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Difference between revisions of "Custom Tags Analysis"

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(Created page with 'The Component_Model proposes using custom HTML tags (prefixed with <code>x-</code>) as a way to express components in markup. This is motivated by the need to provide [http:/...')
 
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The [[Component_Model]] proposes using custom HTML tags (prefixed with <code>x-</code>) as a way to express components in markup. This is motivated by the need to provide [http://wiki.whatwg.org/wiki/Behavior_Attachment element behavior attachment]. This analysis studies the issues associated with using custom tags in HTML.
+
The [[Component_Model | Component Model]] proposes using custom HTML tags (prefixed with <code>x-</code>) as a way to express components in markup. This is motivated by the need to provide [http://wiki.whatwg.org/wiki/Behavior_Attachment element behavior attachment]. This analysis studies the issues associated with using custom tags in HTML.
  
 
==Accessibility==
 
==Accessibility==
  
I contend that the Component Model does not make accessibility any
+
I contend that the Component Model does not make accessibility any worse. And likely the opposite.
worse. And likely the opposite.
 
  
By allowing ATs to traverse into shadow subtrees, and ensuring that
+
By allowing ATs to traverse into shadow subtrees, and ensuring that the shadow subtrees are well-behaving accessibility citizens, you allow authors of components to encapsulate good practices and aid in killing the "re-created poorly" anti-pattern. That's what Sencha, SproutCore, Dijit all try to do -- and the Component Model will enable them do this right. In fact, things like access keys or even z-index are quite hard (impossible) to get right, unless you have something like a well-functioning shadow DOM.
the shadow subtrees are well-behaving accessibility citizens, you
 
allow authors of components to encapsulate good practices and aid in
 
killing the "re-created poorly" anti-pattern. That's what Sencha,
 
SproutCore, Dijit all try to do -- and the Component Model will enable
 
them do this right. In fact, things like access keys or even z-index
 
are quite hard (impossible) to get right, unless you have something
 
like a well-functioning shadow DOM.
 
  
This leaves us with the argument of replacing semantics. Since we're
+
This leaves us with the argument of replacing semantics. Since we're in business of sub-typing HTML elements, we don't necessarily need to forego their semantics:
in business of sub-typing HTML elements, we don't necessarily need to
 
forego their semantics:
 
  
 +
<code>
 +
<pre>
 
// ...
 
// ...
 
var AwesomeButton = HTMLButtonElement.extend(awesomeButtonInitializerBag);
 
var AwesomeButton = HTMLButtonElement.extend(awesomeButtonInitializerBag);
 
Element.register('x-awesome-button', AwesomeButton);
 
Element.register('x-awesome-button', AwesomeButton);
 
// ...
 
// ...
 +
</pre>
 +
</code>
  
should give you a thing that behaves like a button, with the awesome
+
should give you a thing that behaves like a button, with the awesome behavior added.
behavior added.
 
  
In the situations where existing semantics are representative, but
+
In the situations where existing semantics are representative, but deficient, you are much better off replacing them anyway:
deficient, you are much better off replacing them anyway:
 
  
 
<button becomes="x-plus-one-button">+1</button>
 
<button becomes="x-plus-one-button">+1</button>
Line 34: Line 26:
 
==Behavior Fallback==
 
==Behavior Fallback==
  
<x-accordion></x-accordion> is no worse than <div
+
<x-accordion></x-accordion> is no worse than <div class="accordion"></div> in every mechanical sense. In the absence of definition for "x-accordion" (or Component Model plumbing), both mean the same thing, both can be styled in the same way. One is HTMLUnknownElement, the other is HTMLDivElement, and their API surface is identical.
class="accordion"></div> in every mechanical sense. In the absence of
 
definition for "x-accordion" (or Component Model plumbing), both mean
 
the same thing, both can be styled in the same way. One is
 
HTMLUnknownElement, the other is HTMLDivElement, and their API surface
 
is identical. So... no fallback problems.
 
 
 
  
 
==Clarity==
 
==Clarity==
  
The <x-accordion> clearly identifies the type of the behavior expected
+
The <x-accordion> clearly identifies the type of the behavior expected from the element, and conveys element behavior attachment nicely. On the other hand, <div class="accordion"> implies decorator behavior attachement, e.g. that removing the class value (and thus turning it back into a vanilla <div>) is perfectly ok, which by the way, is probably _not_ what the author of the Accordion component expects "in real life". I mean, you can ''make'' the author expect that, but that seems like cruel and unusual punishment. In other words -- it's quite the opposite. Custom tags are more ''clear''. In fact, they are as close as '''saying what you mean''' as it gets.
from the element, and conveys element behavior attachment nicely. On
 
the other hand, <div class="accordion"> implies decorator behavior
 
attachement, e.g. that removing the class value (and thus turning it
 
back into a vanilla <div>) is perfectly ok, which by the way, is
 
probably _not_ what the author of the Accordion component expects "in
 
real life". I mean, you can _make_ the author expect that, but that
 
seems like cruel and unusual punishment.
 
