Fix apple controller to support four players (#2009)

Author: paulocoutinhox

core/base/Controller-apple.mm

@@ -140,7 +140,32 @@ - (void)onControllerDisconnected:(NSNotification*)connectedNotification
         observerConnection:^(GCController* gcController) {
           auto controller                  = new Controller();
           controller->_impl->_gcController = gcController;
-          controller->_deviceName          = [gcController.vendorName UTF8String];
+
+          // get the player index
+          GCControllerPlayerIndex playerIndex = gcController.playerIndex;
+          if (playerIndex == GCControllerPlayerIndexUnset) {
+              // apple support up to 4 players
+              // ref: https://developer.apple.com/documentation/gamecontroller/gccontrollerplayerindex
+              for (int i = 0; i < 4; ++i) {
+                  bool indexInUse = false;
+
+                  for (GCController *existingController in [GCController controllers]) {
+                      if (existingController.playerIndex == i) {
+                          indexInUse = true;
+                          break;
+                      }
+                  }
+
+                  if (!indexInUse) {
+                      gcController.playerIndex = static_cast<GCControllerPlayerIndex>(i);
+                      playerIndex = static_cast<GCControllerPlayerIndex>(i);
+                      break;
+                  }
+              }
+          }
+
+          controller->_deviceId = static_cast<int>(playerIndex);
+          controller->_deviceName = [gcController.vendorName UTF8String];
 
           s_allController.push_back(controller);