RFR: 8305418: [Linux] Replace obsolete XIM as Input Method Editor

[leewyatt]

On Sun, 2 Apr 2023 20:38:25 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

> This replaces obsolete XIM and uses gtk api for IME.
> Gtk uses [ibus](https://github.com/ibus/ibus)
> 
> Gtk3+ uses relative positioning (as Wayland does), so I've added a Relative positioning on `InputMethodRequest`.

Thank you, this PR is extremely, extremely useful.

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PR Comment: https://git.openjdk.org/jfx/pull/1080#issuecomment-1652041588