NewsScroller: Scroller.java
package crackers.Scroller;
/**
* A basic horizontal scrolling text applet. This was written under the
* influence of the examples provided by Sun and copyright by them.
* <P>
* This program is copyrighted 1999 by the author under the GNU Public License
* (GPL). Full text of this license is available at
* <A HREF="http://www.gnu.org">GNU.org</A>.
* <P>
* For full usage information, see
* <A HREF="http://www.io.com/~crackers">my web pages</A>.
*
* @author E. A. Graham, Jr. (crackers@io.com)
* @version 2.0
*/
import java.awt.*;
import java.applet.*;
import java.net.URL;
import java.net.MalformedURLException;
import java.awt.event.*;
public class Scroller extends WebBase implements MouseListener
{
/**
* The message text.
*/
private String message;
/**
* Current x coordinate of the text within the applet.
*/
private int messageX = 0;
/**
* Current y coordinate of the text within the applet.
*/
private int messageY = 0;
/**
* The width of the message.
*/
private int messageWidth = 0;
/**
* The font to draw the message with. Defaults to Serif.
*/
private Font messageFont;
/**
* Flag to indicate whether or not to draw a "shadow" of the message.
*/
private boolean shadowOn;
/**
* The string of the URL to link to. Optional.
*/
private String linkName;
/**
* The url of a link. Optional.
*/
private URL linkURL = null;
/**
* Initialize the applet. Over-rides super class (but calls it).
* @see java.applet.Applet
*/
public void init()
{
super.init();
// get the HTML parameters or set to defaults
message = readParam("MESSAGE","No message supplied!");
String shadowParam = readParam("SHADOW");
shadowOn = (shadowParam== null) ? false : shadowParam.equalsIgnoreCase("true");
linkName = readParam("URL");
if (linkName != null)
{
try
{
if (linkName.indexOf("http://") < 0)
linkURL = new URL(getDocumentBase(),linkName);
else
linkURL = new URL(linkName);
}
catch (MalformedURLException e) {};
}
// make ourselves listen to the mouse
addMouseListener(this);
}
/**
* Called when the applet is started. Over-rides super class (but calls it).
*/
public void start()
{
super.start();
// set up the font and initial positions
int fontAttributes = Font.PLAIN;
String name = readParam("FONT");
String style = readParam("FONTSTYLE");
if (style != null)
{
style = style.toUpperCase();
if (style.indexOf("BOLD") >= 0)
fontAttributes += Font.BOLD;
if (style.indexOf("ITALIC") >= 0)
fontAttributes += Font.ITALIC;
}
// a font size of 14 seems a decent size to start with, especially with
// applets
try
{
messageFont = new Font(name,fontAttributes,14);
}
catch (Exception e) { }
// didn't work?
if (messageFont == null)
{
name = "Serif";
messageFont = new Font(name,fontAttributes,14);
}
// set the font on this applet so we can determine it's "true" size
setFont(messageFont);
FontMetrics fontStuff = getFontMetrics(messageFont);
int fontHeight = fontStuff.getHeight();
// scale this down to the appropriate size (lots of rounding)
// remake the font with the new point size
double height = (double)(maxHeight - (2 * Math.abs(borderWidth)));
fontHeight = (int)Math.floor(14 * height / (double)fontHeight);
messageFont = new Font(name,fontAttributes,fontHeight);
fontStuff = getFontMetrics(messageFont);
messageX = maxWidth;
messageY = ((maxHeight-fontStuff.getHeight()) >> 1) + fontStuff.getAscent() - 1;
messageWidth = fontStuff.stringWidth(message);
}
/**
* Over-rides the super class. Paint the text to the offscreen image and
* place <B>image</B> onto the graphics context.
*/
public synchronized void update(Graphics g)
{
// are we running?
if(loaded)
{
super.update(g);
//...then draw shadow copy of text...
if (shadowOn)
{
Color foreColorD1,foreColorD2;
foreColorD1 = foreColor.darker();
foreColorD2 = foreColorD1.darker();
appGC.setColor(foreColorD2);
appGC.drawString(message, messageX+2, messageY+2);
appGC.setColor(foreColorD1);
appGC.drawString(message, messageX+1, messageY+1);
}
//...then draw the text...
appGC.setColor(foreColor);
appGC.setFont(messageFont);
appGC.drawString(message, messageX, messageY);
//...next comes the border...
drawBorder();
//...and drop the whole thing into place
g.drawImage(appImage, 0, 0, this);
}
}
/**
* Implementation of the abstract method: increment the X-position of the
* message by the indicated amount. This "jump" is the animation for the
* message.
*/
protected synchronized void doAppThing()
{
messageX -= scrollUnit;
// oops! too far - start over
if((messageX + messageWidth) < 0) messageX = maxWidth;
}
/**
* Required method for MouseListener: fired when the mouse button is
* released. Resets the border to it's initial state. If there is a
* link URL to jump to, do so.
*/
public void mouseReleased(MouseEvent e)
{
borderWidth = -borderWidth;
if (linkURL !=null) {
getAppletContext().showDocument(linkURL,frameTarget);
}
}
/**
* Required method for MouseListener: fired when the mouse leaves the
* applet. Clears the status line.
*/
public void mouseExited(MouseEvent e)
{
showStatus("");
}
/**
* Required method for MouseListener: fired when the mouse button is clicked
* (up and down). Note that this method is not used: there are separate
* events for the down and up of the button(s).
*/
public void mouseClicked(MouseEvent e)
{
}
/**
* Required method for MouseListener: fired when the mouse enters the
* applet. If there is a URL link for the applet, show the link in the
* status line.
*/
public void mouseEntered(MouseEvent e)
{
if (linkURL != null) showStatus("Link to " + linkName);
}
/**
* Required method for MouseListener: fired when the mouse button is pressed
* down. Invert the border (this gives a "pressed" look to the applet).
*/
public void mousePressed(MouseEvent e)
{
borderWidth = -borderWidth;
}
}
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