RFR: 8236651: Simplify and update glass gtk backend

[Thiago Milczarek Sayao]

On Thu, 27 Aug 2020 21:21:39 GMT, Tor (torbuntu) <github.com+17347324+Torbuntu at openjdk.org> wrote:

>> I would starting hooking gtk event signals (https://developer.gnome.org/gtk3/stable/GtkWidget.html), specially the
>> "touch-event" to JavaFx events (probably need to add through JNI). Should be simple. Contact me at thiago.sayao (gmail).
>
>> I would starting hooking gtk event signals (https://developer.gnome.org/gtk3/stable/GtkWidget.html), specially the
>> "touch-event" to JavaFx events (probably need to add through JNI). Should be simple. Contact me at thiago.sayao (gmail).
> 
> Would it be safe you think to branch from your PR to have the updated gtk backend? It would be much easier to work with.

Rebased onto "master" and squashed commits.

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

PR: https://git.openjdk.java.net/jfx/pull/77