diff --git a/libs/pbd/base_ui.cc b/libs/pbd/base_ui.cc
index 83df2b76b5..d41d6aac44 100644
--- a/libs/pbd/base_ui.cc
+++ b/libs/pbd/base_ui.cc
@@ -175,5 +175,6 @@ BaseUI::attach_request_source ()
 {
 	DEBUG_TRACE (DEBUG::EventLoop, string_compose ("%1: attach request source\n", event_loop_name()));
 	request_channel.attach (m_context);
+	maybe_install_precall_handler (m_context);
 }
 
diff --git a/libs/pbd/glib_event_source.cc b/libs/pbd/glib_event_source.cc
new file mode 100644
index 0000000000..59ae3d7c86
--- /dev/null
+++ b/libs/pbd/glib_event_source.cc
@@ -0,0 +1,19 @@
+#include "pbd/glib_event_source.h"
+
+bool
+GlibEventLoopSource::prepare (int& timeout)
+{
+	return false;
+}
+
+bool
+GlibEventLoopSource::check ()
+{
+	return false;
+}
+
+bool
+GlibEventLoopSource::dispatch (sigc::slot_base*)
+{
+	return false;
+}
diff --git a/libs/pbd/pbd/base_ui.h b/libs/pbd/pbd/base_ui.h
index fff6f5da84..fe412f2537 100644
--- a/libs/pbd/pbd/base_ui.h
+++ b/libs/pbd/pbd/base_ui.h
@@ -105,6 +105,8 @@ class LIBPBD_API BaseUI : public sigc::trackable, public PBD::EventLoop
 	void signal_new_request ();
 	void attach_request_source ();
 
+	virtual void maybe_install_precall_handler (Glib::RefPtr<Glib::MainContext>) {}
+
 	/** Derived UI objects must implement this method,
 	 * which will be called whenever there are requests
 	 * to be dealt with.
diff --git a/libs/pbd/pbd/glib_event_source.h b/libs/pbd/pbd/glib_event_source.h
new file mode 100644
index 0000000000..22400f0c53
--- /dev/null
+++ b/libs/pbd/pbd/glib_event_source.h
@@ -0,0 +1,34 @@
+#ifndef __libpbd_glib_event_source_h__
+#define __libpbd_glib_event_source_h__
+
+#include <boost/function.hpp>
+
+#include <glibmm/main.h>
+#include "pbd/libpbd_visibility.h"
+
+class LIBPBD_API GlibEventLoopSource : public Glib::Source
+{
+  public:
+	GlibEventLoopSource () {};
+
+	bool prepare (int& timeout);
+	bool check();
+	bool dispatch (sigc::slot_base*);
+};
+
+
+class LIBPBD_API GlibEventLoopCallback : public GlibEventLoopSource
+{
+  public:
+	GlibEventLoopCallback (boost::function<void()> callback) : _callback (callback) {}
+
+	bool check() {
+		_callback();
+		return false;
+	}
+
+  private:
+	boost::function<void()> _callback;
+};
+
+#endif /* __libpbd_glib_event_source_h__ */
diff --git a/libs/pbd/wscript b/libs/pbd/wscript
index 2dda798a45..82960539a2 100644
--- a/libs/pbd/wscript
+++ b/libs/pbd/wscript
@@ -51,6 +51,7 @@ libpbd_sources = [
     'file_archive.cc',
     'file_utils.cc',
     'fpu.cc',
+    'glib_event_source.cc',
     'id.cc',
     'locale_guard.cc',
     'localtime_r.cc',