 
 
In other words -- it's quite the opposite. Custom tags are more
 
_clear_. In fact, they are as close as _saying_what_you_mean_ as it
 
gets.
 
  
  

Revision as of 18:02, 29 September 2011

The Component Model proposes using custom HTML tags (prefixed with x-) as a way to express components in markup. This is motivated by the need to provide element behavior attachment. This analysis studies the issues associated with using custom tags in HTML.

Accessibility

I contend that the Component Model does not make accessibility any worse. And likely the opposite.

By allowing ATs to traverse into shadow subtrees, and ensuring that the shadow subtrees are well-behaving accessibility citizens, you allow authors of components to encapsulate good practices and aid in killing the "re-created poorly" anti-pattern. That's what Sencha, SproutCore, Dijit all try to do -- and the Component Model will enable them do this right. In fact, things like access keys or even z-index are quite hard (impossible) to get right, unless you have something like a well-functioning shadow DOM.

This leaves us with the argument of replacing semantics. Since we're in business of sub-typing HTML elements, we don't necessarily need to forego their semantics:

// ...
var AwesomeButton = HTMLButtonElement.extend(awesomeButtonInitializerBag);
Element.register('x-awesome-button', AwesomeButton);
// ...

should give you a thing that behaves like a button, with the awesome behavior added.

In the situations where existing semantics are representative, but deficient, you are much better off replacing them anyway:

<button becomes="x-plus-one-button">+1</button>

Behavior Fallback

<x-accordion></x-accordion> is no worse than
in every mechanical sense. In the absence of definition for "x-accordion" (or Component Model plumbing), both mean the same thing, both can be styled in the same way. One is HTMLUnknownElement, the other is HTMLDivElement, and their API surface is identical.

Clarity

The <x-accordion> clearly identifies the type of the behavior expected from the element, and conveys element behavior attachment nicely. On the other hand,
implies decorator behavior attachement, e.g. that removing the class value (and thus turning it back into a vanilla
) is perfectly ok, which by the way, is probably _not_ what the author of the Accordion component expects "in real life". I mean, you can make the author expect that, but that seems like cruel and unusual punishment. In other words -- it's quite the opposite. Custom tags are more clear. In fact, they are as close as saying what you mean as it gets.


Local Semantics

Well, friends -- this train had left the station a long time ago. Alex Russell joked once that you already totally can add custom tags in HTML -- as long as you're Hixie. As HTML spec grows new tags, their meaning is only captured in a written document that's meaningless to the UAs that were built a priori. If anything, the Component Model provides an explicit path _learn_ about the need for new elements in the spec. Just grep the Web for "<x-" and look at the common names.

In all seriousness, I expect HTML to grow new tags, and I think it will add a great many new things that will make authors' life easier. I don't expect HTML to grow every element ever needed -- the long tail is far too massive. Addressing this long tail in a local (meaningful in your document), organized fashion is what the Component Model does.


Conflicts with new HTML tags

Well, here, FTFY -- the Component Model explicitly requires prefixing all elements with "x-".


Misuse/Abuse

Indeed they will. I yell regularly at authors (like that old man from his front porch) for using divs to build buttons and links. Those anti-patterns suck. We should not make it worse. If anything, we have an opportunity to provide a progressive enhancement vehicle, whereby authors can use components as a way for hiding implementation specifics and leaving out only the commonly established semantics in markup. Soo.. how would something like this work?

We need a way to let the authors specify a well-known element to describe underlying semantics of their component, coincidentally providing a proper fallback element for non-Component Model-aware UAs. It's similar to ARIA, but the machinery is about populating the DOM tree with the most-specific thing, while keeping markup most-generic.

To put it differently, you want to start with a well-known element in markup, and, through the magic of computing, this element _becomes_ your component in the DOM tree. In other words, the markup:

<button becomes="x-awesome-button">Weee!!</button>

Becomes:

<x-awesome-button>Weee!!</x-awesome-button>

As soon as: 1) the definition of "x-awesome-button" is registered and;

2) the element is in the DOM tree.