Gamepads cannot be easily manually registered or deregistered

[alice-i-cecile]

What problem does this solve or what need does it fill?

Users want to manually register and deregister gamepads as part of tests to verify that gamepad inputs are working correctly.

The critical methods / fields on the Gamepads struct are private however, which makes doing so rather convoluted.

What solution would you like?

Make the register and deregister methods on Gamepads public.

What alternative(s) have you considered?

We could expose the underlying HashSet directly, but that flavor of API is somewhat harder to read.

Users can already do this with a horrible workaround where they manually run the public gamepad_connection_system.

[alice-i-cecile]

The aforementioned terrible workaround:

impl GamepadRegistration for World {
    fn register_gamepad(&mut self, gamepad: Gamepad) {
        // Generate a synthetic event
        let gamepad_event = GamepadEvent(gamepad, GamepadEventType::Connected);
        let mut events_resource = self.resource_mut::<Events<GamepadEvent>>();
        events_resource.send(gamepad_event);

        // Ensure that the Gamepads resource exists to avoid pointless panics
        if self.get_resource::<Gamepads>().is_none() {
            self.init_resource::<Gamepads>();
        }

        // Manually run the gamepad_connection_system on the World to process the event just sent
        let mut system = IntoSystem::into_system(gamepad_connection_system);
        system.initialize(self);
        system.run((), self);
    }

    fn deregister_gamepad(&mut self, gamepad: Gamepad) {
        // Generate a synthetic event
        let gamepad_event = GamepadEvent(gamepad, GamepadEventType::Disconnected);
        let mut events_resource = self.resource_mut::<Events<GamepadEvent>>();
        events_resource.send(gamepad_event);

        // Ensure that the Gamepads resource exists to avoid pointless panics
        if self.get_resource::<Gamepads>().is_none() {
            self.init_resource::<Gamepads>();
        }

        // Manually run the gamepad_connection_system on the World to process the event just sent
        let mut system = IntoSystem::into_system(gamepad_connection_system);
        system.initialize(self);
        system.run((), self);
    }
}

[alice-i-cecile]

This is a duplicate of #3808 apparently. I still disagree with the stance taken by @cart there: I think that being able to mock gamepad inputs correctly is a very important goal, and as shown by the workaround, users can cause the list of registered gamepads to desync from the list of "actually connected" gamepads.