[jdk25u] RFR: 8361381: GlyphLayout behavior differs on JDK 11+ compared to JDK 8

[Volker Simonis]

On Thu, 13 Nov 2025 23:10:47 GMT, Vishal Chand <duke at openjdk.org> wrote:

> Backporting:
> 
> 8361381: GlyphLayout behavior differs on JDK 11+ compared to JDK 8
> 
> Summary of the change:
> * Fixes a regression in HarfBuzz-based text layout in JDK 9+ where GlyphLayout incorrectly clustered characters in complex scripts (e.g., Khmer) due to faulty “each glyph maps to one character” assumptions.
> * Adjusts the clustering algorithm in `ExtendedTextSourceLabel::createCharinfo()` by removing the needless `clusterExtraGlyphs` logic so line-breaking and wrapping behave consistently with JDK 8.
> 
> Testing:
> * tests in `test/jdk/java/awt/font/` are passing locally on Amazon Linux 2.
> 
> Applies cleanly, low risk.

Looks good.
Thanks for downporting.

-------------

Marked as reviewed by simonis (Reviewer).

PR Review: https://git.openjdk.org/jdk25u/pull/379#pullrequestreview-3465130059