mandoc_html.3

   1 .\"     $Id: mandoc_html.3,v 1.23 2020/04/24 13:13:06 schwarze Exp $
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   3 .\" Copyright (c) 2014, 2017, 2018 Ingo Schwarze <schwarze@openbsd.org>
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  17 .Dd $Mdocdate: April 24 2020 $
  18 .Dt MANDOC_HTML 3
  19 .Os
  20 .Sh NAME
  21 .Nm mandoc_html
  22 .Nd internals of the mandoc HTML formatter
  23 .Sh SYNOPSIS
  24 .In sys/types.h
  25 .Fd #include """mandoc.h"""
  26 .Fd #include """roff.h"""
  27 .Fd #include """out.h"""
  28 .Fd #include """html.h"""
  29 .Ft void
  30 .Fn print_gen_decls "struct html *h"
  31 .Ft void
  32 .Fn print_gen_comment "struct html *h" "struct roff_node *n"
  33 .Ft void
  34 .Fn print_gen_head "struct html *h"
  35 .Ft struct tag *
  36 .Fo print_otag
  37 .Fa "struct html *h"
  38 .Fa "enum htmltag tag"
  39 .Fa "const char *fmt"
  40 .Fa ...
  41 .Fc
  42 .Ft void
  43 .Fo print_tagq
  44 .Fa "struct html *h"
  45 .Fa "const struct tag *until"
  46 .Fc
  47 .Ft void
  48 .Fo print_stagq
  49 .Fa "struct html *h"
  50 .Fa "const struct tag *suntil"
  51 .Fc
  52 .Ft void
  53 .Fn html_close_paragraph "struct html *h"
  54 .Ft enum roff_tok
  55 .Fo html_fillmode
  56 .Fa "struct html *h"
  57 .Fa "enum roff_tok tok"
  58 .Fc
  59 .Ft int
  60 .Fo html_setfont
  61 .Fa "struct html *h"
  62 .Fa "enum mandoc_esc font"
  63 .Fc
  64 .Ft void
  65 .Fo print_text
  66 .Fa "struct html *h"
  67 .Fa "const char *word"
  68 .Fc
  69 .Ft void
  70 .Fo print_tagged_text
  71 .Fa "struct html *h"
  72 .Fa "const char *word"
  73 .Fa "struct roff_node *n"
  74 .Fc
  75 .Ft char *
  76 .Fo html_make_id
  77 .Fa "const struct roff_node *n"
  78 .Fa "int unique"
  79 .Fc
  80 .Ft struct tag *
  81 .Fo print_otag_id
  82 .Fa "struct html *h"
  83 .Fa "enum htmltag tag"
  84 .Fa "const char *cattr"
  85 .Fa "struct roff_node *n"
  86 .Fc
  87 .Ft void
  88 .Fn print_endline "struct html *h"
  89 .Sh DESCRIPTION
  90 The mandoc HTML formatter is not a formal library.
  91 However, as it is compiled into more than one program, in particular
  92 .Xr mandoc 1
  93 and
  94 .Xr man.cgi 8 ,
  95 and because it may be security-critical in some contexts,
  96 some documentation is useful to help to use it correctly and
  97 to prevent XSS vulnerabilities.
  98 .Pp
  99 The formatter produces HTML output on the standard output.
 100 Since proper escaping is usually required and best taken care of
 101 at one central place, the language-specific formatters
 102 .Po
 103 .Pa *_html.c ,
 104 see
 105 .Sx FILES
 106 .Pc
 107 are not supposed to print directly to
 108 .Dv stdout
 109 using functions like
 110 .Xr printf 3 ,
 111 .Xr putc 3 ,
 112 .Xr puts 3 ,
 113 or
 114 .Xr write 2 .
 115 Instead, they are expected to use the output functions declared in
 116 .Pa html.h
 117 and implemented as part of the main HTML formatting engine in
 118 .Pa html.c .
 119 .Ss Data structures
 120 These structures are declared in
 121 .Pa html.h .
 122 .Bl -tag -width Ds
 123 .It Vt struct html
 124 Internal state of the HTML formatter.
 125 .It Vt struct tag
 126 One entry for the LIFO stack of HTML elements.
 127 Members include
 128 .Fa "enum htmltag tag"
 129 and
 130 .Fa "struct tag *next" .
