RFR: 8305418: [Linux] Replace obsolete XIM as Input Method Editor [v19]

[Martin Fox]

On Wed, 17 Jan 2024 17:10:24 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`.
>> 
>> [Screencast from 17-09-2023 21:59:04.webm](https://github.com/openjdk/jfx/assets/30704286/6c398e39-55a3-4420-86a2-beff07b549d3)
>
> Thiago Milczarek Sayao has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Add signals to avoid warnings

The code and behavior look good to me. I did notice that you collapse the pango attribute list down to a single attribute but that didn't seem to affect the feedback negatively (the Mac ignores the OS-provided attributes completely so who am I to judge).

When I drag a JavaFX window the JavaFX controls lose focus at the start of the drag and regain it at the end. This behavior is unique to Linux and dates back to at least JavaFX 20. This is a separate bug from the one addressed by this PR but it does cause an annoying interaction with the IME; if you drag the window while composing the text will either get committed or discarded (the IME controls which).

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PR Review: https://git.openjdk.org/jfx/pull/1080#pullrequestreview-1844379573