// file:    testGraphics5.java
// author:  Robert Keller
// purpose: Showing how to redefine update.
//          

/* In this program, we over-ride the 'update' method of the base Frame.
   All drawing is done to an off-screen buffer.  
   The 'paint' method simply paints the buffer contents.
   The 'update' method only calls the paint method, it does not draw the
   background.

   This is the standard model for flicker-free graphics in the JDK 1.0 AWT.

   By setting the background color, even the initial grey will not show.
*/

import java.awt.*;                      // to get awt (abstract window toolkit)
import java.lang.Thread;

class testGraphics5 extends Frame       // needed to allow over-ride of paint
{                                       // consider this to be magic for now

Image image;                            // image provides graphics buffer

// paint(Graphics) will be called by the system to paint the Frame when 
// necessary.  At that time, the Graphics of the frame will be passed as 
// an argument.

public void paint(Graphics g)
  {
  g.drawImage(image, 0, 0, null);
  }


public void update(Graphics g)
  {
  paint(g);
  }

// draw stuff at position x, y

void drawStuff(int x, int y)
  {
  Graphics g= image.getGraphics();
  g.setColor(Color.white);                        // paint image background
  g.fillRect(0, 0, image.getWidth(null), image.getHeight(null));

  g.setColor(Color.black);                        // set the color for drawing
  g.drawRect(x+50, y+50, 400, 300);               // draw a rectangle

  g.setColor(Color.blue);
  g.fillOval(x+100, y+100, 300, 200);             // fill an oval

  g.setColor(Color.yellow);
  g.drawOval(x+100, y+100, 300, 200);             // draw an oval

  g.setFont(new Font("Times", Font.BOLD, 28));  
  g.drawString("Harvey Mudd College", x+140, y+210);  // draw a string
  }


public static void main(String[] arg)
  {
  testGraphics5 frame = new testGraphics5();      // create the frame

  frame.setBackground(Color.white);               // avoid startup flicker

  frame.reshape(50, 50, 600, 500);                // set the location and size

  frame.show();                                   // show the frame 

  // Note: the following must be done AFTER the frame is shown.

  frame.image = frame.createImage(frame.size().width, frame.size().height);

  for( int i = 0; i < 100; i += 10 )
    { 
    frame.drawStuff(i, i);
    try{Thread.sleep(5);} catch(Exception e){}  // delay 5 milliseconds
    frame.repaint();
    }
  }
}