 131 .El
 132 .Ss Private interface functions
 133 The function
 134 .Fn print_gen_decls
 135 prints the opening
 136 .Aq Pf \&! Ic DOCTYPE
 137 declaration.
 138 .Pp
 139 The function
 140 .Fn print_gen_comment
 141 prints the leading comments, usually containing a Copyright notice
 142 and license, as an HTML comment.
 143 It is intended to be called right after opening the
 144 .Aq Ic HTML
 145 element.
 146 Pass the first
 147 .Dv ROFFT_COMMENT
 148 node in
 149 .Fa n .
 150 .Pp
 151 The function
 152 .Fn print_gen_head
 153 prints the opening
 154 .Aq Ic META
 155 and
 156 .Aq Ic LINK
 157 elements for the document
 158 .Aq Ic HEAD ,
 159 using the
 160 .Fa style
 161 member of
 162 .Fa h
 163 unless that is
 164 .Dv NULL .
 165 It uses
 166 .Fn print_otag
 167 which takes care of properly encoding attributes,
 168 which is relevant for the
 169 .Fa style
 170 link in particular.
 171 .Pp
 172 The function
 173 .Fn print_otag
 174 prints the start tag of an HTML element with the name
 175 .Fa tag ,
 176 optionally including the attributes specified by
 177 .Fa fmt .
 178 If
 179 .Fa fmt
 180 is the empty string, no attributes are written.
 181 Each letter of
 182 .Fa fmt
 183 specifies one attribute to write.
 184 Most attributes require one
 185 .Va char *
 186 argument which becomes the value of the attribute.
 187 The arguments have to be given in the same order as the attribute letters.
 188 If an argument is
 189 .Dv NULL ,
 190 the respective attribute is not written.
 191 .Bl -tag -width 1n -offset indent
 192 .It Cm c
 193 Print a
 194 .Cm class
 195 attribute.
 196 .It Cm h
 197 Print a
 198 .Cm href
 199 attribute.
 200 This attribute letter can optionally be followed by a modifier letter.
 201 If followed by
 202 .Cm R ,
 203 it formats the link as a local one by prefixing a
 204 .Sq #
 205 character.
 206 If followed by
 207 .Cm I ,
 208 it interpretes the argument as a header file name
 209 and generates a link using the
 210 .Xr mandoc 1
 211 .Fl O Cm includes
 212 option.
 213 If followed by
 214 .Cm M ,
 215 it takes two arguments instead of one, a manual page name and
 216 section, and formats them as a link to a manual page using the
 217 .Xr mandoc 1
 218 .Fl O Cm man
 219 option.
 220 .It Cm i
 221 Print an
 222 .Cm id
 223 attribute.
 224 .It Cm \&?
 225 Print an arbitrary attribute.
 226 This format letter requires two
 227 .Vt char *
 228 arguments, the attribute name and the value.
 229 The name must not be
 230 .Dv NULL .
 231 .It Cm s
 232 Print a
 233 .Cm style
 234 attribute.
 235 If present, it must be the last format letter.
 236 It requires two
 237 .Va char *
 238 arguments.
 239 The first is the name of the style property, the second its value.
 240 The name must not be
 241 .Dv NULL .
 242 The
 243 .Cm s
 244 .Ar fmt
 245 letter can be repeated, each repetition requiring an additional pair of
 246 .Va char *
 247 arguments.
 248 .El
 249 .Pp
 250 .Fn print_otag
 251 uses the private function
 252 .Fn print_encode
 253 to take care of HTML encoding.
 254 If required by the element type, it remembers in
 255 .Fa h
 256 that the element is open.
 257 The function
 258 .Fn print_tagq
 259 is used to close out all open elements up to and including
 260 .Fa until ;
 261 .Fn print_stagq
 262 is a variant to close out all open elements up to but excluding
 263 .Fa suntil .
 264 The function
 265 .Fn html_close_paragraph
 266 closes all open elements that establish phrasing context,
 267 thus returning to the innermost flow context.
 268 .Pp
 269 The function
 270 .Fn html_fillmode
 271 switches to fill mode if
 272 .Fa want
 273 is
 274 .Dv ROFF_fi
 275 or to no-fill mode if
 276 .Fa want
 277 is
 278 .Dv ROFF_nf .
