Re: [css3-ui] objections to nav-* properties

On Thu, 02 May 2013 23:38:22 +0200, James Craig <jcraig@apple.com> wrote:

> I mentioned these issues to Tantek at the 2012 TPAC in Lyon. I can't  
> recall whether I sent them to the CSS list at the time, but just in  
> case, here it is again.
>
> http://dev.w3.org/csswg/css-ui/#nav-index
> http://dev.w3.org/csswg/css-ui/#nav-dir
>
> I believe the currently at-risk features nav-index, nav-up, nav-right,  
> nav-down, and nav-left should be either be removed from the CSS3 UI  
> specification, or completely overhauled to account for a cascading  
> navigation context.

[snip nav-index objection]

> Another problem the spec does not solve is the potential for infinite  
> navigation loops with circular references using any of the nav-*  
> properties. The specification should define that circular references are  
> illegal, and it should also define recovery behavior when a rendering  
> engine encounters circular navigation loops.

I don't see how navigation cycles present a problem. Consider a set of  
links, for example a script-animated slideshow or featured products,  
arranged horizontally:

[A celebrity] [B celebrity] [C celebrity] [D celebrity] [Related celebrity  
stories]
[A product] [B product] [C product]

It's entirely reasonable to want the user to be able to navigate right  
 from the "Related stories" pane and reach A. (In code, something like '#a  
{nav-right: #b } /* etc. */ #related { nav-right: #a }'). With appropriate  
UI (for instance, a right arrow labeled "Back to start") it could even be  
intuitive. (Granted, ID specification would probably be superfluous, but  
it doesn't seem reasonable to make it illegal.)

I didn't implement this, so I may be overlooking some hidden complexity,  
but I assume the UA can look up elements by ID quite simply. I don't see  
that the UA needs to pre-compute navigation paths, and thus deal  
programmatically with cycles as such.

> Unless these issues are addressed or the features are dropped due to  
> lack of implementations, I'll probably file or otherwise recommend a  
> formal objection

For anybody who reads this in the archives, I'll note that nav-index is  
already resolved to go away from level 3.

-- 
Leif Arne Storset
Opera Software

Received on Wednesday, 31 July 2013 08:52:22 UTC