/**
  * Image Loader for the Moving Map Navigator Demonstrator Applet
  * @author Robert J Morton
  * @version 12 Dec 2007 */


import java.awt.MediaTracker;  // for the new-fangled 1.1 event handling

public class imgldr {
  private static imgldr il;
  private bs hf;                 // instance reference to the bs applet
  private msgpanel mp;           // instance reference for message panel
  private MediaTracker tracker;  // to track when the images have been loaded
  private boolean 
    loadingImages = true,
    trackerError = false,  // true = tracker encountered an error
    loadFTT = true,   // to avoid an erase and repaint of the loading message
    errorFTT = true;  // load-error message once per refresh cycle


  imgldr(bs hf, msgpanel mp) {
    this.hf = hf;  // instance reference to the bs applet
    this.mp = mp;  // instance of message panel

    // create a media tracker and register images with it
    tracker = new MediaTracker(hf);

    il = this;  // instance reference to this instance of the image loader

    if(hf.JarredImages) {  // load images from the applet's own jar file
      hf.IMG1 = hf.getImage(getClass().getResource("map1.png"));
      hf.IMG2 = hf.getImage(getClass().getResource("map2.png"));
      hf.IMG3 = hf.getImage(getClass().getResource("map3.png"));
    } else {               // load images from remote server
      hf.IMG1 = hf.getImage(hf.getDocumentBase(),"map1.png"); 
      hf.IMG2 = hf.getImage(hf.getDocumentBase(),"map2.png"); 
      hf.IMG3 = hf.getImage(hf.getDocumentBase(),"map3.png"); 
    }
    tracker.addImage(hf.IMG1,0);  // register the images with the tracker
    tracker.addImage(hf.IMG2,0);
    tracker.addImage(hf.IMG3,0);
  }


  boolean awaitingImages() {
    if(loadFTT) {       // if this is the first time through here
      mp.showMsg("Loading images from server...", false);
      loadFTT = false;  // avoid repeating display every cycle      
    }
    /* Keep checking the tracker for a completion or error signal.
    If the tracker does not say anything, return without servicing
    the applet 'run' thread. */

    try { tracker.waitForAll(); }
    catch (InterruptedException e) { return true; }

    return false;  // drop thru when tracker gives a completion signal
  }


  // RETURNS TRUE WHEN IMAGE LOADING HAS TERMINATED
  boolean imagesLoaded() {
    if(tracker == null) return true;  // tracker instance no longer exists
    if(loadingImages) {  // if image loading process still running

      /* Get the status of the image loading process. If it has
      finished, set the flag to indicate image loading failure. */

      int ts = tracker.statusAll(false);
      if((ts & MediaTracker.ERRORED) != 0) {
        trackerError = true; 

        /* If this is the first time through here, display error message
        and set the flag to aviod repeated re-display of the same message. */

        if(errorFTT) {
           mp.showMsg("Error: couldn't load images.", true);
           errorFTT = false;
        }
      }
      /* If the tracker has completed its task, set the 
      flag to indicate that image loading has terminated. */

      if(ts == MediaTracker.COMPLETE) { loadingImages = false; }
    }
    /* Else, the image loading process has just finished, 
    so refresh the display if not already done so. */

    else { killTracker(); mp.showMsg("Images Loaded.", false); }
    return false;
  }


  // REMOVE [DE-REGISTER] THE IMAGES FROM TRACKER AND THEN KILL THE TRACKER
  void killTracker() {
    if(tracker != null) {
      tracker.removeImage(hf.IMG1, 0);
      tracker.removeImage(hf.IMG2, 0);
      tracker.removeImage(hf.IMG3, 0);
      tracker = null;
    }
  }

  boolean TrackerError() {return trackerError;}
}