mandoc_html.3

   1 .\"     $Id: mandoc_html.3,v 1.13 2018/06/10 16:47:15 schwarze Exp $
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   3 .\" Copyright (c) 2014, 2017, 2018 Ingo Schwarze <schwarze@openbsd.org>
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  17 .Dd $Mdocdate: June 10 2018 $
  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 "html.h"
  25 .Ft void
  26 .Fn print_gen_decls "struct html *h"
  27 .Ft void
  28 .Fn print_gen_comment "struct html *h" "struct roff_node *n"
  29 .Ft void
  30 .Fn print_gen_head "struct html *h"
  31 .Ft struct tag *
  32 .Fo print_otag
  33 .Fa "struct html *h"
  34 .Fa "enum htmltag tag"
  35 .Fa "const char *fmt"
  36 .Fa ...
  37 .Fc
  38 .Ft void
  39 .Fo print_tagq
  40 .Fa "struct html *h"
  41 .Fa "const struct tag *until"
  42 .Fc
  43 .Ft void
  44 .Fo print_stagq
  45 .Fa "struct html *h"
  46 .Fa "const struct tag *suntil"
  47 .Fc
  48 .Ft void
  49 .Fo print_text
  50 .Fa "struct html *h"
  51 .Fa "const char *word"
  52 .Fc
  53 .Ft char *
  54 .Fo html_make_id
  55 .Fa "const struct roff_node *n"
  56 .Fc
  57 .Ft int
  58 .Fo html_strlen
  59 .Fa "const char *cp"
  60 .Fc
  61 .Sh DESCRIPTION
  62 The mandoc HTML formatter is not a formal library.
  63 However, as it is compiled into more than one program, in particular
  64 .Xr mandoc 1
  65 and
  66 .Xr man.cgi 8 ,
  67 and because it may be security-critical in some contexts,
  68 some documentation is useful to help to use it correctly and
  69 to prevent XSS vulnerabilities.
  70 .Pp
  71 The formatter produces HTML output on the standard output.
  72 Since proper escaping is usually required and best taken care of
  73 at one central place, the language-specific formatters
  74 .Po
  75 .Pa *_html.c ,
  76 see
  77 .Sx FILES
  78 .Pc
  79 are not supposed to print directly to
  80 .Dv stdout
  81 using functions like
  82 .Xr printf 3 ,
  83 .Xr putc 3 ,
  84 .Xr puts 3 ,
  85 or
  86 .Xr write 2 .
  87 Instead, they are expected to use the output functions declared in
  88 .Pa html.h
  89 and implemented as part of the main HTML formatting engine in
  90 .Pa html.c .
  91 .Ss Data structures
  92 These structures are declared in
  93 .Pa html.h .
  94 .Bl -tag -width Ds
  95 .It Vt struct html
  96 Internal state of the HTML formatter.
  97 .It Vt struct tag
  98 One entry for the LIFO stack of HTML elements.
  99 Members are
 100 .Fa "enum htmltag tag"
 101 and
 102 .Fa "struct tag *next" .
 103 .El
 104 .Ss Private interface functions
 105 The function
 106 .Fn print_gen_decls
 107 prints the opening
 108 .Ao Pf \&? Ic xml ? Ac
 109 and
 110 .Aq Pf \&! Ic DOCTYPE
 111 declarations required for the current document type.
 112 .Pp
 113 The function
 114 .Fn print_gen_comment
 115 prints the leading comments, usually containing a Copyright notice
 116 and license, as an HTML comment.
 117 It is intended to be called right after opening the
 118 .Aq Ic HTML
 119 element.
 120 Pass the first
 121 .Dv ROFFT_COMMENT
 122 node in
 123 .Fa n .
 124 .Pp
 125 The function
 126 .Fn print_gen_head
 127 prints the opening
 128 .Aq Ic META
 129 and
 130 .Aq Ic LINK
 131 elements for the document
 132 .Aq Ic HEAD ,
 133 using the
 134 .Fa style
 135 member of
 136 .Fa h
 137 unless that is
 138 .Dv NULL .
