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Component Model Strawman: Declarative Syntax: Difference between revisions

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The <tt>template</tt> element generates an <tt>instantiation</tt> event for  
The <tt>template</tt> element generates an <tt>instantiation</tt> event for  
each template instantiation. Authors can listen it to setup event handlers for
each template instantiation. Authors can listen it to setup event handlers for
generated elements by the template.
generated elements by the template. The event doesn't bubble, and it isn't cancelable.


<pre>
<pre>

Revision as of 00:28, 25 October 2011

Element Registration

Let’s start from the minimum form of the element registration. Authors can use an element element to registering new element name. Now agent recognizes x-comment as HTMLRegisteredElement. This is just a plain old HTML element which has its own name. 


<head>
  <element for="x-comment"></element>
</head>

Scripting

The element element also provides an opportunity to give a behavior for the instance of the registered element. 


<head>
  <element for="x-comment"></element>
  <script>
  var e = document.head.querySelector(“[for=x-comment]”);
  e.close = function(element) {
    element.addEventListener(“click”, function(evt) {
      ..
    });
  };
  </script>
</head>

Using HTMLElementElement.register(), authors can register a set of lifecycle callbacks for each registered element. There are two types of lifecycle event: open and close. The open is for creating the new instance of the Element. You can override the constructor of the element by providing open callback. The close callback provides the way to enhance created instance. This is useful when you use given attributes to define the behavior.

To make the definition self-contained, we can put a script blocks inside an element element. 


<head>
  <element for="x-comment">
    <script>
       class Comment : HTMLElement {
           this.shadow = new ShawowRoot(this);
           ..;
       }

       HTMLElementElement.current.open = function() { return new Comment(); }});
    </script>
  </element>
</head>

In this example, the script refers a static property called HTMLElementElement.current, which points the enclosing element element. This example also shows how we can provide an open lifecycle callback.

Styling

The element element allows a style element as a child, which accept :current pseudo-class to specify the registering element.

Following example gives "color: gray" to the x-comment element. 


<head>
  <element for="x-comment">
    <style>
    :current {
       color: gray;
    }
    </style>
  </element>
</head>

Standalone Form

The element registration is also done in separate HTML files, which registers the element definitions in the host document. Each HTML file which provides the element registration should have a provide attribute on the root html element. This attribute prevents accidental loading of existing HTML files. 


<html provide>
  <head>
    <element for="x-comment">..</element>
  </head>
</html>

The host element can load the html with element definition using a link element with its rel attribute set to component. 


<html>
  <head>
    <link rel=”component” type=”text/html” href="comment.html">
  </head>
</html>

A providing HTML doesn’t have its own document nor the global object. Agents use these of the host.

Effective markup vocabulary of the providing HTML is limited. Agents only recognize a head element as a child of the root element when the HTML document is loaded as required.

Shadow DOM Template

An initial shape of new shadow tree can be defined using a template element. 


<head>
  <template id=”comment-template”>
    <div><content></content></div>
  </template>
</head>

A template is instantiated through

  • ShadowRoot constructor and
  • shadow-template CSS property.

The ShadowRoot constructor

The ShadowRoot constructor accepts a template element to instantiate. 

  ..
  this.shadow = new ShadowRoot(this, document.getElementById(“comment-template”));
  ..

The shadow-template CSS property (brainstorming)

The template for shadow root also can be applied using CSS property. 


.comment {
  shadow-template: url('#comment-template');
}

Note that imperatively-applied shadows always supersede shadows from the styling. Also, there is no way to access style-originated shadows from the scripting environment.

The Instantiation Event and Scripting

Even though the template can be used to define an extra visual representation for an element, It would be useful if author can attach a script for the template-generated shadow tree.

The template element generates an instantiation event for each template instantiation. Authors can listen it to setup event handlers for generated elements by the template. The event doesn't bubble, and it isn't cancelable. 


<head>
  <template id=”comment-template”>
    <div><content></content></div>
  </template>
  <script>
  var e = document.getElementById("comment-template");
  e.addEventListener("instantiation", function(evt) {
    evt.root.querySelector("div").addEventListener("click", function(evt) { ... });
  });
  </script>
</head>

A template element also allows a script element as a child, whose script block can access HTMLTemplateElement.current. 


<head>
  <template id=”comment-template”>
    <div><content></content></div>
    <script>
    HTMLTemplateElement.current.addEventListener("instantiation", function(evt) {
      evt.root.querySelector("div").addEventListener("click", function(evt) { ... });
    });
    </script>
  </template>
</head>
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