com.buildml.eclipse.actions.ActionsEditorDragSource.java Source code

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Here is the source code for com.buildml.eclipse.actions.ActionsEditorDragSource.java

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/*******************************************************************************
 * Copyright (c) 2012 Arapiki Solutions Inc.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *    psmith - initial API and 
 *        implementation and/or initial documentation
 *******************************************************************************/

package com.buildml.eclipse.actions;

import java.util.Iterator;

import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.DragSourceListener;
import org.eclipse.swt.dnd.Transfer;

import com.buildml.eclipse.bobj.UIAction;
import com.buildml.eclipse.bobj.UIInteger;
import com.buildml.eclipse.utils.dnd.BuildMLTransfer;
import com.buildml.eclipse.utils.dnd.BuildMLTransferType;
import com.buildml.model.IBuildStore;

/**
 * Functionality related to dragging actions from the actions editor onto other
 * editors (including the Outline view).
 * 
 * @author Peter Smith <psmith@arapiki.com>
 */
public class ActionsEditorDragSource implements DragSourceListener {

    /*=====================================================================================*
     * FIELDS/TYPES
     *=====================================================================================*/

    /** The ActionEditor's TreeViewer we're dragging an element from */
    private TreeViewer treeViewer;

    /** The BuildStore underlying the action editor */
    private IBuildStore buildStore;

    /*=====================================================================================*
     * CONSTRUCTORS
     *=====================================================================================*/

    /**
     * Create a new ActionsEditorDragSource object. There should be exactly one of these objects
     * for each ActionsEditor object.
     * 
     * @param treeViewer The TreeViewer that elements will be dragged from.
     * @param buildStore The IBuildStore that contains the elements being dragged.
     */
    public ActionsEditorDragSource(TreeViewer treeViewer, IBuildStore buildStore) {
        this.treeViewer = treeViewer;
        this.buildStore = buildStore;

        /* register ourselves as the handler for "drag" operations */
        treeViewer.addDragSupport(DND.DROP_COPY | DND.DROP_MOVE, new Transfer[] { BuildMLTransfer.getInstance() },
                this);
    }

    /*=====================================================================================*
     * PUBLIC METHODS
     *=====================================================================================*/

    /**
     * A drag operation has been started. We need to validate whether the element being
     * dragged is something we can handle. For an ActionsEditor, we can drag one or more
     * UIAction objects.
     */
    @Override
    public void dragStart(DragSourceEvent event) {

        /* 
         * Determine what is being dragged. Assuming everything in the selection is a UIAction,
         * we're OK to proceed.
         */
        IStructuredSelection selection = ((IStructuredSelection) treeViewer.getSelection());
        @SuppressWarnings("unchecked")
        Iterator<Object> iter = selection.iterator();
        while (iter.hasNext()) {
            Object node = iter.next();
            if ((node == null) || (!(node instanceof UIAction))) {

                /* something in the selection is not a UIAction - we can't drag */
                event.doit = false;
                return;
            }
        }

        /* OK, we can drag the selection */
        event.doit = true;
    }

    /*-------------------------------------------------------------------------------------*/

    /** 
     * This method is called by the drag/drop framework to obtain the actual "transfer" data
     * for the tree node that was selected when the drag/drop started. For UIAction, we create
     * a corresponding BuildMLTransferType object. For other things, we abort.
     */
    @Override
    public void dragSetData(DragSourceEvent event) {
        if (BuildMLTransfer.getInstance().isSupportedType(event.dataType)) {

            /*
             * Identify the currently-selected tree node, and create a corresponding
             * BuildMLTransferType object for each selected element. We know how many
             * elements are in the selection, so create a BuildMLTransferType for each.
             */
            IStructuredSelection selection = ((IStructuredSelection) treeViewer.getSelection());
            BuildMLTransferType data[] = new BuildMLTransferType[selection.size()];

            /* populate the array */
            int elementNum = 0;
            @SuppressWarnings("unchecked")
            Iterator<Object> iter = selection.iterator();
            while (iter.hasNext()) {
                Object node = iter.next();
                int transferType;

                /* check the type of the tree node (must be a UIAction). */
                if (node instanceof UIAction) {
                    transferType = BuildMLTransferType.TYPE_ACTION;
                } else {
                    /* we can't proceed, not a recognized type */
                    event.doit = false;
                    return;
                }

                /*
                 * The selected node is valid, create the data to pass to the drag/drop framework.
                 */
                int id = ((UIInteger) node).getId();
                data[elementNum++] = new BuildMLTransferType(buildStore.toString(), transferType, id);
            }
            ;

            /* 
             * We now have a complete array of BuildMLTransferType[], each entry represents
             * a unique UIAction that was part of our selection.
             */
            event.data = data;
        }
    }

    /*-------------------------------------------------------------------------------------*/

    /**
     * Called by the drag/drop framework when the drag operation has completed.
     */
    @Override
    public void dragFinished(DragSourceEvent event) {
        /* nothing - the drop target handles changing the model */
    }

    /*-------------------------------------------------------------------------------------*/
}