.\"	$Id: mandoc_html.3,v 1.1 2014/07/23 18:13:09 schwarze Exp $
.\"
.\" Copyright (c) 2014 Ingo Schwarze <schwarze@openbsd.org>
.\"
.\" Permission to use, copy, modify, and distribute this software for any
.\" purpose with or without fee is hereby granted, provided that the above
.\" copyright notice and this permission notice appear in all copies.
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.\" WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
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.Dd $Mdocdate: July 23 2014 $
.Dt MANDOC_HTML 3
.Os
.Sh NAME
.Nm mandoc_html
.Nd internals of the mandoc HTML formatter
.Sh SYNOPSIS
.In "html.h"
.Ft void
.Fn print_gen_decls "struct html *h"
.Ft void
.Fn print_gen_head "struct html *h"
.Ft struct tag *
.Fo print_otag
.Fa "struct html *h"
.Fa "enum htmltag tag"
.Fa "int sz"
.Fa "const struct htmlpair *p"
.Fc
.Ft void
.Fo print_tagq
.Fa "struct html *h"
.Fa "const struct tag *until"
.Fc
.Ft void
.Fo print_stagq
.Fa "struct html *h"
.Fa "const struct tag *suntil"
.Fc
.Ft void
.Fo print_text
.Fa "struct html *h"
.Fa "const char *word"
.Fc
.Sh DESCRIPTION
The mandoc HTML formatter is not a formal library.
However, as it is compiled into more than one program, in particular
.Xr mandoc 1
and
.Xr man.cgi 8 ,
and because it may be security-critical in some contexts,
some documentation is useful to help to use it correctly and
to prevent XSS vulnerabilities.
.Pp
The formatter produces HTML output on the standard output.
Since proper escaping is usually required and best taken care of
at one central place, the language-specific formatters
.Po
.Pa *_html.c ,
see
.Sx FILES
.Pc
are not supposed to print directly to
.Dv stdout
using functions like
.Xr printf 3 ,
.Xr putc 3 ,
.Xr puts 3 ,
or
.Xr write 2 .
Instead, they are expected to use the output functions declared in
.Pa html.h
and implemented as part of the main HTML formatting engine in
.Pa html.c .
.Ss Data structures
These structures are declared in
.Pa html.h .
.Bl -tag -width Ds
.It Vt struct html
Internal state of the HTML formatter.
.It Vt struct htmlpair
Holds one HTML attribute.
Members are
.Fa "enum htmlattr key"
and
.Fa "const char *val" .
Helper macros
.Fn PAIR_*
are provided to support initialization of such structures.
.It Vt struct tag
One entry for the LIFO stack of HTML elements.
Members are
.Fa "enum htmltag tag"
and
.Fa "struct tag *next" .
.El
.Ss Private interface functions
The function
.Fn print_gen_decls
prints the opening
.Ao Pf \&? Ic xml ? Ac
and
.Aq Pf \&! Ic DOCTYPE
declarations required for the current document type.
.Pp
The function
.Fn print_gen_head
prints the opening
.Aq Ic META
and
.Aq Ic LINK
elements for the document
.Aq Ic HEAD ,
using the
.Fa style
member of
.Fa h
unless that is
.Dv NULL .
It uses
.Fn print_otag
which takes care of properly encoding attributes,
which is relevant for the
.Fa style
link in particular.
.Pp
The function
.Fn print_otag
prints the start tag of an HTML element with the name
.Fa tag ,
including the
.Fa sz
attributes that can optionally be provided in the
.Fa p
array.
It uses the private function
.Fn print_attr
which in turn uses the private function
.Fn print_encode
to take care of HTML encoding.
If required by the element type, it remembers in
.Fa h
that the element is open.
The function
.Fn print_tagq
is used to close out all open elements up to and including
.Fa until ;
.Fn print_stagq
is a variant to close out all open elements up to but excluding
.Fa suntil .
.Pp
The function
.Fn print_text
prints HTML element content.
It uses the private function
.Fn print_encode
to take care of HTML encoding.
If the document has requested a non-standard font, for example using a
.Xr roff 7
.Ic \ef
font escape sequence,
.Fn print_text
wraps
.Fa word
in an HTML font selection element using the
.Fn print_otag
and
.Fn print_tagq
functions.
.Pp
The functions
.Fn bufinit ,
.Fn bufcat* ,
and
.Fn buffmt*
do not directly produce output but buffer text in the
.Fa buf
member of
.Fa h .
They are not used internally by
.Pa html.c
but intended for use by the language-specific formatters
to ease preparation of strings for the
.Fa p
argument of
.Fn print_otag
and for the
.Fa word
argument of
.Fn print_text .
Consequently, these functions do not do any HTML encoding.
.Pp
The functions
.Fn html_strlen ,
.Fn print_eqn ,
.Fn print_tbl ,
and
.Fn print_tblclose
are not yet documented.
.Sh FILES
.Bl -tag -width mandoc_aux.c -compact
.It Pa main.h
declarations of public functions for use by the main program,
not yet documented
.It Pa html.h
declarations of data types and private functions
for use by language-specific HTML formatters
.It Pa html.c
main HTML formatting engine and utility functions
.It Pa mdoc_html.c
.Xr mdoc 7
HTML formatter
.It Pa man_html.c
.Xr man 7
HTML formatter
.It Pa tbl_html.c
.Xr tbl 7
HTML formatter
.It Pa eqn_html.c
.Xr eqn 7
HTML formatter
.It Pa out.h
declarations of data types and private functions
for shared use by all mandoc formatters,
not yet documented
.It Pa out.c
private functions for shared use by all mandoc formatters
.It Pa mandoc_aux.h
declarations of common mandoc utility functions, see
.Xr mandoc 3
.It Pa mandoc_aux.c
implementation of common mandoc utility functions
.El
.Sh SEE ALSO
.Xr mandoc 1 ,
.Xr mandoc 3 ,
.Xr man.cgi 8
.Sh AUTHORS
.An -nosplit
The mandoc HTML formatter was written by
.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
This manual was written by
.An Ingo Schwarze Aq Mt schwarze@openbsd.org .