public void checkDirect() throws VisADException, RemoteException {
    // realCheckDirect();
    //
    // must customize
    setIsDirectManipulation(false);

    DisplayImpl display = getDisplay();
    link = getLinks()[0];
    ref = link.getDataReference();
    type = link.getType();
    if (!(type instanceof TupleType) || !((TupleType) type).getFlat()) {
      whyNotDirect = notFlatTupleType;
      return;
    }
    flowToComponent = new int[] {-1, -1, -1};
    directMap = new ScalarMap[] {null, null, null};
    shadow = (ShadowTupleType) link.getShadow().getAdaptedShadowType();
    DisplayTupleType[] tuples = {null};
    whyNotDirect = findFlow(shadow, display, tuples, flowToComponent);
    if (whyNotDirect != null) return;
    if (coord == null) {
      if (tuples[0] == null || flowToComponent[0] < 0 || flowToComponent[1] < 0) {
        whyNotDirect = noFlow;
        return;
      }
    } else {
      if (tuples[0] == null || flowToComponent[1] < 0 || flowToComponent[2] < 0) {
        whyNotDirect = noFlow;
        return;
      }
    }

    ShadowRealType[] components = shadow.getRealComponents();
    for (int i = 0; i < components.length; i++) {
      DisplayTupleType spatial_tuple = components[i].getDisplaySpatialTuple();
      if (spatial_tuple != null && !Display.DisplaySpatialCartesianTuple.equals(spatial_tuple)) {
        whyNotDirect = nonCartesian;
        return;
      }
    }

    // needs more, will find out when we write drag_direct
    setIsDirectManipulation(true);
  }
  public synchronized void drag_direct(VisADRay ray, boolean first, int mouseModifiers) {
    if (barbValues == null || ref == null || shadow == null) return;

    if (first) {
      stop = false;
    } else {
      if (stop) return;
    }

    // modify direction if mshift != 0
    // modify speed if mctrl != 0
    // modify speed and direction if neither
    int mshift = mouseModifiers & InputEvent.SHIFT_MASK;
    int mctrl = mouseModifiers & InputEvent.CTRL_MASK;

    float o_x = (float) ray.position[0];
    float o_y = (float) ray.position[1];
    float o_z = (float) ray.position[2];
    float d_x = (float) ray.vector[0];
    float d_y = (float) ray.vector[1];
    float d_z = (float) ray.vector[2];

    if (pickCrawlToCursor) {
      if (first) {
        offset_count = OFFSET_COUNT_INIT;
      } else {
        if (offset_count > 0) offset_count--;
      }
      if (offset_count > 0) {
        float mult = ((float) offset_count) / ((float) OFFSET_COUNT_INIT);
        o_x += mult * offsetx;
        o_y += mult * offsety;
        o_z += mult * offsetz;
      }
    }

    if (first || refirst) {
      point_x = barbValues[2];
      point_y = barbValues[3];
      point_z = 0.0f;
      line_x = 0.0f;
      line_y = 0.0f;
      line_z = 1.0f; // lineAxis == 2 in DataRenderer.drag_direct
    } // end if (first || refirst)

    float[] x = new float[3]; // x marks the spot
    // DirectManifoldDimension = 2
    // intersect ray with plane
    float dot = (point_x - o_x) * line_x + (point_y - o_y) * line_y + (point_z - o_z) * line_z;
    float dot2 = d_x * line_x + d_y * line_y + d_z * line_z;
    if (dot2 == 0.0) return;
    dot = dot / dot2;
    // x is intersection
    x[0] = o_x + dot * d_x;
    x[1] = o_y + dot * d_y;
    x[2] = o_z + dot * d_z;
    /*
    System.out.println("x = " + x[0] + " " + x[1] + " " + x[2]);
    */
    try {

