/*%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

	Copyright (c) John D. Mitchell, 1996 -- All Rights Reserved

PROJECT:	JavaWorld
MODULE:		Tips & Tricks
FILE:		DoubleClicker.java

AUTHOR:		John D. Mitchell, Mar 22, 1996

REVISION HISTORY:
	Name	Date		Description
	----	----		-----------
	JDM	96.04.01   	Initial version.

DESCRIPTION:
	This is a demonstration file for the JavaWorld Tips & Tricks
	column.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%*/

import	java.awt.*;
import	java.applet.*;


public class DoubleClicker extends Applet
{
    // The string to display after a single click.
    static private String singleClickString = "Hello JavaWorld!";

    // The string to display after a double click!
    static private String doubleClickString = "Happy April Fools!";

    // Which of the two strings should be displayed?
    private boolean displayDoubleClickString = false;


    // The number of milliseconds that should bound a double click.
    static private long mouseDoubleClickThreshold	= 300L;

    // The previous mouseUp event's time.
    private long mouseUpClickTime = 0;


    // mouseUp() will be called once per mouse button *release*.
    // We treat all clicks as a single click unless the second click
    // event happens within the threshold set above.
    public boolean mouseUp (Event e, int x, int y)
    {
	long eventTime = e.when;
	long timeDiff;
	
	// Make sure the event times difference is a positive number.
	// Note that this is due to the fact that the time value on a
	// long of machines is a 64-bit *unsigned* value but, alas,
	// Java doesn't have unsigned numbers so at a certain point
	// the values roll over into the very high negative numbers
	// which then actually *decrease* (recall that Java mandates a
	// two's complement arithmetic).
	timeDiff = eventTime - mouseUpClickTime;
	if (timeDiff < 0)
	    timeDiff = -timeDiff;

	// Display the event time information.
	showStatus ("Current event :" + eventTime +
		    ":   Previous event :" + mouseUpClickTime +
		    ":   Difference :" + timeDiff + ":");

	// Did this click happen with the given time bound?
	if (mouseDoubleClickThreshold > timeDiff)
	    {
	    // Yep, display the double click message.
	    displayDoubleClickString = true;

	    // Clear out the previous event time so that we don't get
	    // confused in our count.
	    // Note that this means that triple, quadruple,
	    // etc. clicks will *not* be condensed into a double
	    // click.  If you want that sort of behavior change this
	    // to:	mouseUpClickTime = eventTime;
	    mouseUpClickTime = 0;
	    }
	else
	    {
	    // Nope, just a single click so make sure that we display
	    // the single click message.
	    displayDoubleClickString = false;

	    // Update the event time holder.
	    mouseUpClickTime = eventTime;
	    }

	// Force a repaint so we can see what's happening.
	repaint();

	// We've handled the event.
	return true;
    }
    
	    
    public void paint (Graphics g)
    {
	// Let's muck about with the fonts.
	Font font = new Font("Times Roman", Font.PLAIN, 20);
	FontMetrics fm = getFontMetrics(font);
	g.setFont (font);

	// Figure out the width of the string to be displayed.
	int displayStringWidth;
	if (displayDoubleClickString)
	    displayStringWidth = fm.stringWidth (doubleClickString);
	else
	    displayStringWidth = fm.stringWidth (singleClickString);

	// Let's center the string in the window, just for kicks.
	int x = (this.size().width - displayStringWidth) / 2;
	int y = (this.size().height - fm.getHeight()) / 2;

	if (displayDoubleClickString)
	    g.drawString (doubleClickString, x, y);
	else
	    g.drawString (singleClickString, x, y);
    }

}