On Thu, 30 Mar 2023 20:34:13 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
>> This fix introduces immutable sets of `PseudoClass` almost everywhere, as
>> they are rarely modified. These are re-used by caching them in a new class
>> `ImmutablePseudoClassSetsCache`.
>>
>> In order to make this work, `BitSet` had to be cleaned up. It made
>> assumptions about the collections it is given (which may no longer always be
>> another `BitSet`). I also added the appropriate null checks to ensure there
>> weren't any other bugs lurking.
>>
>> Then there was a severe bug in `toArray` in both the subclasses that
>> implement `BitSet`.
>>
>> The bug in `toArray` was incorrect use of the variable `index` which was
>> used for both advancing the pointer in the array to be generated, as well as
>> for the index to the correct `long` in the `BitSet`. This must have
>> resulted in other hard to reproduce problems when dealing with
>> `Set<PseudoClass>` or `Set<StyleClass>` if directly or indirectly calling
>> `toArray` (which is for example used by `List.of` and `Set.of`) -- I fixed
>> this bug because I need to call `Set.copyOf` which uses `toArray` -- as the
>> same bug was also present in `StyleClassSet`, I fixed it there as well.
>>
>> The net result of this change is that there are far fewer `PseudoClassState`
>> objects created; the majority of these are never modified, and the few that
>> are left are where you'd expect to see them modified.
>>
>> A test with 160 nested HBoxes which were given the hover state shows a
>> 99.99% reduction in `PseudoClassState` instances and a 70% reduction in heap
>> use (220 MB -> 68 MB), see the linked ticket for more details.
>>
>> Although the test case above was extreme, this change should have positive
>> effects for most applications.
>
> John Hendrikx has updated the pull request incrementally with one additional
> commit since the last revision:
>
> Simplify ImmutablePseudoClassSetsCache and avoid an unnecessary copy
modules/javafx.graphics/src/main/java/com/sun/javafx/css/BitSet.java line 584:
> 582: * @param obj the object to cast, cannot be {@code null}
> 583: * @return a type T, or {@code null} if the argument was not of this
> type
> 584: * @throws NullPointerException when {@code obj} is {@code null}
Previously, this method always returned an instance of `T`. Now that is not the
case, it might also simply return `null` if the argument passed into it is an
instance of a different class. I think it makes sense to also return `null`
when the argument passed into the method is `null`.
-------------
PR Review Comment: https://git.openjdk.org/jfx/pull/1076#discussion_r1154620769
