Improve admin menu tab navigation

[koopersmith]

Currently, there are no visual indicators when when an admin menu item is focused using the tab key. We should add visual feedback when an item is focused and expand the submenus to allow users to access submenu items via tabbing.

[koopersmith]

In [19198]:

Improve admin menu tab navigation for expanded menus. Folded menus require a few markup improvements. see #19191.

[jane]

Why was this ticket opened instead of using #19088?

[ocean90]

jane, this is for the admin menu and #19088 for the admin bar. I think.

[johnkleinschmidt]

Better patch that fixes tabbing through menus a second time

[johnkleinschmidt]

My original patch did display the visual feedback when an item is focused and expanded the submenus and allowed tabbing through them, but I noticed that if you kept on tabbing eventually you would get to the menus a second time, but they would not expand/navigate properly. This was due to the fact that the wp-menu-image links did not have a tabindex on them and therefore were last in the tabbing order. If these links are assigned a positive value tabindex, it messes up the tabbed navigation because you would have to tab twice to open the submenu. Assigning these items a -1 tabindex takes them out of the tabbing sequence completely.

[koopersmith]

We should definitely prevent those items from opening a second time, but the issue is that the menus will no longer be tabbable when collapsed. A potential fix could unify the image and title into a single link.

[azaozz]

Looking at all the options there, not sure it's good to open the flyouts when the menu is unfolded, they aren't accessible anyways.

Leaving only the <a> tags as tabinedx-ed (default browser behavior) makes tabbing through it work pretty well:

• flyouts are not shown,
• the current screen submenu is expanded, so tabbing goes through all items on it,
• other submenus are accessible after pressing Enter on the top menu item (that loads the other screen making all submenus there accessible with tabbing).

[azaozz]

In [19426]:

DOn't show flyouts on tabbing for now (not accessible), fixes #19191

[toscho]

Oh, this is bad. Searching for a menu entry requires multiple page loads now. Why is this better?