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// PaintDemo.java - Simple painting program.
// Illustrates use of mouse and BufferedImage.
// Fred Swartz 2002-12-02
// Possible Enhancements:
//   * Clear drawing area
//   * Other shapes (line, outline shapes, text, ...)
//   * Color selection.
//   * An eraser.
//   * Create a real toobar.
//   * Save/Load 


import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import java.awt.image.BufferedImage;

////////////////////////////////////////////////////////////// PaintDemo
class PaintDemo {
    //============================================================= main
    public static void main(String[] args) {
        PaintWindow window = new PaintWindow();
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        window.setVisible(true);
    }//end main
}//endclass PaintDemo


//////////////////////////////////////////////////////////// PaintWindow
class PaintWindow extends JFrame {
    PaintPanel canvas = new PaintPanel();
    //====================================================== constructor
    public PaintWindow() {
        //--- create the buttons
        JButton circleButton = new JButton("Circle");
        circleButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                canvas.setShape(PaintPanel.CIRCLE);
            }});
        JButton rectangleButton = new JButton("Rectangle");
        rectangleButton.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                canvas.setShape(PaintPanel.RECTANGLE);
            }});
        
        //--- layout the buttons
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(2, 1));
        buttonPanel.add(circleButton);
        buttonPanel.add(rectangleButton);
        
        //--- layout the window
        Container content = this.getContentPane();
        content.setLayout(new BorderLayout());
        content.add(buttonPanel, BorderLayout.WEST);
        content.add(canvas     , BorderLayout.CENTER);
        this.setTitle("Paint Demo");
        this.pack();
    }//end constructor
}//endclass PaintWindow


///////////////////////////////////////////////////////////// PaintPanel
class PaintPanel extends JPanel implements MouseListener, 
                                           MouseMotionListener {
    //--- Public constants used to specify shape being drawn.          
    public static final int NONE      = 0;
    public static final int LINE      = 1;
    public static final int RECTANGLE = 2;
    public static final int CIRCLE    = 3;
    
    //--- Variables to store the current figure info
    private int _shape = NONE;
    private int _currentStartX = 0;  // where mouse first pressed
    private int _currentStartY = 0;
    private int _currentEndX   = 0;  // where dragged to or released
    private int _currentEndY   = 0;
    
    //--- BufferedImage to store the underlying saved painting.
    //    Will be initialized first time paintComponent is called.
    private BufferedImage _bufImage = null;
    
    //--- Private constant for size of paint area.
    private static final int SIZE = 600; // size of paint area
    
    
    //====================================================== constructor
    public PaintPanel() {
        setPreferredSize(new Dimension(SIZE, SIZE));
        setBackground(Color.white);
        //--- Add the mouse listeners.
        this.addMouseListener(this); 
        this.addMouseMotionListener(this);
    }//endconstructor
    
    
    //========================================================= setShape
    public void setShape(int shape) {
        //--- Provided so users can set the shape.
        _shape = shape;
    }//end setShape
    
    
    //=================================================== paintComponent
    public void paintComponent(Graphics g) {
        super.paintComponent(g);
        
        Graphics2D g2 = (Graphics2D)g;  // downcast to Graphics2D
        if (_bufImage == null) {
            //--- This is the first time, initialize _bufImage
            int w = this.getWidth();
            int h = this.getHeight();
            _bufImage = (BufferedImage)this.createImage(w, h);
            Graphics2D gc = _bufImage.createGraphics();
            gc.setColor(Color.white);
            gc.fillRect(0, 0, w, h); // fill in background
        }
        g2.drawImage(_bufImage, null, 0, 0);  // draw previous shapes
        
        drawCurrentShape(g2);
    }//end paintComponent
    
    
    //================================================= drawCurrentShape
    private void drawCurrentShape(Graphics2D g2) {
        //--- Draws current shape on a graphics context, either
        //    on the context passed to paintComponent, or the
        //    context for the BufferedImage.
        switch (_shape) {
            case NONE  :
                     break;
                     
            case CIRCLE:
                     g2.fillOval(_currentStartX, _currentStartY,
                                 _currentEndX - _currentStartX, 
                                 _currentEndY - _currentStartY);
                     break;
                     
            case RECTANGLE:
                     g2.fillRect(_currentStartX, _currentStartY,
                                 _currentEndX - _currentStartX, 
                                 _currentEndY - _currentStartY);
                     break;
                     
            default:  // should never happen
                     g2.drawString("Huh?", 10, 20);
                     break;
        }
    }//end paintComponent

    //===================================================== mousePressed
    public void mousePressed(MouseEvent e) {
        _currentStartX = e.getX(); // save x coordinate of the click
        _currentStartY = e.getY(); // save y
        _currentEndX   = _currentStartX;   // set end to same pixel
        _currentEndY   = _currentStartY;
    }//end mousePressed

    //===================================================== mouseDragged
    public void mouseDragged(MouseEvent e) {
        _currentEndX = e.getX();   // save new x and y coordinates
        _currentEndY = e.getY();
        this.repaint();            // show new shape
    }//end mouseDragged
    
    //==================================================== mouseReleased
    public void mouseReleased(MouseEvent e) {
        // This will save the shape that has been dragged by
        // drawing it onto the bufferedImage where all shapes
        // are written.
        _currentEndX = e.getX(); // save ending coordinates
        _currentEndY = e.getY();
        
        //--- Draw the current shape onto the buffered image.
        Graphics2D grafarea = _bufImage.createGraphics();
        drawCurrentShape(grafarea);
        
        this.repaint();
    }//end mouseReleased
    
    //========================================== ignored mouse listeners
    public void mouseMoved   (MouseEvent e) {}
    public void mouseEntered (MouseEvent e) {}
    public void mouseExited  (MouseEvent e) {}
    public void mouseClicked (MouseEvent e) {}
}//endclass PaintPanel