RFR: 8091673: Public focus traversal API for use in custom controls [v3]

[Kevin Rushforth]

On Mon, 28 Oct 2024 23:53:44 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> Perhaps we need to further clarify what the focused/focusVisible/focusWithin properties are for?
>
> How about this for `focusVisible`:
> 
>     /**
>      * Indicates whether this {@code Node} should visibly indicate focus.
>      * <p>
>      * This flag is set when the node is {@link #focusedProperty() focused} via keyboard navigation,
>      * or when the input focus was programmatically moved from another node to this node with
>      * {@link #requestFocusTraversal} while the other node visibly indicated focus.
>      * <p>
>      * The {@code focusVisible} flag can be used by applications that do not want a permanent focus
>      * indicator, and opt for a focus indicator that is only visible when it is most helpful to the
>      * user. This is not the case when the user clicks on a control (because they would know which
>      * control they clicked on), but only when a keyboard-initiated focus traversal moves the input
>      * focus to another control.
>      */
> 
> 
> As `requestFocusTraversal` is concerned, I think we can simply this a bit. We don't need users to check whether `focusVisible` is set on the current node; the implementation can do this internally. Here's a revised parameter doc:
> 
> * @param keyNavigation {@code true} if this method is called as a result of keyboard navigation;
> *                      {@code false} otherwise.
> 
> 
> The implementation would then set `focusVisible` to true if either the `keyNavigation` argument is true, or if the current node's `focusVisible` flag is true.

This is better than the previous, since it only asks the caller of this method, typically the Skin of a custom control, to provide the one missing piece of information -- whether or not the method is in response to keyboard navigation -- and not ask the caller to compute the final answer. That's good. The only question I have is: can we do even better? Is there enough information for the implementation of `requestFocusTraversal` to know whether it was called from  keyboard event? If not, then this updated proposal seems reasonable.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1604#discussion_r1820696736