QtUtils: add QueueOnObject

Source/Core/DolphinQt2/QtUtils/QueueOnObject.h

@@ -0,0 +1,20 @@
+// Copyright 2017 Dolphin Emulator Project
+// Licensed under GPLv2+
+// Refer to the license.txt file included.
+
+#pragma once
+
+#include <QObject>
+#include <utility>
+
+// QWidget and subclasses are not thread-safe! However, Qt's signal-slot connection mechanism will
+// invoke slots/functions on the correct thread for any object. We can (ab)use this to queue up
+// arbitrary code from non-GUI threads. For more information, see:
+// https://stackoverflow.com/questions/21646467/
+
+template <typename F>
+static void QueueOnObject(QObject* obj, F&& func)
+{
+  QObject src;
+  QObject::connect(&src, &QObject::destroyed, obj, std::forward<F>(func), Qt::QueuedConnection);
+}