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Scrolling status bar message

Scrolling status bar message

Question:
How can I make a message that will scroll in the status bar?

Answer:
The following applet constructs a thread, passing it a messageand its browser context. The thread perpetually sleeps for 100 miliseconds and computes three strings:

 prefix = last i chars of message;   infix  = first j chars of filler;  // filler = ”     ”   suffix = first k chars of message;
or
prefix = last j chars of filler;   infix  = first k chars of message;     suffix = first i chars of filler;
where i + j + k = blen = fixed banner length, then calls:
 context.showStatus(prefix + infix + suffix);
Each time through the loop, i, j and k are adjusted to createthe illusion of scrolling. (I might add that I’m not terriblyproud of the awkward way I compute i, j and k.)

From the applet, users can suspend or resume the thread, orchange the message.

The code can be modified to create a scrolling text field bypassing the text field rather than a context to the thread.In this case we use the statement:

msgField.setText(prefix + infix + suffix);
Finally, the 100 milisecond figure was arrived at experimentally.Shorter times make the text scroll too fast and make the threaddifficult to interrupt.
*/import java.awt.*;import java.applet.*;class Scroller extends Thread {   AppletContext context;   String msg;   String filler = ”          “;   public Scroller(String m, AppletContext ctxt) {      context = ctxt;      msg = m;   }   public void run() {      int mlen = msg.length(),          flen = filler.length(),          blen = mlen + flen – 2,          i = 0,          j = 0,          k = 0,          h = 0;      String prefix, infix, suffix;      while (true) {         if (i < mlen) {            prefix = msg.substring(i, mlen);            h = mlen - i;            infix = filler.substring(0, j = Math.min(blen - h, flen));            if (blen - (h + j) >= 0)               suffix = msg.substring(0, Math.min(blen – (h + j), mlen));            else               suffix = “”;         }         else {            prefix = filler.substring(j = (i – mlen), flen);            h = flen – j;            infix = msg.substring(0, k = Math.min(blen – h, mlen));            if (blen – (h + k) >= 0)               suffix = filler.substring(0, Math.min(blen – (h + k), flen));            else               suffix = “”;         }         i = (i + 1) % (flen + mlen);                  try {            sleep(100);         }         catch (InterruptedException e) {            e.printStackTrace();         }         context.showStatus(prefix + infix + suffix);      } // while   } // run}         public class BannerDemo extends Applet {   private AppletContext context;   private String message;   private Scroller scrollGuy;   private boolean scrolling = true, msgChanged = false;   private TextField msgField;   public void init() {      add(new Button(“Suspend/Resume”));      context = getAppletContext();      message = getParameter(“msg”);      msgField = new TextField(message, 20);      add(msgField);      scrollGuy = new Scroller(message, context);   }   public void start() {      scrollGuy.start();      scrolling = true;   }   public void stop() {      scrollGuy.stop();      scrolling = false;   }   public boolean handleEvent(Event e) {      if (e.id == Event.WINDOW_DESTROY) System.exit(1);      return super.handleEvent(e);   }   public boolean action(Event e, Object arg) {      if (arg.equals(“Suspend/Resume”) ) {         if (scrolling) {            scrollGuy.suspend();            scrolling = false;         }         else if (msgChanged) {            scrolling = true;            msgChanged = false;            scrollGuy.stop();            scrollGuy = new Scroller(msgField.getText(), context);            scrollGuy.start();         }         else {            scrollGuy.resume();            scrolling = true;         }      }      else if (e.target == msgField)         msgChanged = true;      else return false;      return true;   }   }

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