html.c

   1 /*      $Id: html.c,v 1.122 2010/12/24 00:46:49 kristaps Exp $ */
   2 /*
   3  * Copyright (c) 2008, 2009, 2010 Kristaps Dzonsons <kristaps@bsd.lv>
   4  *
   5  * Permission to use, copy, modify, and distribute this software for any
   6  * purpose with or without fee is hereby granted, provided that the above
   7  * copyright notice and this permission notice appear in all copies.
   8  *
   9  * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
  10  * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
  11  * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
  12  * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
  13  * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
  14  * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
  15  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  16  */
  17 #ifdef HAVE_CONFIG_H
  18 #include "config.h"
  19 #endif
  20
  21 #include <sys/types.h>
  22
  23 #include <assert.h>
  24 #include <ctype.h>
  25 #include <stdarg.h>
  26 #include <stdio.h>
  27 #include <stdint.h>
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include <unistd.h>
  31
  32 #include "mandoc.h"
  33 #include "out.h"
  34 #include "chars.h"
  35 #include "html.h"
  36 #include "main.h"
  37
  38 struct  htmldata {
  39         const char       *name;
  40         int               flags;
  41 #define HTML_CLRLINE     (1 << 0)
  42 #define HTML_NOSTACK     (1 << 1)
  43 #define HTML_AUTOCLOSE   (1 << 2) /* Tag has auto-closure. */
  44 };
  45
  46 static  const struct htmldata htmltags[TAG_MAX] = {
  47         {"html",        HTML_CLRLINE}, /* TAG_HTML */
  48         {"head",        HTML_CLRLINE}, /* TAG_HEAD */
  49         {"body",        HTML_CLRLINE}, /* TAG_BODY */
  50         {"meta",        HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_META */
  51         {"title",       HTML_CLRLINE}, /* TAG_TITLE */
  52         {"div",         HTML_CLRLINE}, /* TAG_DIV */
  53         {"h1",          0}, /* TAG_H1 */
  54         {"h2",          0}, /* TAG_H2 */
  55         {"span",        0}, /* TAG_SPAN */
  56         {"link",        HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_LINK */
  57         {"br",          HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_BR */
  58         {"a",           0}, /* TAG_A */
  59         {"table",       HTML_CLRLINE}, /* TAG_TABLE */
  60         {"tbody",       HTML_CLRLINE}, /* TAG_TBODY */
  61         {"col",         HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_COL */
  62         {"tr",          HTML_CLRLINE}, /* TAG_TR */
  63         {"td",          HTML_CLRLINE}, /* TAG_TD */
  64         {"li",          HTML_CLRLINE}, /* TAG_LI */
  65         {"ul",          HTML_CLRLINE}, /* TAG_UL */
  66         {"ol",          HTML_CLRLINE}, /* TAG_OL */
  67         {"dl",          HTML_CLRLINE}, /* TAG_DL */
  68         {"dt",          HTML_CLRLINE}, /* TAG_DT */
  69         {"dd",          HTML_CLRLINE}, /* TAG_DD */
  70         {"blockquote",  HTML_CLRLINE}, /* TAG_BLOCKQUOTE */
  71         {"p",           HTML_CLRLINE | HTML_NOSTACK | HTML_AUTOCLOSE}, /* TAG_P */
  72         {"pre",         HTML_CLRLINE }, /* TAG_PRE */
  73         {"b",           0 }, /* TAG_B */
  74         {"i",           0 }, /* TAG_I */
  75         {"u",           0 }, /* TAG_U */
  76         {"code",        0 }, /* TAG_CODE */
  77         {"small",       0 }, /* TAG_SMALL */
  78 };
  79
  80 static  const char      *const htmlattrs[ATTR_MAX] = {
  81         "http-equiv", /* ATTR_HTTPEQUIV */
  82         "content", /* ATTR_CONTENT */
  83         "name", /* ATTR_NAME */
  84         "rel", /* ATTR_REL */
  85         "href", /* ATTR_HREF */
  86         "type", /* ATTR_TYPE */
