code: function (control, px) {
          // If a control doesn't have a div at this point, it belongs in the
          // viewport.
          control.outsideViewport = (control.div != null);
          
          // If the map has a displayProjection, and the control doesn't, set 
          // the display projection.
          if (this.displayProjection && !control.displayProjection) {
              control.displayProjection = this.displayProjection;
          }    
          
          control.setMap(this);
          var div = control.draw(px);
          if (div) {
              if(!control.outsideViewport) {
                  div.style.zIndex = this.Z_INDEX_BASE['Control'] +
                                      this.controls.length;
                  this.viewPortDiv.appendChild( div );
              }
          }
          if(control.autoActivate) {
              control.activate();
          }
      }
docs: Method: addControlToMap
  
  Parameters:
  
  control - {<OpenLayers.Control>}
  px - {<OpenLayers.Pixel>}