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[news.eclipse.platform.swt] Cannot drag from a TreeViewer that manage item edition. 
Hello,

I am trying to have a common navigator that manages item edition and drag and drop. So I set a ICellModifier. The drag and drop does not work. It seems that my ICellModifier is called before the drag interaction is activated.

I managed to reproduce the problem in the following code snippet. When I press the left mouse button the edition is not activated but as soon as I move the mouse (without releasing the button) the edition is activated making it impossible to drag the item. Am I doing something wrong ?

Here is the code snippet:

import java.util.ArrayList;

import org.eclipse.jface.viewers.CellEditor;
import org.eclipse.jface.viewers.ICellModifier;
import org.eclipse.jface.viewers.IStructuredSelection;
import org.eclipse.jface.viewers.ITreeContentProvider;
import org.eclipse.jface.viewers.TextCellEditor;
import org.eclipse.jface.viewers.TreeViewer;
import org.eclipse.jface.viewers.Viewer;
import org.eclipse.swt.SWT;
import org.eclipse.swt.dnd.DND;
import org.eclipse.swt.dnd.DragSource;
import org.eclipse.swt.dnd.DragSourceAdapter;
import org.eclipse.swt.dnd.DragSourceEvent;
import org.eclipse.swt.dnd.DropTarget;
import org.eclipse.swt.dnd.DropTargetEvent;
import org.eclipse.swt.dnd.DropTargetListener;
import org.eclipse.swt.dnd.TextTransfer;
import org.eclipse.swt.dnd.Transfer;
import org.eclipse.swt.events.SelectionEvent;
import org.eclipse.swt.events.SelectionListener;
import org.eclipse.swt.layout.FillLayout;
import org.eclipse.swt.widgets.Display;
import org.eclipse.swt.widgets.Menu;
import org.eclipse.swt.widgets.MenuItem;
import org.eclipse.swt.widgets.Shell;
import org.eclipse.swt.widgets.TreeItem;

public class TreeViewerSnippet implements SelectionListener {

	private TreeViewer viewer;

	private class MyContentProvider implements ITreeContentProvider {

		public Object[] getElements(Object inputElement) {
			return ((MyModel) inputElement).child.toArray();
		}

		public void dispose() {

		}

public void inputChanged(Viewer viewer, Object oldInput, Object newInput) {

		}

		public Object[] getChildren(Object parentElement) {
			return getElements(parentElement);
		}

		public Object getParent(Object element) {
			if (element == null) {
				return null;
			}

			return ((MyModel) element).parent;
		}

		public boolean hasChildren(Object element) {
			return ((MyModel) element).child.size() > 0;
		}

	}

	public class MyModel {
		public MyModel parent;
		public ArrayList child = new ArrayList();
		public int counter;

		public MyModel(int counter, MyModel parent) {
			this.parent = parent;
			this.counter = counter;
		}

		public String toString() {
			String rv = "Item ";
			if (parent != null) {
				rv = parent.toString() + ".";
			}

			rv += counter;

			return rv;
		}
	}

	public TreeViewerSnippet(Shell shell) {
		viewer = new TreeViewer(shell, SWT.BORDER);
		viewer.setContentProvider(new MyContentProvider());
		viewer.setCellEditors(new CellEditor[] { new TextCellEditor(viewer
				.getTree()) });
		viewer.setColumnProperties(new String[] { "name" });
		viewer.setCellModifier(new ICellModifier() {

			public boolean canModify(Object element, String property) {
				return true;
			}

			public Object getValue(Object element, String property) {
				return ((MyModel) element).counter + "";
			}

			public void modify(Object element, String property, Object value) {
				TreeItem item = (TreeItem) element;
				((MyModel) item.getData()).counter = Integer.parseInt(value
						.toString());
				viewer.update(item.getData(), null);
			}

		});

DragSource source = new DragSource(viewer.getTree(), DND.DROP_COPY);
source.setTransfer(new Transfer[] {TextTransfer.getInstance()});
source.addDragListener(new DragSourceAdapter() {
public void dragSetData(DragSourceEvent event) {
event.data = "Hello World";
}
});
DropTarget target = new DropTarget(viewer.getTree(), DND.DROP_COPY | DND.DROP_DEFAULT);
target.setTransfer(new Transfer[] {TextTransfer.getInstance()});
target.addDropListener(new DropTargetListener() {
public void dragEnter(DropTargetEvent event) {
}
public void dragOperationChanged(DropTargetEvent event) {
}
public void dragOver(DropTargetEvent event) {
}
public void dragLeave(org.eclipse.swt.dnd.DropTargetEvent event) {
}
public void drop(DropTargetEvent event) {

}
public void dropAccept(DropTargetEvent event) {

}
});

		Menu menu = new Menu(viewer.getControl());
		MenuItem renameItem = new MenuItem(menu, SWT.PUSH);
		renameItem.addSelectionListener(this);
		renameItem.setText("Rename");
		viewer.getTree().setMenu(menu);

		viewer.setInput(createModel());
	}

	public void widgetDefaultSelected(SelectionEvent e) {
	}

	public void widgetSelected(SelectionEvent e) {
		IStructuredSelection selection = (IStructuredSelection) viewer
				.getSelection();
		if (selection != null) {
			viewer.editElement(selection.getFirstElement(), 0);
		}
	}

	private MyModel createModel() {

		MyModel root = new MyModel(0, null);
		root.counter = 0;

		MyModel tmp;
		for (int i = 1; i < 10; i++) {
			tmp = new MyModel(i, root);
			root.child.add(tmp);
			for (int j = 1; j < i; j++) {
				tmp.child.add(new MyModel(j, tmp));
			}
		}

		return root;
	}

	public static void main(String[] args) {
		Display display = new Display();
		Shell shell = new Shell(display);
		shell.setLayout(new FillLayout());
		new TreeViewerSnippet(shell);
		shell.open();

		while (!shell.isDisposed()) {
			if (!display.readAndDispatch())
				display.sleep();
		}

		display.dispose();
	}
}