  87         "media", /* ATTR_MEDIA */
  88         "class", /* ATTR_CLASS */
  89         "style", /* ATTR_STYLE */
  90         "width", /* ATTR_WIDTH */
  91         "id", /* ATTR_ID */
  92         "summary", /* ATTR_SUMMARY */
  93         "align", /* ATTR_ALIGN */
  94 };
  95
  96 static  void              print_spec(struct html *, enum roffdeco,
  97                                 const char *, size_t);
  98 static  void              print_res(struct html *, const char *, size_t);
  99 static  void              print_ctag(struct html *, enum htmltag);
 100 static  void              print_doctype(struct html *);
 101 static  void              print_xmltype(struct html *);
 102 static  int               print_encode(struct html *, const char *, int);
 103 static  void              print_metaf(struct html *, enum roffdeco);
 104 static  void              print_attr(struct html *,
 105                                 const char *, const char *);
 106 static  void             *ml_alloc(char *, enum htmltype);
 107
 108
 109 static void *
 110 ml_alloc(char *outopts, enum htmltype type)
 111 {
 112         struct html     *h;
 113         const char      *toks[4];
 114         char            *v;
 115
 116         toks[0] = "style";
 117         toks[1] = "man";
 118         toks[2] = "includes";
 119         toks[3] = NULL;
 120
 121         h = calloc(1, sizeof(struct html));
 122         if (NULL == h) {
 123                 perror(NULL);
 124                 exit((int)MANDOCLEVEL_SYSERR);
 125         }
 126
 127         h->type = type;
 128         h->tags.head = NULL;
 129         h->symtab = chars_init(CHARS_HTML);
 130
 131         while (outopts && *outopts)
 132                 switch (getsubopt(&outopts, UNCONST(toks), &v)) {
 133                 case (0):
 134                         h->style = v;
 135                         break;
 136                 case (1):
 137                         h->base_man = v;
 138                         break;
 139                 case (2):
 140                         h->base_includes = v;
 141                         break;
 142                 default:
 143                         break;
 144                 }
 145
 146         return(h);
 147 }
 148
 149 void *
 150 html_alloc(char *outopts)
 151 {
 152
 153         return(ml_alloc(outopts, HTML_HTML_4_01_STRICT));
 154 }
 155
 156
 157 void *
 158 xhtml_alloc(char *outopts)
 159 {
 160
 161         return(ml_alloc(outopts, HTML_XHTML_1_0_STRICT));
 162 }
 163
 164
 165 void
 166 html_free(void *p)
 167 {
 168         struct tag      *tag;
 169         struct html     *h;
 170
 171         h = (struct html *)p;
 172
 173         while ((tag = h->tags.head) != NULL) {
 174                 h->tags.head = tag->next;
 175                 free(tag);
 176         }
 177
 178         if (h->symtab)
 179                 chars_free(h->symtab);
 180
 181         free(h);
 182 }
 183
 184
 185 void
 186 print_gen_head(struct html *h)
 187 {
 188         struct htmlpair  tag[4];
 189
 190         tag[0].key = ATTR_HTTPEQUIV;
 191         tag[0].val = "Content-Type";
 192         tag[1].key = ATTR_CONTENT;
 193         tag[1].val = "text/html; charset=utf-8";
 194         print_otag(h, TAG_META, 2, tag);
 195
 196         tag[0].key = ATTR_NAME;
 197         tag[0].val = "resource-type";
 198         tag[1].key = ATTR_CONTENT;
 199         tag[1].val = "document";
 200         print_otag(h, TAG_META, 2, tag);
 201
 202         if (h->style) {
 203                 tag[0].key = ATTR_REL;
 204                 tag[0].val = "stylesheet";
 205                 tag[1].key = ATTR_HREF;
 206                 tag[1].val = h->style;
 207                 tag[2].key = ATTR_TYPE;
