libmythui: Add a generic callback MythEvent

- this will be used by hardware decoder classes to request that GPU
resources are created/destroyed in the UI thread.

mythtv/libs/libmythbase/mythevent.cpp

@@ -26,3 +26,5 @@ QEvent::Type MythEvent::kEnableUDPListenerEventType =
     (QEvent::Type) QEvent::registerEventType();
 QEvent::Type ExternalKeycodeEvent::kEventType =
     (QEvent::Type) QEvent::registerEventType();
+QEvent::Type MythCallbackEvent::kCallbackType =
+    (QEvent::Type) QEvent::registerEventType();

mythtv/libs/libmythbase/mythevent.h

@@ -118,4 +118,24 @@ class MBASE_PUBLIC MythInfoMapEvent : public MythEvent
     InfoMap m_infoMap;
 };
 
+class MBASE_PUBLIC MythCallbackEvent : public QEvent
+{
+  public:
+    typedef void (*Callback)(void*, void*, void*);
+    MythCallbackEvent(Callback Function, void *Opaque1, void *Opaque2, void* Opaque3)
+      : QEvent(kCallbackType),
+        m_function(Function),
+        m_opaque1(Opaque1),
+        m_opaque2(Opaque2),
+        m_opaque3(Opaque3)
+    {
+    }
+
+    static Type kCallbackType;
+    Callback m_function;
+    void* m_opaque1;
+    void* m_opaque2;
+    void* m_opaque3;
+};
+
 #endif /* MYTHEVENT_H */

mythtv/libs/libmythui/mythmainwindow.cpp

@@ -2594,6 +2594,12 @@ void MythMainWindow::customEvent(QEvent *ce)
     {
         GetNotificationCenter()->ProcessQueue();
     }
+    else if (ce->type() == MythCallbackEvent::kCallbackType)
+    {
+        MythCallbackEvent *me = static_cast<MythCallbackEvent*>(ce);
+        if (me && me->m_function)
+            me->m_function(me->m_opaque1, me->m_opaque2, me->m_opaque3);
+    }
 }
 
 QObject *MythMainWindow::getTarget(QKeyEvent &key)