Drag and Drop working differently in Java 11 vs Java 8 - javafx

Question

I wrote a program which makes use of drag and drop in javafx. In JavaFX8 it works perfectly.
In JavaFX11, the drag and drop is dysfunctional: I don't get a different mouse cursor, I don't get a ghost image of the row I'm dragging, and something's wrong with the drops -- they don't trigger on mouse release, and then the drop is triggered each time I click on the table.
Here is minimum runnable example which demonstrates the issue I'm facing. Run on a Java 8 JVM it works as desired. On Java 11 JVM it does not. I am on Ubuntu 18.04.
I'm fine with changing my code to accommodate Java 11, but I don't have any idea what I'm doing wrong.
Java 11 Version
java version "11.0.1" 2018-10-16 LTS
Java(TM) SE Runtime Environment 18.9 (build 11.0.1+13-LTS)
Java HotSpot(TM) 64-Bit Server VM 18.9 (build 11.0.1+13-LTS, mixed mode)
Java 8 Version
openjdk version "1.8.0_181"
OpenJDK Runtime Environment (build 1.8.0_181-8u181-b13-1ubuntu0.18.04.1-b13)
OpenJDK 64-Bit Server VM (build 25.181-b13, mixed mode)
DND11.java
import javafx.application.Application;
import javafx.collections.FXCollections;
import javafx.scene.Scene;
import javafx.scene.control.SelectionMode;
import javafx.scene.control.TableColumn;
import javafx.scene.control.TableRow;
import javafx.scene.control.TableView;
import javafx.scene.control.cell.PropertyValueFactory;
import javafx.scene.input.ClipboardContent;
import javafx.scene.input.DataFormat;
import javafx.scene.input.Dragboard;
import javafx.scene.input.TransferMode;
import javafx.stage.Stage;
public class DND11 extends Application {
public TableView<Person> getTable () {
DataFormat DRAGGED_PERSON = new DataFormat ( "application/example-person" );
TableColumn <Person, String> firstNameColumn = new TableColumn <> ( "First Name" );
TableColumn <Person, String> LastNameColumn = new TableColumn <> ( "Last Name" );
firstNameColumn.setCellValueFactory( new PropertyValueFactory <Person, String>( "firstName" ) );
LastNameColumn.setCellValueFactory( new PropertyValueFactory <Person, String>( "lastName" ) );
TableView <Person> tableView = new TableView <> ();
tableView.getColumns().addAll( firstNameColumn, LastNameColumn );
tableView.setColumnResizePolicy( TableView.CONSTRAINED_RESIZE_POLICY );
tableView.setEditable( false );
tableView.setItems( FXCollections.observableArrayList( Person.generatePersons ( 10 ) ) );
tableView.getSelectionModel().setSelectionMode( SelectionMode.MULTIPLE );
tableView.setRowFactory( tv -> {
TableRow <Person> row = new TableRow <>();
row.setOnDragDetected( event -> {
if ( !row.isEmpty() ) {
Dragboard db = row.startDragAndDrop( TransferMode.COPY );
ClipboardContent cc = new ClipboardContent();
cc.put( DRAGGED_PERSON, row.getItem() );
tableView.getItems().remove( row.getItem() );
db.setContent( cc );
}
});
row.setOnDragOver( event -> {
Dragboard db = event.getDragboard();
event.acceptTransferModes( TransferMode.COPY );
});
row.setOnDragDropped( event -> {
Dragboard db = event.getDragboard();
Person person = (Person)event.getDragboard().getContent( DRAGGED_PERSON );
if ( person != null ) {
tableView.getItems().remove( person );
int dropIndex = row.getIndex();
tableView.getItems().add( dropIndex, person );
}
event.setDropCompleted( true );
event.consume();
});
return row;
});
return tableView;
}
#Override
public void start ( Stage stage ) throws Exception {
stage.setScene( new Scene( getTable(), 800, 400 ) );
stage.show();
}
public static void main ( String[] args ) {
launch( args );
}
}
Person.java
import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
public class Person implements Serializable {
private static final long serialVersionUID = 1L;
private String firstName, lastName;
public Person ( String firstName, String lastName ) {
this.firstName = firstName;
this.lastName = lastName;
}
public String getFirstName() {
return firstName;
}
public String getLastName() {
return lastName;
}
public static List <Person> generatePersons ( int number ) {
List<Person> retMe = new ArrayList<Person> ( number );
for ( int k = 0; k < number; k++ ) {
retMe.add ( new Person ( randomFirstName(), randomLastName() ) );
}
return retMe;
}
private static Random rand = new Random();
private static String randomFirstName() {
return firstNames [ Math.abs( rand.nextInt() ) % firstNames.length ];
}
private static String randomLastName() {
return lastNames [ Math.abs( rand.nextInt() ) % lastNames.length ];
}
private static String[] firstNames = new String[] {
"ANTON","ANTONE","ANTONIA","NTONIO","ANTONY","ANTWAN","ARCHIE","ARDEN","ARIEL","ARLEN",
"ARMAND","ARMANDO","ARNOLD","ARNOLDO","ARNULF","ARON","ARRON","ART","ARTHUR","ARTURO",
"DARRICK","DARRIN","DARRON","DARRYL","DARWIN","DARYL","DAVE","DAVID","DAVIS","DEAN",
};
private static String[] lastNames = new String[] {
"SMITH","JOHNSON","WILLIAMS","BROWN","JONES","MILLER","DAVIS","GARCIA","RODRIGUEZ",
"WILSON","MARTINEZ","ANDERSON","TAYLOR","THOMAS","HERNANDEZ","MOORE","MARTIN","JACKSON"
};
}

Answer 1

While Drag and Drop in JavaFX has a common API for all the platforms (as the rest of the API, of course), its internal implementation is platform dependent, and it is quite different on Windows, Mac or Linux.
But this shouldn't be an issue when migrating from JavaFX 8 to JavaFX 11, though.
The sample posted by the OP works the same on Windows and Mac with both JavaFX 8 and 11, and if it is not the case on Linux, it might have to do with the changes done in the latest release of JavaFX for Linux.
According to the releases note, under the Important Changes section we can see:
Switch default GTK version to 3
JavaFX will now use GTK 3 by default on Linux platforms where the gtk3 library is present. Prior to JavaFX 11, the GTK 2 library was the default. This matches the default for AWT in JDK 11. See JDK-8198654 for more information.
While this change was basically a two lines diff in the JavaFX code, and nothing changed from the implementation details for DND, the GTK 3 implementation might have changed from GTK 2, and those changes haven't been taken into account.
Similar issues related to GTK have been reported for dialogs, windows or Wayland crashes.
Workaround
So far the only known workaround for all of those issues is to run the app with GTK 2, that can be set with the system property: jdk.gtk.version.
So this option can be added on command line:
java -Djdk.gtk.version=2 ...
to run the application.
As posted in the comments, this seems to solve the drag and drop issue.
Report the issue
Definitely, that confirms that this is an issue, and as such it should be filed at the OpenJFX issue tracker, providing the sample code to reproduce it, system details (OS version, Java version, JavaFX version...).