RFR: 8236651: Simplify and update glass gtk backend

[Kevin Rushforth]

On Tue, 15 Dec 2020 12:24:01 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

> This is a new approach to rewrite parts of gtk glass backend to be more clean.
> 
> I will provide small "manageable" PR to incrementally make the backend better.
> 
> This PR adresses cleanup of the Size and Positioning code. It makes code more "straightforward" and easier to maintain.
> 
> Current status (Ubuntu 20.04):
> ![image](https://user-images.githubusercontent.com/30704286/102702414-1b1b1800-4241-11eb-90bf-8ab737ce2e04.png)
> 
> (*) Some of the iconify tests are also failing on the main branch. 
> 
> `gradlew -PFULL_TEST=true -PUSE_ROBOT=true :systemTests:test --tests test.robot.javafx.stage.IconifyTest` on a second run produces 4 tests, 2 failures.

This does look like a much more manageable approach.

One thing to be aware of from a bookkeeping point of view is that a JBS issues is resolved by a single PR. Once a PR has been integrated for a given JBS bug ID, that bug ID cannot be reused.

This means that each separate PR will need it's own JBS issue to be filed, even if those enhancements taken together are part of a larger set of improvements. Incremental improvements are fine (and in this case a good way to proceed), but you might give some thought to the title of each such improvement. I wouldn't want to see 5 fixes go in each with the same title of `Simplify and update glass gtk backend`.

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

PR: https://git.openjdk.java.net/jfx/pull/367