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SciJava Common is a shared library for SciJava software. It provides a plugin framework, with an extensible mechanism for service discovery, backed by its own annotation processor, so that plugins can be loaded dynamically. It is used by downstream projects in the SciJava ecosystem, such as ImageJ and SCIFIO.

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/*
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 * Wisconsin-Madison, Broad Institute of MIT and Harvard, and Max Planck
 * Institute of Molecular Cell Biology and Genetics.
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 *    this list of conditions and the following disclaimer.
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package org.scijava.ui.dnd;

import org.scijava.app.StatusService;
import org.scijava.event.EventHandler;
import org.scijava.plugin.AbstractHandlerService;
import org.scijava.plugin.Parameter;
import org.scijava.plugin.Plugin;
import org.scijava.service.Service;
import org.scijava.ui.dnd.event.DragEnterEvent;
import org.scijava.ui.dnd.event.DragExitEvent;
import org.scijava.ui.dnd.event.DragOverEvent;
import org.scijava.ui.dnd.event.DropEvent;

/**
 * Default service for handling drag and drop events.
 * 
 * @author Curtis Rueden
 */
@Plugin(type = Service.class)
public class DefaultDragAndDropService extends
	AbstractHandlerService> implements
	DragAndDropService
{

	private static final String SUPPORTED = "Drag and Drop";
	private static final String UNSUPPORTED = "Unsupported Object";

	@Parameter
	private StatusService statusService;

	// -- Event handlers --

	@EventHandler
	protected void onEvent(final DragEnterEvent e) {
		// determine whether the given drop operation is supported
		final boolean compatible = supports(e.getData(), e.getDisplay());

		// update the status accordingly
		final String message = compatible ? SUPPORTED : UNSUPPORTED;
		statusService.showStatus("< <" + message + "> >");

		// accept the drag if the operation is supported
		if (compatible) e.setAccepted(true);
	}

	@EventHandler
	protected void onEvent(@SuppressWarnings("unused") final DragExitEvent e) {
		statusService.clearStatus();
	}

	@EventHandler
	protected void onEvent(@SuppressWarnings("unused") final DragOverEvent e) {
		// NB: No action needed.
	}

	@EventHandler
	protected void onEvent(final DropEvent e) {
		if (!supports(e.getData(), e.getDisplay())) return;

		// perform the drop
		final boolean success = drop(e.getData(), e.getDisplay());
		e.setSuccessful(success);
	}

}