      Tuple data = (Tuple) link.getData();
      int n = ((TupleType) data.getType()).getNumberOfRealComponents();
      Real[] reals = new Real[n];

      int k = 0;
      int m = data.getDimension();
      for (int i = 0; i < m; i++) {
        Data component = data.getComponent(i);
        if (component instanceof Real) {
          reals[k++] = (Real) component;
        } else if (component instanceof RealTuple) {
          for (int j = 0; j < ((RealTuple) component).getDimension(); j++) {
            reals[k++] = (Real) ((RealTuple) component).getComponent(j);
          }
        }
      }

      if (first || refirst) {
        // get first Data flow vector
        for (int i = 0; i < 3; i++) {
          int j = flowToComponent[i];
          data_flow[i] = (j >= 0) ? (float) reals[j].getValue() : 0.0f;
        }

        if (coord != null) {
          float[][] ds = {{data_flow[0]}, {data_flow[1]}, {data_flow[2]}};
          ds = coord.toReference(ds);
          data_flow[0] = ds[0][0];
          data_flow[1] = ds[1][0];
          data_flow[2] = ds[2][0];
        }

        data_speed =
            (float)
                Math.sqrt(
                    data_flow[0] * data_flow[0]
                        + data_flow[1] * data_flow[1]
                        + data_flow[2] * data_flow[2]);
        float barb0 = barbValues[2] - barbValues[0];
        float barb1 = barbValues[3] - barbValues[1];
        /*
        System.out.println("data_flow = " + data_flow[0] + " " + data_flow[1] +
                           " " + data_flow[2]);
        System.out.println("barbValues = " + barbValues[0] + " " + barbValues[1] +
                           "   " + barbValues[2] + " " + barbValues[3]);
        System.out.println("data_speed = " + data_speed);
        */
      } // end if (first || refirst)

      // convert x to a flow vector, and from spatial to earth
      if (getRealVectorTypes(which_barb) instanceof EarthVectorType) {
        // don't worry about vector magnitude -
        // data_speed & display_speed take care of that
        float eps = 0.0001f; // estimate derivative with a little vector
        float[][] spatial_locs = {
          {barbValues[0], barbValues[0] + eps * (x[0] - barbValues[0])},
          {barbValues[1], barbValues[1] + eps * (x[1] - barbValues[1])},
          {0.0f, 0.0f}
        };
        /*
        System.out.println("spatial_locs = " + spatial_locs[0][0] + " " +
                           spatial_locs[0][1] + " " + spatial_locs[1][0] + " " +
                           spatial_locs[1][1]);
        */
        float[][] earth_locs = spatialToEarth(spatial_locs);
        // WLH - 18 Aug 99
        if (earth_locs == null) return;
        /*
        System.out.println("earth_locs = " + earth_locs[0][0] + " " +
                           earth_locs[0][1] + " " + earth_locs[1][0] + " " +
                           earth_locs[1][1]);
        */
        x[2] = 0.0f;
        x[0] =
            (earth_locs[1][1] - earth_locs[1][0])
                * ((float) Math.cos(Data.DEGREES_TO_RADIANS * earth_locs[0][0]));
        x[1] = earth_locs[0][1] - earth_locs[0][0];
        /*
        System.out.println("x = " + x[0] + " " + x[1] + " " + x[2]);
        */
      } else { // if (!(getRealVectorTypes(which_barb) instanceof EarthVectorType))
        // convert x to vector
        x[0] -= barbValues[0];
        x[1] -= barbValues[1];

        // adjust for spatial map scalings but don't worry about vector
        // magnitude - data_speed & display_speed take care of that
        // also, spatial is Cartesian
        double[] ranges = getRanges();
        for (int i = 0; i < 3; i++) {
          x[i] /= ranges[i];
        }
        /*
        System.out.println("ranges = " + ranges[0] + " " + ranges[1] +
                           " " + ranges[2]);
        System.out.println("x = " + x[0] + " " + x[1] + " " + x[2]);
        */
      }

      // WLH 6 August 99
      x[0] = -x[0];
      x[1] = -x[1];
      x[2] = -x[2];

      /* may need to do this for performance
            float[] xx = {x[0], x[1], x[2]};
            addPoint(xx);
      */

      float x_speed = (float) Math.sqrt(x[0] * x[0] + x[1] * x[1] + x[2] * x[2]);
      /* WLH 16 April 2002 - from Ken
            if (x_speed < 0.000001f) x_speed = 0.000001f;
      */
      if (x_speed < 0.01f) x_speed = 0.01f;
      if (first || refirst) {
        display_speed = x_speed;
      }
      refirst = false;

