code: public void activateSnapping(List<SnappingRuleInfo> rules, SnapMode mode) {
  		if (rules != null) {
  			snapper = new Snapper(mapWidget.getMapModel(), rules, mode);
  			snappingActive = true;
  		}
  	}
docs: Activate snapping on this controller. When snapping is activated, the methods "getScreenPosition" and
  "getWorldPosition" (to ask the position of an event), will return snapped positions.
  
  @param rules
  A list of <code>SnappingRuleInfo</code>s. These determine to what layers to snap, using what distances
  and what algorithms.
  @param mode
  The snapper mode. Either the snapper considers all geometries equal, or it tries to snap to
  intersecting geometries before snapping to other geometries. Basically:
  <ul>
  <li>SnapMode.MODE_ALL_GEOMTRIES_EQUAL</li>
  <li>SnapMode.MODE_PRIORITY_TO_INTERSECTING_GEOMETRIES</li>
  </ul>