RFR: 8273379 - GTK3 stops sending key events during drag and drop [v13]

[Thiago Milczarek Sayao]

On Fri, 6 Jan 2023 01:26:09 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>> This PR fixes 8273379.
>> 
>> I reverted back to use GDK (from [8225571](https://bugs.openjdk.org/browse/JDK-8225571)) to handle the events. 
>> 
>> It may also fix [8280383](https://bugs.openjdk.org/browse/JDK-8280383).
>> 
>> There's also some cleaup.
>> 
>> The most changed part is that I had to move `process_events` to `glass_evloop`  because it's reused in glass_dnd.
>> 
>> To do general testing:
>> `java @build/run.args -jar apps/toys/DragDrop/dist/DragDrop.jar`
>
> Thiago Milczarek Sayao has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Replace g_warning
>  - Improvements

There are still some issues I've found testing:
- Closing the Application while dragging
- Drag begin sometimes doesn't set the cursor

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PR: https://git.openjdk.org/jfx/pull/986