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
* The viewer to which this drop support has been added.
     */
    private Viewer viewer;
    /**
     * The current operation.
     */
    private int currentOperation = DND.DROP_NONE;
    /**
     * The last valid operation.
     */
    private int lastValidOperation = DND.DROP_NONE;
    /**
     * The data item currently under the mouse.
     */
    private Object currentTarget;
    /**
     * Information about the position of the mouse relative to the
     * target (before, on, or after the target.  Location is one of
     * the <code>LOCATION_* </code> constants defined in this type.
     */
    private int currentLocation;
    /**
     * A flag that allows adapter users to turn the insertion
     * feedback on or off. Default is <code>true</code>.
     */
    private boolean feedbackEnabled = true;
    /**
     * A flag that allows adapter users to turn auto scrolling
     * and expanding on or off. Default is <code>true</code>.
     */