当NSPopover在屏幕上时，使NSStatusItem的按钮保持突出显示

import Cocoa

class ViewController: NSViewController {
    var statusItem: NSStatusItem?
    var popover: NSPopover?
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        // 创建NSPopover对象并设置内容视图
        popover = NSPopover()
        popover?.contentViewController = NSViewController()
        
        // 创建NSStatusItem对象
        statusItem = NSStatusBar.system.statusItem(withLength: NSStatusItem.squareLength)
        
        if let button = statusItem?.button {
            // 设置按钮的标题和样式
            button.title = "Popover Button"
            button.action = #selector(togglePopover(_:))
        }
    }
    
    @objc func togglePopover(_ sender: Any?) {
        if let button = statusItem?.button {
            if popover?.isShown == true {
                // 关闭NSPopover并取消按钮的突出显示状态
                popover?.performClose(sender)
                button.highlight(false)
            } else {
                // 显示NSPopover并使按钮保持突出显示状态
                popover?.show(relativeTo: button.bounds, of: button, preferredEdge: NSRectEdge.minY)
                button.highlight(true)
            }
        }
    }
}