RFR: 8354813: Parent.isNeedsLayout() may return wrong value in property listener

[Andy Goryachev]

On Wed, 16 Apr 2025 18:23:07 GMT, Michael Strauß <mstrauss at openjdk.org> wrote:

>> modules/javafx.graphics/src/main/java/javafx/scene/Parent.java line 996:
>> 
>>> 994:         // Needs to be set before needsLayout is updated, as otherwise a listener that
>>> 995:         // calls isNeedsLayout() might see the old value.
>>> 996:         layoutFlag = flag;
>> 
>> This is the right change, but I suspect it might cause regression.
>> 
>> The JavaFX entities which call `isNeedsLayout()`:
>> 
>> `VirtualFlow::layoutChildren`
>> `VirtualFlow::setCellIndex`
>> 
>> We may need to focus on List/Table/Tree/TableViews during testing.
>> 
>> (Anecdata: I've seen continuous layout calls in the TableView before)
>
> It's very unlikely to cause regressions, because `needsLayoutProperty()` is not used anywhere in JavaFX. The only thing that is different now is that a listener added to this property will see the correct value when calling `isNeedsLayout()`.

you are probably right, re:javafx.  applications might listen to this property, though it's rather unlikely.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1781#discussion_r2047492892