RFR: 8334495: Use FFM instead of jdk.internal.misc.Unsafe in java.desktop font implementation

[Damon Nguyen]

On Tue, 18 Jun 2024 20:31:58 GMT, Phil Race <prr at openjdk.org> wrote:

> Migrate font code from jdk.internal.misc.Unsafe to using FFM.
> This reduces the coupling between the java.desktop module and the internals of the java.base module.
> 
> The code being changed here is not particularly performance sensitive, and it is not executed in the most common cases.
> The main impact performance-wise is a total of around 37ms in initialisation costs on my x64 macbook.
> A minimal program that just draws a string to an image - does not even put up a window - runs at around 690-700ms.
> There's variability in that number and the overall time for a JDK without the change is around (660-670ms)
> In the small test, this is the first and only use of FFM, so the one-off part cost should move elsewhere when FFM starts
> to be used earlier in the JDK itself.

Changes look good as far as I can tell. I tested it on Ubuntu 22.04 on SwingSet2. Everything working as expected. Can't give any exact details on performance, but it runs smoothly as far as I can tell. No major difference performance-wise, which I suppose is a good thing.

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Marked as reviewed by dnguyen (Committer).

PR Review: https://git.openjdk.org/jdk/pull/19777#pullrequestreview-2133347008