 279 Switching from fill mode to no-fill mode closes the current paragraph
 280 and opens a
 281 .Aq Ic PRE
 282 element.
 283 Switching in the opposite direction closes the
 284 .Aq Ic PRE
 285 element, but does not open a new paragraph.
 286 If
 287 .Fa want
 288 matches the mode that is already active, no elements are closed nor opened.
 289 If
 290 .Fa want
 291 is
 292 .Dv TOKEN_NONE ,
 293 the mode remains as it is.
 294 .Pp
 295 The function
 296 .Fn html_setfont
 297 selects the
 298 .Fa font ,
 299 which can be
 300 .Dv ESCAPE_FONTROMAN ,
 301 .Dv ESCAPE_FONTBOLD ,
 302 .Dv ESCAPE_FONTITALIC ,
 303 .Dv ESCAPE_FONTBI ,
 304 or
 305 .Dv ESCAPE_FONTCW ,
 306 for future text output and internally remembers
 307 the font that was active before the change.
 308 If the
 309 .Fa font
 310 argument is
 311 .Dv ESCAPE_FONTPREV ,
 312 the current and the previous font are exchanged.
 313 This function only changes the internal state of the
 314 .Fa h
 315 object; no HTML elements are written yet.
 316 Subsequent text output will write font elements when needed.
 317 .Pp
 318 The function
 319 .Fn print_text
 320 prints HTML element content.
 321 It uses the private function
 322 .Fn print_encode
 323 to take care of HTML encoding.
 324 If the document has requested a non-standard font, for example using a
 325 .Xr roff 7
 326 .Ic \ef
 327 font escape sequence,
 328 .Fn print_text
 329 wraps
 330 .Fa word
 331 in an HTML font selection element using the
 332 .Fn print_otag
 333 and
 334 .Fn print_tagq
 335 functions.
 336 .Pp
 337 The function
 338 .Fn print_tagged_text
 339 is a variant of
 340 .Fn print_text
 341 that wraps
 342 .Fa word
 343 in an
 344 .Aq Ic A
 345 element of class
 346 .Qq permalink
 347 if
 348 .Fa n
 349 is not
 350 .Dv NULL
 351 and yields a segment identifier when passed to
 352 .Fn html_make_id .
 353 .Pp
 354 The function
 355 .Fn html_make_id
 356 allocates a string to be used for the
 357 .Cm id
 358 attribute of an HTML element and/or as a segment identifier for a URI in an
 359 .Aq Ic A
 360 element.
 361 If
 362 .Fa n
 363 contains a
 364 .Fa tag
 365 attribute, it is used; otherwise, child nodes are used.
 366 If
 367 .Fa n
 368 is an
 369 .Ic \&Sh ,
 370 .Ic \&Ss ,
 371 .Ic \&Sx ,
 372 .Ic SH ,
 373 or
 374 .Ic SS
 375 node, the resulting string is the concatenation of the child strings;
 376 for other node types, only the first child is used.
 377 Bytes not permitted in URI-fragment strings are replaced by underscores.
 378 If any of the children to be used is not a text node,
 379 no string is generated and
 380 .Dv NULL
 381 is returned instead.
 382 If the
 383 .Fa unique
 384 argument is non-zero, deduplication is performed by appending an
 385 underscore and a decimal integer, if necessary.
 386 If the
 387 .Fa unique
 388 argument is 1, this is assumed to be the first call for this tag
 389 at this location, typically for use by
 390 .Dv NODE_ID ,
 391 so the integer is incremented before use.
 392 If the
 393 .Fa unique
 394 argument is 2, this is ssumed to be the second call for this tag
 395 at this location, typically for use by
 396 .Dv NODE_HREF ,
 397 so the existing integer, if any, is used without incrementing it.
 398 .Pp
 399 The function
 400 .Fn print_otag_id
 401 opens a
 402 .Fa tag
 403 element of class
 404 .Fa cattr
 405 for the node
 406 .Fa n .
 407 If the flag
 408 .Dv NODE_ID
 409 is set in
 410 .Fa n ,
 411 it attempts to generate an
 412 .Cm id
 413 attribute with
 414 .Fn html_make_id .
