src/vs/editor/browser/widget/inlineDiffMargin.ts/InlineDiffMargin/_updateLightBulbPosition
class InlineDiffMargin:	private _updateLightBulbPosition(marginDomNode: HTMLElement, y: number, lineHeight: number): number {
		const { top } = dom.getDomNodePagePosition(marginDomNode);
		const offset = y - top;
		const lineNumberOffset = Math.floor(offset / lineHeight);
		const newTop = lineNumberOffset * lineHeight;
		this._diffActions.style.top = `${newTop}px`;
		if (this.diff.viewLineCounts) {
			let acc = 0;
			for (let i = 0; i < this.diff.viewLineCounts.length; i++) {
				acc += this.diff.viewLineCounts[i];
				if (lineNumberOffset < acc) {
					return i;
				}
			}
		}
		return lineNumberOffset;
	}