RFR: 8290040: Provide simplified deterministic way to manage listeners [v9]

[Nir Lisker]

On Fri, 2 Dec 2022 09:10:34 GMT, John Hendrikx <jhendrikx at openjdk.org> wrote:

>> I didn't look too far for alternative names after I discovered `showing` would not be possible.  The name comes from `isTreeShowing` which is used for a similar purpose (inside `Node`) and from `conditionOnShowing` in ReactFX.
>> 
>> The name needs to imply that visibility has no effect on it (ie, `setVisible(false)` won't toggle it).  Neither does it check if the node isn't covered or off screen.
>> 
>> In theory you could use a more general name (like `active` as in "part of an active currently showing scene graph").  `isActive` seems to even be available...
>> 
>> A name like "used" or "inUse" may also work (as in "indicates the node is currently used as part of a currently showing scene graph".
>
> That reminds me... `parent` is described as:
> 
>>  The parent of this {@code Node}. If this {@code Node} has not been added to a scene graph, then parent will be null.
> 
> Which I think is incorrect; parent can easily be non-null while not being part of a scene graph.

`displayed`/`displaying`?

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PR: https://git.openjdk.org/jfx/pull/830