/*
 * @file:	TranslateTest.java
 * @source:	David Geary [Graphic Java, p.57]
 *
 * @purpose:
 *	This class TranslateTest is an applet that reads an image,
 *	and display the image in its natural size in a limited size
 *	window.  Using the mouse, you can "pan" the image, i.e.,
 *	by dragging the mouse, the image translates in the window.
 *
 *	Several exercises for extending this example are given below.
 *
 * @history:
 *	Adapted by Chee Yap for 
 *	Visualization Class, Spring 2003
 * 
 */


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

public class TranslateTest
	extends Applet
{
   Image image;
   Point pressed = new Point(), lastTranslate = new Point();

   public void init() {

      ////////////////////////////////////////////////////////////////
      // Load Image:
      ////////////////////////////////////////////////////////////////
      image = getImage(getCodeBase(), "saint.gif");
					// getCodeBase() is current path
      try {
         MediaTracker mt = new MediaTracker(this);
					// make *this* a MediaTracker
         mt.addImage(image, 0);		// image has ID=0
         mt.waitForID(0);		// wait till ID 0 load
      }
      catch(InterruptedException e) {
         e.printStackTrace();
      }

      ////////////////////////////////////////////////////////////////
      // Mouse Listener:
      ////////////////////////////////////////////////////////////////
      addMouseListener(new MouseAdapter() {		// get new (anonymous) MouseAdapter &
         public void mousePressed(MouseEvent e) {	// register it with "addMouseListener"
            Point loc = e.getPoint();
            pressed.x = loc.x - lastTranslate.x;	// adjust absolute position of "loc"
            pressed.y = loc.y - lastTranslate.y;	//    using the "lastTranslate" point.
         }
      });

      ////////////////////////////////////////////////////////////////
      // Mouse Motion Listener:
      ////////////////////////////////////////////////////////////////
      addMouseMotionListener(new MouseMotionAdapter() {
         public void mouseDragged(MouseEvent e) {
            Point loc = e.getPoint();
            Point translate = new Point(loc.x - pressed.x, // NOTE: pressed point is unchanged 
                                 loc.y - pressed.y);	//   during dragging
            Graphics g = getGraphics();

            try {
               g.clearRect(0,0,
                        getSize().width,getSize().height);
               g.translate(translate.x, translate.y);
               showStatus("Translating Graphics:  " + 
                        translate);
               g.drawImage(image, 0, 0, TranslateTest.this);
				// *this* is the ImageObserver
            }
            finally {		// The third clause in "try-catch-finally".
               g.dispose();	// It is executed whether or not the exception 
            }			//    is caught.
            lastTranslate = translate;
         }
      });
   }

   ////////////////////////////////////////////////////////////////
   // paint method
   ////////////////////////////////////////////////////////////////
   public void paint(Graphics g) {
      g.drawImage(image, 0, 0, this);	// image is the loaded image
					// *this* (i.e., TranslateTest) is
					//    the ImageObserver argument.
   }

} // TranslateTest class

/************************************************************
	EXERCISE 1: Merge the present program (TranslateTest.java)
	with the previous program (PanelTest2.java).
	Call the result ZoomPan.java.  In particular, the
	current image translation demo should be placed in the
	centerPanel of a workPanel.

	EXERCISE 2: Introduce into ZoomPan.java the ability to zoom.
	Add two buttons named "+" and "-" into the controlPanel.
	Clicking these will double or half the image size.

	EXERCISE 3: It is easy to get lost when you pan and zoom.
	Please introduce a "navigator" component.   This can be
	a Canvas component that has a fixed size (about 70x70 may be good).
	In this navigator, you draw a PINK rectangle, representing
	a scaled outline of the full extent of the image.  Inside
	this pink rectangle, you draw a BLUE rectangle, representing
	a scaled outline of your current centerPanel.

	EXERCISE 4: In good GUI design, we know that it is important to
	provide feedback to the user.  We want the following visual
	feedback:  when the mouse button is pressed,
	the cursor changes
	into an "open hand" image.  This cursor returns to the
	default ("arrow") when the mouse is released.

 ************************************************************/