Every SWT interop example has a black rectangle on the right when resized,

Here is some code that shows it:

import org.eclipse.swt.SWT;
import org.eclipse.swt.events.SelectionAdapter;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.graphics.Rectangle;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.layout.GridData;
import org.eclipse.swt.layout.GridLayout;
import org.eclipse.swt.widgets.Composite;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Event;
import org.eclipse.swt.widgets.Listener;
import org.eclipse.swt.widgets.Monitor;
import org.eclipse.swt.widgets.Scale;
import org.eclipse.swt.widgets.Shell;

import javafx.scene.control.Button;
import javafx.scene.Scene;
import javafx.scene.layout.VBox;
import javafx.embed.swt.FXCanvas;
import javafx.event.EventHandler;
import javafx.scene.control.CheckBox;
import javafx.scene.control.TextField;
import javafx.scene.layout.HBox;
//import test.javaclient.shared.Utils;


public class FXCanvasApp {

    public static String TEXT_INPUT_ID = "text.input.id";
    public static String BUTTON_ID = "button.id";
    public static String MAIN_CONTAINER_ID = "main.container.id";
    public static String HEAVY_POPUP_CONTAINER_ID = "heavy.container.id";
    public static String LIGHT_POPUP_CONTAINER_ID = "light.container.id";
    public static String MENU_POPUP_CONTAINER_ID = "menu.container.id";
    public static String CHECK_ID = "check.id";

    public static String HEAVYWEIGHT_POPUP_BTN = "Show heavywieght popup";
    public static String LIGHTWEIGHT_POPUP_BTN = "Show lightwieght popup";
    public static String MENU_POPUP_BTN = "Create popup menu";

    public static String RESET_BTN = "Reset content";

    public static int SCENE_WIDTH = 200;
    public static int SCENE_HEIGHT = 200;

    protected Scene scene;
    Shell lightPopup = null;
    Shell heavyPopup = null;

    TransparentJFXPanel lightweight_popup_fx_panel;
    TransparentJFXPanel heavyweight_popup_fx_panel;
    TransparentJFXPanel menu_popup_fx_panel;
    TransparentJFXPanel mainJavafxPanel;
    
    Shell shell;
    Scale alpha;

    protected FXCanvasApp() {
        shell = new Shell();
        shell.setText(this.getClass().getSimpleName());
        GridLayout layout = new GridLayout();
        shell.setLayout(layout);
        

        final org.eclipse.swt.widgets.Button popup_button_light = new org.eclipse.swt.widgets.Button(shell, SWT.TOGGLE);
        popup_button_light.setText(LIGHTWEIGHT_POPUP_BTN);
        popup_button_light.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                if (lightPopup == null) {
                    final Shell popup = lightPopup = new Shell (shell, SWT.NONE);
                    popup.setLayout(new FillLayout());
                    lightweight_popup_fx_panel = new TransparentJFXPanel(popup, SWT.BORDER);
                    lightweight_popup_fx_panel.setScene(createScene(LIGHT_POPUP_CONTAINER_ID));
                    lightweight_popup_fx_panel.setAlpha(alpha.getSelection());
                    popup.pack();
                    popup.setLocation(200, 200);
                    popup.setVisible(true);
                } else {
                    lightPopup.dispose();
                    lightPopup = null;
                    lightweight_popup_fx_panel = null;
                }
            }
        });

        
        final org.eclipse.swt.widgets.Button popup_button_heavy = new org.eclipse.swt.widgets.Button(shell, SWT.TOGGLE);
        popup_button_heavy.setText(HEAVYWEIGHT_POPUP_BTN);
        popup_button_heavy.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                if (heavyPopup == null) {
                    final Shell popup = heavyPopup = new Shell (shell, SWT.NONE);
                    popup.setLayout(new FillLayout());
                    heavyweight_popup_fx_panel = new TransparentJFXPanel(popup, SWT.BORDER);
                    heavyweight_popup_fx_panel.setScene(createScene(HEAVY_POPUP_CONTAINER_ID));
                    heavyweight_popup_fx_panel.setAlpha(alpha.getSelection());
                    popup.pack();
                    Rectangle rect = popup.getMonitor().getClientArea();
                    popup.setLocation(rect.x, rect.y);
                    popup.setVisible(true);
                } else {
                    heavyPopup.dispose();
                    heavyPopup = null;
                    heavyweight_popup_fx_panel = null;
                }
            }
        });

        
        final org.eclipse.swt.widgets.Button popup_menu_button = new org.eclipse.swt.widgets.Button(shell, SWT.PUSH);
        popup_menu_button.setText(MENU_POPUP_BTN);
        popup_menu_button.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                final Shell popup = new Shell (shell, SWT.ON_TOP);
                popup.addListener(SWT.Deactivate, new Listener () {
                    public void handleEvent (Event e) {
                        menu_popup_fx_panel = null;
                        popup.dispose();
                    }
                });
                popup.setLayout(new FillLayout());
                menu_popup_fx_panel = new TransparentJFXPanel(popup, SWT.BORDER);
                menu_popup_fx_panel.setScene(createScene(MENU_POPUP_CONTAINER_ID));
                menu_popup_fx_panel.setAlpha(alpha.getSelection());
                popup.pack();
                System.out.println("menu_popup_fx_panel.getPreferredSize(): " + menu_popup_fx_panel.getSize());
                popup.setLocation(200, 100);
                popup.open();
            }
        });

        mainJavafxPanel = new TransparentJFXPanel(shell, SWT.BORDER);

