TerminalViewportState
constructor(historySize: Int, scrollbackOffset: Double, renderOffset: Int, visibleRows: Int, requestedRows: Int, visualScrollOffsetPixels: Double = scrollbackOffset, visualScrollRangePixels: Int = historySize, viewportHeightPixels: Int = visibleRows, contentHeightPixels: Int = requestedRows, cellHeightPixels: Int = 1)