+ // FIXME: prepending events messes with keysate -- make a "no re-ordering" invariant?
+
+ // Public API Exposed to org.xwt /////////////////////////////////////////////////
+
+ 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); }
+
+ /** adds a task to the front of the queue (guaranteed to run next) */
+ public static void addAtFront(Task t) { singleton.runnable.prepend(t); }
+
+ public static void init() { if (singleton == null) (singleton = Platform.getScheduler()).run(); }
+
+ private static Task current = null;
+ public static Task current() { return current; }
+
+ /** synchronizd so that we can safely call it from an event-delivery thread, in-context */
+ private static volatile boolean rendering = false;
+ private static volatile boolean again = false;
+ public static void renderAll() {
+ if (rendering) { again = true; return; }
+ synchronized(Scheduler.class) {
+ try {
+ rendering = true;
+ do {
+ again = false;
+ for(int i=0; i<Surface.allSurfaces.size(); i++) {
+ Surface s = ((Surface)Surface.allSurfaces.elementAt(i));
+ do { s.render(); } while(s.abort);
+ }
+ } while(again);
+ } finally {
+ rendering = false;
+ }
+ }
+ }
+
+
+
+ // API which must be supported by subclasses /////////////////////////////////////
+
+ /**
+ * 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(); }