Tasks related to providing native menus (popup/context/menubar) for Widgets and Quick

While we have QtGui platform abstractions for native menus, menu items, and menu bars, they are only used in a few places:

• QMenuBar
  • Shows a native menu as a popup iff
    • QMenuBar::isNativeMenuBar() is false
      • Which is not normally the case on macOS
      • But is the case on Window
    • qt_set_sequence_auto_mnemonic() is true
      • Which it is not on macOS unless called explicitly
      • But is the case on Windows
    • A menu item is triggered via its corresponding mnemonic, and that item is/has a menu that should open
    • That menu has a platform menu
      • Which it normally does not have, unless
        • Someone has called toNSMenu() earlier
        • Or the internal QMenu::setPlatformMenu()
          • Used by QSystemTrayIconPrivate::addPlatformMenu()
            • (Plumbed to QPlatformTheme::createPlatformMenu() via QPlatformSystemTrayIcon::createMenu())
            • But the system tray icon's menu is not tied to QMenuBar in any way, so this is not relevant
  • In summary
    • The logic is only triggered on Windows (unless the user jumps through many hoops that's not really supported)
    • But requires a platform menu, which is only likely to be the case on macOS via toNSMenu
    • Ie, the QMenuBar QPlatformMenu::showPopup() logic can likely be removed
      • Everything else works on a QPlatformMenuBar level already, so native menus still work

• QComboBox::showPopup()
  • Iff

• • • On an Apple OS
    • If the style reports true for SH_ComboBox_UseNativePopup, which only the iOS plugin does

• QQuickLabsPlatformMenu
  • Provides support for both menu bars and context menus