Jeronimus

import javax.swing.*;
import java.util.ArrayList;
import java.awt.*;
import java.awt.image.BufferStrategy;
import static java.lang.Math.*;
import java.awt.event.*;
import java.awt.image.BufferedImage;

class Spacetime {

  public static void main(String[] args) {

    new MainClass();

  }
}


class MainClass {

  public MainClass() {

    createFrameAndCanvases();
    generateEvents();

    mainLoop();
  }

  public void mainLoop(){

    render();
    jFrame.paintComponents(g2DjFrame);
    jFrame.repaint();

    do{
      updateState();
      render();
      try{Thread.sleep(20);} catch (Exception e){};
    } while(true);
  }

  public void updateState(){

    if(!lock) {
      if (v_rel<1) {
        v_rel+=0.001;
      }
    }
  }

  public void render(){

    g2Dcanvas1 = (Graphics2D) strategyCanvas1.getDrawGraphics();
    g2Dcanvas2 = (Graphics2D) strategyCanvas2.getDrawGraphics();
    g2DjFrame = (Graphics2D) strategyJFrame.getDrawGraphics();

    g2Dcanvas1.setStroke(new BasicStroke(3));
    g2Dcanvas2.setStroke(new BasicStroke(3));

    g2Dcanvas1.setColor(backgroundColor);
    g2Dcanvas2.setColor(backgroundColor);
    g2DjFrame.setColor(backgroundColor);

    g2Dcanvas1.fillRect(0,0,501,501);
    g2Dcanvas2.fillRect(0,0,501,501);
    g2DjFrame.fillRect(0,0,1280,720);

    plotDiagrams();
    plotLightbeams();
    plotEvents(v_rel);

    if (showPaths) {
      g2Dcanvas2.drawImage(bufferedImage,0,0,501,501,null);}

    jFrame.paintComponents(g2DjFrame);

    g2DjFrame.setColor(Color.RED);
    g2DjFrame.setFont(stringFont3);
    g2DjFrame.drawString("Vrel "+(Double.toString(round(v_rel*10000)/10000.0)),600,600);

    strategyCanvas2.show();
    strategyCanvas1.show();
    strategyJFrame.show();

    g2Dcanvas1.dispose();
    g2Dcanvas2.dispose();
    g2DjFrame.dispose();
  }


  public void plotLightbeams() {

    g2Dcanvas1.setColor(Color.YELLOW);
    g2Dcanvas2.setColor(Color.YELLOW);

    g2Dcanvas1.drawLine(0,0,501,501);
    g2Dcanvas1.drawLine(0,501,501,0);

    g2Dcanvas2.drawLine(0,0,501,501);
    g2Dcanvas2.drawLine(0,501,501,0);
  }


  public void plotEvents(double v_rel){

    g2Dcanvas1.setFont(stringFont);
    g2Dcanvas2.setFont(stringFont);

    double x,t,x_p,t_p;
    vrel = v_rel;

    gamma = 1/(sqrt(1-pow(vrel,2))); // c^2 = 1 when vrel is multiple of c

    for (int i=0; i<eventsArraylist.size();i++){
      x=eventsArraylist.get(i).xPosInLightSeconds;
      t=eventsArraylist.get(i).timeInSeconds;
      g2Dcanvas1.setColor(Color.RED);
      if (x==8 && t==4) { g2Dcanvas1.setColor(Color.GREEN);}
      if (x==4 || x==-4) { g2Dcanvas1.setColor(Color.GREEN);}
      if (x==0 ) { g2Dcanvas1.setColor(Color.BLUE);}
      g2Dcanvas1.drawString(Integer.toString((int)t),(int)(x*25+251-4),(int)(251+4-t*25));


      x_p = gamma*(x - vrel * t);  // c^2 = 1 when vrel is multiple of c so no need for /c^2 in the formula
      t_p = gamma*(t - (vrel*x));

      g2Dcanvas2.setColor(Color.RED); g2Dimg.setColor(Color.RED);
      if (x==8 && t==4) { g2Dcanvas2.setColor(Color.GREEN); g2Dimg.setColor(Color.GREEN);}
      if (x==4 || x==-4) { g2Dcanvas2.setColor(Color.GREEN); g2Dimg.setColor(Color.GREEN);}
      if (x==0 ) { g2Dcanvas2.setColor(Color.BLUE); g2Dimg.setColor(Color.BLUE);}
      g2Dcanvas2.drawString(Integer.toString((int)t),(int)(x_p*25+251-4),(int)(251+4-t_p*25));

      g2Dimg.drawLine((int)(x_p*25+251),(int)(251-t_p*25),(int)(x_p*25+251),(int)(251-t_p*25));
    }
  }


  public void createFrameAndCanvases(){

    jFrame = new JFrame();
    jFrame.setLayout(null);
    jFrame.setSize(1280,720);
    jFrame.setResizable(false);
    jFrame.setIgnoreRepaint(true);

    button1 = new JButton("start/stop");
    button1.setBounds(100,530,130,130);
    button1.addActionListener(actionListener);
    button1.setActionCommand("start/stop");
    jFrame.add(button1);


