/* DemoApplet: Demonstrating GUI + EVENT HANDLING */
import java.awt.*;
import java.awt.event.*;
import java.applet.*;

interface IGeometryConstants 
  {
    int SQUARE  = 0;
    int CIRCLE  = 1;
    int ELLIPSE = 2;
    String[] shapeNames = {"Square", "Circle", "Ellipse"};
    int SMALL  = 0;
    int MEDIUM = 1;
    int LARGE  = 2;
    String[] sizeNames = {"Small", "Medium", "Large"};
  }

public class DemoApplet extends Applet implements IGeometryConstants 
  {
    // Panel for shape
    Panel         shapePanel;
    CheckboxGroup shapeCBG;
    Checkbox      squareCB;
    Checkbox      circleCB;
    Checkbox      ellipseCB;

    // Panel for x,y coordinates
    Panel     xyPanel;
    Label     xLabel;
    TextField xInput;
    Label     yLabel;
    TextField yInput;

    // Panel for size and fill
    Panel    sizePanel;
    Label    sizeLabel;
    Choice   sizeChoices;
    Checkbox fillCB;

    // Panel for shape, coordinates, size and fill
    Panel leftPanel;

    // Panel for Message display, draw button and canvas
    Panel      rightPanel;
    Button     drawButton;
    DrawRegion drawRegion;
    TextField  messageDisplay;

    public void init() 
      {
        makeShapePanel();
        makeXYPanel();
        makeSizePanel();
        makeLeftPanel();
        makeRightPanel();
        addListeners();
        add(leftPanel);
        add(rightPanel);
      }

    // Panel for shape
    void makeShapePanel() 
      {
        shapePanel = new Panel();
        shapeCBG   = new CheckboxGroup();
        squareCB   = new Checkbox(shapeNames[SQUARE],  shapeCBG, true);
        circleCB   = new Checkbox(shapeNames[CIRCLE],  shapeCBG, false);
        ellipseCB  = new Checkbox(shapeNames[ELLIPSE], shapeCBG, false);
        shapePanel.setLayout(new FlowLayout());
        shapePanel.add(squareCB);
        shapePanel.add(circleCB);
        shapePanel.add(ellipseCB);
      }

    // Panel for x,y coordinates
    void makeXYPanel() 
      {
        xyPanel = new Panel();
        xLabel  = new Label("X Coordinate:");
        yLabel  = new Label("Y Coordinate:");
        xInput  = new TextField(5);
        yInput  = new TextField(5);
        xyPanel.setLayout(new GridLayout(2,2));
        xyPanel.add(xLabel);
        xyPanel.add(xInput);
        xyPanel.add(yLabel);
        xyPanel.add(yInput);
      }

    // Panel for size and fill
    void makeSizePanel()
      {
        sizePanel   = new Panel();
        sizeLabel   = new Label("Size:");
        sizeChoices = new Choice();
        sizeChoices.add(sizeNames[0]);
        sizeChoices.add(sizeNames[1]);
        sizeChoices.add(sizeNames[2]);
        fillCB = new Checkbox("Fill", false);
        sizePanel.setLayout(new FlowLayout());
        sizePanel.add(sizeLabel);
        sizePanel.add(sizeChoices);
        sizePanel.add(fillCB);
      }

    // Panel for shape, coordinates, size and fill
    void makeLeftPanel() 
      {
        leftPanel = new Panel();
        leftPanel.setLayout(new BorderLayout());
        leftPanel.add(shapePanel, "North");
        leftPanel.add(xyPanel,    "Center");
        leftPanel.add(sizePanel,  "South");
      }

    // Panel for Message display, draw button, and canvas
    void makeRightPanel() 
      {
        rightPanel = new Panel();
        messageDisplay = new TextField("MESSAGE DISPLAY");
        messageDisplay.setEditable(false);
        messageDisplay.setBackground(Color.yellow);
        drawButton = new Button("Draw");
        drawButton.setBackground(Color.lightGray);
        drawRegion = new DrawRegion();
        drawRegion.setSize(150,150);
        drawRegion.setBackground(Color.white);
        rightPanel.setLayout(new BorderLayout());
        rightPanel.add(drawButton,     BorderLayout.NORTH);
        rightPanel.add(messageDisplay, BorderLayout.SOUTH);
        rightPanel.add(drawRegion,     BorderLayout.CENTER);
      }

    // Add the listeners.
    void addListeners() 
      {
        drawButton.addActionListener(new ActionListener() 
          {
            public void actionPerformed(ActionEvent evt) 
              {
                int shape, xCoord, yCoord, width;
                messageDisplay.setText("");
                
                // Get the shape   
                if (squareCB.getState())        shape = SQUARE;
                else if (circleCB.getState())   shape = CIRCLE;
                else if (ellipseCB.getState())  shape = ELLIPSE;
                else {
                       messageDisplay.setText("Unknown shape.");
                       return;
                     }
 
                // Get the coordinates          
                try {
                      xCoord = Integer.parseInt(xInput.getText());
                      yCoord = Integer.parseInt(yInput.getText());
                    } 
                catch (NumberFormatException e) 
                    {
                      messageDisplay.setText("Illegal coordinates.");
                      return;
                    }

                // Get the size     
                switch (sizeChoices.getSelectedIndex())
                  {
                    case SMALL:  width = 30;  break;
                    case MEDIUM: width = 60;  break;
                    case LARGE:  width = 120; break;
                    default:     messageDisplay.setText("Unknown size."); return;
                  }
       
                messageDisplay.setText("Drawing" + shapeNames[shape]);
                drawRegion.doDraw( shape, xCoord, yCoord, fillCB.getState(), width );
              }
          });

        xInput.addTextListener(new TextListener() 
          {
            public void textValueChanged(TextEvent evt)
              {
                checkTF(xInput);
              }
          });

        yInput.addTextListener(new TextListener() 
          {
            public void textValueChanged(TextEvent evt) 
              {
                checkTF(yInput);
              }
          });
      }
 
   // Check for legal integer value in the text field
    void checkTF(TextField tf) 
      {
        messageDisplay.setText("");
        try {
              Integer.parseInt(tf.getText());
            } 
       catch (NumberFormatException e) 
            {
              messageDisplay.setText("Illegal coordinate.");
            }
      }
  }


/** Canvas for doing the drawing */

class DrawRegion extends Canvas implements IGeometryConstants
  {
    // Values needed for drawing the shape
    private int     shape;
    private int     xCoord;
    private int     yCoord;
    private boolean fillFlag;
    private int     width;
    public DrawRegion() 
      {
        setSize(150,150);
        setBackground(Color.white);

      }
    // Set the values and repaint the drawing region.
    public void doDraw(int shape, int xCoord, int yCoord, boolean fillFlag, int width)
      {
        this.shape     = shape;
        this.xCoord    = xCoord;
        this.yCoord    = yCoord;
        this.fillFlag  = fillFlag;
        this.width     = width;
        repaint(); 
      }

    // Do the drawing of the shape
    public void paint(Graphics g) 
      {
        switch (shape) 
          {
            case SQUARE:
                if (fillFlag) g.fillRect(xCoord, yCoord, width, width);
                else g.drawRect(xCoord, yCoord, width, width);
                break;
            case CIRCLE:
                if (fillFlag) g.fillOval(xCoord, yCoord, width, width);
                else g.drawOval(xCoord, yCoord, width, width);
                break;
            case ELLIPSE:
                if (fillFlag) g.fillOval(xCoord, yCoord, width, width/2);
                else g.drawOval(xCoord, yCoord, width, width/2);
          }
      }
  }