如何使用Cocoa在Dock图标上绘制徽章？

import Cocoa

class BadgeView: NSView {
    var badgeText: String?

    override func draw(_ dirtyRect: NSRect) {
        super.draw(dirtyRect)

        guard let badgeText = badgeText else { return }

        let font = NSFont.systemFont(ofSize: 12)
        let textSize = badgeText.size(withAttributes: [.font: font])
        let rect = NSRect(x: self.bounds.width - textSize.width - 8,
                          y: 2,
                          width: textSize.width + 8,
                          height: textSize.height + 4)

        let path = NSBezierPath(roundedRect: rect, xRadius: 4, yRadius: 4)
        NSColor.red.setFill()
        path.fill()

        let textRect = NSRect(x: rect.origin.x + 4,
                               y: rect.origin.y + 2,
                               width: textSize.width,
                               height: textSize.height)
        NSColor.white.set()
        badgeText.draw(in: textRect, withAttributes: [.font: font])
    }
}

let dockTile = NSDockTile(contentRect: NSZeroRect)
NSApp.dockTile = dockTile

let badgeView = BadgeView(frame: NSRect(x: 0, y: 0, width: 30, height: 30))
badgeView.badgeText = "99"
dockTile.contentView = badgeView