 139 It uses
 140 .Fn print_otag
 141 which takes care of properly encoding attributes,
 142 which is relevant for the
 143 .Fa style
 144 link in particular.
 145 .Pp
 146 The function
 147 .Fn print_otag
 148 prints the start tag of an HTML element with the name
 149 .Fa tag ,
 150 optionally including the attributes specified by
 151 .Fa fmt .
 152 If
 153 .Fa fmt
 154 is the empty string, no attributes are written.
 155 Each letter of
 156 .Fa fmt
 157 specifies one attribute to write.
 158 Most attributes require one
 159 .Va char *
 160 argument which becomes the value of the attribute.
 161 The arguments have to be given in the same order as the attribute letters.
 162 If an argument is
 163 .Dv NULL ,
 164 the respective attribute is not written.
 165 .Bl -tag -width 1n -offset indent
 166 .It Cm c
 167 Print a
 168 .Cm class
 169 attribute.
 170 This attribute letter can optionally be followed by the modifier letter
 171 .Cm T .
 172 In that case, a
 173 .Cm title
 174 attribute with the same value is also printed.
 175 .It Cm h
 176 Print a
 177 .Cm href
 178 attribute.
 179 This attribute letter can optionally be followed by a modifier letter.
 180 If followed by
 181 .Cm R ,
 182 it formats the link as a local one by prefixing a
 183 .Sq #
 184 character.
 185 If followed by
 186 .Cm I ,
 187 it interpretes the argument as a header file name
 188 and generates a link using the
 189 .Xr mandoc 1
 190 .Fl O Cm includes
 191 option.
 192 If followed by
 193 .Cm M ,
 194 it takes two arguments instead of one, a manual page name and
 195 section, and formats them as a link to a manual page using the
 196 .Xr mandoc 1
 197 .Fl O Cm man
 198 option.
 199 .It Cm i
 200 Print an
 201 .Cm id
 202 attribute.
 203 .It Cm \&?
 204 Print an arbitrary attribute.
 205 This format letter requires two
 206 .Vt char *
 207 arguments, the attribute name and the value.
 208 The name must not be
 209 .Dv NULL .
 210 .It Cm s
 211 Print a
 212 .Cm style
 213 attribute.
 214 If present, it must be the last format letter.
 215 In contrast to the other format letters, this one does not yet
 216 print the value and does not take an argument.
 217 Instead, the rest of the format string consists of pairs of
 218 argument type letters and style name letters.
 219 .El
 220 .Pp
 221 Argument type letters each require one argument as follows:
 222 .Bl -tag -width 1n -offset indent
 223 .It Cm h
 224 Requires one
 225 .Vt int
 226 argument, interpreted as a horizontal length in units of
 227 .Dv SCALE_EN .
 228 .It Cm s
 229 Requires one
 230 .Vt char *
 231 argument, used as a style value.
 232 .It Cm u
 233 Requires one
 234 .Vt struct roffsu *
 235 argument, used as a length.
 236 .It Cm w
 237 Requires one
 238 .Vt char *
 239 argument, interpreted as an
 240 .Xr mdoc 7 Ns -style
 241 width specifier.
 242 If the argument is
 243 .Dv NULL ,
 244 nothing is printed for this pair.
 245 .Pp
 246 The
 247 .Cm w
 248 argument type letter can optionally be followed by the modifier
 249 .Cm +
 250 which increases the width by 20% to make even bold text fit
 251 and adds three units for padding between columns.
 252 .El
 253 .Pp
 254 Style name letters decide what to do with the preceding argument:
 255 .Bl -tag -width 1n -offset indent
 256 .It Cm i
 257 Set
 258 .Cm text-indent
 259 to the given length.
 260 .It Cm l
 261 Set
 262 .Cm margin-left
 263 to the given length.
