/************************************/
/*  直線（ベクトル）の角度を求める  */
/************************************/

import java.awt.*;

public class mathvecs extends java.applet.Applet {

	Image screen;
	Graphics g_screen;
	Panel ppoint,pdegree;

	TextField tx,ty,ts;
	
	Label dg;

	int i,j,x,y;
	final double pie=3.1416; /* πの値 */

	public void init(){

		resize(288,320);
		setBackground(Color.green); /*アプレットの背景を緑にする*/
		setFont(new Font("TimesRoman",Font.PLAIN,12));

		screen=createImage(258,258); 
		g_screen=screen.getGraphics();

		ppoint=new Panel();
		pdegree=new Panel();

		this.setLayout((LayoutManager)null);
		add(ppoint);
		add(pdegree);

		ppoint.setBounds(8,272,152,48);
		pdegree.setBounds(160,272,116,48);

		ppoint.setLayout(new FlowLayout(FlowLayout.CENTER,4,4));
		pdegree.setLayout(new FlowLayout(FlowLayout.CENTER,4,4));

		dg=new Label("degree",Label.LEFT);

		tx=new TextField(4);
		ty=new TextField(4);
		ts=new TextField(4);

		tx.setEditable(false); /*テキスト編集不可*/
		ty.setEditable(false);
		ts.setEditable(false);

		ppoint.add(tx);
		ppoint.add(ty);

		pdegree.add(ts);
		pdegree.add(dg);

		tx.setBackground(Color.white);
		ty.setBackground(Color.white);
		ts.setBackground(Color.white);
		dg.setBackground(Color.green);

		screenInit();
		repaint();

	}

	public void screenInit() {

		g_screen.setColor(Color.white);
		g_screen.fillRect(0,0,258,258);

		g_screen.setColor(Color.black);

		g_screen.drawRect(0,0,257,257);

		g_screen.drawLine(0,128,256,128);
		g_screen.drawLine(128,0,128,256);

		g_screen.drawOval(114,131,10,12);

	}


	public boolean mouseMove(Event evt,int mx,int my){ /*マウス移動*/

		if (mx<16 ||mx>272 ||my<8 ||my>264)
			return false;

		x=mx-144; /*画面の座標をグラフの座標に変換*/
		y=136-my;

		if (x==0 && y==0) /*原点（ゼロベクトル）なら計算不可*/
			return false;

		screenInit();

		g_screen.setColor(Color.blue);
		g_screen.drawLine(128,128,x+128,128-y);
		repaint();

		tx.setText(String.valueOf(x));
		ty.setText(String.valueOf(y));

		ts.setText(String.valueOf(kakudo((double)x,(double)y)));

		return true;

	}						

	public int kakudo(double x,double y) { /*ベクトルの角度を計算*/

		double s;
		int deg;

		s=Math.acos(x/Math.sqrt(x*x+y*y)); /*角度θを求める*/

		s=(s/pie)*180.0; /* ラジアンを度に変換 */

		if (y<0) /* θ＞πの時 */
			s=360-s;

		deg=(int)Math.floor(s);

		if ((s-deg)>=0.5) /*小数点を四捨五入*/
			deg++;

		return deg; /*角度θを返す*/

	}

	public void paint(Graphics g){

		g.drawImage(screen,15,7,this);

	}

	public void update(Graphics g){

		paint(g);

	}

}