if(offGfx == null) return;
	public void scrollRepaint(int oldFirstLine, int newFirstLine)	{		TextAreaModel model = textArea.getModel();		int y = model.getLineHeight() * (oldFirstLine - newFirstLine);		offGfx.copyArea(0,0,offImg.getWidth(this),offImg.getHeight(this),0,y);		int visibleLines = textArea.getVisibleLines();		if(oldFirstLine < newFirstLine)		{			invalidateLineRange(oldFirstLine + visibleLines,				newFirstLine + visibleLines);		}		else		{			invalidateLineRange(newFirstLine, oldFirstLine);		}	}