src/vs/workbench/browser/parts/compositeBar.ts/CompositeBar/updateFromDragging
class CompositeBar:	private updateFromDragging(element: HTMLElement, showFeedback: boolean, front: boolean, isDragging: boolean): Before2D | undefined {
		element.classList.toggle('dragged-over', isDragging);
		element.classList.toggle('dragged-over-head', showFeedback && front);
		element.classList.toggle('dragged-over-tail', showFeedback && !front);

		if (!showFeedback) {
			return undefined;
		}

		return { verticallyBefore: front, horizontallyBefore: front };
	}