src/vs/editor/common/viewLayout/viewLinesViewportData.ts/ViewportData/constructor
class ViewportData:	constructor(
		selections: Selection[],
		partialData: IPartialViewLinesViewportData,
		whitespaceViewportData: IViewWhitespaceViewportData[],
		model: IViewModel
	) {
		this.selections = selections;
		this.startLineNumber = partialData.startLineNumber | 0;
		this.endLineNumber = partialData.endLineNumber | 0;
		this.relativeVerticalOffset = partialData.relativeVerticalOffset;
		this.bigNumbersDelta = partialData.bigNumbersDelta | 0;
		this.whitespaceViewportData = whitespaceViewportData;

		this._model = model;

		this.visibleRange = new Range(
			partialData.startLineNumber,
			this._model.getLineMinColumn(partialData.startLineNumber),
			partialData.endLineNumber,
			this._model.getLineMaxColumn(partialData.endLineNumber)
		);
	}