Revert ProgressConnector

Doesn't work with `IdleRegister`.

rtgui/progressconnector.h

@@ -65,36 +65,32 @@ public:
 template<class T>
 class ProgressConnector
 {
-private:
+
     sigc::signal0<T> opStart;
     sigc::signal0<bool> opEnd;
     T retval;
     Glib::Thread *workThread;
-    IdleRegister idle_register;
+
+    static int emitEndSignalUI (void* data)
+    {
+
+        sigc::signal0<bool>* opEnd = (sigc::signal0<bool>*) data;
+        int r = opEnd->emit ();
+        delete opEnd;
+
+        return r;
+    }
 
     void workingThread ()
     {
-        retval = opStart.emit();
-
-        const auto func = [](gpointer data) -> gboolean {
-            sigc::signal0<bool>* const opEnd = static_cast<sigc::signal0<bool>*>(data);
-            const gboolean res = opEnd->emit();
-            delete opEnd;
-
-            return res;
-        };
-
-        idle_register.add(func, new sigc::signal0<bool>(opEnd));
-
+        retval = opStart.emit ();
+        gdk_threads_add_idle(ProgressConnector<T>::emitEndSignalUI, new sigc::signal0<bool>(opEnd));
         workThread = nullptr;
     }
 
 public:
+
     ProgressConnector (): retval( 0 ), workThread( nullptr ) { }
-    ~ProgressConnector()
-    {
-        idle_register.destroy();
-    }
 
     void startFunc (const sigc::slot0<T>& startHandler, const sigc::slot0<bool>& endHandler )
     {