    button2 = new JButton("reset");
    button2.setBounds(300,530,130,130);
    button2.addActionListener(actionListener);
    button2.setActionCommand("reset");
    button2.setVisible(true);
    jFrame.add(button2);

    canvas1 = new Canvas();
    canvas1.setSize(501,501);
    canvas1.setLocation(75,0);
    canvas1.setIgnoreRepaint(true);
    canvas1.setBackground(new Color(222,222,222));
    jFrame.add(canvas1);

    canvas2 = new Canvas();
    canvas2.setSize(501,501);
    canvas2.setLocation(1280-501-75,0);
    canvas2.setIgnoreRepaint(true);
    canvas2.setBackground(new Color(222,222,222));
    jFrame.add(canvas2);

    checkBox = new JCheckBox("show/hide paths",false);
    checkBox.addActionListener(actionListener);
    checkBox.setActionCommand("show/hide paths");
    checkBox.setBounds(500,600,200,20);
    jFrame.add(checkBox);


    jFrame.setVisible(true);

    jFrame.createBufferStrategy(2);

    canvas1.createBufferStrategy(2);
    canvas2.createBufferStrategy(2);

    strategyCanvas1 = canvas1.getBufferStrategy();
    strategyCanvas2 = canvas2.getBufferStrategy();

    strategyJFrame = jFrame.getBufferStrategy();

    g2DjFrame = (Graphics2D) strategyJFrame.getDrawGraphics();

    g2Dcanvas1 = (Graphics2D) strategyCanvas1.getDrawGraphics();
    g2Dcanvas2 = (Graphics2D) strategyCanvas2.getDrawGraphics();


  }


  public void plotDiagrams() {

    g2Dcanvas1.setFont(stringFont2);
    g2Dcanvas2.setFont(stringFont2);

    g2Dcanvas1.setColor(Color.BLACK);
    g2Dcanvas2.setColor(Color.BLACK);

    g2Dcanvas1.drawLine(0,250,500,250);
    g2Dcanvas1.drawLine(250,0,250,500);

    g2Dcanvas2.drawLine(0,250,500,250);
    g2Dcanvas2.drawLine(250,0,250,500);

    int x,t;
    for (x=0; x<21;x++){
      if (x!=10) {
        g2Dcanvas1.drawLine(x*(500/20),245, x*(500/20),255);
        g2Dcanvas1.drawString(Integer.toString(x-10),x*(500/20)-5,268);
        g2Dcanvas2.drawLine(x*(500/20),245, x*(500/20),255);
        g2Dcanvas2.drawString(Integer.toString(x-10),x*(500/20)-5,268);
      }
    }

    for (t=0; t<21;t++){
      if (t!=10) {
        g2Dcanvas1.drawLine(245,t*(500/20), 255,t*(500/20));
        g2Dcanvas1.drawString(Integer.toString(10-t),258,t*(500/20)+5);
        g2Dcanvas2.drawLine(245,t*(500/20), 255,t*(500/20));
        g2Dcanvas2.drawString(Integer.toString(10-t),258,t*(500/20)+5);
      }
    }
  }


  public void generateEvents(){

    int x,t;
    for (x=-10; x<11;x++){
      for (t=-10; t<11;t++){

        eventsArraylist.add( new Event(x,t));

      }
    }
  }


  class Event {

    double xPosInLightSeconds;
    double timeInSeconds;

    public Event(int x, int t) {

      xPosInLightSeconds = x;
      timeInSeconds = t;

    }
  }


  JFrame jFrame;
  Canvas canvas1,canvas2;

  boolean lock=true, showPaths=false;

  BufferedImage bufferedImage = new BufferedImage(501, 501,BufferedImage.TYPE_INT_ARGB);

  Color backgroundColor = new Color(211,222,222);
  BufferStrategy strategyCanvas1,strategyCanvas2,strategyJFrame;
  Graphics2D g2Dcanvas1, g2Dcanvas2, g2DjFrame, g2Dimg = bufferedImage.createGraphics();;

  JButton button1,button2;
  JCheckBox checkBox;

  ArrayList<Event> eventsArraylist = new ArrayList<Event>();

  double gamma,vrel,v_rel;

  Font stringFont = new Font( "SansSerif", Font.BOLD, 14 );
  Font stringFont2 = new Font( "SansSerif", Font.PLAIN, 10 );
  Font stringFont3 = new Font( "SansSerif", Font.PLAIN, 20 );

  ActionListener actionListener = new ActionListener() {

    public void actionPerformed(ActionEvent e) {
      String str=e.getActionCommand();

      if (str.equals("show/hide paths")) {

        if (showPaths) {showPaths=false;} else {showPaths=true;};

      }

      if (str.equals("reset")) {

        vrel=0;
        v_rel=0;
        g2Dimg.setBackground(new Color(0,0,0,0));
        g2Dimg.clearRect(0,0,501,501);
        lock = true;
      }

      if (str.equals("start/stop")){
        if (lock){lock=false;} else {lock=true;};
      }
    }
  };
}