====== Improving Tab Navigation ======

There have been a number of concerns raised with the current 'nav-index' property. This page is to document them and the resulting discussions, with the aim of addressing these issues in a future revision of the UI module.

===== External Issues To Be Incorporated =====
Extract issues from these and document here as subsections explicitly:
  * [[http://lists.w3.org/Archives/Public/www-style/2012Jun/0479.html|Visual vs. logical ordering switch]]
  * [[http://lists.w3.org/Archives/Public/www-style/2011Nov/0712.html|Handling HTML5's new 0 and -1 behaviors]]
  * Scoping tab navigation indices, so that it can be used in complex pages.

More issues:
  * http://lists.w3.org/Archives/Public/wai-xtech/2011Nov/0034.html
  * http://lists.w3.org/Archives/Public/wai-xtech/2011Nov/0035.html
  * http://lists.w3.org/Archives/Public/www-style/2011Nov/thread.html#msg440

===== Should HTML specify something =====
HTML has the tabindex attribute (with various levels of browser support) which has been specified there to some extent:
* http://www.whatwg.org/specs/web-apps/current-work/#sequential-focus-navigation

===== HTML or CSS or both =====
Does nav-index belong in HTML or CSS or both?

Current thinking: likely both.

HTML already has tabindex (see previous).

CSS should specify nav-index because:
  * CSS3-UI already specifies directional nav-* properties
  * Any style sheet that explicitly specifies the 2 dimensional directional nav-* properties will likely want to also explicitly specify sequential navigation order as well.
  * Keeping both sequential and directional nav-* in the same style sheet will help them stay "in sync" across site changes etc.
    * Or rather, having to do them separately in HTML vs CSS will likely cause them to get out of sync.

However, nav-index was in a CSS3-UI CR draft for MANY years and there was no implementation.

Thus only when there is a strong demonstration of implementer interest (2+ commitment to implement) should we consider adding it to CSS4-UI.

===== within a dialog and browsing context =====
We should define how to pick the next/previous element in sequential focus navigation, to make sure it's clear that it stays within a dialog and browsing context.

More details and follow-up:
  * https://www.w3.org/Bugs/Public/show_bug.cgi?id=24719

===== contextual scoping =====
Need contextual scoping for sequential focus navigation.

More details and follow-up:
  * https://www.w3.org/Bugs/Public/show_bug.cgi?id=23960
  * http://lists.w3.org/Archives/Public/www-style/2011Nov/thread.html#msg441