NSComboBox - fixed disappearing list

FixedComboBox.swift

//
//  FixedComboBox.swift
//  Snippety
//
//  Created by Wojciech Kulik on 03/09/2020.
//  Copyright © 2020 Wojciech Kulik. All rights reserved.
//

import Cocoa

final class ClickView: NSView {
    var onMouseDown: () -> (Bool) = { return false }

    override func mouseDown(with event: NSEvent) {
        if !onMouseDown() {
            super.mouseDown(with: event)
        }
    }
}

/// https://stackoverflow.com/questions/63726518/nscombobox-closes-immediately-after-click
final class FixedComboBox: NSComboBox {
    private let clickView = ClickView()

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        fix()
    }

    required init?(coder: NSCoder) {
        super.init(coder: coder)
    }

    override func awakeFromNib() {
        super.awakeFromNib()
        fix()
    }

    private func fix() {
        clickView.onMouseDown = { [weak self] in
            guard let cell = self?.cell else { return false }

            // first expand will be immediately closed because of Cocoa bug
            cell.setAccessibilityExpanded(true)

            // we need to expand it again to fix the issue

            // this one we schedule almost immediately to avoid blinking
            DispatchQueue.main.async { cell.setAccessibilityExpanded(true) }

            // in case the first one didn't "catch" the right moment (sometimes it happens)
            DispatchQueue.main.asyncAfter(deadline: .now() + .milliseconds(100)) { cell.setAccessibilityExpanded(true) }

            return true
        }

        addSubview(clickView)

        clickView.snp.makeConstraints { make in
            make.width.equalTo(20)
            make.trailing.top.bottom.equalToSuperview()
        }
    }
}