      if (mshift != 0) {
        // only modify data_flow direction
        float ratio = data_speed / x_speed;
        x[0] *= ratio;
        x[1] *= ratio;
        x[2] *= ratio;
        /*
        System.out.println("direction, ratio = " + ratio + " " +
                           data_speed + " " + x_speed);
        System.out.println("x = " + x[0] + " " + x[1] + " " + x[2]);
        */
      } else if (mctrl != 0) {
        // only modify data_flow speed
        float ratio = x_speed / display_speed;
        if (data_speed < EPS) {
          data_flow[0] = 2.0f * EPS;
          refirst = true;
        }
        x[0] = ratio * data_flow[0];
        x[1] = ratio * data_flow[1];
        x[2] = ratio * data_flow[2];
        /*
        System.out.println("speed, ratio = " + ratio + " " +
                           x_speed + " " + display_speed);
        System.out.println("x = " + x[0] + " " + x[1] + " " + x[2]);
        */
      } else {
        // modify data_flow speed and direction
        float ratio = data_speed / display_speed;
        /*
        System.out.println("data_speed = " + data_speed +
                           " display_speed = " + display_speed +
                           " ratio = " + ratio + " EPS = " + EPS);
        System.out.println("x = " + x[0] + " " + x[1] +" " + x[2] +
                           " x_speed = " + x_speed);
          data_speed = 21.213203 display_speed = 0.01 ratio = 2121.3203 EPS = 0.2
          x = 1.6170928E-4 1.6021729E-4 -0.0 x_speed = 0.01
          wind = (0.3430372, 0.33987218) at (-35.0, 5.0)
        */
        if (data_speed < EPS) {
          data_flow[0] = 2.0f * EPS;
          x[0] = data_flow[0];
          x[1] = data_flow[1];
          x[2] = data_flow[2];
          refirst = true;
        } else {
          x[0] *= ratio;
          x[1] *= ratio;
          x[2] *= ratio;
        }
      }

      if (coord != null) {
        float[][] xs = {{x[0]}, {x[1]}, {x[2]}};
        xs = coord.fromReference(xs);
        x[0] = xs[0][0];
        x[1] = xs[1][0];
        x[2] = xs[2][0];
      }

      // now replace flow values
      Vector vect = new Vector();
      for (int i = 0; i < 3; i++) {
        int j = flowToComponent[i];
        if (j >= 0) {
          RealType rtype = (RealType) reals[j].getType();
          reals[j] = new Real(rtype, (double) x[i], rtype.getDefaultUnit(), null);

          // WLH 31 Aug 2000
          Real r = reals[j];
          Unit overrideUnit = null;
          if (directMap[i] != null) {
            overrideUnit = directMap[i].getOverrideUnit();
          }
          Unit rtunit = rtype.getDefaultUnit();
          // units not part of Time string
          if (overrideUnit != null
              && !overrideUnit.equals(rtunit)
              && !RealType.Time.equals(rtype)) {
            double d = (float) overrideUnit.toThis((double) x[0], rtunit);
            r = new Real(rtype, d, overrideUnit);
            String valueString = r.toValueString();
            vect.addElement(rtype.getName() + " = " + valueString);
          } else {
            // create location string
            vect.addElement(rtype.getName() + " = " + x[i]);
          }
        }
      }
      getDisplayRenderer().setCursorStringVector(vect);

      Data newData = null;
      // now build new RealTuple or Flat Tuple
      if (data instanceof RealTuple) {
        newData =
            new RealTuple(
                ((RealTupleType) data.getType()), reals, ((RealTuple) data).getCoordinateSystem());
      } else {
        Data[] new_components = new Data[m];
        k = 0;
        for (int i = 0; i < m; i++) {
          Data component = data.getComponent(i);
          if (component instanceof Real) {
            new_components[i] = reals[k++];
          } else if (component instanceof RealTuple) {
            Real[] sub_reals = new Real[((RealTuple) component).getDimension()];
            for (int j = 0; j < ((RealTuple) component).getDimension(); j++) {
              sub_reals[j] = reals[k++];
            }
            new_components[i] =
                new RealTuple(
                    ((RealTupleType) component.getType()),
                    sub_reals,
                    ((RealTuple) component).getCoordinateSystem());
          }
        }
        newData = new Tuple(new_components, false);
      }
      ref.setData(newData);
    } catch (VisADException e) {
      // do nothing
      System.out.println("drag_direct " + e);
      e.printStackTrace();
    } catch (RemoteException e) {
      // do nothing
      System.out.println("drag_direct " + e);
      e.printStackTrace();
    }
  }