feat(android): honor textDecorationStyle on Text decorations

[quantizor]

Summary:

textDecorationStyle is declared on TextStyleAndroid in the public types but TA_KEY_TEXT_DECORATION_STYLE was a no-op handler: every value silently rendered as a solid line, and wavy was additionally rejected at the Fabric C++ enum boundary with an Unsupported value log. This PR wires the prop through the existing C++ → Kotlin pipeline and implements solid, double, dotted, dashed, and wavy for both underlines and strikethroughs.

Android's Layout.draw paints the underline produced by setUnderlineText(true) using paint.color only and offers no native way to draw a dotted / dashed / wavy decoration. ReactUnderlineSpan and ReactStrikethroughSpan now extend DrawCommandSpan and paint the decoration themselves in onDraw via Canvas.drawLine / Canvas.drawPath, dispatching by style. As a side effect this also makes textDecorationColor reach the paint, closing the separate long-standing gap filed as #4579 in 2015 — the companion color-focused PR #56767 isolates that fix for reviewers who only want the color change.

TextDecorationStyle::Wavy is added to the Fabric C++ primitives / conversions so the wavy JS value flows through; the same enum is shared with iOS (see companion iOS PR #56769).

The wavy curve uses Chromium/Blink's formula from decoration_line_painter.cc (wavelength = 1 + 2 * round(2 * thickness + 0.5), controlPointDistance = 0.5 + round(3 * thickness + 0.5), one cubic Bezier per wavelength with both control points at the midpoint, one above and one below the y-axis). The minimum stroke thickness is density-aware (1.5 dp) so decorations read consistently across display densities. The drawing loop iterates while x < x2 so the final cycle continues through the last character (including trailing punctuation that would otherwise be visually uncovered when the run width is not an integer multiple of the wavelength).

ReactTextView.onDraw invokes DrawCommandSpan.onDraw after super.onDraw, mirroring what PreparedLayoutTextView.onDraw already did. Without this, the new spans have no effect on the older view class, which is what some Text components on the new architecture still route through.

Companion PRs (independent, also targeting main):

• fix(android): track textAlignVertical in custom decoration draw offset #56767 — fix(android): textDecorationColor on underlines + strikethroughs. Resolves [Android] Issue with textDecoration #4579.
• feat(ios): honor textDecorationStyle on Text decorations #56769 — feat(ios): textDecorationStyle wavy/dotted/dashed via custom CG paths. Shares the TextDecorationStyle::Wavy enum addition; whichever lands first leaves the other with a trivial conflict to resolve.

Changelog:

[GENERAL] [ADDED] - textDecorationStyle: 'wavy' for <Text> (see corresponding iOS PR for the iOS counterpart)
[ANDROID] [ADDED] - Text decorations honor textDecorationStyle (solid, double, dotted, dashed, wavy)

Test Plan:

Rendered <Text> components with textDecorationLine set to "underline" or "line-through" and textDecorationStyle cycling through solid / double / dotted / dashed / wavy. On stock 0.85.2 every value renders as a solid line and wavy logs an Unsupported value warning; with this patch each style renders with the requested stroke geometry. Verified single-line and wrapped multi-line cases on an Android API 36 emulator: each visual line within a wrapped block receives its own correctly-styled decoration that starts and ends at the line's content boundaries.

<Text style={{
  color: 'black',
  textDecorationLine: 'underline',
  textDecorationStyle: 'wavy',
}}>
  Hello
</Text>

[meta-codesync]

@CalixTang has imported this pull request. If you are a Meta employee, you can view this in D104680895.

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING

[quantizor]

@CalixTang following up, is any further action needed here? What's the typical merge timeline for RN fixes?

[CalixTang]

thanks for the follow-up. Let me check in with someone on the team.

[cortinico]

@CalixTang following up, is any further action needed here? What's the typical merge timeline for RN fixes?

@quantizor would you be able to rebase this one to start with?

[meta-codesync]

@cortinico merged this pull request in 87184c8.

[react-native-bot]

This pull request was successfully merged by @quantizor in 87184c8

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