2003/12/16 22:35:20

[org.ibex.core.git] / src / org / xwt / Scheduler.java

diff --git a/src/org/xwt/Scheduler.java b/src/org/xwt/Scheduler.java
index a46c75c..3dcc7f5 100644 (file)
--- a/src/org/xwt/Scheduler.java
+++ b/src/org/xwt/Scheduler.java
@@ -10,39 +10,47 @@ public class Scheduler {
 
     // Public API Exposed to org.xwt /////////////////////////////////////////////////
 
-    public static abstract class Task { public abstract void perform(); }
+    private static Scheduler singleton;
+    public static interface Task { public abstract void perform() throws Exception; }
+
+    /** adds a task to the back of the queue */
     public static void add(Task t) { singleton.runnable.append(t); }
-    public static void init() { singleton.run(); }
 
+    /** adds a task to the front of the queue (guaranteed to run next) */
+    public static void addAtFront(Task t) { singleton.runnable.prepend(t); }
 
-    // API which must be supported by subclasses /////////////////////////////////////
+    public static void init() { if (singleton == null) (singleton = Platform.getScheduler()).run(); }
 
-    protected Scheduler() { }
+    // API which must be supported by subclasses /////////////////////////////////////
 
     /**
-     *  INVARIANT: all scheduler implementations MUST invoke
+     *  SCHEDULER INVARIANT: all scheduler implementations MUST invoke
      *  Surface.renderAll() after performing a Task if no tasks remain
      *  in the queue.  A scheduler may choose to invoke
      *  Surface.renderAll() more often than that if it so chooses.
      */
     public void run() { defaultRun(); }
+    protected Scheduler() { }
 
 
-    // Default Implementation /////////////////////////////////////
+    // Default Implementation //////////////////////////////////////////////////////
 
     protected static Queue runnable = new Queue(50);
-    private static final Scheduler singleton = Platform.getScheduler();
     public void defaultRun() {
         while(true) {
             Task t = (Task)runnable.remove(true);
             try {
                 t.perform();
-                // FIXME: be smarter about this
-                Surface.renderAll();
+                // FEATURE: be smarter about this
+                if (t != Surface.renderAll) add(Surface.renderAll);
+            } catch (JSExn e) {
+                Log.log(Scheduler.class, "a JavaScript thread spawned with xwt.thread() threw an exception:");
+                Log.log(Scheduler.class, e.toString());
             } catch (Exception e) {
-                Log.log(Scheduler.class, "Task threw an exception: " + e);
+                Log.log(Scheduler.class, "a Task threw an exception which was caught by the scheduler:");
                 Log.log(Scheduler.class, e);
             }
+            // if an Error is thrown it will cause the engine to quit
         }
     }
 }