/*
   In this simple drawing applet, the user can draw lines by pressing
   the mouse button and moving the mouse before releasing the button.
   A line is drawn from the point where the mouse button is pressed to the
   point where it is released.  A choice of colors is offered.
*/


import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;

public class SimpleDrawApplet extends Applet implements ItemListener {

   static final Color[] colorList = {
              // List of available colors; having this in an array makes
              // it much easier to write the itemStateChanged() routine.
          Color.black, Color.gray, Color.red, Color.green, Color.blue,
          new Color(200,0,0), new Color(0,180,0), new Color(0,0,180),
          Color.cyan, Color.magenta, Color.yellow, new Color(100,90,20)
       };

   Choice colorChoice; // A menu of available colors.

   SimpleDrawCanvas canvas;  // This is where the drawing is actually done.
                             // This applet displayes this canvas with some
                             // controls below it.

   public void init() {
           // Create components and lay out the applet

      canvas = new SimpleDrawCanvas();

      Panel bottom = new Panel();
      Button b1 = new Button("Clear");
      b1.addActionListener(canvas);    // Note that canvas will handle button events.
      bottom.add(b1);
      Button b2 = new Button("Undo");
      b2.addActionListener(canvas);
      bottom.add(b2);

      colorChoice = new Choice();
      colorChoice.add("Black");
      colorChoice.add("Gray");
      colorChoice.add("Red");
      colorChoice.add("Green");
      colorChoice.add("Blue");
      colorChoice.add("Dark Red");
      colorChoice.add("Dark Green");
      colorChoice.add("Dark Blue");
      colorChoice.add("Cyan");
      colorChoice.add("Magenta");
      colorChoice.add("Yellow");
      colorChoice.add("Brown");
      colorChoice.addItemListener(this);
      bottom.add(colorChoice);

      setBackground(Color.lightGray);
      setLayout(new BorderLayout(3,3));
      add("Center",canvas);
      add("South",bottom);

   } // end init()

   public Insets getInsets() {
         // Say how much of a border to leave around the edges of the applet.
      return new Insets(3,3,3,3);
   }

   public void itemStateChanged(ItemEvent evt) {
         // This is called when the user selects an item from the colorChoice
         // menu.  The index of the selected item specifies the color to use
         // for drawing.  The canvas is notified of the new drawing color
         // by calling its setDrawing Color method.
      int colorIndex = colorChoice.getSelectedIndex();
      canvas.setDrawingColor(colorList[colorIndex]);
   }

} // end class SimpleDrawApplet



class Line {  // an object of this class represents a colored line segment
   int x1, y1;   // One endpoint of the line segment.
   int x2, y2;   // The other endpoint of the line segment.
   Color color;  // The color of the line segment.
}



class SimpleDrawCanvas extends Canvas implements ActionListener, MouseListener {
       // A canvas where the use can draw lines in various colors.

   Color currentColor;  // Color that is currently being used for drawing new lines.

   SimpleDrawCanvas() {
         // Construct the canvas, and set it to listen for mouse events.
      setBackground(Color.white);
      currentColor = Color.black;
      addMouseListener(this);
   }

   void setDrawingColor(Color c) { 
         // Set current color to c.
      currentColor = c;
   }

   void doClear() {
        // Clear all the lines from the picture.
      repaint();
   }

   void doUndo() { 
        // Remove most recently added line from the picture.
   }

   public void actionPerformed(ActionEvent evt) {
        // A button has been clicked; do the appropriate command.
      String command = evt.getActionCommand();
      if (command.equals("Clear"))
          doClear();
      else if (command.equals("Undo"))
          doUndo();
   }

   int startX, startY;  // When the user presses the mouse button, the
                        // location of the mouse is stored in these variables.
                        // This information is needed when the mouse button
                        // is released.

   public void mousePressed(MouseEvent evt) {
         // This is called by the system when the user presses the mouse button.
         // Record the location at which the mouse was pressed.  This location
         // is one endpoint of the line that will be drawn when the mouse is
         // released.  This method is part of the MouseLister interface.
      startX = evt.getX();
      startY = evt.getY();
   }

   public void mouseReleased(MouseEvent evt) {
         // This is called by the system when the user releases the mouse button.
         // Draw a line in the current color.  The line starts at the point
         // (startX, startY), which is where the mouse button was pressed, and
         // it ends at the point where the mouse release occurs.  This method
         // is part of the MouseListener interface.

      int endX = evt.getX();  // Where the mouse was released.
      int endY = evt.getY();

      Graphics g = getGraphics();  // Get a graphics context for drawing on the canvas.

      g.setColor(currentColor);  // Draw the line in the current drawing color.
      g.drawLine(startX, startY, endX, endY);

      g.dispose();  // To be nice to the operating system, free the graphics context.

   } // end mouseReleased

   public void mouseClicked(MouseEvent evt) { }  // Other methods in the MouseListener interface
   public void mouseEntered(MouseEvent evt) { }
   public void mouseExited(MouseEvent evt) { }

} // end class SimpleDrawCanvas