<Swing Dev> [Accessibility]Focus unable to traverse in the menubar

[Anton Tarasov]

Hi Neil,

On 10/10/2011 7:01 PM, Neil Richards wrote:
> On Mon, 2011-10-10 at 16:56 +0400, Anton Tarasov wrote:
>> Hi Neil and Jing,
>> I'm afraid that it's wrong to use ContainerOrderFocusTraversalPolicy
>> for swing components. This policy is designed for AWT.
>> JMenuBar calls setFocusTraversalKeysEnabled(false) in its ctor which
>> means that it "swallows" focus traversal keys (like TAB/SHIFT-TAB
>> etc.)
>> and so it can't be a member of a focus traversal chain. Swing's
>> default traversal policy (LayoutFocusTraversalPolicy) excludes
>> JMenuBar
>> from a focus traversal cycle. ContainerOrderFocusTraversalPolicy is
>> not "aware" about JMenuBar and so it allows it.
>>
>> So, either a default Swing policy should be used, or a custom policy.
>> At worst, ContainerOrderFocusTraversalPolicy should be overriden
>> to exclude JMenuBar from a cycle (override its accept(Component)
>> method).
>>
>> Thanks,
>> Anton.
> Hi Anton,
> Thanks for reviewing the suggestion, and for your insights into this
> scenario.
>
> > From the Javadoc, it seems that setFocusTraversalKeysEnabled() is mainly
> concerned with choosing whether focus traversal key presses (normally
> TAB and SHIFT-TAB) are processed "automatically" (when 'true') or are
> delivered to the Component as key events (for the component's code to
> process "manually").
>
> (In the case of JMenuBar, it makes them come through as key events, but
> doesn't do anything special to process these events, which is why they
> get discarded.)

That is right, though it doesn't directly relate to the issue we're 
talking about =)

> Your description above, though, seems to suggest that it is generally
> undesirable for the JMenuBar to be given the focus, as all the
> Swing-aware focus traversal policies make a point of not giving focus to
> JMenuBar items.
>
> If this is so, then wouldn't it make sense to call setFocusable(false)
> from its constructor (too), to ensure it doesn't get focus ?
>
> Or, to put it another way, could you explain a little of the reasoning
> or scenario behind why it is desirable for JMenuBar items to be
> generally focusable, even though they aren't focus-traversable ?
>
> I think such an explanation would be really helpful in clearing up my
> confusion on this point.
>
> Thanks, Neil
>

Well, I suspect that the core of the problem is that adding JMenuBar as 
JComponent to a swing
container doesn't make much sense. Though it is not directly prohibited, 
doing so may cause
side effects like the one you've discovered. When JMenuBar is set 
properly onto a JFrame its focus
is managed by JRootPane and its focusability just isn't taken into 
account. That's may be the reason
it's not declared unfocusable. Honestly, I can't tell you exactly.

If you do it, you probably won't make any harm, but I personally don't 
think this is a vital fix
(unless you have a good use case of the scenario you've provided). 
Anyway, this is a swing question
(I'm, as an AWT dev member, leaving the decision to swing guys).

Thanks,
Anton.