/* Part of XPCE --- The SWI-Prolog GUI toolkit Author: Jan Wielemaker and Anjo Anjewierden E-mail: jan@swi.psy.uva.nl WWW: http://www.swi.psy.uva.nl/projects/xpce/ Copyright (c) 2000-2011, University of Amsterdam All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: 1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. 2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ :- module(html_write, [ page/3, % generate an HTML page page/4, % page from head and body html/3, % Useful primitives for expanding html_begin/3, % +EnvName[(Attribute...)] html_end/3, % +EnvName html_quoted/3, % +Text html_quoted_attribute/3, % +Attribute % Emitting the HTML code print_html/1, % +List print_html/2, % +Stream, +List html_print_length/2 % +List, -Length ]). :- use_module(library(quintus)). % for meta_predicate/1 :- meta_predicate html(:, -, +), page(:, -, +), page(:, :, -, +), pagehead(:, -, +), pagebody(:, -, +). /* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - library(html_write) The purpose of this library is to simplify writing HTML pages. Of course, it is possible to use format/[2,3] to write to the HTML stream directly, but this is generally not very satisfactory: * It is a lot of typing * It does not guarantee proper HTML syntax. You have to deal with HTML quoting, proper nesting and reasonable layout. * It is hard to use satisfactory abstraction This module tries to remedy these problems. The idea is to translate a Prolog term into an HTML document. We use DCG for most of the generation. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */ page(Content) --> [ '\n', '', nl(1) ], html(Content), [ nl(1), '\n' ]. page(Head, Body) --> [ '\n', '', nl(1) ], pagehead(Head), pagebody(Body), [ nl(1), '\n' ]. pagehead(Head) --> { strip_module(Head, M, _), hook_module(M, head(_,_,_)) }, !, M:head(Head). pagehead(Head) --> html(head(Head)). pagebody(Body) --> { strip_module(Body, M, _), hook_module(M, body(_,_,_)) }, !, M:body(Body). pagebody(Body) --> html(body([bgcolor(white)], Body)). hook_module(M, P) :- current_predicate(_, M:P), !. hook_module(user, P) :- current_predicate(_, user:P). html(Spec) --> { strip_module(Spec, M, T) }, html(T, M). html([], _) --> !, []. html([H|T], M) --> !, ( do_expand(H, M) -> [] ; { print_message(error, html(expand_failed(H))) } ), html(T, M). html(X, M) --> do_expand(X, M). :- multifile expand/3. do_expand(Token, _) --> % call user hooks expand(Token), !. do_expand(Fmt-Args, _) --> !, { sformat(String, Fmt, Args) }, html_quoted(String). do_expand(\List, _) --> { is_list(List) }, !, List. do_expand(\Term, Module, In, Rest) :- !, call(Module:Term, In, Rest). do_expand(Module:Term, _, In, Rest) :- !, call(Module:Term, In, Rest). do_expand(script(Content), _) --> % general CDATA declared content elements? !, html_begin(script), [ Content ], html_end(script). do_expand(&(Entity), _) --> !, { atomic_list_concat([&, Entity, ;], HTML) }, [ HTML ]. do_expand(Token, _) --> { atomic(Token) }, !, html_quoted(Token). do_expand(element(Env, Attributes, Contents), M) --> !, html_begin(Env, Attributes), html(Contents, M), html_end(Env). do_expand(Term, M) --> { Term =.. [Env, Contents] }, !, ( { layout(Env, _, empty) } -> html_begin(Env, Contents) ; html_begin(Env), html(Contents, M), html_end(Env) ). do_expand(Term, M) --> { Term =.. [Env, Attributes, Contents] }, !, html_begin(Env, Attributes), html(Contents, M), html_end(Env). html_begin(Env) --> { Env =.. [Name|Attributes] }, html_begin(Name, Attributes). html_begin(Env, Attributes) --> pre_open(Env), [<], [Env], attributes(Attributes), [>], post_open(Env). html_end(Env) --> % empty element or omited close { layout(Env, _, -) ; layout(Env, _, empty) }, !, []. html_end(Env) --> pre_close(Env), [''], post_close(Env). attributes([]) --> !, []. attributes([H|T]) --> !, attribute(H), attributes(T). attributes(One) --> attribute(One). attribute(Name=Value) --> !, [' ', Name, '="' ], html_quoted_attribute(Value), ['"']. attribute(Term) --> { Term =.. [Name, Value] }, !, attribute(Name=Value). attribute(Atom) --> % Value-abbreviated attribute { atom(Atom) }, [ ' ', Atom ]. /******************************* * QUOTING RULES * *******************************/ % html_quoted(Text) % % Quote the value for normal text. html_quoted(Text) --> { sub_atom(Text, _, _, _, <) ; sub_atom(Text, _, _, _, >) ; sub_atom(Text, _, _, _, &) }, !, { atom_chars(Text, Chars), quote_chars(Chars, QuotedChars), atomic_list_concat(QuotedChars, Quoted) }, [ Quoted ]. html_quoted(Text) --> [ Text ]. quote_chars([], []). quote_chars([H0|T0], [H|T]) :- quote_char(H0, H), quote_chars(T0, T). quote_char(<, '<') :- !. quote_char(>, '>') :- !. quote_char(&, '&') :- !. quote_char(X, X). % html_quoted_attribute(+Text) % % Quote the value according to the rules for tag-attributes html_quoted_attribute(Text) --> { sub_atom(Text, _, _, _, <) ; sub_atom(Text, _, _, _, >) % ; sub_atom(Text, _, _, _, &) ; sub_atom(Text, _, _, _, '"') % ; sub_atom(Text, _, _, _, '''') }, !, { atom_chars(Text, Chars), quote_att_chars(Chars, QuotedChars), atomic_list_concat(QuotedChars, Quoted) }, [ Quoted ]. html_quoted_attribute(Text) --> [ Text ]. quote_att_chars([], []). quote_att_chars([H0|T0], [H|T]) :- quote_att_char(H0, H), quote_att_chars(T0, T). quote_att_char(<, '<') :- !. quote_att_char(>, '>') :- !. %quote_att_char(&, '&') :- !. quote_att_char('"', '"') :- !. %quote_att_char('''', ''') :- !. quote_att_char(X, X). /******************************* * LAYOUT * *******************************/ pre_open(Env) --> { layout(Env, N-_, _) }, !, [ nl(N) ]. pre_open(_) --> []. post_open(Env) --> { layout(Env, _-N, _) }, !, [ nl(N) ]. post_open(_) --> []. pre_close(Env) --> { layout(Env, _, N-_) }, !, [ nl(N) ]. pre_close(_) --> []. post_close(Env) --> { layout(Env, _, _-N) }, !, [ nl(N) ]. post_close(_) --> []. % layout(Tag, PreOpen-PostOpen, PreClose-PostClose) % % Define required newlines before and after tags. This table is % rather incomplete. :- multifile layout/3. layout(table, 2-1, 1-2). layout(blockquote, 2-1, 1-2). layout(center, 2-1, 1-2). layout(dl, 2-1, 1-2). layout(ul, 2-1, 1-2). layout(form, 2-1, 1-2). layout(frameset, 2-1, 1-2). layout(head, 1-1, 1-1). layout(body, 1-1, 1-1). layout(script, 1-1, 1-1). layout(select, 1-1, 1-1). layout(map, 1-1, 1-1). layout(html, 1-1, 1-1). layout(tr, 1-0, 0-1). layout(option, 1-0, 0-1). layout(li, 1-0, 0-1). layout(dt, 1-0, -). layout(dd, 0-0, -). layout(title, 1-0, 0-1). layout(h1, 2-0, 0-2). layout(h2, 2-0, 0-2). layout(h3, 2-0, 0-2). layout(h4, 2-0, 0-2). layout(hr, 1-1, empty). % empty elements layout(br, 0-1, empty). layout(img, 0-0, empty). layout(meta, 1-1, empty). layout(base, 1-1, empty). layout(link, 1-1, empty). layout(input, 0-0, empty). layout(frame, 1-1, empty). layout(col, 0-0, empty). layout(area, 1-0, empty). layout(input, 1-0, empty). layout(option, 1-0, empty). layout(p, 2-1, -). % omited close layout(td, 0-0, 0-0). /******************************* * PRINTING * *******************************/ % print_html(+Stream, +List) % % Print list of atoms and layout instructions. Currently used layout % instructions: % % nl(N) Use at minimum N newlines here. print_html(List) :- current_output(Out), write_html(List, Out). print_html(Out, List) :- write_html(List, Out). write_html([], _). write_html([nl(N)|T], Out) :- !, join_nl(T, N, Lines, T2), write_nl(Lines, Out), write_html(T2, Out). write_html([H|T], Out) :- write(Out, H), write_html(T, Out). join_nl([nl(N0)|T0], N1, N, T) :- !, N2 is max(N0, N1), join_nl(T0, N2, N, T). join_nl(L, N, N, L). write_nl(0, _) :- !. write_nl(N, Out) :- nl(Out), N1 is N - 1, write_nl(N1, Out). % html_print_length(+List, -Len) % % Determine the content length of the list. html_print_length(List, Len) :- html_print_length(List, 0, Len). html_print_length([], L, L). html_print_length([nl(N)|T], L0, L) :- !, join_nl(T, N, Lines, T1), L1 is L0 + Lines, % assume only \n! html_print_length(T1, L1, L). html_print_length([H|T], L0, L) :- atom_length(H, Hlen), L1 is L0+Hlen, html_print_length(T, L1, L). /******************************* * MESSAGES * *******************************/ :- multifile prolog:message/3. prolog:message(html(expand_failed(What))) --> [ 'Failed to translate to HTML: ~p'-[What] ].