[jfx20] RFR: 8300013: Node.focusWithin doesn't account for nested focused nodes [v2]

[Michael Strauß]

On Tue, 31 Jan 2023 17:08:40 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> modules/javafx.graphics/src/main/java/javafx/scene/Node.java line 8325:
>> 
>>> 8323:             } else if (count == 0) {
>>> 8324:                 set(false);
>>> 8325:             }
>> 
>> Is it worth adding a check for `count < 0` and logging a warning (possibly treating it as if it were 0)? In theory, it shouldn't happen, but if it ever did, `focusWithin` would be wrong after that. This could be done as a P4 follow-up for 21, unless you are certain that it cannot ever happen.
>
> On the one hand, this might make the code a little bit more robust, but on the other hand, it might hide a bug elsewhere. Surely `count` should never be negative. I lean slightly towards not protecting code against bugs in this way, mostly because it might expose potential bugs sooner.
> 
> If we want to validate that this method is not called with an incorrect argument, maybe just throwing an exception would be better.

I've created a ticket to investigate this: https://bugs.openjdk.org/browse/JDK-8301556

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PR: https://git.openjdk.org/jfx/pull/993