QMLManager: helper function for devivePixelRatio

This allows us to use the single manager object to keep track of the dpr of the
screen and to pass it on if it changes (or when it first becomes known).

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

qt-mobile/qmlmanager.cpp

@@ -954,3 +954,14 @@ void QMLManager::setAccessingCloud(bool status)
 	m_accessingCloud = status;
 	emit accessingCloudChanged();
 }
+
+qreal QMLManager::lastDevicePixelRatio()
+{
+	return m_lastDevicePixelRatio;
+}
+
+void QMLManager::screenChanged(QScreen *screen)
+{
+	m_lastDevicePixelRatio = screen->devicePixelRatio();
+	emit sendScreenChanged(screen);
+}