On Fri, 31 Mar 2023 21:56:08 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 three > additional commits since the last revision: > > - 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 modules/javafx.graphics/src/main/java/com/sun/javafx/css/ImmutablePseudoClassSetsCache.java line 53: > 51: return CACHE.computeIfAbsent( > 52: Objects.requireNonNull(pseudoClasses, "pseudoClasses cannot > be null"), > 53: k -> Set.copyOf(pseudoClasses) The call to `computeIfAbsent` will always do the following things: 1. Capture the `pseudoClasses` argument 2. Call `Map.get` internally 3. ...which calls `Set.hashCode` 4. ...which, for `AbstractSet.hashCode`, iterates over the entire set using an iterator and calls `hashCode` for each element. Since there is no fast path, I wonder whether this may have negative performance implications for larger scene graphs. ------------- PR Review Comment: https://git.openjdk.org/jfx/pull/1076#discussion_r1155524739
