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diff --git a/src/libs/engine/QueuedEvent.hpp b/src/libs/engine/QueuedEvent.hpp
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+/* This file is part of Ingen.
+ * Copyright (C) 2007 Dave Robillard <http://drobilla.net>
+ * 
+ * Ingen is free software; you can redistribute it and/or modify it under the
+ * terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 2 of the License, or (at your option) any later
+ * version.
+ * 
+ * Ingen is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE.  See the GNU General Public License for details.
+ * 
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef QUEUEDEVENT_H
+#define QUEUEDEVENT_H
+
+#include "Event.hpp"
+
+namespace Ingen {
+
+class QueuedEventSource;
+
+
+/** An Event with a not-time-critical preprocessing stage.
+ *
+ * These events are events that aren't able to be executed immediately by the
+ * Jack thread (because they allocate memory or whatever).  They are pushed
+ * on to the QueuedEventQueue where they are preprocessed then pushed on
+ * to the realtime Event Queue when they are ready.
+ *
+ * Lookups for these events should go in the pre_process() method, since they are
+ * not time critical and shouldn't waste time in the audio thread doing
+ * lookups they can do beforehand.  (This applies for any expensive operation that
+ * could be done before the execute() method).
+ *
+ * \ingroup engine
+ */
+class QueuedEvent : public Event
+{
+public:
+	/** Process this event into a realtime-suitable event.
+	 */
+	virtual void pre_process() {
+		assert(ThreadManager::current_thread_id() == THREAD_PRE_PROCESS);
+		assert(_pre_processed == false);
+		_pre_processed = true;
+	}
+
+	virtual void execute(SampleCount nframes, FrameTime start, FrameTime end) {
+		assert(_pre_processed);
+		assert(_time <= end);
+
+		// Didn't prepare in time.  QueuedEvents aren't (necessarily) sample accurate
+		// so just run at the beginning of this cycle
+		if (_time <= start)
+			_time = start;
+			
+		Event::execute(nframes, start, end);
+	}
+
+	virtual void post_process() {}
+
+	/** If this event blocks the prepare phase of other slow events */
+	bool is_blocking() { return _blocking; }
+
+	bool is_prepared() { return _pre_processed; }
+	
+protected:
+	QueuedEvent(Engine&                      engine,
+	            SharedPtr<Shared::Responder> responder,
+	            FrameTime                    time, 
+	            bool                         blocking = false,
+	            QueuedEventSource*           source = NULL)
+	: Event(engine, responder, time)
+	, _pre_processed(false), _blocking(blocking), _source(source)
+	{
+		if (blocking)
+			assert(_source);
+	}
+	
+	// NULL event base (for internal events only!)
+	QueuedEvent(Engine& engine)
+	: Event(engine, SharedPtr<Shared::Responder>(), 0)
+	, _pre_processed(false), _blocking(false), _source(NULL)
+	{}
+
+	bool               _pre_processed;
+	bool               _blocking;
+	QueuedEventSource* _source;
+};
+
+
+} // namespace Ingen
+
+#endif // QUEUEDEVENT_H