 415 If the flag
 416 .Dv NODE_HREF
 417 is set in
 418 .Fa n ,
 419 an
 420 .Aq Ic A
 421 element of class
 422 .Qq permalink
 423 is added:
 424 outside if
 425 .Fa n
 426 generates an element that can only occur in phrasing context,
 427 or inside otherwise.
 428 This function is a wrapper around
 429 .Fn html_make_id
 430 and
 431 .Fn print_otag ,
 432 automatically chosing the
 433 .Fa unique
 434 argument appropriately and setting the
 435 .Fa fmt
 436 arguments to
 437 .Qq chR
 438 and
 439 .Qq ci ,
 440 respectively.
 441 .Pp
 442 The function
 443 .Fn print_endline
 444 makes sure subsequent output starts on a new HTML output line.
 445 If nothing was printed on the current output line yet, it has no effect.
 446 Otherwise, it appends any buffered text to the current output line,
 447 ends the line, and updates the internal state of the
 448 .Fa h
 449 object.
 450 .Pp
 451 The functions
 452 .Fn print_eqn ,
 453 .Fn print_tbl ,
 454 and
 455 .Fn print_tblclose
 456 are not yet documented.
 457 .Sh RETURN VALUES
 458 The functions
 459 .Fn print_otag
 460 and
 461 .Fn print_otag_id
 462 return a pointer to a new element on the stack of HTML elements.
 463 When
 464 .Fn print_otag_id
 465 opens two elements, a pointer to the outer one is returned.
 466 The memory pointed to is owned by the library and is automatically
 467 .Xr free 3 Ns d
 468 when
 469 .Fn print_tagq
 470 is called on it or when
 471 .Fn print_stagq
 472 is called on a parent element.
 473 .Pp
 474 The function
 475 .Fn html_fillmode
 476 returns
 477 .Dv ROFF_fi
 478 if fill mode was active before the call or
 479 .Dv ROFF_nf
 480 otherwise.
 481 .Pp
 482 The function
 483 .Fn html_make_id
 484 returns a newly allocated string or
 485 .Dv NULL
 486 if
 487 .Fa n
 488 lacks text data to create the attribute from.
 489 The caller is responsible for
 490 .Xr free 3 Ns ing
 491 the returned string after using it.
 492 .Pp
 493 In case of
 494 .Xr malloc 3
 495 failure, these functions do not return but call
 496 .Xr err 3 .
 497 .Sh FILES
 498 .Bl -tag -width mandoc_aux.c -compact
 499 .It Pa main.h
 500 declarations of public functions for use by the main program,
 501 not yet documented
 502 .It Pa html.h
 503 declarations of data types and private functions
 504 for use by language-specific HTML formatters
 505 .It Pa html.c
 506 main HTML formatting engine and utility functions
 507 .It Pa mdoc_html.c
 508 .Xr mdoc 7
 509 HTML formatter
 510 .It Pa man_html.c
 511 .Xr man 7
 512 HTML formatter
 513 .It Pa tbl_html.c
 514 .Xr tbl 7
 515 HTML formatter
 516 .It Pa eqn_html.c
 517 .Xr eqn 7
 518 HTML formatter
 519 .It Pa roff_html.c
 520 .Xr roff 7
 521 HTML formatter, handling requests like
 522 .Ic br ,
 523 .Ic ce ,
 524 .Ic fi ,
 525 .Ic ft ,
 526 .Ic nf ,
 527 .Ic rj ,
 528 and
 529 .Ic sp .
 530 .It Pa out.h
 531 declarations of data types and private functions
 532 for shared use by all mandoc formatters,
 533 not yet documented
 534 .It Pa out.c
 535 private functions for shared use by all mandoc formatters
 536 .It Pa mandoc_aux.h
 537 declarations of common mandoc utility functions, see
 538 .Xr mandoc 3
 539 .It Pa mandoc_aux.c
 540 implementation of common mandoc utility functions
 541 .El
 542 .Sh SEE ALSO
 543 .Xr mandoc 1 ,
 544 .Xr mandoc 3 ,
 545 .Xr man.cgi 8
 546 .Sh AUTHORS
 547 .An -nosplit
 548 The mandoc HTML formatter was written by
 549 .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
 550 It is maintained by
 551 .An Ingo Schwarze Aq Mt schwarze@openbsd.org ,
 552 who also wrote this manual.