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Re: [ResourcePriorities] Error in example

From: Boris Zbarsky <bzbarsky@MIT.EDU>
Date: Thu, 12 Sep 2013 10:20:24 -0400
Message-ID: <5231CDA8.1010406@mit.edu>
To: Ivan Kotenkov <kotenkov@yandex-team.ru>
CC: public-web-perf@w3.org
On 9/12/13 4:15 AM, Ivan Kotenkov wrote:
> http://www.w3.org/TR/WebIDL/#dfn-read-only .
> "The attribute is read only if the readonly keyword is used before the
> attribute keyword.

This is talking about IDL attributes (properties of the JS object)

> I think, using setAttribute is a direct assignment

setAttribute sets a _content_ attribute, not an IDL attribute.  Please 
read up on the difference between the two.

> Next let's look at an example. As a developer of chromium-based browser
> I'll use chromium code as an example.
> /interface HTMLInputElement/ is defined in HTMLInputElement.idl. Among
> other attributes it has
> /readonly attribute boolean willValidate;/

Right, but it doesn't have a defined "willvalidate" content attribute at 
all.  As in, <input willvalidate="something"> has no efeect whatsoever.

> Now let's create a simple webpage that will try to change the attribute:

> /  input = document.getElementById('inp');/
> /  alert(input.willValidate);/
> /  input.setAttribute('willValidate', false);/
> /  alert(input.willValidate);/

That's because the content "willValidate" attribute and the IDL 
"willValidate" attribute are completely unrelated.  Try 
getAttribute("willValidate") after your setAttribute call.

> Also, grepping the *.idl files for 'readonly' gives us attributes that
> obviously should not be change by using setters, for example:
> /HTMLFormElement.idl:    readonly attribute HTMLCollection elements;/
> /HTMLFormElement.idl:    readonly attribute long length;/

Those don't correspond to content attributes either.

But the attribute we're discussing here _does_ correspond to a content 
attribute.  <script lazyload> is supposed to change the behavior of the 
<script>.

Again, the real problem the spec has here is that it doesn't actually 
define the behavior of the "lazyload" IDL attribute.  It needs to do that.

-Boris
Received on Thursday, 12 September 2013 14:21:32 UTC

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