public void onDragStart(DragStartEvent event) {
startScrollLeft = getScrollLeft();
startScrollTop = getScrollTop();
}
});
addDragMoveHandler(new DragMoveHandler() {
public void onDragMove(DragMoveEvent event) {
int left = startScrollLeft - EventHandler.getX() + EventHandler.getMouseDownX();
int top = startScrollTop - EventHandler.getY() + EventHandler.getMouseDownY();
scrollTo(left,top);
}