RFR: 8236651: Simplify and update glass gtk backend

[Thiago Milczarek Sayao]

On Fri, 12 Jun 2020 13:51:58 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>>> After the latest commit on June 10, this is not building for me on my Ubuntu 18.04. I am attaching the build log for
>>> reference. [build.log](https://github.com/openjdk/jfx/files/4770864/build.log)
>> 
>> It's now fixed. 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.
>
>> 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.

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