(in-package #:spinneret)

 (defparameter *shopping-list*
   '("Atmospheric ponds"
     "Electric gumption socks"
     "Mrs. Leland's embyronic television combustion"
     "Savage gymnatic aggressors"
     "Pharmaceutical pianos"
     "Intravenous retribution champions"))

 (defparameter *user-name* "John Q. Lisper")

 (defparameter *last-login* "12th Never")

 (defmacro with-page ((&key title) &body body)
   `(with-html
      (:doctype)
      (:html
        (:head
         (:title ,title))
        (:body ,@body))))

 (defun shopping-list ()
   (with-page (:title "Home page")
     (:header
      (:h1 "Home page"))
     (:section
      ("~A, here is *your* shopping list: " *user-name*)
      (:ol (dolist (item *shopping-list*)
             (:li (1+ (random 10)) item))))
     (:footer ("Last login: ~A" *last-login*))))

Printing style

Spinneret tries hard to produce human-writable output – output that
looks like a human being wrote it. Sometimes, however, you may have
markup to render that there is no human-writable way to render,
because no human being would ever write it.

In these cases you can set or bind the *html-style* variable to
control Spinneret’s print style. The default is :human, which means
to attempt to produce human-writable output. It can also be set to
:tree, which simply prints every element as if it were a block
element, and every run of text on a new line.

(let ((*html-style* :human))
  (with-html
    (:div
      (:p "Text " (:a "link text") " more text"))))
=> 

    
Text link text more text
   
"

(let ((*html-style* :tree))
  (with-html-string
    (:div
      (:p "Text " (:a "link text") " more text"))))
=> 

    

     Text
     
      link text
     
      more text
    
   

With *html-style* bound to :tree, and *print-pretty* bound to
nil, output is verbose but predictable:

(let ((*html-style* :tree)
      (*print-pretty* nil))
  (with-html-string
    (:div
      (:p "Text " (:a "link text") " more text"))))
=> "
Text link text  more text
"

Notice that binding *html-style* to :tree ensures that all tags are
closed.

Inserted spaces

By default, when objects are output to HTML, spaces are inserted betweeen them. This is nearly always the right thing to do, but in some special cases, the spaces may be a problem. They can be turned off by setting the flag *suppress-inserted-spaces* to t.

Line wrapping

When pretty-printing, Spinneret makes the best decisions about line
wrapping that it can, given the information it has about how to get
the print length of various types. But, in the case of user-defined
types, it has no way to tell in advance how long they will be when
printed. If you find Spinneret is making bad line-breaking decisions
with your types, you can help it out by specializing html-length.
For example, if you use PURI, you could help Spinneret pretty-print
PURI URIs by teaching it how to get their length:

(defmethod html-length ((uri puri:uri))
  ;; Doesn't cons.
  (length (puri:render-uri uri nil)))

Syntax

The rules for WITH-HTML are these:

• All generated forms write to *html*.

• A keyword in function position is interpreted as a tag name. If the
  name is not valid as a tag, it is ignored.

  Certain keywords are recognized as pseudo-tags and given special
  treatment:

  :RAW :DOCTYPE :!DOCTYPE :CDATA :!– :COMMENT :HTML :HEAD :H* :TAG

  • The pseudotag :RAW can be used to bypass Spinneret’s implicit
    escaping for raw output. This allows inserting HTML literals, and
    bypasses pretty printing.

    Note that you need :RAW for inline stylesheets and scripts,
    otherwise angle brackets will be escaped as if they were HTML:

    p{color: white;}”))
    => “

    ”

    (with-html-string (:style (:raw “a > p{color: white;}”)))
    => “

    ”
    ” dir=”auto”>

    (with-html-string (:style "a > p{color: white;}"))
    => ""
    
    (with-html-string (:style (:raw "a > p{color: white;}")))
    => ""
    

  • The pseudotags :!– and :COMMENT insert comments into the output.

  • The pseudotag :H* renders as one of :H1 through :H6 depending on
    how many :SECTION elements it is dynamically nested inside. At the
    top level, :H* is equivalent to :H1. Inside the dynamic extent of
    one :SECTION tag, it is equivalent to :H2; inside two section
    tags, it is equivalent to :H3; and so forth up to :H6.

  • The pseudotag :TAG allows dynamic selection of a tag.

  The value of the LANG attribute of HTML is controlled by
  *html-lang*; the value of the meta charset attribute is controlled
  by *html-charset*. These are defaults; passing an explicit
  attribute takes precedence.

  Constant classes and ids can be specified with a selector-like
  syntax. E.g.:

    (:div#wrapper (:div.section ...))
    ≡ (:div :id "wrapper" (:div :class "section" ...))
  

• Keyword-value pairs following a tag are interpreted as attributes.
  HTML syntax may not be used in attribute values. Attributes with nil
  values are omitted from the output. Boolean attributes with non-nil
  values are minimized.

  Duplicate attributes are handled like duplicate keyword arguments:
  all values are evaluated, but only the leftmost value is used. The
  exception is the handling of tokenized attributes, such as :CLASS or
  :REL. The class of a tag is the union of all its :CLASS arguments.

  The argument :DATASET introduces a list of :DATA-FOO arguments:

    (:p :dataset (:duck (dolomphious) :fish 'fizzgigious
                        :spoon "runcible"))
    ≡ (:p :data-duck (dolomphious) :data-fish 'fizzgigious
          :data-spoon "runcible")
  

  For flexibility, even at the cost of efficiency, the argument :ATTRS
  introduces a form to evaluate at run time for a plist of extra
  attributes and values.

• Forms after the attributes are treated as arguments. Each non-nil
  (primary) value returned by an argument to a tag is written to the
  stream by HTML, a generic function on which you can define your own
  methods. By default only literal arguments are printed. Literal
  arguments are strings, characters, numbers and symbols beside NIL.

WITH-HTML-STRING is like WITH-HTML, but intercepts the generated HTML
at run time and returns a string.

Dynamic output

For flexibility, even at the cost of efficiency, the pseudo-attribute
:ATTRS introduces a form to evaluate at run time for a plist of extra
attributes and values.

(:p :attrs (list :id "dynamic!"))
=> 

Similarly, the pseudo-tag :TAG allows you to select a tag at run time.

(:tag :name "div"
 (:tag :name "p"
  (:tag :name "span"
    "Hello.")))
≡ (:div (:p (:span "Hello")))

Note that :TAG only allows you to select a tag, not create one.
The tag must still be one that is known to Spinneret to be valid. (That is, either defined as part of HTML or matching the requirements for a custom element.)

For maximum dynamicity, you can combine :TAG and :ATTRS:

(:tag :name "div" :attrs (list :id "dynamic!"))
=> 

Interpreting trees

For the ne plus ultra of flexibility, you can interpret trees at runtime using a subset of Spinneret syntax:

(interpret-html-tree `(:div :id "dynamic!"))
=> 

The interpreter is still under development; it supports most but not yet all Spinneret syntax.

Markdown

If the additional system spinneret/cl-markdown is loaded, then a
string in function position is first compile