This library provides predicates for generating HTML content using either HTML 5 or XHTML 1.1 formats from a term representation. The library performs minimal validation, checking only that all elements are valid. No attempt is made to generate nicely indented output.
Normal elements are represented using a compound term with one argument
(the element content) or two arguments (the element attributes
represented by a list of
Key-Value pairs and the
element content). The element content can be another element or a list
of elements. For example:
ol([type-a], [li(foo), li(bar), li(baz)])
The two exceptions are the
code elements whose content is
never interpreted as an element or a list of elements. For example, the
is translated to:
<pre> [foo,bar,baz] </pre>
Void elements are represented using a compound term with one argument,
the (possibly empty) list of attributes represented by a list of
Key-Value pairs. For example:
Atomic arguments of the compound terms are interpreted as element
content. Non atomic element content can be represented as a quoted atom
or by using the
code elements as explained above.
This library is a work in progress.
Open the ../../docs/library_index.html#html link in a web browser.
To load all entities in this library, load the
| ?- logtalk_load(html(loader)).
To test this library predicates, load the
| ?- logtalk_load(html(tester)).
Generating a HTML document¶
HTML documents can be generated from a compound term representation and written to a file or a stream. For example, assuming we want to generate a HTML 5 file:
| ?- html5::generate( file('hello.html'), html([lang=en], [head(title('Hello world!')), body(p('Bye!'))]) ).
When the second argument is a
html/2 compound term, a
doctype is automatically written. If we prefer instead e.g. a XHTML
1.1 document, we use the
| ?- xhtml11::generate( file('hello.html'), html([lang=en], [head(title('Hello world!')), body(p('Bye!'))]) ).
Generating a HTML fragment¶
It’s also possible to generate just a fragment of a (X)HTML document by
using a list of compound terms or a compound term for an element other
html. For example:
| ?- current_output(Stream), html5::generate(stream(Stream), ul([li(foo), li(bar), li(baz)])). <ul> <li> foo</li> <li> bar</li> <li> baz</li> </ul> Stream = ...
Working with callbacks to generate content¶
Often we need to programmatically generate HTML content from queries. In
other cases, we may have fixed content that we don’t want to keep
repeating (e.g. a navigation bar). The library supports a
pseudo-element that sends a message to an object to retrieve content. As
an example, assume the following predicate definition in
This predicate can then be called from the HTML term representation. For example:
| ?- current_output(Stream), html5::generate(stream(Stream), span(user::content)). <span><strong>Hello world!</strong></span> Stream = ...
Note that the callback always takes the form
Closure is extended with a single argument (to be bound to the
generated content). More complex callbacks are possible by using lambda
Working with custom elements¶
xhtml11 objects recognize the same set of standard
HTML 5 normal and void elements and generate an error for non-standard
elements. If you need to generate HTML content containing custom
elements, define a new object that extends one of the library objects.
:- object(html5custom, extends(html5)). normal_element(foo, inline). normal_element(bar, block). normal_element(Name, Display) :- ^^normal_element(Name, Display). :- end_object.