code: function show() {
  
                popupTimeout = null;
  
                // If there is a pending remove transition, we must cancel it, lest the
                // tooltip be mysteriously removed.
                if ( transitionTimeout ) {
                  $timeout.cancel( transitionTimeout );
                  transitionTimeout = null;
                }
  
                // Don't show empty tooltips.
                if ( ! scope.tt_content ) {
                  return angular.noop;
                }
  
                createTooltip();
  
                // Set the initial positioning.
                tooltip.css({ top: 0, left: 0, display: 'block' });
  
                // Now we add it to the DOM because need some info about it. But it's not 
                // visible yet anyway.
                if ( appendToBody ) {
                    $document.find( 'body' ).append( tooltip );
                } else {
                  element.after( tooltip );
                }
  
                positionTooltip();
  
                // And show the tooltip.
                scope.tt_isOpen = true;
                scope.$digest(); // digest required as $apply is not called
  
                // Return positioning function as promise callback for correct
                // positioning after draw.
                return positionTooltip;
              }
docs: Show the tooltip popup element.