 208                 tag[2].val = "text/css";
 209                 tag[3].key = ATTR_MEDIA;
 210                 tag[3].val = "all";
 211                 print_otag(h, TAG_LINK, 4, tag);
 212         }
 213 }
 214
 215
 216 static void
 217 print_spec(struct html *h, enum roffdeco d, const char *p, size_t len)
 218 {
 219         int              cp;
 220         const char      *rhs;
 221         size_t           sz;
 222
 223         if ((cp = chars_spec2cp(h->symtab, p, len)) > 0) {
 224                 printf("&#%d;", cp);
 225                 return;
 226         } else if (-1 == cp && DECO_SSPECIAL == d) {
 227                 fwrite(p, 1, len, stdout);
 228                 return;
 229         } else if (-1 == cp)
 230                 return;
 231
 232         if (NULL != (rhs = chars_spec2str(h->symtab, p, len, &sz)))
 233                 fwrite(rhs, 1, sz, stdout);
 234 }
 235
 236
 237 static void
 238 print_res(struct html *h, const char *p, size_t len)
 239 {
 240         int              cp;
 241         const char      *rhs;
 242         size_t           sz;
 243
 244         if ((cp = chars_res2cp(h->symtab, p, len)) > 0) {
 245                 printf("&#%d;", cp);
 246                 return;
 247         } else if (-1 == cp)
 248                 return;
 249
 250         if (NULL != (rhs = chars_res2str(h->symtab, p, len, &sz)))
 251                 fwrite(rhs, 1, sz, stdout);
 252 }
 253
 254
 255 static void
 256 print_metaf(struct html *h, enum roffdeco deco)
 257 {
 258         enum htmlfont    font;
 259
 260         switch (deco) {
 261         case (DECO_PREVIOUS):
 262                 font = h->metal;
 263                 break;
 264         case (DECO_ITALIC):
 265                 font = HTMLFONT_ITALIC;
 266                 break;
 267         case (DECO_BOLD):
 268                 font = HTMLFONT_BOLD;
 269                 break;
 270         case (DECO_ROMAN):
 271                 font = HTMLFONT_NONE;
 272                 break;
 273         default:
 274                 abort();
 275                 /* NOTREACHED */
 276         }
 277
 278         if (h->metaf) {
 279                 print_tagq(h, h->metaf);
 280                 h->metaf = NULL;
 281         }
 282
 283         h->metal = h->metac;
 284         h->metac = font;
 285
 286         if (HTMLFONT_NONE != font)
 287                 h->metaf = HTMLFONT_BOLD == font ?
 288                         print_otag(h, TAG_B, 0, NULL) :
 289                         print_otag(h, TAG_I, 0, NULL);
 290 }
 291
 292
 293 static int
 294 print_encode(struct html *h, const char *p, int norecurse)
 295 {
 296         size_t           sz;
 297         int              len, nospace;
 298         const char      *seq;
 299         enum roffdeco    deco;
 300         static const char rejs[6] = { '\\', '<', '>', '&', ASCII_HYPH, '\0' };
 301
 302         nospace = 0;
 303
 304         for (; *p; p++) {
 305                 sz = strcspn(p, rejs);
 306
 307                 fwrite(p, 1, sz, stdout);
 308                 p += /* LINTED */
 309                         sz;
 310
 311                 if ('<' == *p) {
 312                         printf("&lt;");
 313                         continue;
 314                 } else if ('>' == *p) {
 315                         printf("&gt;");
 316                         continue;
 317                 } else if ('&' == *p) {
 318                         printf("&amp;");
 319                         continue;
 320                 } else if (ASCII_HYPH == *p) {
 321                         /*
 322                          * Note: "soft hyphens" aren't graphically
 323                          * displayed when not breaking the text; we want
 324                          * them to be displayed.
