import java.awt.*;

/**
 * A class which shows a piece of a real line for the graphical display
 * and entry of axis distances.
 *
 * @author Jonathan A. Poritz
 * @version 1.7, 10 Sep 1998
 */

public class DistLinePanel extends Plane {

  /**
   * A reference to the containing <b>inputpanel</b>.
   *
   * @see FDBApplet#inputpanel
   */
  public InputPanel inputpanel;

  /**
   * The location of a mousedown in this plane, to compute the extent of
   * a drag that may occur; in pixel coordinates.
   */
  protected int[] previ = new int[2];

  /**
   * The abstract x-coordinate of the left side of the axis distance display.
   */
  public static final double CX = -1D;
  /**
   * The abstract y-coordinate of the upper edge of the axis distance display.
   */
  public static final double CY = 5D;
  /**
   * The width, in abstract units, of the axis distance display.
   */
  public static final double SX = 2D;
  /**
   * The height, in abstract units, of the axis distance display.
   */
  public static final double SY = 5D;
  /**
   * The width, in pixels, of the axis distance display.  Good defaults are:
   * <ul><dl><dt><b>25</b>
   * <dd>for small screens, and 
   * <dt><b>50</b>
   * <dd>for large screens</dl></ul>
   */
  public static final int X = 50;
  /**
   * The height, in pixels, of the axis distance display.  Good defaults are:
   * <ul><dl><dt><b>200</b>
   * <dd>for small screens, and 
   * <dt><b>300</b>
   * <dd>for large screens</dl></ul>
   */
  public static final int Y = 300;

  /**
   * Constructor for DistLinePanels.
   *
   * @param nptpnl the ambient <b>inputpanel</b>
   */
  public DistLinePanel(InputPanel nptpnl) {
    // make the basic plane with axes but no xticks
    super(CX, CY, SX, SY, X, Y);
    draw_axes = true;
    show_xticks = false;

    // save a reference to the inputpanel
    inputpanel = nptpnl;
  }

  /**
   * <b>Java 1.0</b> handling of mouseDown events.
   *
   * @param e the event to be handled
   * @param x the x-coordinate (in pixels) of the mouseDown
   * @param y the y-coordinate (in pixels) of the mouseDown
   */
  public boolean mouseDown(Event e, int x, int y) {
    // convert to abstract coordinates
    double xx = (pixelsToAbstract(x, y))[0];
    double yy = (pixelsToAbstract(x, y))[1];

    // axis distances are non-negative, so
    if (yy < 0D)
      yy = 0D;

    if ((e.modifiers & e.META_MASK) != 0) {
      // right button: zoom, so save mouse down location
      previ[0] = x;
      previ[1] = y;
    }
    else if ((yy != 0D) || (inputpanel.trace.y != 0D) || (Math.abs(inputpanel.trace.x) >= 2D)) {
      // left or middle button AD selection: only make the change if allowed,
      // i.e., no change of AD if the trace is elliptic or parabolic and the
      // new selected AD is 0
      inputpanel.traceplanepanel.decomposed = false;
      inputpanel.traceplanepanel.draw_axes= true;
      inputpanel.traceplanepanel.repaint();
      inputpanel.dist = yy;
      inputpanel.update();
      repaint();
    }

    return true;
  }

  /**
   * <b>Java 1.0</b> handling of mouseDrag events.
   *
   * @param e the event to be handled
   * @param x the x-coordinate (in pixels) of the mouseDrag
   * @param y the y-coordinate (in pixels) of the mouseDrag
   */
  public boolean mouseDrag(Event e, int x, int y) {
     // convert to abstract coordinates
    double xx = (pixelsToAbstract(x, y))[0];
    double yy = (pixelsToAbstract(x, y))[1];

    // never go negative
    if (yy < 0D) yy = 0D;

    if ((e.modifiers & e.META_MASK) != 0) {
      // right button zoom by amount proportional to the distance from
      // previous location
      zoom(1D - ((double)(previ[1] - y)) / 50D);
    }
    else if ((yy != 0D) || (inputpanel.trace.y != 0D) || (Math.abs(inputpanel.trace.x) >= 2D)) {
      // left or middle button AD selection: only make the change if allowed,
      // i.e., no change of AD if the trace is elliptic or parabolic and the
      // new selected AD is 0
      inputpanel.traceplanepanel.decomposed = false;
      inputpanel.traceplanepanel.draw_axes = true;
      inputpanel.traceplanepanel.repaint();
      inputpanel.dist = yy;
      inputpanel.update();
      repaint();
    }

    previ[0] = x;
    previ[1] = y;

    return true;
  }

  /**
   * Paint the DistLinePanel, by painting the parent Plane, putting a mark
   * at the currently selected axis distance and making tickmarks.
   *
   * @param g the Graphics object upon which to paint the DistLinePanel
   */
  public void paint(Graphics g) {
    // paint the parent Plane
    super.paint(g);

    // draw a small disk on the site of the axis distance
    g.setColor(Color.black);
    int[] tp = abstractToPixels(0, inputpanel.dist);
    g.fillOval(tp[0] - 2, tp[1] - 2, 4, 4);

    // draw the tickmarks on the y-axis
    drawTickmarks(g);
  }

  /**
   * Scales the size of the visible window onto the line of axis distances
   *
   * @param factor the scaling factor, can be any positive number
   */
  public void zoom(double factor) {
    corner[0] = corner[0] + .5D * size[0] - .5D * size[0] * factor;
    size[0] *= factor;
    corner[1] = corner[1] - size[1] + size[1] * factor;
    size[1] *= factor;

    repaint();
  }

}