for (i = start + 1; i <= end; i++) {
 641         sum += x * (points[i].y - y) - y * (points[i].x - x);
 642         x = points[i].x;
 643         y = points[i].y;
 644     }
 645     sum += x * (points[start].y - y) - y * (points[start].x - x);
 646     return sum > 0;
 647 }
 648
 649 /**
 650  * \brief Apply fixups to please the FreeType stroker and improve the
 651  * rendering result, especially in case the outline has some anomalies.
 652  * At the moment, the following fixes are done:
 653  *
 654  * 1. Reverse contours that have "inside" winding direction but are not
 655  *    contained in any other contours' cbox.
 656  * 2. Remove "inside" contours depending on border size, so that large
 657  *    borders do not reverse the winding direction, which leads to "holes"
 658  *    inside the border. The inside will be filled by the border of the
 659  *    outside contour anyway in this case.
 660  *
 661  * \param outline FreeType outline, modified in-place
 662  * \param border_x border size, x direction, d6 format
 663  * \param border_x border size, y direction, d6 format
 664  */
 665 void fix_freetype_stroker(FT_Outline *outline, int border_x, int border_y)
 666 {
 667     int nc = outline->n_contours;
 668     int begin, stop;
 669     char modified = 0;
 670     char *valid_cont = malloc(nc);
 671     int start = 0;
 672     int end = -1;
 673     FT_BBox *boxes = malloc(nc * sizeof(FT_BBox));
 674     int i, j;
 675     int inside_direction;
 676
 677     inside_direction = FT_Outline_Get_Orientation(outline) ==
 678         FT_ORIENTATION_TRUETYPE;
 679
 680     // create a list of cboxes of the contours
 681     for (i = 0; i < nc; i++) {
 682         start = end + 1;
 683         end = outline->contours[i];
 684         get_contour_cbox(&boxes[i], outline->points, start, end);
 685     }
 686
 687     // for each contour, check direction and whether it's "outside"
 688     // or contained in another contour
 689     end = -1;
 690     for (i = 0; i < nc; i++) {
 691         start = end + 1;
 692         end = outline->contours[i];
 693         int dir = get_contour_direction(outline->points, start, end);
 694         valid_cont[i] = 1;
 695         if (dir == inside_direction) {
 696             for (j = 0; j < nc; j++) {
 697                 if (i == j)
 698                     continue;
 699                 if (boxes[i].xMin >= boxes[j].xMin &&
 700                     boxes[i].xMax <= boxes[j].xMax &&
 701                     boxes[i].yMin >= boxes[j].yMin &&
 702                     boxes[i].yMax <= boxes[j].yMax)
 703                     goto check_inside;
 704             }
 705             /* "inside" contour but we can't find anything it could be
 706              * inside of - assume the font is buggy and it should be
 707              * an "outside" contour, and reverse it */
 708             for (j = 0; j < (end + 1 - start) / 2; j++) {
 709                 FT_Vector temp = outline->points[start + j];
 710                 char temp2 = outline->tags[start + j];
 711                 outline->points[start + j] = outline->points[end - j];
 712                 outline->points[end - j] = temp;
 713                 outline->tags[start + j] = outline->tags[end - j];
 714                 outline->tags[end - j] = temp2;
 715             }
 716             dir ^= 1;
 717         }
 718         check_inside:
 719         if (dir == inside_direction) {
 720             FT_BBox box;
 721             get_contour_cbox(&box, outline->points, start, end);
 722             int width = box.xMax - box.xMin;
 723             int height = box.yMax - box.yMin;
 724             if (width < border_x * 2 || height < border_y * 2) {
 725                 valid_cont[i] = 0;
 726                 modified = 1;
 727             }
 728         }
 729     }
 730
 731     // if we need to modify the outline, rewrite it and skip
 732     // the contours that we determined should be removed.
 733     if (modified) {
 734         int p = 0, c = 0;
 735         for (i = 0; i < nc; i++) {
 736             if (!valid_cont[i])
 737                 continue;
 738             begin = (i == 0) ? 0 : outline->contours[i - 1] + 1;
 739             stop = outline->contours[i];
 740             for (j = begin; j <= stop; j++) {
 741                 outline->points[p].x = outline->points[j].x;
 742                 outline->points[p].y = outline->points[j].y;
 743                 outline->tags[p] = outline->tags[j];
 744                 p++;
 745             }
 746             outline->contours[c] = p - 1;
 747             c++;
 748         }
 749         outline->n_points = p;
 750         outline->n_contours = c;
 751     }
 752
 753     free(boxes);
 754     free(valid_cont);
 755 }
 756