 325                          */
 326                         /*printf("&#173;");*/
 327                         putchar('-');
 328                         continue;
 329                 } else if ('\0' == *p)
 330                         break;
 331
 332                 seq = ++p;
 333                 len = a2roffdeco(&deco, &seq, &sz);
 334
 335                 switch (deco) {
 336                 case (DECO_RESERVED):
 337                         print_res(h, seq, sz);
 338                         break;
 339                 case (DECO_SSPECIAL):
 340                         /* FALLTHROUGH */
 341                 case (DECO_SPECIAL):
 342                         print_spec(h, deco, seq, sz);
 343                         break;
 344                 case (DECO_PREVIOUS):
 345                         /* FALLTHROUGH */
 346                 case (DECO_BOLD):
 347                         /* FALLTHROUGH */
 348                 case (DECO_ITALIC):
 349                         /* FALLTHROUGH */
 350                 case (DECO_ROMAN):
 351                         if (norecurse)
 352                                 break;
 353                         print_metaf(h, deco);
 354                         break;
 355                 default:
 356                         break;
 357                 }
 358
 359                 p += len - 1;
 360
 361                 if (DECO_NOSPACE == deco && '\0' == *(p + 1))
 362                         nospace = 1;
 363         }
 364
 365         return(nospace);
 366 }
 367
 368
 369 static void
 370 print_attr(struct html *h, const char *key, const char *val)
 371 {
 372         printf(" %s=\"", key);
 373         (void)print_encode(h, val, 1);
 374         putchar('\"');
 375 }
 376
 377
 378 struct tag *
 379 print_otag(struct html *h, enum htmltag tag,
 380                 int sz, const struct htmlpair *p)
 381 {
 382         int              i;
 383         struct tag      *t;
 384
 385         /* Push this tags onto the stack of open scopes. */
 386
 387         if ( ! (HTML_NOSTACK & htmltags[tag].flags)) {
 388                 t = malloc(sizeof(struct tag));
 389                 if (NULL == t) {
 390                         perror(NULL);
 391                         exit((int)MANDOCLEVEL_SYSERR);
 392                 }
 393                 t->tag = tag;
 394                 t->next = h->tags.head;
 395                 h->tags.head = t;
 396         } else
 397                 t = NULL;
 398
 399         if ( ! (HTML_NOSPACE & h->flags))
 400                 if ( ! (HTML_CLRLINE & htmltags[tag].flags)) {
 401                         /* Manage keeps! */
 402                         if ( ! (HTML_KEEP & h->flags)) {
 403                                 if (HTML_PREKEEP & h->flags)
 404                                         h->flags |= HTML_KEEP;
 405                                 putchar(' ');
 406                         } else
 407                                 printf("&#160;");
 408                 }
 409
 410         if ( ! (h->flags & HTML_NONOSPACE))
 411                 h->flags &= ~HTML_NOSPACE;
 412         else
 413                 h->flags |= HTML_NOSPACE;
 414
 415         /* Print out the tag name and attributes. */
 416
 417         printf("<%s", htmltags[tag].name);
 418         for (i = 0; i < sz; i++)
 419                 print_attr(h, htmlattrs[p[i].key], p[i].val);
 420
 421         /* Add non-overridable attributes. */
 422
 423         if (TAG_HTML == tag && HTML_XHTML_1_0_STRICT == h->type) {
 424                 print_attr(h, "xmlns", "http://www.w3.org/1999/xhtml");
 425                 print_attr(h, "xml:lang", "en");
 426                 print_attr(h, "lang", "en");
 427         }
 428
 429         /* Accomodate for XML "well-formed" singleton escaping. */
 430
 431         if (HTML_AUTOCLOSE & htmltags[tag].flags)
 432                 switch (h->type) {
 433                 case (HTML_XHTML_1_0_STRICT):
 434                         putchar('/');
 435                         break;
 436                 default:
 437                         break;
 438                 }
 439
 440         putchar('>');
 441
 442         h->flags |= HTML_NOSPACE;
 443
 444         if ((HTML_AUTOCLOSE | HTML_CLRLINE) & htmltags[tag].flags)
 445                 putchar('\n');
 446
 447         return(t);
 448 }
 449
 450
 451 static void
 452 print_ctag(struct html *h, enum htmltag tag)
 453 {
 454
 455         printf("</%s>", htmltags[tag].name);
 456         if (HTML_CLRLINE & htmltags[tag].flags) {
 457                 h->flags |= HTML_NOSPACE;
 458                 putchar('\n');
 459         }
 460 }
 461
 462
 463 void
 464 print_gen_decls(struct html *h)
 465 {
 466
 467         print_xmltype(h);
 468         print_doctype(h);
 469 }
 470
 471
 472 static void
 473 print_xmltype(struct html *h)
 474 {
 475
 476         if (HTML_XHTML_1_0_STRICT == h->type)
 477                 puts("<?xml version=\"1.0\" encoding=\"UTF-8\"?>");
 478 }
