src/captors/sigma.captors.mouse.js
function _wheelHandler(e) {
      var pos,
          ratio,
          animation,
          wheelDelta = sigma.utils.getDelta(e);

      if (_settings('mouseEnabled') && _settings('mouseWheelEnabled') && wheelDelta !== 0) {
        ratio = wheelDelta > 0 ?
          1 / _settings('zoomingRatio') :
          _settings('zoomingRatio');

        pos = _camera.cameraPosition(
          sigma.utils.getX(e) - sigma.utils.getCenter(e).x,
          sigma.utils.getY(e) - sigma.utils.getCenter(e).y,
          true
        );

        animation = {
          duration: _settings('mouseZoomDuration')
        };

        sigma.utils.zoomTo(_camera, pos.x, pos.y, ratio, animation);

        if (e.preventDefault)
          e.preventDefault();
        else
          e.returnValue = false;

        e.stopPropagation();
        return false;
      }
    }
function _wheelHandler(e) {
      var pos,
          ratio,
          animation,
          wheelDelta = sigma.utils.getDelta(e);

      if (_settings('mouseEnabled') && _settings('mouseWheelEnabled') && wheelDelta !== 0) {
        ratio = wheelDelta > 0 ?
          1 / _settings('zoomingRatio') :
          _settings('zoomingRatio');

        pos = _camera.cameraPosition(
          sigma.utils.getX(e) - sigma.utils.getCenter(e).x,
          sigma.utils.getY(e) - sigma.utils.getCenter(e).y,
          true
        );

        animation = {
          duration: _settings('mouseZoomDuration')
        };

        sigma.utils.zoomTo(_camera, pos.x, pos.y, ratio, animation);

        if (e.preventDefault)
          e.preventDefault();
        else
          e.returnValue = false;

        e.stopPropagation();
        return false;
      }
    }
function _wheelHandler ( e ) { var pos , ratio , animation , wheelDelta = sigma . utils . getDelta ( e ) ; if ( _settings ( 'mouseEnabled' ) && _settings ( 'mouseWheelEnabled' ) && wheelDelta !== 0 ) { ratio = wheelDelta > 0 ? 1 / _settings ( 'zoomingRatio' ) : _settings ( 'zoomingRatio' ) ; pos = _camera . cameraPosition ( sigma . utils . getX ( e ) - sigma . utils . getCenter ( e ) . x , sigma . utils . getY ( e ) - sigma . utils . getCenter ( e ) . y , true ) ; animation = { duration : _settings ( 'mouseZoomDuration' ) } ; sigma . utils . zoomTo ( _camera , pos . x , pos . y , ratio , animation ) ; if ( e . preventDefault ) e . preventDefault ( ) ; else e . returnValue = false ; e . stopPropagation ( ) ; return false ; } }
The handler listening to the 'wheel' mouse event. It will basically zoom
in or not into the graph.

@param {event} e A mouse event.
The handler listening to the wheel mouse event . It will basically zoom in or not into the graph .