[hryhoriiK97]

Summary:

On Android, TextAttributeProps.setTextDecorationLine splits the textDecorationLine value with "-".toRegex(). That compiles a new java.util.regex.Pattern on every call. The call happens for every text fragment that has a textDecorationLine (underlines, strikethroughs, links), each time its text is laid out on the JS thread.

The serialized value is none, underline, strikethrough or underline-strikethrough, so splitting on the '-' character gives the same parts without a regex. The old code also dropped trailing empty parts, but the loop only compares against underline and strikethrough, so they make no difference.

This adds no state or cache. It only helps text with a textDecorationLine.

Changelog:

[ANDROID] [CHANGED] - Parse textDecorationLine without compiling a regex

Test Plan:

Unit test: TextAttributePropsTest gets mapBufferSetsTextDecorationLine, which checks none, underline, strikethrough and underline-strikethrough through TextAttributeProps.fromMapBuffer. It also passes without this change, because the behavior is the same.

./gradlew :packages:react-native:ReactAndroid:testDebugUnitTest --tests 'com.facebook.react.views.text.*'

102 tests, 0 failures. ktfmt reports no changes in the two files.

Measurements: two release RNTester APKs built from this commit's base, one with and one without this change, on a Galaxy A16 and a Pixel 9a (both Android 16), compiled with cmd package compile -m speed. Both APKs have the same temporary benchmark edits. A Playground screen shows the rows and changes some of them every 100 ms for 20 s (10 of 60 underlined rows, 20 of 100 rows with no textDecorationLine), with new strings each time so the measure cache doesn't hide the work. Each run is a fresh process, in A/B/B/A order, twice, so 4 runs per APK. JS thread CPU comes from /proc/<pid>/task/<tid>/stat. The table shows the median per changed row, with the range in brackets.

Row	Phone	Without this change	With this change	Change
7 text fragments, one an underlined link	Galaxy A16	1840 µs (1820–1845)	1772 µs (1755–1805)	−3.7%
7 text fragments, one an underlined link	Pixel 9a	2432 µs (2310–2545)	2330 µs (2265–2375)	−4.2%
About 4 fragments, no textDecorationLine	Galaxy A16	940 µs (932–948)	942 µs (940–960)	no change
About 4 fragments, no textDecorationLine	Pixel 9a	1256 µs (1220–1278)	1230 µs (1225–1232)	no clear change

The ranges for the underlined row overlap on the Pixel 9a. The row with no textDecorationLine never reaches this code, so it serves as a control.

The row measurements above are all from this commit's base. On an older base, a simpleperf profile of a similar rich text list on a moto g57 power showed Pattern.compile and Pattern.matcher under TextAttributeProps.fromMapBuffer at 2.9% of the JS thread.

Not measured: the main thread, because this code runs on the JS thread when text is laid out.

🤖 Generated with Claude Code

[meta-codesync]

@Abbondanzo has imported this pull request. If you are a Meta employee, you can view this in D128941371.