 264 .It Cm w
 265 Set
 266 .Cm width
 267 to the given length.
 268 .It Cm W
 269 Set
 270 .Cm min-width
 271 to the given length.
 272 .It Cm \&?
 273 The special pair
 274 .Cm s?
 275 requires two
 276 .Vt char *
 277 arguments.
 278 The first is the style name, the second its value.
 279 The style name must not be
 280 .Dv NULL .
 281 .El
 282 .Pp
 283 .Fn print_otag
 284 uses the private function
 285 .Fn print_encode
 286 to take care of HTML encoding.
 287 If required by the element type, it remembers in
 288 .Fa h
 289 that the element is open.
 290 The function
 291 .Fn print_tagq
 292 is used to close out all open elements up to and including
 293 .Fa until ;
 294 .Fn print_stagq
 295 is a variant to close out all open elements up to but excluding
 296 .Fa suntil .
 297 .Pp
 298 The function
 299 .Fn print_text
 300 prints HTML element content.
 301 It uses the private function
 302 .Fn print_encode
 303 to take care of HTML encoding.
 304 If the document has requested a non-standard font, for example using a
 305 .Xr roff 7
 306 .Ic \ef
 307 font escape sequence,
 308 .Fn print_text
 309 wraps
 310 .Fa word
 311 in an HTML font selection element using the
 312 .Fn print_otag
 313 and
 314 .Fn print_tagq
 315 functions.
 316 .Pp
 317 The function
 318 .Fn html_make_id
 319 takes a node containing one or more text children
 320 and returns a newly allocated string containing the concatenation
 321 of the child strings, with blanks replaced by underscores.
 322 If the node
 323 .Fa n
 324 contains any non-text child node,
 325 .Fn html_make_id
 326 returns
 327 .Dv NULL
 328 instead.
 329 The caller is responsible for freeing the returned string.
 330 .Pp
 331 The function
 332 .Fn html_strlen
 333 counts the number of characters in
 334 .Fa cp .
 335 It is used as a crude estimate of the width needed to display a string.
 336 .Pp
 337 The functions
 338 .Fn print_eqn ,
 339 .Fn print_tbl ,
 340 and
 341 .Fn print_tblclose
 342 are not yet documented.
 343 .Sh FILES
 344 .Bl -tag -width mandoc_aux.c -compact
 345 .It Pa main.h
 346 declarations of public functions for use by the main program,
 347 not yet documented
 348 .It Pa html.h
 349 declarations of data types and private functions
 350 for use by language-specific HTML formatters
 351 .It Pa html.c
 352 main HTML formatting engine and utility functions
 353 .It Pa mdoc_html.c
 354 .Xr mdoc 7
 355 HTML formatter
 356 .It Pa man_html.c
 357 .Xr man 7
 358 HTML formatter
 359 .It Pa tbl_html.c
 360 .Xr tbl 7
 361 HTML formatter
 362 .It Pa eqn_html.c
 363 .Xr eqn 7
 364 HTML formatter
 365 .It Pa out.h
 366 declarations of data types and private functions
 367 for shared use by all mandoc formatters,
 368 not yet documented
 369 .It Pa out.c
 370 private functions for shared use by all mandoc formatters
 371 .It Pa mandoc_aux.h
 372 declarations of common mandoc utility functions, see
 373 .Xr mandoc 3
 374 .It Pa mandoc_aux.c
 375 implementation of common mandoc utility functions
 376 .El
 377 .Sh SEE ALSO
 378 .Xr mandoc 1 ,
 379 .Xr mandoc 3 ,
 380 .Xr man.cgi 8
 381 .Sh AUTHORS
 382 .An -nosplit
 383 The mandoc HTML formatter was written by
 384 .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
 385 It is maintained by
 386 .An Ingo Schwarze Aq Mt schwarze@openbsd.org ,
 387 who also wrote this manual.