curveapplet.java

Beginning Java 2, SDK 1.4 Edition Exercise Code samples for this book

          g2D.draw(tangent);
        }
      }
    }
  }
  
  // Inner class defining a point marker.
  class Marker {
    public Marker(Point2D.Double point, Color color)  {
      center = point;                   // Save point as circle center
      this.color = color;

      // Create circle around control point
      circle = new Ellipse2D.Double(center.x-radius, center.y-radius,
                                    2.0*radius, 2.0*radius); 
    }

      // Draw the marker
      public void draw(Graphics2D g2D) {
        g2D.setColor(color);
        g2D.draw(circle);
      }

     // Get center of marker - the control point position
      Point2D.Double getCenter() {
        return center;
    }

    // Test if a point x,y is inside the marker
    public boolean contains(double x, double y) {
      return circle.contains(x,y); 
    }

    // Sets a new control point location
    public void setLocation(double x, double y) {
      center.x = x;                      // Update control point
      center.y = y;                      // coordinates
      circle.x = x-radius;               // Change circle position
      circle.y = y-radius;               // correspondingly
    }

    Ellipse2D.Double circle;               // Circle around control point
    Point2D.Double center;                 // Circle center - the control point
    Color color;                           // Color of this marker, controls red, curve pts blue
    static final double radius = 3;        // Radius of circle
  }

  class MouseHandler extends MouseInputAdapter {
    // In this method we are defining a new curve point when curveComplete is false
    // or potentially selecting a control or defining point when curveComplete is true.
    public void mousePressed(MouseEvent e) {
      Point p = e.getPoint();
      if(curveComplete) {
        // Check if the cursor is inside any marker
        Marker marker = null;
        // First check the point markers
        for(int i = 0 ; i<pointMarkers.size() ;i++) {
          marker = (Marker)(pointMarkers.elementAt(i));
          if(marker.contains(p.x,p.y)) {
            selected = marker;
            selectedIndex = i;
            return;
          }
        }
        // It was not a point marker so check the control markers
        for(int i = 0 ; i<controlMarkers.length ;i++) {
          if(controlMarkers[i].contains(p.x,p.y)) {
            selected = controlMarkers[i];
            selectedIndex = i;
            return;
          }
        }
      } else {
        // We are adding a new defining point
        pointMarkers.add(new Marker(new Point2D.Double(p.x,p.y), Color.BLUE)); 
        if(pointMarkers.size()>3)
          createCurves();
        pane.repaint();
      }     
    }

    public void mouseReleased(MouseEvent e) {
      selected = null;                             // Deselect any selected marker
    }
    
    // If selected is not null, this method moves the selected marker
    // and modifies the curve segments that are affected.
    public void mouseDragged(MouseEvent e) {
      if(selected != null) {                       // If a marker is selected
        // Set the marker to current cursor position
        selected.setLocation(e.getX(), e.getY());
        if(selected == controlMarkers[selectedIndex]){
          // It must be a control marker so update it in the curve
          if(selectedIndex%2 == 0) { 
            // It is the 1st control point that was changed
            curveSegments[selectedIndex/2].setCurve(curveSegments[selectedIndex/2].getP1(),
                                             selected.getCenter(),
                                             curveSegments[selectedIndex/2].getCtrlP2(),
                                             curveSegments[selectedIndex/2].getP2());
            /* For control points interior to the set of curve segments, we must adjust
               the control marker the other side of curve point. This will be the
               second marker for the preceding curve segment.

               There are two control markers for each point apart from the first and the
               last, so ifselectedIndex than the index for the first and less than the
               index for the last, we have another control marker and curve segment to
               adjust.
            */ 
            if(selectedIndex>0 && selectedIndex<controlMarkers.length-1) {
              Point2D.Double point = (Point2D.Double)(curveSegments[selectedIndex/2-1].getP2());
              double x = point.x + (point.x - selected.getCenter().x);
              double y = point.y + (point.y - selected.getCenter().y);
              controlMarkers[selectedIndex-1].setLocation(x, y);
              curveSegments[selectedIndex/2-1].setCurve(
                                         curveSegments[selectedIndex/2-1].getP1(),
                                             curveSegments[selectedIndex/2-1].getCtrlP1(),
                                             controlMarkers[selectedIndex-1].getCenter(),
                                             curveSegments[selectedIndex/2-1].getP2());
              
            }

          } else {
            // It is the 2nd control point that was changed
            curveSegments[selectedIndex/2].setCurve(curveSegments[selectedIndex/2].getP1(),
                                             curveSegments[selectedIndex/2].getCtrlP1(),
                                             selected.getCenter(),
                                             curveSegments[selectedIndex/2].getP2());
            // For interior control markers we must adjust the next one analogous
            // to the previous case
            if(selectedIndex>0 && selectedIndex<controlMarkers.length-1) {
              Point2D.Double point = (Point2D.Double)(curveSegments[selectedIndex/2+1].getP1());
              double x = point.x + (point.x - selected.getCenter().x);
              double y = point.y + (point.y - selected.getCenter().y);
              controlMarkers[selectedIndex+1].setLocation(x, y);
              curveSegments[selectedIndex/2+1].setCurve(
                                         curveSegments[selectedIndex/2+1].getP1(),
                                         controlMarkers[selectedIndex+1].getCenter(),
                                         curveSegments[selectedIndex/2+1].getCtrlP2(),
                                         curveSegments[selectedIndex/2+1].getP2());
            }
          }
        }  else {
          // It must be a point marker. If the index is other than the first or
          // the last, two curve segments have to be updated
          double xDelta = 0.0;
          double yDelta = 0.0;
          Point2D point = null;
          if(selectedIndex>0){
            // Change the segment where this is the second point
            point = curveSegments[selectedIndex-1].getP2();
            xDelta = selected.getCenter().getX() - point.getX();
            yDelta = selected.getCenter().getY() - point.getY();
            point = curveSegments[selectedIndex-1].getCtrlP2();
            controlMarkers[2*selectedIndex-1].setLocation(point.getX()+xDelta,
                                                         point.getY()+yDelta);
            curveSegments[selectedIndex-1].setCurve(curveSegments[selectedIndex-1].getP1(),
                                             curveSegments[selectedIndex-1].getCtrlP1(),
                                             controlMarkers[2*selectedIndex-1].getCenter(),
                                             selected.getCenter());
          }
          if(selectedIndex<curveSegments.length) {
            // Change the segment where this is the first point
            point = curveSegments[selectedIndex].getP1();
            xDelta = selected.getCenter().getX() - point.getX();
            yDelta = selected.getCenter().getY() - point.getY();
            point = curveSegments[selectedIndex].getCtrlP1();
            controlMarkers[2*selectedIndex].setLocation(point.getX()+xDelta, point.getY()+yDelta);
            curveSegments[selectedIndex].setCurve(selected.getCenter(),
                                             controlMarkers[2*selectedIndex].getCenter(),
                                             curveSegments[selectedIndex].getCtrlP2(),
                                             curveSegments[selectedIndex].getP2());
          }
        }
        pane.repaint();                             // Redraw pane contents
      }
    }

    Marker selected = null;                 // Stores reference to selected marker
    int selectedIndex = 0;                  // Index position of selected Marker
  }

  Vector pointMarkers = new Vector();           // Vector of Marker objects
  CubicCurve2D.Double[] curveSegments = null;   // Array of cubic curve segments
  Point2D.Double[] controlVec = null;           // Tngent vectors for control points  
  Marker[] controlMarkers = null;               // Array of control point markers
  CurvePane pane = new CurvePane();             // Pane to contain curves
  boolean curveComplete = false;                // Indicator for complete curve
}