There are two optimal cell design and focus behavior combinations:
A cell contains one widget whose operation does not require arrow keys and grid navigation keys set focus on that widget. Examples of such widgets include link, button, menubutton, toggle button, radio button (not radio group), switch, and checkbox.
A cell contains text or a single graphic and grid navigation keys set focus on the cell.
This ticket is for the first behavior: Rather than navigating to the cell, make the arrow keys navigate directly to the widget it contains.
The reasons for the enhancement are:
Better keyboard support: only one keystroke needed to activate the link/button/etc. I.E. no preliminary F2/Enter keystroke needed.
Better screen reader support: since the focus is on the <button> the screen reader will announce that the focus is on a button.
List should only focus a contained widget if the cell contains other widgets, or contains text. It should also only focus if the descendantSelector() method matches that widget rather than the cell.
The latter test is to avoid navigation getting trapped inside of controls that widgets up/down/left/right arrow keystrokes.
The exception is for DropDownButton (and similar controls). We want focus to directly go to the DropDownButton but the up/down arrow keys should navigate to other grid cells, rather than opening the dropdown.
As explained in https://www.w3.org/TR/wai-aria-practices/#gridNav_focus:
This ticket is for the first behavior: Rather than navigating to the cell, make the arrow keys navigate directly to the widget it contains.
The reasons for the enhancement are:
<button>the screen reader will announce that the focus is on a button.List should only focus a contained widget if the cell contains other widgets, or contains text. It should also only focus if the
descendantSelector()method matches that widget rather than the cell.The latter test is to avoid navigation getting trapped inside of controls that widgets up/down/left/right arrow keystrokes.
The exception is for DropDownButton (and similar controls). We want focus to directly go to the DropDownButton but the up/down arrow keys should navigate to other grid cells, rather than opening the dropdown.