src/vs/editor/common/viewLayout/linesLayout.ts/LinesLayout/getWhitespaceAtVerticalOffset
class LinesLayout:	public getWhitespaceAtVerticalOffset(verticalOffset: number): IViewWhitespaceViewportData | null {
		this._checkPendingChanges();
		verticalOffset = verticalOffset | 0;

		const candidateIndex = this.getWhitespaceIndexAtOrAfterVerticallOffset(verticalOffset);

		if (candidateIndex < 0) {
			return null;
		}

		if (candidateIndex >= this.getWhitespacesCount()) {
			return null;
		}

		const candidateTop = this.getVerticalOffsetForWhitespaceIndex(candidateIndex);

		if (candidateTop > verticalOffset) {
			return null;
		}

		const candidateHeight = this.getHeightForWhitespaceIndex(candidateIndex);
		const candidateId = this.getIdForWhitespaceIndex(candidateIndex);
		const candidateAfterLineNumber = this.getAfterLineNumberForWhitespaceIndex(candidateIndex);

		return {
			id: candidateId,
			afterLineNumber: candidateAfterLineNumber,
			verticalOffset: candidateTop,
			height: candidateHeight
		};
	}