[wp-trac] [WordPress Trac] #27705: Keyboard navigation should be constrained to the theme installer overlay

[WordPress Trac]

#27705: Keyboard navigation should be constrained to the theme installer overlay
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 Reporter:  nacin         |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  low           |   Milestone:  Future Release
Component:  Themes        |     Version:  3.4
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:  accessibility, administration
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Comment (by afercia):

 Thinking this kind of issues where there's the need to remove from the tab
 order relevant parts of the UI can be solved without any JavaScript and
 using just CSS.

 Unlike `display: none`, `visibility` can be overridden by setting the
 'visibility' property on the descendants.

 http://www.w3.org/TR/CSS21/visufx.html#visibility
 The generated box is invisible (fully transparent, nothing is drawn), but
 still affects layout. Furthermore, '''descendants of the element will be
 visible if they have 'visibility: visible''''.

 This feature can be used as a handy way to remove elements from the tab
 order.

 Applying `visibility: hidden` to the main body and `visibility: visible`
 to the Customizer, would allow to completely remove from the tab order all
 the main body focusable elements and bring back in the tab order just the
 Customizer descendants. The Customizer content would be the only visible
 (and tabbable) content available to assistive technologies.

 In practice, this would emulate the native tabbing behavior: once users
 reach the end of the page, the tab order will start again from the
 beginning (the browser's URL bar) and vice-versa.

 This could help with the Customizer sliding panels too, see #32493. cc
 @celloexpressions

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Ticket URL: <https://core.trac.wordpress.org/ticket/27705#comment:6>
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