On Sat, 9 Mar 2024 06:48:25 GMT, John Hendrikx <jhendr...@openjdk.org> wrote:
>> Improves performance of selector matching in the CSS subsystem. This is done
>> by using custom set implementation which are highly optimized for the most
>> common cases where the number of selectors is small (most commonly 1 or 2).
>> It also should be more memory efficient for medium sized and large
>> applications which have many style names defined in various CSS files.
>>
>> Due to the optimization, the concept of `StyleClass`, which was only
>> introduced to assign a fixed bit index for each unique style class name
>> encountered, is no longer needed. This is because style classes are no
>> longer stored in a `BitSet` which required a fixed index per encountered
>> style class.
>>
>> The performance improvements are the result of several factors:
>> - Less memory use when only very few style class names are used in selectors
>> and styles from a large pool of potential styles (a `BitSet` for potentially
>> 1000 different style names needed 1000 bits (worst case) as it was not
>> sparse).
>> - Specialized sets for small number of elements (0, 1, 2, 3-9 and 10+)
>> - Specialized sets are append only (reduces code paths) and can be made read
>> only without requiring a wrapper
>> - Iterator creation is avoided when doing `containsAll` check thanks to the
>> inverse function `isSuperSetOf`
>> - Avoids making a copy of the list of style class names to compare (to
>> convert them to `StyleClass` and put them into a `Set`) -- this copy could
>> not be cached and was always discarded immediately after...
>>
>> The overall performance was tested using the JFXCentral application which
>> displays about 800 nodes on its start page with about 1000 styles in various
>> style sheets (and which allows to refresh this page easily).
>>
>> On JavaFX 20, the fastest refresh speed was 121 ms on my machine. With the
>> improvements in this PR, the fastest refresh had become 89 ms. The speed
>> improvement is the result of a 30% faster `Scene#doCSSPass`, which takes up
>> the bulk of the time to refresh the JFXCentral main page (about 100 ms
>> before vs 70 ms after the change).
>
> John Hendrikx has updated the pull request incrementally with two additional
> commits since the last revision:
>
> - Remove commented code in BitSetTest
> - Remove unnecessary addAll overrides
modules/javafx.graphics/src/main/java/javafx/css/StyleClass.java line 32:
> 30: * @deprecated for removal
> 31: */
> 32: public final class StyleClass {
Needs the `@Deprecated(forRemoval = true)` annotation on the class, and the doc
tag needs an explanation of why it's being removed ("erroneously exposed", "no
longer needed", "flawed from the start"...) and what should be used instead, if
at all.
-------------
PR Review Comment: https://git.openjdk.org/jfx/pull/1316#discussion_r1518566872
