RFR: 8320912: IME should commit on focus change

[Andy Goryachev]

On Tue, 30 Jan 2024 20:32:36 GMT, Martin Fox <mfox at openjdk.org> wrote:

> This is a Mac only bug. If the user was in the middle of IM text composition and clicked on a different node the partially composed text was left in the old node and the IM window wasn't dismissed. This PR implements the existing finishInputMethodComposition call so it can commit the text and dismiss the IM window before focus moves away from the node where composition was taking place.
> 
> This PR changes the implementation of `unmarkText` to match what we want and what Apple says it should do ("The text view should accept the marked text as if it had been inserted normally"). With that said I haven't found an IME that calls this routine.

Noticed two issues:

1. using the MonkeyTester, open TextField page and the Native-to-ascii tool (Tools ->  Native-to-ascii).
2. switch to Japanese input
3. type "a" into the text field in the main window
4. click on a "native" text area in the other window
PROBLEM 1:
notice how the underline under あ is still there in the first text field.  the input might have been committed, because when I click back on the first text field, the underline disappears.  It works correctly when clicking on the second text field *in the same* window (add 

        op.option(new TextField());

to TextFieldPage:111 in the Monkey Tester https://github.com/andy-goryachev-oracle/MonkeyTest


![Screenshot 2024-01-31 at 10 36 32](https://github.com/openjdk/jfx/assets/107069028/96861c47-e5b2-4dfd-967f-97ab4b098b1e)

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

PR Comment: https://git.openjdk.org/jfx/pull/1356#issuecomment-1919719343