~~~~~~~~~~~~~~~~~~~
~~ Clipboard.java
~~~~~~~~~~~~~~~~~~~
~~ Shows only the modifications.
~~ Unchanged code segments are indicated by "..."

package org.eclipse.swt.dnd;

...

public class Clipboard
{
	private int preferredDropEffect = COM.DROPEFFECT_COPY;

	...

	private int GetData(int pFormatetc, int pmedium)
	{
		...
		if (transferData.type == CFSTR_PREFERREDDROPEFFECT) {
			...
			OS.MoveMemory(stgmedium.unionField,
				new int[]{ preferredDropEffect }, 4);
			...
		}
	}

	public void setContents(Object[] data, Transfer[] dataTypes)
	{
		setContents(DND.DROP_COPY, data, dataTypes, DND.CLIPBOARD);
	}

	public void setContents(int preferredDropEffect, Object[] data,
		Transfer[] dataTypes)
	{
		setContents(preferredDropEffect, data, dataTypes, DND.CLIPBOARD);
	}

	public void setContents(Object[] data, Transfer[] dataTypes,
		int clipboards)
	{
		setContents(DND.DROP_COPY, data, dataTypes, clipboards);
	}

	public void setContents(int preferredDropEffect, Object[] data,
		Transfer[] dataTypes, int clipboards)
	{
		if ((preferredDropEffect & DND.DROP_MOVE) != 0)
			preferredDropEffect = COM.DROPEFFECT_MOVE;
		else
			preferredDropEffect = COM.DROPEFFECT_COPY;
		this.preferredDropEffect = preferredDropEffect;

		... the contents of the original method setContents(Object[], Transfer, int)
	}

	/**
	 * Returns the preferred drop effect. If none is available DND.DROP_COPY
	 * is returned.
	 *
	 * @return the preferred drop effect
	 */
	public int getPreferredDropEffect()
	{
		PreferredDropEffectTransfer pdet = PreferredDropEffectTransfer
			.getInstance();
		Integer effect = (Integer) getContents(pdet);
		if (effect == null)
			return DND.DROP_COPY;
		else
			return effect.intValue();
	}
}

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
~~ PreferredDropEffectTransfer.java
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
package org.eclipse.swt.dnd;


import org.eclipse.swt.internal.ole.win32.COM;
import org.eclipse.swt.internal.ole.win32.FORMATETC;
import org.eclipse.swt.internal.ole.win32.IDataObject;
import org.eclipse.swt.internal.ole.win32.STGMEDIUM;
import org.eclipse.swt.internal.win32.OS;


/**
 * Used to read the preferred drop effect from the clipboard.
 *
 * @author Thomas Braun
 */
class PreferredDropEffectTransfer extends ByteArrayTransfer
{
	private static PreferredDropEffectTransfer _instance =
		new PreferredDropEffectTransfer();
	private static final String CFSTR_PREFERREDDROPEFFECT =
		"Preferred DropEffect"; //$NON-NLS-1$
	private static final int CF_ID =
		registerType(CFSTR_PREFERREDDROPEFFECT);

	private PreferredDropEffectTransfer()
	{}

	/**
	 * Returns the singleton instance of the class.
	 *
	 * @return the singleton instance of the class
	 */
	public static PreferredDropEffectTransfer getInstance()
	{
		return _instance;
	}

	/**
	 * Not needed.
	 */
	@Override
	public void javaToNative(Object object, TransferData transferData)
	{
	}

	/**
	 * The method returns the preferred drop operation as integer object.
	 * The default result is DND.DROP_COPY.
	 *
	 * @see DND#DROP_COPY
	 * @see DND#DROP_LINK
	 * @see DND#DROP_MOVE
	 * @return an <code>Integer</code> containing the preferred drop operation
	 */
	@Override
	public Object nativeToJava(TransferData transferData)
	{
		if (!isSupportedType(transferData) || transferData.pIDataObject == 0)
			return DND.DROP_COPY;

		IDataObject dataObject = new IDataObject(transferData.pIDataObject);
		dataObject.AddRef();
		FORMATETC formatetc = new FORMATETC();
		formatetc.cfFormat = CF_ID;
		formatetc.ptd = 0;
		formatetc.dwAspect = COM.DVASPECT_CONTENT;
		formatetc.lindex = -1;
		formatetc.tymed = COM.TYMED_HGLOBAL;
		STGMEDIUM stgmedium = new STGMEDIUM();
		stgmedium.tymed = COM.TYMED_HGLOBAL;
		transferData.result = dataObject.GetData(formatetc, stgmedium);
		int[] i1 = new int[1];
		OS.MoveMemory(i1, stgmedium.unionField, 4);
		int res = 0;
		if (i1[0] < 100) {	// i1 contains the preferred drop effect value
			res = i1[0];
		}
		else {				// i1 contains the address of the preferred drop
							// effect value
			int[] i2 = new int[1];
			OS.MoveMemory(i2, i1[0], 4);
			res = i2[0];
		}
		dataObject.Release();

		if (transferData.result != COM.S_OK)
			return DND.DROP_COPY;
		else
			return osToOp(res);
	}

	@Override
	protected int[] getTypeIds()
	{
		return new int[]{
			CF_ID
		};
	}

	private int osToOp(int osOperation)
	{
		int operation = 0;
		if ((osOperation & COM.DROPEFFECT_COPY) != 0) {
			operation |= DND.DROP_COPY;
		}
		if ((osOperation & COM.DROPEFFECT_LINK) != 0) {
			operation |= DND.DROP_LINK;
		}
		if ((osOperation & COM.DROPEFFECT_MOVE) != 0) {
			operation |= DND.DROP_MOVE;
		}
		return operation;
	}

	@Override
	protected String[] getTypeNames()
	{
		return new String[]{
			CFSTR_PREFERREDDROPEFFECT
		};
	}

	@Override
	protected boolean validate(Object object)
	{
		return object instanceof Integer;
	}
}