EDIT

/**

* Copyright (C) 2017 EDIT

* European Distributed Institute of Taxonomy

* http://www.e-taxonomy.eu

*

* The contents of this file are subject to the Mozilla Public License Version 1.1

* See LICENSE.TXT at the top of this package for the full license terms.

*/

import org.eclipse.swt.graphics.Image;

import org.eclipse.swt.graphics.Point;

import org.eclipse.swt.widgets.Display;

import eu.etaxonomy.taxeditor.featuretree.CharacterTransfer;

/**

 * @author pplitzner

 * @since Jun 2, 2017

 *

 */

public class CharacterDragListener extends FeatureNodeDragListener {

    private TreeViewer structureViewer;

    private TreeViewer propertyViewer;

    private Image image;

    private GC gc;

    public CharacterDragListener(TreeViewer structureViewer, TreeViewer propertyViewer) {

        super(propertyViewer);

        this.structureViewer = structureViewer;

        this.propertyViewer = propertyViewer;

    }

    @Override

        characters = null;

        if(image!=null){

            image.dispose();

            image = null;

        }

        if(gc!=null){

            gc.dispose();

            gc = null;

        }

        super.dragFinished(event);

    }

    public void dragSetData(DragSourceEvent event) {

        if (CharacterTransfer.getInstance().isSupportedType(event.dataType)) {

            event.data = characters;

    }

    public void dragStart(DragSourceEvent event) {

        event.doit =

                !structureViewer.getSelection().isEmpty()

                && !propertyViewer.getSelection().isEmpty()

                && ((IStructuredSelection) structureViewer.getSelection()).toList()

                .stream().allMatch(element -> element instanceof FeatureNode)

                && ((IStructuredSelection) propertyViewer.getSelection()).toList()

                .stream().allMatch(element -> element instanceof FeatureNode);

            return;

        }

        TreeSelection structureSelection = (TreeSelection) structureViewer.getSelection();

        TreeSelection propertySelection = (TreeSelection) propertyViewer.getSelection();

        if(structureSelection!=null && propertySelection!=null

                && !structureSelection.isEmpty() && !propertySelection.isEmpty()){

            //create all possible characters

            characters = CharacterEditor.createCharacters(structureSelection, propertySelection);

        }

        String text = characters.stream().map(character->character.generateTitle()).collect(Collectors.joining("\n"));

        // creating temporary GC for size calculation

        gc = new GC(Display.getDefault());

        // Calculate text extent

        Point compositeSize = gc.textExtent(text);

        //remove temporary gc

        gc.dispose();

        gc = null;

        // Creating new Image

        image = new Image(Display.getCurrent(),compositeSize.x+10,compositeSize.y+10);

        //create gc for image to be able to draw on it

        gc = new GC(image);

        //set and fill with bg color

        gc.setBackground(GUIHelper.COLOR_LIST_BACKGROUND);

        gc.fillRectangle(0, 0, compositeSize.x+10, compositeSize.y+10);

        //draw text

        gc.drawText(text, 5, 5, true);

        //draw border

        gc.drawRectangle(0, 0, compositeSize.x+9, compositeSize.y+9);

        // Setting widget to DnD image

        event.image = image;