src/vs/base/browser/ui/scrollbar/scrollbarState.ts/ScrollbarState/getDesiredScrollPositionFromOffset
class ScrollbarState:	public getDesiredScrollPositionFromOffset(offset: number): number {
		if (!this._computedIsNeeded) {
			// no need for a slider
			return 0;
		}

		const desiredSliderPosition = offset - this._arrowSize - this._computedSliderSize / 2;
		return Math.round(desiredSliderPosition / this._computedSliderRatio);
	}