 479
 480
 481 static void
 482 print_doctype(struct html *h)
 483 {
 484         const char      *doctype;
 485         const char      *dtd;
 486         const char      *name;
 487
 488         switch (h->type) {
 489         case (HTML_HTML_4_01_STRICT):
 490                 name = "HTML";
 491                 doctype = "-//W3C//DTD HTML 4.01//EN";
 492                 dtd = "http://www.w3.org/TR/html4/strict.dtd";
 493                 break;
 494         default:
 495                 name = "html";
 496                 doctype = "-//W3C//DTD XHTML 1.0 Strict//EN";
 497                 dtd = "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd";
 498                 break;
 499         }
 500
 501         printf("<!DOCTYPE %s PUBLIC \"%s\" \"%s\">\n",
 502                         name, doctype, dtd);
 503 }
 504
 505
 506 void
 507 print_text(struct html *h, const char *word)
 508 {
 509
 510         if (word[0] && '\0' == word[1])
 511                 switch (word[0]) {
 512                 case('.'):
 513                         /* FALLTHROUGH */
 514                 case(','):
 515                         /* FALLTHROUGH */
 516                 case(';'):
 517                         /* FALLTHROUGH */
 518                 case(':'):
 519                         /* FALLTHROUGH */
 520                 case('?'):
 521                         /* FALLTHROUGH */
 522                 case('!'):
 523                         /* FALLTHROUGH */
 524                 case(')'):
 525                         /* FALLTHROUGH */
 526                 case(']'):
 527                         if ( ! (HTML_IGNDELIM & h->flags))
 528                                 h->flags |= HTML_NOSPACE;
 529                         break;
 530                 default:
 531                         break;
 532                 }
 533
 534         if ( ! (HTML_NOSPACE & h->flags)) {
 535                 /* Manage keeps! */
 536                 if ( ! (HTML_KEEP & h->flags)) {
 537                         if (HTML_PREKEEP & h->flags)
 538                                 h->flags |= HTML_KEEP;
 539                         putchar(' ');
 540                 } else
 541                         printf("&#160;");
 542         }
 543
 544         assert(NULL == h->metaf);
 545         if (HTMLFONT_NONE != h->metac)
 546                 h->metaf = HTMLFONT_BOLD == h->metac ?
 547                         print_otag(h, TAG_B, 0, NULL) :
 548                         print_otag(h, TAG_I, 0, NULL);
 549
 550         assert(word);
 551         if ( ! print_encode(h, word, 0))
 552                 if ( ! (h->flags & HTML_NONOSPACE))
 553                         h->flags &= ~HTML_NOSPACE;
 554
 555         if (h->metaf) {
 556                 print_tagq(h, h->metaf);
 557                 h->metaf = NULL;
 558         }
 559
 560         h->flags &= ~HTML_IGNDELIM;
 561
 562         /*
 563          * Note that we don't process the pipe: the parser sees it as
 564          * punctuation, but we don't in terms of typography.
 565          */
 566         if (word[0] && '\0' == word[1])
 567                 switch (word[0]) {
 568                 case('('):
 569                         /* FALLTHROUGH */
 570                 case('['):
 571                         h->flags |= HTML_NOSPACE;
 572                         break;
 573                 default:
 574                         break;
 575                 }
 576 }
 577
 578
 579 void
 580 print_tagq(struct html *h, const struct tag *until)
 581 {
 582         struct tag      *tag;
 583
 584         while ((tag = h->tags.head) != NULL) {
 585                 if (tag == h->metaf)
 586                         h->metaf = NULL;
 587                 print_ctag(h, tag->tag);
 588                 h->tags.head = tag->next;
 589                 free(tag);
 590                 if (until && tag == until)
 591                         return;
 592         }
 593 }
 594
 595
 596 void
 597 print_stagq(struct html *h, const struct tag *suntil)
 598 {
 599         struct tag      *tag;
 600
 601         while ((tag = h->tags.head) != NULL) {
 602                 if (suntil && tag == suntil)
 603                         return;
 604                 if (tag == h->metaf)
 605                         h->metaf = NULL;
 606                 print_ctag(h, tag->tag);
 607                 h->tags.head = tag->next;
 608                 free(tag);
 609         }
 610 }
 611
 612
 613 void
 614 bufinit(struct html *h)
 615 {
 616
 617         h->buf[0] = '\0';
 618         h->buflen = 0;
 619 }
 620
 621
 622 void
 623 bufcat_style(struct html *h, const char *key, const char *val)
 624 {
 625
 626         bufcat(h, key);
 627         bufncat(h, ":", 1);
 628         bufcat(h, val);
 629         bufncat(h, ";", 1);
 630 }
 631
 632
 633 void
 634 bufcat(struct html *h, const char *p)
 635 {
 636
 637         bufncat(h, p, strlen(p));
 638 }
 639
 640
 641 void
 642 buffmt(struct html *h, const char *fmt, ...)
