Bug 72297 [DnD] ViewerDropAdapter impossible to set DND.FEEDBACK_NONE
It is not possible to disable selection feedback in ViewerDropAdapter. There are setFeedbackEnabled(false) and setScrollExpandEnabled(false) methods to turn off the feedback effects. If those methods are used, selection feedback still provided. It is not possible to turn it off, elements are still selected when drag is over them. Overriding method; private void setFeedback(DropTargetEvent event, int location) { event.feedback = DND.FEEDBACK_NONE; } - does not chenge the feedback either. setFeedbackEnabled() should be extended to disable SELECTION feedback or new method created, setSelectionFeedback().
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/ViewerDropAdapter.java
}
    /**
     * Returns the object currently selected by the viewer.
     *
     * @return the selected object, or <code>null</code> if either no object or 
     *   multiple objects are selected
     */
    protected Object getSelectedObject() {
        ISelection selection = viewer.getSelection();
        if (selection instanceof IStructuredSelection && !selection.isEmpty()) {
            IStructuredSelection structured = (IStructuredSelection) selection;
            return structured.getFirstElement();
        }
        return null;
    }
    /**
     * Returns the viewer to which this drop support has been added.
     */
    protected Viewer getViewer() {
        return viewer;
    }
    /**
     * @deprecated this method should not be used. Exception handling has been 
     * 	removed from DropTargetAdapter methods overridden by this class.
     * Handles any exception that occurs during callback, including 
     * rethrowing behavior.
     * <p>
     * [Issue: Implementation prints stack trace and eats exception to avoid
     *  crashing VA/J.
     *  Consider conditionalizing the implementation to do one thing in VAJ