RFR: JDK-8199216: Quadratic layout time with nested nodes and pseudo-class in style sheet [v8]

[John Hendrikx]

On Tue, 15 Aug 2023 16:10:46 GMT, Nir Lisker <nlisker at openjdk.org> wrote:

>> John Hendrikx has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 16 commits:
>> 
>>  - Merge branch 'master' of https://git.openjdk.org/jfx into
>>    feature/immutable-pseudoclassstate
>>  - Merge remote-tracking branch 'upstream/master' into feature/immutable-pseudoclassstate
>>  - Avoid using Lambda in ImmutablePseudoClassSetsCache.of()
>>  - Merge branch 'master' of https://git.openjdk.org/jfx into
>>    feature/immutable-pseudoclassstate
>>  - Fix another edge case in BitSet equals
>>    
>>    When arrays are not the same size, but there are no set bits in the ones
>>    the other set doesn't have, two bit sets can still be considered equal
>>  - Take element type into account for BitSet.equals()
>>  - Base BitSet on AbstractSet to inherit correct equals/hashCode/toArray
>>    
>>    - Removed faulty toArray implementations in PseudoClassState and
>>    StyleClassSet
>>    - Added test that verifies equals/hashCode for PseudoClassState respect
>>    Set contract now
>>    - Made getBits package private so it can't be inherited
>>  - Remove unused code
>>  - Ensure Match doesn't allow modification
>>  - Simplify ImmutablePseudoClassSetsCache and avoid an unnecessary copy
>>  - ... and 6 more: https://git.openjdk.org/jfx/compare/9ad0e908...7975ae99
>
> modules/javafx.graphics/src/main/java/com/sun/javafx/css/ImmutablePseudoClassSetsCache.java line 61:
> 
>> 59:         CACHE.put(copy, copy);
>> 60: 
>> 61:         return copy;
> 
> Isn't this just `return CACHE.computeIfAbsent(pseudoClasses, Set::copyOf);`?

Almost, but the key is also the copied set.  In your version the key is the original object, which may be a modifiable set.  If the key is modified, the cache will not function correctly anymore.

I had a different version before, but @mstr2 pointed out that there was an unnecessary allocation in that version which this version avoids.

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PR Review Comment: https://git.openjdk.org/jfx/pull/1076#discussion_r1295028373