Created attachment 4206 [details]
Dirty patch

I have an annoying issue on MacOS about gamepad detection. Note that with the same code, I have no issue on Windows.

If a gamepad (USB or Bluetooth) is plugged before application start, I get the correct device count when doing:
    SDL_GameControllerUpdate();
    SDL_NumJoysticks();

However, if I unplug my device, I don't get an correct device count. If I plug another device, the deconnection of the first one will be detected at the same time.

I also made some tests on Chrome + https://html5gamepad.com. This test case is working perfectly.

I have compared the gamepad implementation of SDL vs Chromium :
* SDL: https://github.com/spurious/SDL-mirror/blob/c9f0264cf3a254128c1d406720c5a4bcce8485d5/src/joystick/hidapi/SDL_hidapijoystick.c#L219
* Chromium: https://cs.chromium.org/chromium/src/services/device/hid/hid_service_mac.cc?q=IOServiceAddMatchingNotification&sq=package:chromium&g=0&l=93

There is a difference : Chromium calls IOServiceAddMatchingNotification(kIOTerminatedNotification), and that isn't done by SDL. If I add the same call in SDL, the runtime plug/unplug detection is working correctly.

I have attached my dirty patch to the issue. It is working, but because I'm not a macOS developper, I'm pretty sure it is invalid and/or incomplete. Furthermore, I have copied some Chromium parameters that are different in SDL code.

Not sure about the real root cause of the issue, and about my patch correctness, but I think some macOS devs can confirm/reject my issue and provide a correct fix.