RFR: 8236651: Simplify and update glass gtk backend

[Thiago Milczarek Sayao]

On Mon, 6 Jan 2020 22:41:07 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>>> Please, mark it as WIP.
>> 
>> You can do this by editing the title and adding `WIP: ` as a prefix.
>
> This sort of enhancement needs to be discussed on the openjfx-dev mailing list first. While the WIP PR might be used to illustrate what you have in mind to propose, it is premature to actually review the implementation without first discussing whether and it makes sense to do it, what the high-level goals are, etc.

I understand. Will do that when the code works 100%. I have submitted the PR to avoid duplicated efforts and let people test it (if anyone is willing).

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