html_head.pl -- Automatic inclusion of CSS and scripts links
Declarations come in two forms. First of all http locations are declared
using the http_path.pl library. Second, html_resource/2 specifies HTML
resources to be used in the
head and their dependencies. Resources are
is trivial to add support for other material in the head. See
For usage in HTML generation, there is the DCG rule html_requires//1 that demands named resources in the HTML head.
About resource ordering
All calls to html_requires//1 for the page are collected and duplicates are removed. Next, the following steps are taken:
- Add all dependencies to the set
- Replace multiple members by `aggregate' scripts or css files. see use_agregates/4.
- Order all resources by demanding that their dependencies preceede the resource itself. Note that the ordering of resources in the dependency list is ignored. This implies that if the order matters the dependency list must be split and only the primary dependency must be added.
debug(html(script)). to see the requested and final set of
resources. All declared resources are in html_resource/3. The edit/1
command recognises the names of HTML resources.
- html_resource(+About, +Properties) is det
- Register an HTML head resource. About is either an atom that
specifies an HTTP location or a term Alias(Sub). This works
similar to absolute_file_name/2. See location_path/2 for
details. Recognised properties are:
- Other required script and css files. If this is a plain file name, it is interpreted relative to the declared resource. Requirements can be a list, which is equivalent to multiple requires properties.
false), do not include About itself, but only its dependencies. This allows for defining an alias for one or more resources.
- Defines that the list of requirements is ordered, which means that each requirement in the list depends on its predecessor.
- May be specified for non-virtual resources to specify the mime-type of the resource. By default, the mime type is derived from the file name using file_mime_type/2.
Registering the same About multiple times extends the properties defined for About. In particular, this allows for adding additional dependencies to a (virtual) resource.
- html_current_resource(?About) is nondet
- True when About is a currently known resource.
- html_requires(+ResourceOrList)// is det
- Include ResourceOrList and all dependencies derived from it and
add them to the HTML
headusing html_post/2. The actual dependencies are computed during the HTML output phase by html_insert_resource//1.
- html_insert_resource(+ResourceOrList)// is det
- Actually include HTML head resources. Called through
html_post//2 from html_requires//1 after rewrite by
html_head_expansion/2. We are guaranteed we will only get one
call that is passed a flat list of requested requirements. We
have three jobs:
- Figure out all indirect requirements
- See whether we can use any `aggregate' resources
- Put required resources before their requiree.
- mime_include(+Mime, +Path)// is semidet[multifile]
- Hook called to include a link to an HTML resource of type Mime
into the HTML head. The Mime type is computed from Path using
file_mime_type/2. If the hook fails, two built-in rules for
:- multifile html_head:mime_include//2. html_head:mime_include(text/'x-prolog', Path) --> !, html(script([ type('text/x-prolog'), src(Path) ], )).