Code cleanup: implement window title update via signal

This seems quite convoluted to me but I can't seem to make a more straight
forward implementation work. The idea is that core code should never
directly call into the UI.

So instead the core code (this is C code) calls a helper function. That
helper function calls a member function of a class which in return emits a
signal. The UI code connects to that signal and acts accordingly when it
is received.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>

windowtitleupdate.cpp

@@ -0,0 +1,31 @@
+#include "windowtitleupdate.h"
+
+WindowTitleUpdate *WindowTitleUpdate::m_instance = NULL;
+
+WindowTitleUpdate::WindowTitleUpdate(QObject *parent) : QObject(parent)
+{
+	Q_ASSERT_X(m_Instance == NULL, "WindowTitleUpdate", "WindowTitleUpdate recreated!");
+
+	m_instance = this;
+}
+
+WindowTitleUpdate *WindowTitleUpdate::instance()
+{
+	return m_instance;
+}
+
+WindowTitleUpdate::~WindowTitleUpdate()
+{
+	m_instance = NULL;
+}
+
+void WindowTitleUpdate::emitSignal()
+{
+	emit updateTitle();
+}
+
+extern "C" void updateWindowTitle()
+{
+	WindowTitleUpdate *wt = WindowTitleUpdate::instance();
+	wt->emitSignal();
+}