src/vs/workbench/browser/layout.ts/Layout/offset
class Layout:	get offset() {
		let top = 0;
		let quickPickTop = 0;
		if (this.isVisible(Parts.TITLEBAR_PART)) {
			top = this.getPart(Parts.TITLEBAR_PART).maximumHeight;
			quickPickTop = this.titleService.isCommandCenterVisible ? 0 : top;
		}
		return { top, quickPickTop };
	}