- To be done
- - Possibly we should add img//2 to include
images from symbolic path notation.
- It would be nice if the HTTP file server could use our location
This library allows for abstract declaration of available CSS and
Based on these declarations, html generating code can declare that it
library ensures that the proper links appear in the HTML head. The
implementation is based on mail system implemented by html_post/2
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
and style sheets (.css). It 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.
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.
- 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
- 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 http: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.
- States that About is an aggregate of the resources in
List. This means that if both About and one of the
elements of List appears in the dependencies, About
is kept and the smaller one is dropped. If there are a number of
dependencies on the small members, these are replaced with dependency on
is actually the composition of a number of smaller ones.
- 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
Registering the same About multiple times extends the
properties defined for About. In particular, this allows for
adding additional dependencies to a (virtual) resource.
- True when About is a currently known resource.
- Include ResourceOrList and all dependencies derived from it
and add them to the HTML
head using html_post/2.
The actual dependencies are computed during the HTML output phase by
- 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.
- Hook called to include a link to an HTML resource of type Mime
into the HTML head. The Mime type is computed from Path
file_mime_type/2. If the hook fails, two
built-in rules for
example, to include a =.pl= files as a Prolog script, use:
html_head:mime_include(text/'x-prolog', Path) --> !,