        //final FXCanvas scrollJavafxPanel = new FXCanvas(shell, SWT.BORDER);

        alpha = new Scale(shell, SWT.HORIZONTAL);
        alpha.setMaximum(255);
        alpha.setSelection(255);
        alpha.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                int val = alpha.getSelection();
                mainJavafxPanel.setAlpha(val);
                if (menu_popup_fx_panel != null) {
                    menu_popup_fx_panel.setAlpha(val);
                }
                if (heavyweight_popup_fx_panel != null) {
                    heavyweight_popup_fx_panel.setAlpha(val);
                }
                if (lightweight_popup_fx_panel != null) {
                    lightweight_popup_fx_panel.setAlpha(val);
                }
            }
        });

        final org.eclipse.swt.widgets.Button reset_button = new org.eclipse.swt.widgets.Button(shell, SWT.PUSH);
        reset_button.setText(RESET_BTN);
        reset_button.addSelectionListener(new SelectionAdapter() {
            public void widgetSelected(SelectionEvent e) {
                reset();
            }
        });
        
        mainJavafxPanel.moveAbove(null);
        reset_button.moveBelow(mainJavafxPanel);
        popup_menu_button.moveBelow(reset_button);
        popup_button_light.moveBelow(popup_menu_button);
        popup_button_heavy.moveBelow(popup_button_light);

        mainJavafxPanel.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
        alpha.setLayoutData(new GridData(SWT.FILL, SWT.CENTER, true, false));

        reset();

        shell.pack();
        Monitor monitor = shell.getMonitor();
        Rectangle monitorRect = monitor.getClientArea();
        Rectangle shellRect = shell.getBounds();
        shellRect.x = Math.max(0, (monitorRect.width - shellRect.width) / 2);
        shellRect.y = Math.max(0, (monitorRect.height - shellRect.height) / 2);
        shell.setBounds(shellRect);
        shell.open();
    }

    protected void reset() {
        if (heavyweight_popup_fx_panel != null) {
            heavyweight_popup_fx_panel.setScene(createScene(HEAVY_POPUP_CONTAINER_ID));
        }
        if (lightweight_popup_fx_panel != null) {
            lightweight_popup_fx_panel.setScene(createScene(LIGHT_POPUP_CONTAINER_ID));
        }
        if (menu_popup_fx_panel != null) {
            menu_popup_fx_panel.setScene(createScene(MENU_POPUP_CONTAINER_ID));
        }
        mainJavafxPanel.setScene(createScene(MAIN_CONTAINER_ID));
    }

    protected Scene createScene(String id) {
        final VBox pane = new VBox();
        pane.setMinSize(SCENE_WIDTH, SCENE_HEIGHT);
        pane.setMaxSize(SCENE_WIDTH, SCENE_HEIGHT);
        pane.setPrefSize(SCENE_WIDTH, SCENE_HEIGHT);
        pane.setId(id);
        Scene scene = new Scene(pane, SCENE_WIDTH, SCENE_HEIGHT);
        final TextField text_input = new TextField("TextInput");
        text_input.setId(TEXT_INPUT_ID);
        pane.getChildren().add(text_input);

        HBox button_box = new HBox(5);
        pane.getChildren().add(button_box);

        final CheckBox check = new CheckBox("Button pressed");
        check.setId(CHECK_ID);

        final Button button = new Button("Button");
        button.setId(BUTTON_ID);
        button.setOnAction(new EventHandler<javafx.event.ActionEvent>() {
            public void handle(javafx.event.ActionEvent t) {
                check.setSelected(true);
            }
        });

        button_box.getChildren().add(button);
        button_box.getChildren().add(check);

        //Utils.setCustomFont(scene);

        return scene;
    }

    static class TransparentJFXPanel extends FXCanvas {
        int alpha = 255;
        static boolean FilterAdded;
        static boolean USE_SHELL_ALPHA;
        
        public TransparentJFXPanel(Composite parent, int style) {
            super(parent, style | SWT.DOUBLE_BUFFERED);
            if (!FilterAdded) {
                //TODO - filter is left dangling in Display
                getDisplay().addFilter(SWT.Paint, new Listener () {
                    public void handleEvent (Event e) {
                        paint (e);
                    }
                });
                FilterAdded = true;
            }
        }

        public void setAlpha(int alpha) {
            this.alpha = alpha;
            if (USE_SHELL_ALPHA && (getShell().getStyle() & SWT.TITLE) == 0) {
                getShell().setAlpha(alpha);
            } else {
                this.redraw();
            }
        }

        public void paint(Event e) {
            if (USE_SHELL_ALPHA && (getShell().getStyle() & SWT.TITLE) == 0) return;
            if (e.widget instanceof TransparentJFXPanel) {
                Rectangle rect = getClientArea();
                drawBackground(e.gc, rect.x, rect.y, rect.width, rect.height);
                e.gc.setAlpha(alpha);
            }
        }
    }

    public static void main(String[] args) {
        Display display = new Display ();
        Shell shell = new FXCanvasApp().shell;
        while (!shell.isDisposed()) {
            if (!display.readAndDispatch()) display.sleep();
        }
        display.dispose();
    }
}