 643 {
 644         va_list          ap;
 645
 646         va_start(ap, fmt);
 647         (void)vsnprintf(h->buf + (int)h->buflen,
 648                         BUFSIZ - h->buflen - 1, fmt, ap);
 649         va_end(ap);
 650         h->buflen = strlen(h->buf);
 651 }
 652
 653
 654 void
 655 bufncat(struct html *h, const char *p, size_t sz)
 656 {
 657
 658         if (h->buflen + sz > BUFSIZ - 1)
 659                 sz = BUFSIZ - 1 - h->buflen;
 660
 661         (void)strncat(h->buf, p, sz);
 662         h->buflen += sz;
 663 }
 664
 665
 666 void
 667 buffmt_includes(struct html *h, const char *name)
 668 {
 669         const char      *p, *pp;
 670
 671         pp = h->base_includes;
 672
 673         while (NULL != (p = strchr(pp, '%'))) {
 674                 bufncat(h, pp, (size_t)(p - pp));
 675                 switch (*(p + 1)) {
 676                 case('I'):
 677                         bufcat(h, name);
 678                         break;
 679                 default:
 680                         bufncat(h, p, 2);
 681                         break;
 682                 }
 683                 pp = p + 2;
 684         }
 685         if (pp)
 686                 bufcat(h, pp);
 687 }
 688
 689
 690 void
 691 buffmt_man(struct html *h,
 692                 const char *name, const char *sec)
 693 {
 694         const char      *p, *pp;
 695
 696         pp = h->base_man;
 697
 698         /* LINTED */
 699         while (NULL != (p = strchr(pp, '%'))) {
 700                 bufncat(h, pp, (size_t)(p - pp));
 701                 switch (*(p + 1)) {
 702                 case('S'):
 703                         bufcat(h, sec ? sec : "1");
 704                         break;
 705                 case('N'):
 706                         buffmt(h, name);
 707                         break;
 708                 default:
 709                         bufncat(h, p, 2);
 710                         break;
 711                 }
 712                 pp = p + 2;
 713         }
 714         if (pp)
 715                 bufcat(h, pp);
 716 }
 717
 718
 719 void
 720 bufcat_su(struct html *h, const char *p, const struct roffsu *su)
 721 {
 722         double           v;
 723         const char      *u;
 724
 725         v = su->scale;
 726
 727         switch (su->unit) {
 728         case (SCALE_CM):
 729                 u = "cm";
 730                 break;
 731         case (SCALE_IN):
 732                 u = "in";
 733                 break;
 734         case (SCALE_PC):
 735                 u = "pc";
 736                 break;
 737         case (SCALE_PT):
 738                 u = "pt";
 739                 break;
 740         case (SCALE_EM):
 741                 u = "em";
 742                 break;
 743         case (SCALE_MM):
 744                 if (0 == (v /= 100))
 745                         v = 1;
 746                 u = "em";
 747                 break;
 748         case (SCALE_EN):
 749                 u = "ex";
 750                 break;
 751         case (SCALE_BU):
 752                 u = "ex";
 753                 break;
 754         case (SCALE_VS):
 755                 u = "em";
 756                 break;
 757         default:
 758                 u = "ex";
 759                 break;
 760         }
 761
 762         /*
 763          * XXX: the CSS spec isn't clear as to which types accept
 764          * integer or real numbers, so we just make them all decimals.
 765          */
 766         buffmt(h, "%s: %.2f%s;", p, v, u);
 767 }
 768
 769
 770 void
 771 html_idcat(char *dst, const char *src, int sz)
 772 {
 773         int              ssz;
 774
 775         assert(sz);
 776
 777         /* Cf. <http://www.w3.org/TR/html4/types.html#h-6.2>. */
 778
 779         for ( ; *dst != '\0' && sz; dst++, sz--)
 780                 /* Jump to end. */ ;
 781
 782         assert(sz > 2);
 783
 784         /* We can't start with a number (bah). */
 785
 786         *dst++ = 'x';
 787         *dst = '\0';
 788         sz--;
 789
 790         for ( ; *src != '\0' && sz > 1; src++) {
 791                 ssz = snprintf(dst, (size_t)sz, "%.2x", *src);
 792                 sz -= ssz;
 793                 dst += ssz;
 794         }
 795 }