W3C home > Mailing lists > Public > public-html@w3.org > July 2007

Re: HTML Extensibility Through Script

From: Maciej Stachowiak <mjs@apple.com>
Date: Tue, 10 Jul 2007 12:37:51 -0700
To: Andrew Fedoniouk <news@terrainformatica.com>
Message-Id: <5555CFB0-AAD5-4BD4-A811-8239FF5913FF@apple.com>
Cc: Doug Schepers <doug.schepers@vectoreal.com>, public-html@w3.org


On Jul 10, 2007, at 9:17 AM, Andrew Fedoniouk wrote:

>
>
> ----- Original Message ----- From: "Doug Schepers" <doug.schepers@vectoreal.com 
> >
> To: <public-html@w3.org>
> Sent: Tuesday, July 10, 2007 7:33 AM
> Subject: HTML Extensibility Through Script
>
>
>> ... The conversation then turned to how one might use this lib,  
>> given that some browsers might support MathML natively and some  
>> not.  There was a suggestion (a good one, I think) that a <script>  
>> element might be made somehow conditional (through a parameter, an  
>> attribute, or through encapsulation as the fallback for an  
>> <object>, doesn't matter to me), such that if the browser supported  
>> a that feature natively, the script implementation of that feature  
>> wouldn't run.
>>
>
> <script type="application/ecmascript">
>  if( featureXsupported() )
>      return;
>  // featureXemulation goes here.
> </script>

That's not exactly correct JavaScript (you can only exit a function,  
not a top-level block), but in general I agree, any features that  
scripts would want to switch on should be exposed for testing to  
script. That way you can either conditionally load whole different  
scripts, or change parts of scripts based on what is available.

> It is IMO not realistic to have some universal attribute that will  
> allow to filter all possible features of UA.
>
> It would be nice though if UA vendors implement some
> flag attribute like __ua_vendor/__ua_version  for the root element.
> Such an attribute may be added while parsing DOM tree.
> So scripts and CSS can reliably use it as a selector .

Scripts can already get this info from navigator.userAgent. I think  
the fact that it's not exposed to CSS is by design - if CSS were  
allowed to have UA vendor/version targeted rules I think there are  
better ways to do it than by attributes on the root element.

Regards,
Maciej
Received on Tuesday, 10 July 2007 19:38:02 GMT

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