/**
* Draw the decoration. If the curve is null when this is called, then curve will be set to the
* exhibit displayed in the View, which should be of type PlaneCurveParameteric, if this
* decoration is being used correctly.
*/
public void doDraw(Graphics2D g, View view, Transform limits) {
if (curve == null && view != null) {
Exhibit c = view.getExhibit();
if (c instanceof PlaneCurveParametric) // It better be!
curve = (PlaneCurveParametric) c;
else return;
}
if (Double.isNaN(t)) return;
double x = curve.xValue(t);
if (Double.isNaN(x) || Double.isInfinite(x)) return;
double y = curve.yValue(t);
if (Double.isNaN(y) || Double.isInfinite(y)) return;
double dx = curve.xDerivativeValue(t);
if (Double.isNaN(dx) || Double.isInfinite(dx)) return;
double dy = curve.yDerivativeValue(t);
if (Double.isNaN(dy) || Double.isInfinite(dy)) return;
double length = Math.sqrt(dx * dx + dy * dy);
if (length == 0) return;
dx = dx / length * 40 * limits.getPixelWidth();
dy = dy / length * 40 * limits.getPixelHeight();
Color saveColor = g.getColor();
Stroke saveStroke = g.getStroke();
g.setStroke(new BasicStroke(2 * limits.getDefaultStrokeSize()));
g.setColor(Color.red);
g.draw(new Line2D.Double(x, y, x + dx, y + dy));
g.setColor(Color.blue);
g.draw(new Line2D.Double(x, y, x - dy, y + dx));
g.setColor(saveColor);
g.setStroke(saveStroke);
}
/**
* Set the t-value to be at one of the points that are used for drawing the curve. If the curve is
* null when this is called, it has no effect.
*
* @param tIndex An index into the array of t-values that the curve uses to generate the curve.
* The index should be in the legal range; if not, nothing is drawn. The range is from 0 to
* getCurve().getPointCount().
*/
public void setIndex(int tIndex) {
if (curve != null) setT(curve.getT(tIndex));
}