RFR: 8368478: RichTextArea: add IME support

[Martin Fox]

On Thu, 16 Oct 2025 19:59:06 GMT, Andy Goryachev <angorya at openjdk.org> wrote:

> Adds Input Method Editor (IME) support to `RichTextArea`/`CodeArea`.
> 
> Tested on macOS and Windows 11 with Japanese and Chinese (pinyin) input methods.
> Please test this on Linux, even though there is no platform-specific code in this PR (should work the same way it does in `TextArea`/`TextField`)
> 
> For testing, one can use the updated Monkey Tester
> https://github.com/andy-goryachev-oracle/MonkeyTest
> (optionally enable IME events in stdout with Logging -> IME Monitor)

On Mac and Linux dead key sequences are delivered as InputMethodEvents. When typing ü using dead keys the user previews the diacritic mark (¨) as composed text and then the final character (ü) is delivered as committed text.

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PR Comment: https://git.openjdk.org/jfx/pull/1938#issuecomment-3443679439