On Thu, 4 Jan 2024 12:21:15 GMT, John Hendrikx <[email protected]> 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).
Left a couple inline comments.
modules/javafx.graphics/src/main/java/com/sun/javafx/css/FixedCapacitySet.java
line 1:
> 1: package com.sun.javafx.css;
This needs a standard copyright header block.
modules/javafx.graphics/src/main/java/javafx/css/SimpleSelector.java line 140:
> 138: public Set<String> getStyleClassNames() {
> 139: return selectorStyleClassNames;
> 140: }
This is new API, and as such needs an `@since 23`.
-------------
PR Review: https://git.openjdk.org/jfx/pull/1316#pullrequestreview-1804292170
PR Review Comment: https://git.openjdk.org/jfx/pull/1316#discussion_r1441838456
PR Review Comment: https://git.openjdk.org/jfx/pull/1316#discussion_r1441835248
