Tab key should navigate groups, arrows within groups

[dhardy]

Not sure if here is the most appropriate place to report this, but the Tab key should not circle through all focusable widgets. Cases I have seen so far: tabs, list boxes and radio buttons. These grouped widgets should be navigable using the arrow keys instead and tabbing into the group should place the focus to the currently selected/checked item. Whether to use up/down or left/right arrow keys will depend on the orientation of the group.

I know arrow keys work inside list boxes already, but tab shouldn't move focus between items.

Originally posted by @DataTriny in #344

[dhardy]

As you can tell, navigation focus currently works on an individual widget basis. Navigation groups could maybe be supported simply by having a "group" widget by the navigation focus, but likely the event handler would need group-specific code.

tabs

This should be possible using a special tab bar.

list boxes

I'm not sure on this one. It isn't the list box which gains focus, but rather the items within them (e.g. see examples/data-list-view.rs).

What may change is that currently some lists use a NavFrame to make each item selectable; we should likely have a specific ListItem widget for this.

radio buttons

There is no radio group; each button is an independent widget with nothing tying them together (excepting some closure which tells each button whether it is selected). I don't intend to change this. Radio boxes are little different from check boxes which can also have interdependencies (e.g. clicking one automatically enables another box if it is a dependency).

(Specific cases could be handled differently however: e.g. someone could use RadioBox widgets within a 6-way mode switch and give this 6-way switch special behaviour, though I think enabling this requires some tweaks to the widget model.)

[DataTriny]

It isn't the list box which gains focus, but rather the items within them

From an outsider's point of view, I'm not sure to understand the difference in the context of kas. When I use the Tab key on both a tab list and a list box, the focus goes through each item. What I was asking for is that both tab lists and list boxes appear as a single node in the focus chain. In both cases, the focus should somehow be delegated to the selected item, and then arrow keys can be used to move the focus in the group. Please note that a list box itself can typically be focused when it is empty.

There is no radio group; each button is an independent widget with nothing tying them together

Sorry to bring some bad news again, but radio groups definitely need to be inside a radio group in the accessibility tree.

+--------------------------------------+
| How did you find out about kas?     |
| o Friends  o Social Media  o Search |
+-------------------------------------+

The diagram above depicts a typical radio group. Here's how the nodes would look like in code (simplified, without standalone label nodes):

let mut group = Node::new(Role::RadioGroup);
group.set_label("How did you find out about kas?");
group.set_children([radio1_id, radio2_id, radio3_id]);
group.set_size_of_set(3);

let mut radio1 = Node::new(Role::RadioButton);
radio1.set_toggled(Toggled::False);
radio1.set_label("Friends");
radio1.set_position_in_set(0);

let mut radio2 = Node::new(Role::RadioButton);
radio2.set_toggled(Toggled::False);
radio2.set_label("Social Media");
radio2.set_position_in_set(1);

let mut radio3 = Node::new(Role::RadioButton);
radio3.set_toggled(Toggled::False);
radio3.set_label("Search");
radio3.set_position_in_set(2);

You may not realize why it is important if you don't understand how a screen reader would present this interface to the user. Since labels aren't focusable, a screen reader would attach textual information to the radio buttons. But here we need to convey two things: the name/label of each button and the question which justify their presence in the first place. The presentation will vary whether the user relies on speech output or Braille, but with speech for instance the label of the group will be announced the first time the user tabs into the group, and only then would the label of the focused radio button be announced. Here's a textual representation of what you'd hear from a screen reader if you tab into this widget:

< Pressing tab key
> How did you find out about kas? Friends radio button unchecked one of three
< Pressing right arrow
> Social Media radio button checked two of three
< Pressing right arrow
> Search radio button checked three of three