void 
DataVisualizer::adjustSize(void)
{
	// determine the current difference between window size and viewport size
	int margin = size().height() - gvDisplay->viewport()->size().height();
	int scrollBarWidth = 0;
	// get scrollbar height offset
	QScrollBar * vscroll = gvDisplay->horizontalScrollBar();
	if (vscroll) scrollBarWidth = vscroll->sizeHint().height();
	margin += scrollBarWidth;

	QSize newSize(size());
	// update height only
	newSize.setHeight(int(gvDisplay->sceneRect().height()) + margin);
	// resize nescessary ?
	if (size().height() != newSize.height()) {
		resize(newSize);
	}
}