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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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 * 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.display.Display;
import org.scijava.plugin.AbstractHandlerPlugin;

/**
 * Abstract superclass for {@link DragAndDropHandler}s.
 * 
 * @author Curtis Rueden
 */
public abstract class AbstractDragAndDropHandler extends
	AbstractHandlerPlugin implements DragAndDropHandler
{

	// -- DragAndDropHandler methods --

	@Override
	public boolean supports(final D dataObject, final Display display) {
		return supportsDisplay(display) && supports(dataObject);
	}

	@Override
	public boolean supportsData(final DragAndDropData data) {
		return data.isSupported(getType()) && supports(convertDataUnchecked(data));
	}

	@Override
	public boolean supportsData(final DragAndDropData data,
		final Display display)
	{
		return supportsDisplay(display) && supportsData(data);
	}

	@Override
	public boolean supportsObject(final Object object) {
		return object != null && getType().isAssignableFrom(object.getClass()) &&
			supports(convertObjectUnchecked(object));
	}

	@Override
	public boolean supportsObject(final Object object, final Display display) {
		return supportsDisplay(display) && supportsObject(object);
	}

	@Override
	public boolean supportsDisplay(final Display display) {
		return true;
	}

	@Override
	public D convertData(final DragAndDropData data) {
		if (!supportsData(data)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		return convertDataUnchecked(data);
	}

	@Override
	public D convertObject(final Object object) {
		if (!supportsObject(object)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		return convertObjectUnchecked(object);
	}

	@Override
	public boolean dropData(final DragAndDropData data, final Display display)
	{
		return drop(convertData(data), display);
	}

	@Override
	public boolean dropObject(final Object object, final Display display) {
		return drop(convertObject(object), display);
	}

	// -- Internal methods --

	/**
	 * Throws {@link IllegalArgumentException} if (data, display) pair is
	 * incompatible.
	 */
	protected void check(final D dataObject, final Display display) {
		// NB: First check compatibility of data and display individually.
		if (!supports(dataObject)) {
			throw new IllegalArgumentException("Incompatible data object");
		}
		if (!supportsDisplay(display)) {
			throw new IllegalArgumentException("Incompatible display");
		}
		// NB: The data and display are individually compatible,
		// but are they compatible with one another?
		if (!supports(dataObject, display)) {
			throw new IllegalArgumentException(
				"Data object and display are incompatible");
		}
	}

	/**
	 * Converts the given data to this handler's native data type, without
	 * verifying compatibility first.
	 */
	protected D convertDataUnchecked(final DragAndDropData data) {
		return data.getData(getType());
	}

	/**
	 * Converts the given object to this handler's native data type, without
	 * verifying compatibility first.
	 */
	protected D convertObjectUnchecked(final Object object) {
		@SuppressWarnings("unchecked")
		final D dataObject = (D) object;
		return dataObject;
	}

}