src/vs/editor/common/viewModel/viewModelImpl.ts/ViewModel/getCompletelyVisibleViewRangeAtScrollTop
class ViewModel:	public getCompletelyVisibleViewRangeAtScrollTop(scrollTop: number): Range {
		const partialData = this.viewLayout.getLinesViewportDataAtScrollTop(scrollTop);
		const startViewLineNumber = partialData.completelyVisibleStartLineNumber;
		const endViewLineNumber = partialData.completelyVisibleEndLineNumber;

		return new Range(
			startViewLineNumber, this.getLineMinColumn(startViewLineNumber),
			endViewLineNumber, this.getLineMaxColumn(endViewLineNumber)
		);
	}