RFR: 8236651: Simplify and update glass gtk backend

[Pankaj Bansal]

On Fri, 12 Jun 2020 20:22:12 GMT, Thiago Milczarek Sayao <tsayao at openjdk.org> wrote:

>>> I had used two compilation parameters to limit Gtk on 3.8 (so it would generate error if any symbol > 3.8 were used).
>>> But that does not seem to work on 18.04, so I removed it.
>> 
>> Good. I was going to ask you about that, so I'm happy to see it gone.
>
> I have investigated the Tab Pane Drag Test and it works manually.
> 
> import javafx.application.Application;
> import javafx.scene.Scene;
> import javafx.scene.control.Tab;
> import javafx.scene.control.TabPane;
> import javafx.stage.Stage;
> 
> public class Test
>         extends Application {
> 
>     @Override
>     public void start(Stage stage) {
>         TabPane tabPane = new TabPane();
>         tabPane.setTabDragPolicy(TabPane.TabDragPolicy.REORDER);
>         Scene scene = new Scene(tabPane, 800, 600);
>         stage.setScene(scene);
>         Tab tab1 = new Tab("Tab1");
>         Tab tab2 = new Tab("Tab2");
> 
>         tabPane.getTabs().addAll(tab1, tab2);
> 
> 
>         stage.setAlwaysOnTop(true);
>         stage.show();
>     }
> 
>     public static class Main {
>         public static void main(String[] args) {
>             Application.launch(Test.class, args);
>         }
>     }
> }
> 
> It also works if I switch back to GDK Events instead of Gtk Signals. But it is a drag test, by experience they don't
> work well on Robot.

Following are results in Ubuntu 18.04 after fix for tab pane tests.
<img width="516" alt="Results_18 04"
src="https://user-images.githubusercontent.com/6153953/84587007-3abc2880-ae39-11ea-8b61-0cbb86e4d4b5.png">

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

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