mandoc_html.3

   1 .\"     $Id: mandoc_html.3,v 1.19 2019/01/11 12:56:43 schwarze Exp $
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   3 .\" Copyright (c) 2014, 2017, 2018 Ingo Schwarze <schwarze@openbsd.org>
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  17 .Dd $Mdocdate: January 11 2019 $
  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 .It Cm h
 171 Print a
 172 .Cm href
 173 attribute.
 174 This attribute letter can optionally be followed by a modifier letter.
 175 If followed by
 176 .Cm R ,
 177 it formats the link as a local one by prefixing a
 178 .Sq #
 179 character.
 180 If followed by
 181 .Cm I ,
 182 it interpretes the argument as a header file name
 183 and generates a link using the
 184 .Xr mandoc 1
 185 .Fl O Cm includes
 186 option.
 187 If followed by
 188 .Cm M ,
 189 it takes two arguments instead of one, a manual page name and
 190 section, and formats them as a link to a manual page using the
 191 .Xr mandoc 1
 192 .Fl O Cm man
 193 option.
 194 .It Cm i
 195 Print an
 196 .Cm id
 197 attribute.
 198 .It Cm \&?
 199 Print an arbitrary attribute.
 200 This format letter requires two
 201 .Vt char *
 202 arguments, the attribute name and the value.
 203 The name must not be
 204 .Dv NULL .
 205 .It Cm s
 206 Print a
 207 .Cm style
 208 attribute.
 209 If present, it must be the last format letter.
 210 It requires two
 211 .Va char *
 212 arguments.
 213 The first is the name of the style property, the second its value.
 214 The name must not be
 215 .Dv NULL .
 216 The
 217 .Cm s
 218 .Ar fmt
 219 letter can be repeated, each repetition requiring an additional pair of
 220 .Va char *
 221 arguments.
 222 .El
 223 .Pp
 224 .Fn print_otag
 225 uses the private function
 226 .Fn print_encode
 227 to take care of HTML encoding.
 228 If required by the element type, it remembers in
 229 .Fa h
 230 that the element is open.
 231 The function
 232 .Fn print_tagq
 233 is used to close out all open elements up to and including
 234 .Fa until ;
 235 .Fn print_stagq
 236 is a variant to close out all open elements up to but excluding
 237 .Fa suntil .
 238 .Pp
 239 The function
 240 .Fn print_text
 241 prints HTML element content.
 242 It uses the private function
 243 .Fn print_encode
 244 to take care of HTML encoding.
 245 If the document has requested a non-standard font, for example using a
 246 .Xr roff 7
 247 .Ic \ef
 248 font escape sequence,
 249 .Fn print_text
 250 wraps
 251 .Fa word
 252 in an HTML font selection element using the
 253 .Fn print_otag
 254 and
 255 .Fn print_tagq
 256 functions.
 257 .Pp
 258 The function
 259 .Fn html_make_id
 260 takes a node containing one or more text children
 261 and returns a newly allocated string containing the concatenation
 262 of the child strings, with blanks replaced by underscores.
 263 If the node
 264 .Fa n
 265 contains any non-text child node,
 266 .Fn html_make_id
 267 returns
 268 .Dv NULL
 269 instead.
 270 The caller is responsible for freeing the returned string.
 271 .Pp
 272 The function
 273 .Fn html_strlen
 274 counts the number of characters in
 275 .Fa cp .
 276 It is used as a crude estimate of the width needed to display a string.
 277 .Pp
 278 The functions
 279 .Fn print_eqn ,
 280 .Fn print_tbl ,
 281 and
 282 .Fn print_tblclose
 283 are not yet documented.
 284 .Sh FILES
 285 .Bl -tag -width mandoc_aux.c -compact
 286 .It Pa main.h
 287 declarations of public functions for use by the main program,
 288 not yet documented
 289 .It Pa html.h
 290 declarations of data types and private functions
 291 for use by language-specific HTML formatters
 292 .It Pa html.c
 293 main HTML formatting engine and utility functions
 294 .It Pa mdoc_html.c
 295 .Xr mdoc 7
 296 HTML formatter
 297 .It Pa man_html.c
 298 .Xr man 7
 299 HTML formatter
 300 .It Pa tbl_html.c
 301 .Xr tbl 7
 302 HTML formatter
 303 .It Pa eqn_html.c
 304 .Xr eqn 7
 305 HTML formatter
 306 .It Pa out.h
 307 declarations of data types and private functions
 308 for shared use by all mandoc formatters,
 309 not yet documented
 310 .It Pa out.c
 311 private functions for shared use by all mandoc formatters
 312 .It Pa mandoc_aux.h
 313 declarations of common mandoc utility functions, see
 314 .Xr mandoc 3
 315 .It Pa mandoc_aux.c
 316 implementation of common mandoc utility functions
 317 .El
 318 .Sh SEE ALSO
 319 .Xr mandoc 1 ,
 320 .Xr mandoc 3 ,
 321 .Xr man.cgi 8
 322 .Sh AUTHORS
 323 .An -nosplit
 324 The mandoc HTML formatter was written by
 325 .An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
 326 It is maintained by
 327 .An Ingo Schwarze Aq Mt schwarze@openbsd.org ,
 328 who also wrote this manual.