gann-cdf / graphics

import org.gannacademy.cdf.graphics.Text;

import org.gannacademy.cdf.graphics.geom.Path;

import org.gannacademy.cdf.graphics.ui.AppWindow;

import java.awt.event.MouseEvent;

import java.awt.event.MouseListener;

import java.awt.geom.AffineTransform;

import java.awt.geom.PathIterator;

import java.awt.geom.Point2D;

public class RotationExample extends AppWindow implements MouseListener {

    private static final double

            BASE = 50,

            HEIGHT = 100,

            THETA = Math.PI / 180.0;

    private Path path;

    private double x, y;

    private boolean mouseDown;

    private int button;

    @Override

    protected void setup() {

        // show instructions to user

        new Text("Left, middle, or right-click to rotate the triangle", 10, 40, getDrawingPanel());

        x = getDrawingPanel().getWidth() / 2.0;

        // calculate top point of triangle

        y = (getDrawingPanel().getHeight() - HEIGHT) / 2.0;

        // define the triangle path

        path = new Path(getDrawingPanel());

        path.moveTo(x, y); // move to top point

        path.lineTo(x + BASE / 2.0, y + HEIGHT); // line to bottom-right point

        path.lineTo(x - BASE / 2.0, y + HEIGHT); // line to bottom-left point

        path.lineTo(x, y); // line back to top point

        // register to be notified of mouse events (and assume no one is clicking right now)

        mouseDown = false;

        getDrawingPanel().addMouseListener(this);

        getDrawingPanel().requestFocus();

    }

    @Override

    protected void loop() {

        if (mouseDown) {

            double theta = THETA; // default, rotate clockwise around mouse

            if (button == MouseEvent.BUTTON1) theta *= -1; // left button, rotate counter-clockwise around mouse

            else if (button == MouseEvent.BUTTON2) { // middle button, rotate around center of gravity

                // use center of gravity calculation as rotation axis

                Point2D center = getCenterOfGravity();

                x = center.getX();

                y = center.getY();

            }

            // rotate, using any adjustments to theta and axis of rotiation

            path.transform(AffineTransform.getRotateInstance(theta, x, y));

        }

        sleep(25);

    }

    public Point2D getCenterOfGravity() {

        PathIterator i = path.getPathIterator(null);

        double[] coords = new double[6]; // to hold coordinates

        int points = 0; // haven't visited any points yet

        while (!i.isDone()) {

            if (points != 0) { // skip the first visit to the top point

                i.currentSegment(coords);

                x += coords[0];

                y += coords[1];

            }

            i.next();

            if (!i.isDone()) points++; // don't double-count last point!

        }

        // package (x, y) coordinates into a single object

    }

    @Override

    }

    @Override

    public void mousePressed(MouseEvent e) {

        mouseDown = true;

        button = e.getButton();

        x = e.getX();

        y = e.getY();

    }

    @Override

    public void mouseReleased(MouseEvent e) {

        mouseDown = false;

    }

    @Override

    }

    public static void main(String[] args) {

        new RotationExample();

    }

}