Workaround updating frame (and thus darkening the image)

by only updating when there is new data.
This essentially limits the frame rate to the buffer update rate

This will be fixed when painting is done in smaller chunks of the buffer

osciwidget.cpp

@@ -62,6 +62,9 @@ void OsciWidget::paintEvent(QPaintEvent *event)
 
 void OsciWidget::updateFrameBuffer()
 {
+    // Workaround for flickering (do not update, when there is no new data)
+    if(m_buffer.empty()) return;
+
     if (m_pixmap.size() != size())
         m_pixmap = QPixmap(size());