Apple certainly seem to think that WebKit is at least a partial alternative to Cocoa, given their use of it in parts of the system preferences. Apple is keeping

Apple certainly seem to think that WebKit is at least a partial alternative to Cocoa, given their use of it in parts of the system preferences. Apple is keeping those two in sync so things don't look out of place. Microsoft has widgets in WinAPI, and then there's WinForms, WPF, WinUI, WinJS and don't forget Electron which Microsoft themselves also ship apps with. There's also the whole win32 & UWP distinction. If you dig deep enough into the system settings you'll even find Dialogs that use the wrong window decorations.