src/org/ibex/Scheduler.java

   1 // Copyright 2004 Adam Megacz, see the COPYING file for licensing [GPL]
   2 package org.ibex;
   3
   4 import org.ibex.js.*;
   5 import org.ibex.util.*;
   6
   7 /** Implements cooperative multitasking */
   8 public class Scheduler {
   9
  10     // Public API Exposed to org.ibex /////////////////////////////////////////////////
  11
  12     private static Scheduler singleton;
  13     public static interface Task { public abstract void perform() throws Exception; }
  14     public static void add(Task t) { singleton.runnable.append(t); }
  15     public static void init() { if (singleton == null) (singleton = Platform.getScheduler()).run(); }
  16
  17     private static Task current = null;
  18
  19     private static volatile boolean rendering = false;
  20     private static volatile boolean again = false;
  21
  22     /** synchronizd so that we can safely call it from an event-delivery thread, in-context */
  23     public static void renderAll() {
  24         if (rendering) { again = true; return; }
  25         synchronized(Scheduler.class) {
  26             try {
  27                 rendering = true;
  28                 do {
  29                     // FEATURE: this could be cleaner
  30                     again = false;
  31                     for(int i=0; i<Surface.allSurfaces.size(); i++) {
  32                         Surface s = ((Surface)Surface.allSurfaces.elementAt(i));
  33                         do { s.render(); } while(s.abort);
  34                     }
  35                 } while(again);
  36             } finally {
  37                 rendering = false;
  38             }
  39         }
  40     }
  41
  42
  43
  44     // API which must be supported by subclasses /////////////////////////////////////
  45
  46     /**
  47      *  SCHEDULER INVARIANT: all scheduler implementations MUST invoke
  48      *  Surface.renderAll() after performing a Task if no tasks remain
  49      *  in the queue.  A scheduler may choose to invoke
  50      *  Surface.renderAll() more often than that if it so chooses.
  51      */
  52     public void run() { defaultRun(); }
  53     protected Scheduler() { }
  54
  55
  56     // Default Implementation //////////////////////////////////////////////////////
  57
  58     protected static Queue runnable = new Queue(50);
  59     public void defaultRun() {
  60         while(true) {
  61             current = (Task)runnable.remove(true);
  62             try {
  63                 // FIXME hideous
  64                 synchronized(this) {
  65                     for(int i=0; i<Surface.allSurfaces.size(); i++) {
  66                         Surface s = (Surface)Surface.allSurfaces.elementAt(i);
  67                         if (current instanceof JS) {
  68                             s._mousex = Integer.MAX_VALUE;
  69                             s._mousey = Integer.MAX_VALUE;
  70                         } else {
  71                             s._mousex = s.mousex;
  72                             s._mousey = s.mousey;
  73                         }
  74                     }
  75                     current.perform();
  76                 }
  77                 renderAll();
  78             } catch (JSExn e) {
  79                 Log.info(Scheduler.class, "a JavaScript thread spawned with ibex.thread() threw an exception:");
  80                 Log.info(Scheduler.class, "JS Exception: " + e.getObject() + "\n" + e.backtrace());
  81                 Log.info(Scheduler.class,e);
  82             } catch (Exception e) {
  83                 Log.info(Scheduler.class, "a Task threw an exception which was caught by the scheduler:");
  84                 Log.info(Scheduler.class, e);
  85             }
  86             // if an Error is thrown it will cause the engine to quit
  87         }
  88     }
  89 }