1485335 - Keyboard navigation should follow DOM order by default, not frame tree order

Status: NEW

(Core :: DOM: UI Events & Focus Handling, defect, P3)

Description

[Mats Palmgren (inactive)]

Keyboard navigation (tabbing) is incompatible with other UAs because
nsFocusManager::GetNextTabbableContent traverses the frame tree
rather than the DOM.

For example:
http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=6132
In Firefox you reach the <input> inside the <legend> first,
in Chrome it's second.

Comment 1

[Olli Pettay [:smaug][[e-mail]]]

Or we should fix the spec to have better behavior from user's point of view.

Comment 2

[Mats Palmgren (inactive)]

I agree that traversing <legend> (and <caption>?) first probably makes
more sense from a user's POV (at least when it's placed on a logical
start side), but the CSSWG explicitly decided that the CSS 'order'
property shouldn't affect tabbing order (see bug 812687).  So there's
some precedent that box order shouldn't affect tabbing.

This came up in https://github.com/whatwg/html/issues/3950#issuecomment-414974294
BTW, in case you want to argue for it there.

It seems like an edge case though since focusable elements inside
legend/caption are probably rare.  So I don't feel that strongly
about it as long as UAs are compatible and it appears other UAs
use DOM order.